MFC r347990:

[FreeBSD/stable/10.git] / contrib / libarchive / libarchive / archive_read_support_format_rar5.c

/*-
* Copyright (c) 2018 Grzegorz Antoniak (http://antoniak.org)
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include "archive_platform.h"
#include "archive_endian.h"

#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#include <time.h>
#ifdef HAVE_ZLIB_H
#include <zlib.h> /* crc32 */
#endif
#ifdef HAVE_LIMITS_H
#include <limits.h>
#endif

#include "archive.h"
#ifndef HAVE_ZLIB_H
#include "archive_crc32.h"
#endif

#include "archive_entry.h"
#include "archive_entry_locale.h"
#include "archive_ppmd7_private.h"
#include "archive_entry_private.h"

#ifdef HAVE_BLAKE2_H
#include <blake2.h>
#else
#include "archive_blake2.h"
#endif

/*#define CHECK_CRC_ON_SOLID_SKIP*/
/*#define DONT_FAIL_ON_CRC_ERROR*/
/*#define DEBUG*/

#define rar5_min(a, b) (((a) > (b)) ? (b) : (a))
#define rar5_max(a, b) (((a) > (b)) ? (a) : (b))
#define rar5_countof(X) ((const ssize_t) (sizeof(X) / sizeof(*X)))

#if defined DEBUG
#define DEBUG_CODE if(1)
#else
#define DEBUG_CODE if(0)
#endif

/* Real RAR5 magic number is:
 *
 * 0x52, 0x61, 0x72, 0x21, 0x1a, 0x07, 0x01, 0x00
 * "Rar!→•☺·\x00"
 *
 * It's stored in `rar5_signature` after XOR'ing it with 0xA1, because I don't
 * want to put this magic sequence in each binary that uses libarchive, so
 * applications that scan through the file for this marker won't trigger on
 * this "false" one.
 *
 * The array itself is decrypted in `rar5_init` function. */

static unsigned char rar5_signature[] = { 243, 192, 211, 128, 187, 166, 160, 161 };
static const ssize_t rar5_signature_size = sizeof(rar5_signature);
static const size_t g_unpack_window_size = 0x20000;

/* These could have been static const's, but they aren't, because of
 * Visual Studio. */
#define MAX_NAME_IN_CHARS 2048
#define MAX_NAME_IN_BYTES (4 * MAX_NAME_IN_CHARS)

struct file_header {
        ssize_t bytes_remaining;
        ssize_t unpacked_size;
        int64_t last_offset;         /* Used in sanity checks. */
        int64_t last_size;           /* Used in sanity checks. */

        uint8_t solid : 1;           /* Is this a solid stream? */
        uint8_t service : 1;         /* Is this file a service data? */
        uint8_t eof : 1;             /* Did we finish unpacking the file? */
        uint8_t dir : 1;             /* Is this file entry a directory? */

        /* Optional time fields. */
        uint64_t e_mtime;
        uint64_t e_ctime;
        uint64_t e_atime;
        uint32_t e_unix_ns;

        /* Optional hash fields. */
        uint32_t stored_crc32;
        uint32_t calculated_crc32;
        uint8_t blake2sp[32];
        blake2sp_state b2state;
        char has_blake2;

        /* Optional redir fields */
        uint64_t redir_type;
        uint64_t redir_flags;
};

enum EXTRA {
        EX_CRYPT = 0x01,
        EX_HASH = 0x02,
        EX_HTIME = 0x03,
        EX_VERSION = 0x04,
        EX_REDIR = 0x05,
        EX_UOWNER = 0x06,
        EX_SUBDATA = 0x07
};

#define REDIR_SYMLINK_IS_DIR    1

enum REDIR_TYPE {
        REDIR_TYPE_NONE = 0,
        REDIR_TYPE_UNIXSYMLINK = 1,
        REDIR_TYPE_WINSYMLINK = 2,
        REDIR_TYPE_JUNCTION = 3,
        REDIR_TYPE_HARDLINK = 4,
        REDIR_TYPE_FILECOPY = 5,
};

#define OWNER_USER_NAME         0x01
#define OWNER_GROUP_NAME        0x02
#define OWNER_USER_UID          0x04
#define OWNER_GROUP_GID         0x08
#define OWNER_MAXNAMELEN        256

enum FILTER_TYPE {
        FILTER_DELTA = 0,   /* Generic pattern. */
        FILTER_E8    = 1,   /* Intel x86 code. */
        FILTER_E8E9  = 2,   /* Intel x86 code. */
        FILTER_ARM   = 3,   /* ARM code. */
        FILTER_AUDIO = 4,   /* Audio filter, not used in RARv5. */
        FILTER_RGB   = 5,   /* Color palette, not used in RARv5. */
        FILTER_ITANIUM = 6, /* Intel's Itanium, not used in RARv5. */
        FILTER_PPM   = 7,   /* Predictive pattern matching, not used in
                               RARv5. */
        FILTER_NONE  = 8,
};

struct filter_info {
        int type;
        int channels;
        int pos_r;

        int64_t block_start;
        ssize_t block_length;
        uint16_t width;
};

struct data_ready {
        char used;
        const uint8_t* buf;
        size_t size;
        int64_t offset;
};

struct cdeque {
        uint16_t beg_pos;
        uint16_t end_pos;
        uint16_t cap_mask;
        uint16_t size;
        size_t* arr;
};

struct decode_table {
        uint32_t size;
        int32_t decode_len[16];
        uint32_t decode_pos[16];
        uint32_t quick_bits;
        uint8_t quick_len[1 << 10];
        uint16_t quick_num[1 << 10];
        uint16_t decode_num[306];
};

struct comp_state {
        /* Flag used to specify if unpacker needs to reinitialize the
           uncompression context. */
        uint8_t initialized : 1;

        /* Flag used when applying filters. */
        uint8_t all_filters_applied : 1;

        /* Flag used to skip file context reinitialization, used when unpacker
           is skipping through different multivolume archives. */
        uint8_t switch_multivolume : 1;

        /* Flag used to specify if unpacker has processed the whole data block
           or just a part of it. */
        uint8_t block_parsing_finished : 1;

        int notused : 4;

        int flags;                   /* Uncompression flags. */
        int method;                  /* Uncompression algorithm method. */
        int version;                 /* Uncompression algorithm version. */
        ssize_t window_size;         /* Size of window_buf. */
        uint8_t* window_buf;         /* Circular buffer used during
                                        decompression. */
        uint8_t* filtered_buf;       /* Buffer used when applying filters. */
        const uint8_t* block_buf;    /* Buffer used when merging blocks. */
        size_t window_mask;          /* Convenience field; window_size - 1. */
        int64_t write_ptr;           /* This amount of data has been unpacked
                                        in the window buffer. */
        int64_t last_write_ptr;      /* This amount of data has been stored in
                                        the output file. */
        int64_t last_unstore_ptr;    /* Counter of bytes extracted during
                                        unstoring. This is separate from
                                        last_write_ptr because of how SERVICE
                                        base blocks are handled during skipping
                                        in solid multiarchive archives. */
        int64_t solid_offset;        /* Additional offset inside the window
                                        buffer, used in unpacking solid
                                        archives. */
        ssize_t cur_block_size;      /* Size of current data block. */
        int last_len;                /* Flag used in lzss decompression. */

        /* Decode tables used during lzss uncompression. */

#define HUFF_BC 20
        struct decode_table bd;      /* huffman bit lengths */
#define HUFF_NC 306
        struct decode_table ld;      /* literals */
#define HUFF_DC 64
        struct decode_table dd;      /* distances */
#define HUFF_LDC 16
        struct decode_table ldd;     /* lower bits of distances */
#define HUFF_RC 44
        struct decode_table rd;      /* repeating distances */
#define HUFF_TABLE_SIZE (HUFF_NC + HUFF_DC + HUFF_RC + HUFF_LDC)

        /* Circular deque for storing filters. */
        struct cdeque filters;
        int64_t last_block_start;    /* Used for sanity checking. */
        ssize_t last_block_length;   /* Used for sanity checking. */

        /* Distance cache used during lzss uncompression. */
        int dist_cache[4];

        /* Data buffer stack. */
        struct data_ready dready[2];
};

/* Bit reader state. */
struct bit_reader {
        int8_t bit_addr;    /* Current bit pointer inside current byte. */
        int in_addr;        /* Current byte pointer. */
};

/* RARv5 block header structure. Use bf_* functions to get values from
 * block_flags_u8 field. I.e. bf_byte_count, etc. */
struct compressed_block_header {
        /* block_flags_u8 contain fields encoded in little-endian bitfield:
         *
         * - table present flag (shr 7, and 1),
         * - last block flag    (shr 6, and 1),
         * - byte_count         (shr 3, and 7),
         * - bit_size           (shr 0, and 7).
         */
        uint8_t block_flags_u8;
        uint8_t block_cksum;
};

/* RARv5 main header structure. */
struct main_header {
        /* Does the archive contain solid streams? */
        uint8_t solid : 1;

        /* If this a multi-file archive? */
        uint8_t volume : 1;
        uint8_t endarc : 1;
        uint8_t notused : 5;

        unsigned int vol_no;
};

struct generic_header {
        uint8_t split_after : 1;
        uint8_t split_before : 1;
        uint8_t padding : 6;
        int size;
        int last_header_id;
};

struct multivolume {
        unsigned int expected_vol_no;
        uint8_t* push_buf;
};

/* Main context structure. */
struct rar5 {
        int header_initialized;

        /* Set to 1 if current file is positioned AFTER the magic value
         * of the archive file. This is used in header reading functions. */
        int skipped_magic;

        /* Set to not zero if we're in skip mode (either by calling
         * rar5_data_skip function or when skipping over solid streams).
         * Set to 0 when in * extraction mode. This is used during checksum
         * calculation functions. */
        int skip_mode;

        /* Set to not zero if we're in block merging mode (i.e. when switching
         * to another file in multivolume archive, last block from 1st archive
         * needs to be merged with 1st block from 2nd archive). This flag
         * guards against recursive use of the merging function, which doesn't
         * support recursive calls. */
        int merge_mode;

        /* An offset to QuickOpen list. This is not supported by this unpacker,
         * because we're focusing on streaming interface. QuickOpen is designed
         * to make things quicker for non-stream interfaces, so it's not our
         * use case. */
        uint64_t qlist_offset;

        /* An offset to additional Recovery data. This is not supported by this
         * unpacker. Recovery data are additional Reed-Solomon codes that could
         * be used to calculate bytes that are missing in archive or are
         * corrupted. */
        uint64_t rr_offset;

        /* Various context variables grouped to different structures. */
        struct generic_header generic;
        struct main_header main;
        struct comp_state cstate;
        struct file_header file;
        struct bit_reader bits;
        struct multivolume vol;

        /* The header of currently processed RARv5 block. Used in main
         * decompression logic loop. */
        struct compressed_block_header last_block_hdr;
};

/* Forward function declarations. */

static int verify_global_checksums(struct archive_read* a);
static int rar5_read_data_skip(struct archive_read *a);
static int push_data_ready(struct archive_read* a, struct rar5* rar,
        const uint8_t* buf, size_t size, int64_t offset);

/* CDE_xxx = Circular Double Ended (Queue) return values. */
enum CDE_RETURN_VALUES {
        CDE_OK, CDE_ALLOC, CDE_PARAM, CDE_OUT_OF_BOUNDS,
};

/* Clears the contents of this circular deque. */
static void cdeque_clear(struct cdeque* d) {
        d->size = 0;
        d->beg_pos = 0;
        d->end_pos = 0;
}

/* Creates a new circular deque object. Capacity must be power of 2: 8, 16, 32,
 * 64, 256, etc. When the user will add another item above current capacity,
 * the circular deque will overwrite the oldest entry. */
static int cdeque_init(struct cdeque* d, int max_capacity_power_of_2) {
        if(d == NULL || max_capacity_power_of_2 == 0)
                return CDE_PARAM;

        d->cap_mask = max_capacity_power_of_2 - 1;
        d->arr = NULL;

        if((max_capacity_power_of_2 & d->cap_mask) > 0)
                return CDE_PARAM;

        cdeque_clear(d);
        d->arr = malloc(sizeof(void*) * max_capacity_power_of_2);

        return d->arr ? CDE_OK : CDE_ALLOC;
}

/* Return the current size (not capacity) of circular deque `d`. */
static size_t cdeque_size(struct cdeque* d) {
        return d->size;
}

/* Returns the first element of current circular deque. Note that this function
 * doesn't perform any bounds checking. If you need bounds checking, use
 * `cdeque_front()` function instead. */
static void cdeque_front_fast(struct cdeque* d, void** value) {
        *value = (void*) d->arr[d->beg_pos];
}

/* Returns the first element of current circular deque. This function
 * performs bounds checking. */
static int cdeque_front(struct cdeque* d, void** value) {
        if(d->size > 0) {
                cdeque_front_fast(d, value);
                return CDE_OK;
        } else
                return CDE_OUT_OF_BOUNDS;
}

/* Pushes a new element into the end of this circular deque object. If current
 * size will exceed capacity, the oldest element will be overwritten. */
static int cdeque_push_back(struct cdeque* d, void* item) {
        if(d == NULL)
                return CDE_PARAM;

        if(d->size == d->cap_mask + 1)
                return CDE_OUT_OF_BOUNDS;

        d->arr[d->end_pos] = (size_t) item;
        d->end_pos = (d->end_pos + 1) & d->cap_mask;
        d->size++;

        return CDE_OK;
}

/* Pops a front element of this circular deque object and returns its value.
 * This function doesn't perform any bounds checking. */
static void cdeque_pop_front_fast(struct cdeque* d, void** value) {
        *value = (void*) d->arr[d->beg_pos];
        d->beg_pos = (d->beg_pos + 1) & d->cap_mask;
        d->size--;
}

/* Pops a front element of this circular deque object and returns its value.
 * This function performs bounds checking. */
static int cdeque_pop_front(struct cdeque* d, void** value) {
        if(!d || !value)
                return CDE_PARAM;

        if(d->size == 0)
                return CDE_OUT_OF_BOUNDS;

        cdeque_pop_front_fast(d, value);
        return CDE_OK;
}

/* Convenience function to cast filter_info** to void **. */
static void** cdeque_filter_p(struct filter_info** f) {
        return (void**) (size_t) f;
}

/* Convenience function to cast filter_info* to void *. */
static void* cdeque_filter(struct filter_info* f) {
        return (void**) (size_t) f;
}

/* Destroys this circular deque object. Deallocates the memory of the
 * collection buffer, but doesn't deallocate the memory of any pointer passed
 * to this deque as a value. */
static void cdeque_free(struct cdeque* d) {
        if(!d)
                return;

        if(!d->arr)
                return;

        free(d->arr);

        d->arr = NULL;
        d->beg_pos = -1;
        d->end_pos = -1;
        d->cap_mask = 0;
}

static inline
uint8_t bf_bit_size(const struct compressed_block_header* hdr) {
        return hdr->block_flags_u8 & 7;
}

static inline
uint8_t bf_byte_count(const struct compressed_block_header* hdr) {
        return (hdr->block_flags_u8 >> 3) & 7;
}

static inline
uint8_t bf_is_table_present(const struct compressed_block_header* hdr) {
        return (hdr->block_flags_u8 >> 7) & 1;
}

static inline struct rar5* get_context(struct archive_read* a) {
        return (struct rar5*) a->format->data;
}

/* Convenience functions used by filter implementations. */
static void circular_memcpy(uint8_t* dst, uint8_t* window, const uint64_t mask,
    int64_t start, int64_t end)
{
        if((start & mask) > (end & mask)) {
                ssize_t len1 = mask + 1 - (start & mask);
                ssize_t len2 = end & mask;

                memcpy(dst, &window[start & mask], len1);
                memcpy(dst + len1, window, len2);
        } else {
                memcpy(dst, &window[start & mask], (size_t) (end - start));
        }
}

static uint32_t read_filter_data(struct rar5* rar, uint32_t offset) {
        uint8_t linear_buf[4];
        circular_memcpy(linear_buf, rar->cstate.window_buf,
            rar->cstate.window_mask, offset, offset + 4);
        return archive_le32dec(linear_buf);
}

static void write_filter_data(struct rar5* rar, uint32_t offset,
    uint32_t value)
{
        archive_le32enc(&rar->cstate.filtered_buf[offset], value);
}

/* Allocates a new filter descriptor and adds it to the filter array. */
static struct filter_info* add_new_filter(struct rar5* rar) {
        struct filter_info* f =
                (struct filter_info*) calloc(1, sizeof(struct filter_info));

        if(!f) {
                return NULL;
        }

        cdeque_push_back(&rar->cstate.filters, cdeque_filter(f));
        return f;
}

static int run_delta_filter(struct rar5* rar, struct filter_info* flt) {
        int i;
        ssize_t dest_pos, src_pos = 0;

        for(i = 0; i < flt->channels; i++) {
                uint8_t prev_byte = 0;
                for(dest_pos = i;
                                dest_pos < flt->block_length;
                                dest_pos += flt->channels)
                {
                        uint8_t byte;

                        byte = rar->cstate.window_buf[
                            (rar->cstate.solid_offset + flt->block_start +
                            src_pos) & rar->cstate.window_mask];

                        prev_byte -= byte;
                        rar->cstate.filtered_buf[dest_pos] = prev_byte;
                        src_pos++;
                }
        }

        return ARCHIVE_OK;
}

static int run_e8e9_filter(struct rar5* rar, struct filter_info* flt,
                int extended)
{
        const uint32_t file_size = 0x1000000;
        ssize_t i;

        circular_memcpy(rar->cstate.filtered_buf,
            rar->cstate.window_buf, rar->cstate.window_mask,
            rar->cstate.solid_offset + flt->block_start,
            rar->cstate.solid_offset + flt->block_start + flt->block_length);

        for(i = 0; i < flt->block_length - 4;) {
                uint8_t b = rar->cstate.window_buf[
                    (rar->cstate.solid_offset + flt->block_start +
                    i++) & rar->cstate.window_mask];

                /*
                 * 0xE8 = x86's call <relative_addr_uint32> (function call)
                 * 0xE9 = x86's jmp <relative_addr_uint32> (unconditional jump)
                 */
                if(b == 0xE8 || (extended && b == 0xE9)) {

                        uint32_t addr;
                        uint32_t offset = (i + flt->block_start) % file_size;

                        addr = read_filter_data(rar,
                            (uint32_t)(rar->cstate.solid_offset +
                            flt->block_start + i) & rar->cstate.window_mask);

                        if(addr & 0x80000000) {
                                if(((addr + offset) & 0x80000000) == 0) {
                                        write_filter_data(rar, (uint32_t)i,
                                            addr + file_size);
                                }
                        } else {
                                if((addr - file_size) & 0x80000000) {
                                        uint32_t naddr = addr - offset;
                                        write_filter_data(rar, (uint32_t)i,
                                            naddr);
                                }
                        }

                        i += 4;
                }
        }

        return ARCHIVE_OK;
}

static int run_arm_filter(struct rar5* rar, struct filter_info* flt) {
        ssize_t i = 0;
        uint32_t offset;

        circular_memcpy(rar->cstate.filtered_buf,
            rar->cstate.window_buf, rar->cstate.window_mask,
            rar->cstate.solid_offset + flt->block_start,
            rar->cstate.solid_offset + flt->block_start + flt->block_length);

        for(i = 0; i < flt->block_length - 3; i += 4) {
                uint8_t* b = &rar->cstate.window_buf[
                    (rar->cstate.solid_offset +
                    flt->block_start + i) & rar->cstate.window_mask];

                if(b[3] == 0xEB) {
                        /* 0xEB = ARM's BL (branch + link) instruction. */
                        offset = read_filter_data(rar,
                            (rar->cstate.solid_offset + flt->block_start + i) &
                             rar->cstate.window_mask) & 0x00ffffff;

                        offset -= (uint32_t) ((i + flt->block_start) / 4);
                        offset = (offset & 0x00ffffff) | 0xeb000000;
                        write_filter_data(rar, (uint32_t)i, offset);
                }
        }

        return ARCHIVE_OK;
}

static int run_filter(struct archive_read* a, struct filter_info* flt) {
        int ret;
        struct rar5* rar = get_context(a);

        free(rar->cstate.filtered_buf);

        rar->cstate.filtered_buf = malloc(flt->block_length);
        if(!rar->cstate.filtered_buf) {
                archive_set_error(&a->archive, ENOMEM,
                    "Can't allocate memory for filter data.");
                return ARCHIVE_FATAL;
        }

        switch(flt->type) {
                case FILTER_DELTA:
                        ret = run_delta_filter(rar, flt);
                        break;

                case FILTER_E8:
                        /* fallthrough */
                case FILTER_E8E9:
                        ret = run_e8e9_filter(rar, flt,
                            flt->type == FILTER_E8E9);
                        break;

                case FILTER_ARM:
                        ret = run_arm_filter(rar, flt);
                        break;

                default:
                        archive_set_error(&a->archive,
                            ARCHIVE_ERRNO_FILE_FORMAT,
                            "Unsupported filter type: 0x%x", flt->type);
                        return ARCHIVE_FATAL;
        }

        if(ret != ARCHIVE_OK) {
                /* Filter has failed. */
                return ret;
        }

        if(ARCHIVE_OK != push_data_ready(a, rar, rar->cstate.filtered_buf,
            flt->block_length, rar->cstate.last_write_ptr))
        {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_PROGRAMMER,
                    "Stack overflow when submitting unpacked data");

                return ARCHIVE_FATAL;
        }

        rar->cstate.last_write_ptr += flt->block_length;
        return ARCHIVE_OK;
}

/* The `push_data` function submits the selected data range to the user.
 * Next call of `use_data` will use the pointer, size and offset arguments
 * that are specified here. These arguments are pushed to the FIFO stack here,
 * and popped from the stack by the `use_data` function. */
static void push_data(struct archive_read* a, struct rar5* rar,
    const uint8_t* buf, int64_t idx_begin, int64_t idx_end)
{
        const uint64_t wmask = rar->cstate.window_mask;
        const ssize_t solid_write_ptr = (rar->cstate.solid_offset +
            rar->cstate.last_write_ptr) & wmask;

        idx_begin += rar->cstate.solid_offset;
        idx_end += rar->cstate.solid_offset;

        /* Check if our unpacked data is wrapped inside the window circular
         * buffer.  If it's not wrapped, it can be copied out by using
         * a single memcpy, but when it's wrapped, we need to copy the first
         * part with one memcpy, and the second part with another memcpy. */

        if((idx_begin & wmask) > (idx_end & wmask)) {
                /* The data is wrapped (begin offset sis bigger than end
                 * offset). */
                const ssize_t frag1_size = rar->cstate.window_size -
                    (idx_begin & wmask);
                const ssize_t frag2_size = idx_end & wmask;

                /* Copy the first part of the buffer first. */
                push_data_ready(a, rar, buf + solid_write_ptr, frag1_size,
                    rar->cstate.last_write_ptr);

                /* Copy the second part of the buffer. */
                push_data_ready(a, rar, buf, frag2_size,
                    rar->cstate.last_write_ptr + frag1_size);

                rar->cstate.last_write_ptr += frag1_size + frag2_size;
        } else {
                /* Data is not wrapped, so we can just use one call to copy the
                 * data. */
                push_data_ready(a, rar,
                    buf + solid_write_ptr, (idx_end - idx_begin) & wmask,
                    rar->cstate.last_write_ptr);

                rar->cstate.last_write_ptr += idx_end - idx_begin;
        }
}

/* Convenience function that submits the data to the user. It uses the
 * unpack window buffer as a source location. */
static void push_window_data(struct archive_read* a, struct rar5* rar,
    int64_t idx_begin, int64_t idx_end)
{
        push_data(a, rar, rar->cstate.window_buf, idx_begin, idx_end);
}

static int apply_filters(struct archive_read* a) {
        struct filter_info* flt;
        struct rar5* rar = get_context(a);
        int ret;

        rar->cstate.all_filters_applied = 0;

        /* Get the first filter that can be applied to our data. The data
         * needs to be fully unpacked before the filter can be run. */
        if(CDE_OK == cdeque_front(&rar->cstate.filters,
            cdeque_filter_p(&flt))) {
                /* Check if our unpacked data fully covers this filter's
                 * range. */
                if(rar->cstate.write_ptr > flt->block_start &&
                    rar->cstate.write_ptr >= flt->block_start +
                    flt->block_length) {
                        /* Check if we have some data pending to be written
                         * right before the filter's start offset. */
                        if(rar->cstate.last_write_ptr == flt->block_start) {
                                /* Run the filter specified by descriptor
                                 * `flt`. */
                                ret = run_filter(a, flt);
                                if(ret != ARCHIVE_OK) {
                                        /* Filter failure, return error. */
                                        return ret;
                                }

                                /* Filter descriptor won't be needed anymore
                                 * after it's used, * so remove it from the
                                 * filter list and free its memory. */
                                (void) cdeque_pop_front(&rar->cstate.filters,
                                    cdeque_filter_p(&flt));

                                free(flt);
                        } else {
                                /* We can't run filters yet, dump the memory
                                 * right before the filter. */
                                push_window_data(a, rar,
                                    rar->cstate.last_write_ptr,
                                    flt->block_start);
                        }

                        /* Return 'filter applied or not needed' state to the
                         * caller. */
                        return ARCHIVE_RETRY;
                }
        }

        rar->cstate.all_filters_applied = 1;
        return ARCHIVE_OK;
}

static void dist_cache_push(struct rar5* rar, int value) {
        int* q = rar->cstate.dist_cache;

        q[3] = q[2];
        q[2] = q[1];
        q[1] = q[0];
        q[0] = value;
}

static int dist_cache_touch(struct rar5* rar, int idx) {
        int* q = rar->cstate.dist_cache;
        int i, dist = q[idx];

        for(i = idx; i > 0; i--)
                q[i] = q[i - 1];

        q[0] = dist;
        return dist;
}

static void free_filters(struct rar5* rar) {
        struct cdeque* d = &rar->cstate.filters;

        /* Free any remaining filters. All filters should be naturally
         * consumed by the unpacking function, so remaining filters after
         * unpacking normally mean that unpacking wasn't successful.
         * But still of course we shouldn't leak memory in such case. */

        /* cdeque_size() is a fast operation, so we can use it as a loop
         * expression. */
        while(cdeque_size(d) > 0) {
                struct filter_info* f = NULL;

                /* Pop_front will also decrease the collection's size. */
                if (CDE_OK == cdeque_pop_front(d, cdeque_filter_p(&f)))
                        free(f);
        }

        cdeque_clear(d);

        /* Also clear out the variables needed for sanity checking. */
        rar->cstate.last_block_start = 0;
        rar->cstate.last_block_length = 0;
}

static void reset_file_context(struct rar5* rar) {
        memset(&rar->file, 0, sizeof(rar->file));
        blake2sp_init(&rar->file.b2state, 32);

        if(rar->main.solid) {
                rar->cstate.solid_offset += rar->cstate.write_ptr;
        } else {
                rar->cstate.solid_offset = 0;
        }

        rar->cstate.write_ptr = 0;
        rar->cstate.last_write_ptr = 0;
        rar->cstate.last_unstore_ptr = 0;

        rar->file.redir_type = REDIR_TYPE_NONE;
        rar->file.redir_flags = 0;

        free_filters(rar);
}

static inline int get_archive_read(struct archive* a,
    struct archive_read** ar)
{
        *ar = (struct archive_read*) a;
        archive_check_magic(a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_NEW,
            "archive_read_support_format_rar5");

        return ARCHIVE_OK;
}

static int read_ahead(struct archive_read* a, size_t how_many,
    const uint8_t** ptr)
{
        if(!ptr)
                return 0;

        ssize_t avail = -1;
        *ptr = __archive_read_ahead(a, how_many, &avail);
        if(*ptr == NULL) {
                return 0;
        }

        return 1;
}

static int consume(struct archive_read* a, int64_t how_many) {
        int ret;

        ret = how_many == __archive_read_consume(a, how_many)
                ? ARCHIVE_OK
                : ARCHIVE_FATAL;

        return ret;
}

/**
 * Read a RAR5 variable sized numeric value. This value will be stored in
 * `pvalue`. The `pvalue_len` argument points to a variable that will receive
 * the byte count that was consumed in order to decode the `pvalue` value, plus
 * one.
 *
 * pvalue_len is optional and can be NULL.
 *
 * NOTE: if `pvalue_len` is NOT NULL, the caller needs to manually consume
 * the number of bytes that `pvalue_len` value contains. If the `pvalue_len`
 * is NULL, this consuming operation is done automatically.
 *
 * Returns 1 if *pvalue was successfully read.
 * Returns 0 if there was an error. In this case, *pvalue contains an
 *           invalid value.
 */

static int read_var(struct archive_read* a, uint64_t* pvalue,
    uint64_t* pvalue_len)
{
        uint64_t result = 0;
        size_t shift, i;
        const uint8_t* p;
        uint8_t b;

        /* We will read maximum of 8 bytes. We don't have to handle the
         * situation to read the RAR5 variable-sized value stored at the end of
         * the file, because such situation will never happen. */
        if(!read_ahead(a, 8, &p))
                return 0;

        for(shift = 0, i = 0; i < 8; i++, shift += 7) {
                b = p[i];

                /* Strip the MSB from the input byte and add the resulting
                 * number to the `result`. */
                result += (b & (uint64_t)0x7F) << shift;

                /* MSB set to 1 means we need to continue decoding process.
                 * MSB set to 0 means we're done.
                 *
                 * This conditional checks for the second case. */
                if((b & 0x80) == 0) {
                        if(pvalue) {
                                *pvalue = result;
                        }

                        /* If the caller has passed the `pvalue_len` pointer,
                         * store the number of consumed bytes in it and do NOT
                         * consume those bytes, since the caller has all the
                         * information it needs to perform */
                        if(pvalue_len) {
                                *pvalue_len = 1 + i;
                        } else {
                                /* If the caller did not provide the
                                 * `pvalue_len` pointer, it will not have the
                                 * possibility to advance the file pointer,
                                 * because it will not know how many bytes it
                                 * needs to consume. This is why we handle
                                 * such situation here automatically. */
                                if(ARCHIVE_OK != consume(a, 1 + i)) {
                                        return 0;
                                }
                        }

                        /* End of decoding process, return success. */
                        return 1;
                }
        }

        /* The decoded value takes the maximum number of 8 bytes.
         * It's a maximum number of bytes, so end decoding process here
         * even if the first bit of last byte is 1. */
        if(pvalue) {
                *pvalue = result;
        }

        if(pvalue_len) {
                *pvalue_len = 9;
        } else {
                if(ARCHIVE_OK != consume(a, 9)) {
                        return 0;
                }
        }

        return 1;
}

static int read_var_sized(struct archive_read* a, size_t* pvalue,
    size_t* pvalue_len)
{
        uint64_t v;
        uint64_t v_size = 0;

        const int ret = pvalue_len ? read_var(a, &v, &v_size)
                                   : read_var(a, &v, NULL);

        if(ret == 1 && pvalue) {
                *pvalue = (size_t) v;
        }

        if(pvalue_len) {
                /* Possible data truncation should be safe. */
                *pvalue_len = (size_t) v_size;
        }

        return ret;
}

static int read_bits_32(struct rar5* rar, const uint8_t* p, uint32_t* value) {
        uint32_t bits = ((uint32_t) p[rar->bits.in_addr]) << 24;
        bits |= p[rar->bits.in_addr + 1] << 16;
        bits |= p[rar->bits.in_addr + 2] << 8;
        bits |= p[rar->bits.in_addr + 3];
        bits <<= rar->bits.bit_addr;
        bits |= p[rar->bits.in_addr + 4] >> (8 - rar->bits.bit_addr);
        *value = bits;
        return ARCHIVE_OK;
}

static int read_bits_16(struct rar5* rar, const uint8_t* p, uint16_t* value) {
        int bits = (int) ((uint32_t) p[rar->bits.in_addr]) << 16;
        bits |= (int) p[rar->bits.in_addr + 1] << 8;
        bits |= (int) p[rar->bits.in_addr + 2];
        bits >>= (8 - rar->bits.bit_addr);
        *value = bits & 0xffff;
        return ARCHIVE_OK;
}

static void skip_bits(struct rar5* rar, int bits) {
        const int new_bits = rar->bits.bit_addr + bits;
        rar->bits.in_addr += new_bits >> 3;
        rar->bits.bit_addr = new_bits & 7;
}

/* n = up to 16 */
static int read_consume_bits(struct rar5* rar, const uint8_t* p, int n,
    int* value)
{
        uint16_t v;
        int ret, num;

        if(n == 0 || n > 16) {
                /* This is a programmer error and should never happen
                 * in runtime. */
                return ARCHIVE_FATAL;
        }

        ret = read_bits_16(rar, p, &v);
        if(ret != ARCHIVE_OK)
                return ret;

        num = (int) v;
        num >>= 16 - n;

        skip_bits(rar, n);

        if(value)
                *value = num;

        return ARCHIVE_OK;
}

static int read_u32(struct archive_read* a, uint32_t* pvalue) {
        const uint8_t* p;
        if(!read_ahead(a, 4, &p))
                return 0;

        *pvalue = archive_le32dec(p);
        return ARCHIVE_OK == consume(a, 4) ? 1 : 0;
}

static int read_u64(struct archive_read* a, uint64_t* pvalue) {
        const uint8_t* p;
        if(!read_ahead(a, 8, &p))
                return 0;

        *pvalue = archive_le64dec(p);
        return ARCHIVE_OK == consume(a, 8) ? 1 : 0;
}

static int bid_standard(struct archive_read* a) {
        const uint8_t* p;

        if(!read_ahead(a, rar5_signature_size, &p))
                return -1;

        if(!memcmp(rar5_signature, p, rar5_signature_size))
                return 30;

        return -1;
}

static int rar5_bid(struct archive_read* a, int best_bid) {
        int my_bid;

        if(best_bid > 30)
                return -1;

        my_bid = bid_standard(a);
        if(my_bid > -1) {
                return my_bid;
        }

        return -1;
}

static int rar5_options(struct archive_read *a, const char *key,
    const char *val) {
        (void) a;
        (void) key;
        (void) val;

        /* No options supported in this version. Return the ARCHIVE_WARN code
         * to signal the options supervisor that the unpacker didn't handle
         * setting this option. */

        return ARCHIVE_WARN;
}

static void init_header(struct archive_read* a) {
        a->archive.archive_format = ARCHIVE_FORMAT_RAR_V5;
        a->archive.archive_format_name = "RAR5";
}

enum HEADER_FLAGS {
        HFL_EXTRA_DATA = 0x0001,
        HFL_DATA = 0x0002,
        HFL_SKIP_IF_UNKNOWN = 0x0004,
        HFL_SPLIT_BEFORE = 0x0008,
        HFL_SPLIT_AFTER = 0x0010,
        HFL_CHILD = 0x0020,
        HFL_INHERITED = 0x0040
};

static int process_main_locator_extra_block(struct archive_read* a,
    struct rar5* rar)
{
        uint64_t locator_flags;

        if(!read_var(a, &locator_flags, NULL)) {
                return ARCHIVE_EOF;
        }

        enum LOCATOR_FLAGS {
                QLIST = 0x01, RECOVERY = 0x02,
        };

        if(locator_flags & QLIST) {
                if(!read_var(a, &rar->qlist_offset, NULL)) {
                        return ARCHIVE_EOF;
                }

                /* qlist is not used */
        }

        if(locator_flags & RECOVERY) {
                if(!read_var(a, &rar->rr_offset, NULL)) {
                        return ARCHIVE_EOF;
                }

                /* rr is not used */
        }

        return ARCHIVE_OK;
}

static int parse_file_extra_hash(struct archive_read* a, struct rar5* rar,
    ssize_t* extra_data_size)
{
        size_t hash_type;
        size_t value_len;

        if(!read_var_sized(a, &hash_type, &value_len))
                return ARCHIVE_EOF;

        *extra_data_size -= value_len;
        if(ARCHIVE_OK != consume(a, value_len)) {
                return ARCHIVE_EOF;
        }

        enum HASH_TYPE {
                BLAKE2sp = 0x00
        };

        /* The file uses BLAKE2sp checksum algorithm instead of plain old
         * CRC32. */
        if(hash_type == BLAKE2sp) {
                const uint8_t* p;
                const int hash_size = sizeof(rar->file.blake2sp);

                if(!read_ahead(a, hash_size, &p))
                        return ARCHIVE_EOF;

                rar->file.has_blake2 = 1;
                memcpy(&rar->file.blake2sp, p, hash_size);

                if(ARCHIVE_OK != consume(a, hash_size)) {
                        return ARCHIVE_EOF;
                }

                *extra_data_size -= hash_size;
        } else {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Unsupported hash type (0x%x)", (int) hash_type);
                return ARCHIVE_FATAL;
        }

        return ARCHIVE_OK;
}

static uint64_t time_win_to_unix(uint64_t win_time) {
        const size_t ns_in_sec = 10000000;
        const uint64_t sec_to_unix = 11644473600LL;
        return win_time / ns_in_sec - sec_to_unix;
}

static int parse_htime_item(struct archive_read* a, char unix_time,
    uint64_t* where, ssize_t* extra_data_size)
{
        if(unix_time) {
                uint32_t time_val;
                if(!read_u32(a, &time_val))
                        return ARCHIVE_EOF;

                *extra_data_size -= 4;
                *where = (uint64_t) time_val;
        } else {
                uint64_t windows_time;
                if(!read_u64(a, &windows_time))
                        return ARCHIVE_EOF;

                *where = time_win_to_unix(windows_time);
                *extra_data_size -= 8;
        }

        return ARCHIVE_OK;
}

static int parse_file_extra_version(struct archive_read* a,
    struct archive_entry* e, ssize_t* extra_data_size)
{
        size_t flags = 0;
        size_t version = 0;
        size_t value_len = 0;
        struct archive_string version_string;
        struct archive_string name_utf8_string;

        /* Flags are ignored. */
        if(!read_var_sized(a, &flags, &value_len))
                return ARCHIVE_EOF;

        *extra_data_size -= value_len;
        if(ARCHIVE_OK != consume(a, value_len))
                return ARCHIVE_EOF;

        if(!read_var_sized(a, &version, &value_len))
                return ARCHIVE_EOF;

        *extra_data_size -= value_len;
        if(ARCHIVE_OK != consume(a, value_len))
                return ARCHIVE_EOF;

        /* extra_data_size should be zero here. */

        const char* cur_filename = archive_entry_pathname_utf8(e);
        if(cur_filename == NULL) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_PROGRAMMER,
                    "Version entry without file name");
                return ARCHIVE_FATAL;
        }

        archive_string_init(&version_string);
        archive_string_init(&name_utf8_string);

        /* Prepare a ;123 suffix for the filename, where '123' is the version
         * value of this file. */
        archive_string_sprintf(&version_string, ";%zu", version);

        /* Build the new filename. */
        archive_strcat(&name_utf8_string, cur_filename);
        archive_strcat(&name_utf8_string, version_string.s);

        /* Apply the new filename into this file's context. */
        archive_entry_update_pathname_utf8(e, name_utf8_string.s);

        /* Free buffers. */
        archive_string_free(&version_string);
        archive_string_free(&name_utf8_string);
        return ARCHIVE_OK;
}

static int parse_file_extra_htime(struct archive_read* a,
    struct archive_entry* e, struct rar5* rar, ssize_t* extra_data_size)
{
        char unix_time = 0;
        size_t flags;
        size_t value_len;

        enum HTIME_FLAGS {
                IS_UNIX       = 0x01,
                HAS_MTIME     = 0x02,
                HAS_CTIME     = 0x04,
                HAS_ATIME     = 0x08,
                HAS_UNIX_NS   = 0x10,
        };

        if(!read_var_sized(a, &flags, &value_len))
                return ARCHIVE_EOF;

        *extra_data_size -= value_len;
        if(ARCHIVE_OK != consume(a, value_len)) {
                return ARCHIVE_EOF;
        }

        unix_time = flags & IS_UNIX;

        if(flags & HAS_MTIME) {
                parse_htime_item(a, unix_time, &rar->file.e_mtime,
                    extra_data_size);
                archive_entry_set_mtime(e, rar->file.e_mtime, 0);
        }

        if(flags & HAS_CTIME) {
                parse_htime_item(a, unix_time, &rar->file.e_ctime,
                    extra_data_size);
                archive_entry_set_ctime(e, rar->file.e_ctime, 0);
        }

        if(flags & HAS_ATIME) {
                parse_htime_item(a, unix_time, &rar->file.e_atime,
                    extra_data_size);
                archive_entry_set_atime(e, rar->file.e_atime, 0);
        }

        if(flags & HAS_UNIX_NS) {
                if(!read_u32(a, &rar->file.e_unix_ns))
                        return ARCHIVE_EOF;

                *extra_data_size -= 4;
        }

        return ARCHIVE_OK;
}

static int parse_file_extra_redir(struct archive_read* a,
    struct archive_entry* e, struct rar5* rar, ssize_t* extra_data_size)
{
        uint64_t value_size = 0;
        size_t target_size = 0;
        char target_utf8_buf[MAX_NAME_IN_BYTES];
        const uint8_t* p;

        if(!read_var(a, &rar->file.redir_type, &value_size))
                return ARCHIVE_EOF;
        if(ARCHIVE_OK != consume(a, (int64_t)value_size))
                return ARCHIVE_EOF;
        *extra_data_size -= value_size;

        if(!read_var(a, &rar->file.redir_flags, &value_size))
                return ARCHIVE_EOF;
        if(ARCHIVE_OK != consume(a, (int64_t)value_size))
                return ARCHIVE_EOF;
        *extra_data_size -= value_size;

        if(!read_var_sized(a, &target_size, NULL))
                return ARCHIVE_EOF;
        *extra_data_size -= target_size + 1;

        if(!read_ahead(a, target_size, &p))
                return ARCHIVE_EOF;

        if(target_size > (MAX_NAME_IN_CHARS - 1)) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Link target is too long");
                return ARCHIVE_FATAL;
        }

        if(target_size == 0) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "No link target specified");
                return ARCHIVE_FATAL;
        }

        memcpy(target_utf8_buf, p, target_size);
        target_utf8_buf[target_size] = 0;

        if(ARCHIVE_OK != consume(a, (int64_t)target_size))
                return ARCHIVE_EOF;

        switch(rar->file.redir_type) {
                case REDIR_TYPE_UNIXSYMLINK:
                case REDIR_TYPE_WINSYMLINK:
                        archive_entry_set_filetype(e, AE_IFLNK);
                        archive_entry_update_symlink_utf8(e, target_utf8_buf);
                        if (rar->file.redir_flags & REDIR_SYMLINK_IS_DIR) {
                                archive_entry_set_symlink_type(e,
                                        AE_SYMLINK_TYPE_DIRECTORY);
                        } else {
                                archive_entry_set_symlink_type(e,
                                AE_SYMLINK_TYPE_FILE);
                        }
                        break;

                case REDIR_TYPE_HARDLINK:
                        archive_entry_set_filetype(e, AE_IFREG);
                        archive_entry_update_hardlink_utf8(e, target_utf8_buf);
                        break;

                default:
                        /* Unknown redir type, skip it. */
                        break;
        }
        return ARCHIVE_OK;
}

static int parse_file_extra_owner(struct archive_read* a,
    struct archive_entry* e, ssize_t* extra_data_size)
{
        uint64_t flags = 0;
        uint64_t value_size = 0;
        uint64_t id = 0;
        size_t name_len = 0;
        size_t name_size = 0;
        char namebuf[OWNER_MAXNAMELEN];
        const uint8_t* p;

        if(!read_var(a, &flags, &value_size))
                return ARCHIVE_EOF;
        if(ARCHIVE_OK != consume(a, (int64_t)value_size))
                return ARCHIVE_EOF;
        *extra_data_size -= value_size;

        if ((flags & OWNER_USER_NAME) != 0) {
                if(!read_var_sized(a, &name_size, NULL))
                        return ARCHIVE_EOF;
                *extra_data_size -= name_size + 1;

                if(!read_ahead(a, name_size, &p))
                        return ARCHIVE_EOF;

                if (name_size >= OWNER_MAXNAMELEN) {
                        name_len = OWNER_MAXNAMELEN - 1;
                } else {
                        name_len = name_size;
                }

                memcpy(namebuf, p, name_len);
                namebuf[name_len] = 0;
                if(ARCHIVE_OK != consume(a, (int64_t)name_size))
                        return ARCHIVE_EOF;

                archive_entry_set_uname(e, namebuf);
        }
        if ((flags & OWNER_GROUP_NAME) != 0) {
                if(!read_var_sized(a, &name_size, NULL))
                        return ARCHIVE_EOF;
                *extra_data_size -= name_size + 1;

                if(!read_ahead(a, name_size, &p))
                        return ARCHIVE_EOF;

                if (name_size >= OWNER_MAXNAMELEN) {
                        name_len = OWNER_MAXNAMELEN - 1;
                } else {
                        name_len = name_size;
                }

                memcpy(namebuf, p, name_len);
                namebuf[name_len] = 0;
                if(ARCHIVE_OK != consume(a, (int64_t)name_size))
                        return ARCHIVE_EOF;

                archive_entry_set_gname(e, namebuf);
        }
        if ((flags & OWNER_USER_UID) != 0) {
                if(!read_var(a, &id, &value_size))
                        return ARCHIVE_EOF;
                if(ARCHIVE_OK != consume(a, (int64_t)value_size))
                        return ARCHIVE_EOF;
                *extra_data_size -= value_size;

                archive_entry_set_uid(e, (la_int64_t)id);
        }
        if ((flags & OWNER_GROUP_GID) != 0) {
                if(!read_var(a, &id, &value_size))
                        return ARCHIVE_EOF;
                if(ARCHIVE_OK != consume(a, (int64_t)value_size))
                        return ARCHIVE_EOF;
                *extra_data_size -= value_size;

                archive_entry_set_gid(e, (la_int64_t)id);
        }
        return ARCHIVE_OK;
}

static int process_head_file_extra(struct archive_read* a,
    struct archive_entry* e, struct rar5* rar, ssize_t extra_data_size)
{
        size_t extra_field_size;
        size_t extra_field_id = 0;
        int ret = ARCHIVE_FATAL;
        size_t var_size;

        while(extra_data_size > 0) {
                if(!read_var_sized(a, &extra_field_size, &var_size))
                        return ARCHIVE_EOF;

                extra_data_size -= var_size;
                if(ARCHIVE_OK != consume(a, var_size)) {
                        return ARCHIVE_EOF;
                }

                if(!read_var_sized(a, &extra_field_id, &var_size))
                        return ARCHIVE_EOF;

                extra_data_size -= var_size;
                if(ARCHIVE_OK != consume(a, var_size)) {
                        return ARCHIVE_EOF;
                }

                switch(extra_field_id) {
                        case EX_HASH:
                                ret = parse_file_extra_hash(a, rar,
                                    &extra_data_size);
                                break;
                        case EX_HTIME:
                                ret = parse_file_extra_htime(a, e, rar,
                                    &extra_data_size);
                                break;
                        case EX_REDIR:
                                ret = parse_file_extra_redir(a, e, rar,
                                    &extra_data_size);
                                break;
                        case EX_UOWNER:
                                ret = parse_file_extra_owner(a, e,
                                    &extra_data_size);
                                break;
                        case EX_VERSION:
                                ret = parse_file_extra_version(a, e,
                                    &extra_data_size);
                                break;
                        case EX_CRYPT:
                                /* fallthrough */
                        case EX_SUBDATA:
                                /* fallthrough */
                        default:
                                /* Skip unsupported entry. */
                                return consume(a, extra_data_size);
                }
        }

        if(ret != ARCHIVE_OK) {
                /* Attribute not implemented. */
                return ret;
        }

        return ARCHIVE_OK;
}

static int process_head_file(struct archive_read* a, struct rar5* rar,
    struct archive_entry* entry, size_t block_flags)
{
        ssize_t extra_data_size = 0;
        size_t data_size = 0;
        size_t file_flags = 0;
        size_t file_attr = 0;
        size_t compression_info = 0;
        size_t host_os = 0;
        size_t name_size = 0;
        uint64_t unpacked_size, window_size;
        uint32_t mtime = 0, crc = 0;
        int c_method = 0, c_version = 0;
        char name_utf8_buf[MAX_NAME_IN_BYTES];
        const uint8_t* p;

        archive_entry_clear(entry);

        /* Do not reset file context if we're switching archives. */
        if(!rar->cstate.switch_multivolume) {
                reset_file_context(rar);
        }

        if(block_flags & HFL_EXTRA_DATA) {
                size_t edata_size = 0;
                if(!read_var_sized(a, &edata_size, NULL))
                        return ARCHIVE_EOF;

                /* Intentional type cast from unsigned to signed. */
                extra_data_size = (ssize_t) edata_size;
        }

        if(block_flags & HFL_DATA) {
                if(!read_var_sized(a, &data_size, NULL))
                        return ARCHIVE_EOF;

                rar->file.bytes_remaining = data_size;
        } else {
                rar->file.bytes_remaining = 0;

                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                                "no data found in file/service block");
                return ARCHIVE_FATAL;
        }

        enum FILE_FLAGS {
                DIRECTORY = 0x0001, UTIME = 0x0002, CRC32 = 0x0004,
                UNKNOWN_UNPACKED_SIZE = 0x0008,
        };

        enum FILE_ATTRS {
                ATTR_READONLY = 0x1, ATTR_HIDDEN = 0x2, ATTR_SYSTEM = 0x4,
                ATTR_DIRECTORY = 0x10,
        };

        enum COMP_INFO_FLAGS {
                SOLID = 0x0040,
        };

        if(!read_var_sized(a, &file_flags, NULL))
                return ARCHIVE_EOF;

        if(!read_var(a, &unpacked_size, NULL))
                return ARCHIVE_EOF;

        if(file_flags & UNKNOWN_UNPACKED_SIZE) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_PROGRAMMER,
                    "Files with unknown unpacked size are not supported");
                return ARCHIVE_FATAL;
        }

        rar->file.dir = (uint8_t) ((file_flags & DIRECTORY) > 0);

        if(!read_var_sized(a, &file_attr, NULL))
                return ARCHIVE_EOF;

        if(file_flags & UTIME) {
                if(!read_u32(a, &mtime))
                        return ARCHIVE_EOF;
        }

        if(file_flags & CRC32) {
                if(!read_u32(a, &crc))
                        return ARCHIVE_EOF;
        }

        if(!read_var_sized(a, &compression_info, NULL))
                return ARCHIVE_EOF;

        c_method = (int) (compression_info >> 7) & 0x7;
        c_version = (int) (compression_info & 0x3f);

        /* RAR5 seems to limit the dictionary size to 64MB. */
        window_size = (rar->file.dir > 0) ?
                0 :
                g_unpack_window_size << ((compression_info >> 10) & 15);
        rar->cstate.method = c_method;
        rar->cstate.version = c_version + 50;

        /* Check if window_size is a sane value. Also, if the file is not
         * declared as a directory, disallow window_size == 0. */
        if(window_size > (64 * 1024 * 1024) ||
            (rar->file.dir == 0 && window_size == 0))
        {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Declared dictionary size is not supported.");
                return ARCHIVE_FATAL;
        }

        /* Values up to 64M should fit into ssize_t on every
         * architecture. */
        rar->cstate.window_size = (ssize_t) window_size;

        rar->file.solid = (compression_info & SOLID) > 0;
        rar->file.service = 0;

        if(!read_var_sized(a, &host_os, NULL))
                return ARCHIVE_EOF;

        enum HOST_OS {
                HOST_WINDOWS = 0,
                HOST_UNIX = 1,
        };

        if(host_os == HOST_WINDOWS) {
                /* Host OS is Windows */

                __LA_MODE_T mode;

                if(file_attr & ATTR_DIRECTORY) {
                        if (file_attr & ATTR_READONLY) {
                                mode = 0555 | AE_IFDIR;
                        } else {
                                mode = 0755 | AE_IFDIR;
                        }
                } else {
                        if (file_attr & ATTR_READONLY) {
                                mode = 0444 | AE_IFREG;
                        } else {
                                mode = 0644 | AE_IFREG;
                        }
                }

                archive_entry_set_mode(entry, mode);

                if (file_attr & (ATTR_READONLY | ATTR_HIDDEN | ATTR_SYSTEM)) {
                        char *fflags_text, *ptr;
                        /* allocate for "rdonly,hidden,system," */
                        fflags_text = malloc(22 * sizeof(char));
                        if (fflags_text != NULL) {
                                ptr = fflags_text;
                                if (file_attr & ATTR_READONLY) {
                                        strcpy(ptr, "rdonly,");
                                        ptr = ptr + 7;
                                }
                                if (file_attr & ATTR_HIDDEN) {
                                        strcpy(ptr, "hidden,");
                                        ptr = ptr + 7;
                                }
                                if (file_attr & ATTR_SYSTEM) {
                                        strcpy(ptr, "system,");
                                        ptr = ptr + 7;
                                }
                                if (ptr > fflags_text) {
                                        /* Delete trailing comma */
                                        *(ptr - 1) = '\0';
                                        archive_entry_copy_fflags_text(entry,
                                            fflags_text);
                                }
                                free(fflags_text);
                        }
                }
        } else if(host_os == HOST_UNIX) {
                /* Host OS is Unix */
                archive_entry_set_mode(entry, (__LA_MODE_T) file_attr);
        } else {
                /* Unknown host OS */
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                                "Unsupported Host OS: 0x%x", (int) host_os);

                return ARCHIVE_FATAL;
        }

        if(!read_var_sized(a, &name_size, NULL))
                return ARCHIVE_EOF;

        if(!read_ahead(a, name_size, &p))
                return ARCHIVE_EOF;

        if(name_size > (MAX_NAME_IN_CHARS - 1)) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                                "Filename is too long");

                return ARCHIVE_FATAL;
        }

        if(name_size == 0) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                                "No filename specified");

                return ARCHIVE_FATAL;
        }

        memcpy(name_utf8_buf, p, name_size);
        name_utf8_buf[name_size] = 0;
        if(ARCHIVE_OK != consume(a, name_size)) {
                return ARCHIVE_EOF;
        }

        archive_entry_update_pathname_utf8(entry, name_utf8_buf);

        if(extra_data_size > 0) {
                int ret = process_head_file_extra(a, entry, rar,
                    extra_data_size);

                /* Sanity check. */
                if(extra_data_size < 0) {
                        archive_set_error(&a->archive, ARCHIVE_ERRNO_PROGRAMMER,
                            "File extra data size is not zero");
                        return ARCHIVE_FATAL;
                }

                if(ret != ARCHIVE_OK)
                        return ret;
        }

        if((file_flags & UNKNOWN_UNPACKED_SIZE) == 0) {
                rar->file.unpacked_size = (ssize_t) unpacked_size;
                if(rar->file.redir_type == REDIR_TYPE_NONE)
                        archive_entry_set_size(entry, unpacked_size);
        }

        if(file_flags & UTIME) {
                archive_entry_set_mtime(entry, (time_t) mtime, 0);
        }

        if(file_flags & CRC32) {
                rar->file.stored_crc32 = crc;
        }

        if(!rar->cstate.switch_multivolume) {
                /* Do not reinitialize unpacking state if we're switching
                 * archives. */
                rar->cstate.block_parsing_finished = 1;
                rar->cstate.all_filters_applied = 1;
                rar->cstate.initialized = 0;
        }

        if(rar->generic.split_before > 0) {
                /* If now we're standing on a header that has a 'split before'
                 * mark, it means we're standing on a 'continuation' file
                 * header. Signal the caller that if it wants to move to
                 * another file, it must call rar5_read_header() function
                 * again. */

                return ARCHIVE_RETRY;
        } else {
                return ARCHIVE_OK;
        }
}

static int process_head_service(struct archive_read* a, struct rar5* rar,
    struct archive_entry* entry, size_t block_flags)
{
        /* Process this SERVICE block the same way as FILE blocks. */
        int ret = process_head_file(a, rar, entry, block_flags);
        if(ret != ARCHIVE_OK)
                return ret;

        rar->file.service = 1;

        /* But skip the data part automatically. It's no use for the user
         * anyway.  It contains only service data, not even needed to
         * properly unpack the file. */
        ret = rar5_read_data_skip(a);
        if(ret != ARCHIVE_OK)
                return ret;

        /* After skipping, try parsing another block automatically. */
        return ARCHIVE_RETRY;
}

static int process_head_main(struct archive_read* a, struct rar5* rar,
    struct archive_entry* entry, size_t block_flags)
{
        (void) entry;

        int ret;
        size_t extra_data_size = 0;
        size_t extra_field_size = 0;
        size_t extra_field_id = 0;
        size_t archive_flags = 0;

        if(block_flags & HFL_EXTRA_DATA) {
                if(!read_var_sized(a, &extra_data_size, NULL))
                        return ARCHIVE_EOF;
        } else {
                extra_data_size = 0;
        }

        if(!read_var_sized(a, &archive_flags, NULL)) {
                return ARCHIVE_EOF;
        }

        enum MAIN_FLAGS {
                VOLUME = 0x0001,         /* multi-volume archive */
                VOLUME_NUMBER = 0x0002,  /* volume number, first vol doesn't
                                          * have it */
                SOLID = 0x0004,          /* solid archive */
                PROTECT = 0x0008,        /* contains Recovery info */
                LOCK = 0x0010,           /* readonly flag, not used */
        };

        rar->main.volume = (archive_flags & VOLUME) > 0;
        rar->main.solid = (archive_flags & SOLID) > 0;

        if(archive_flags & VOLUME_NUMBER) {
                size_t v = 0;
                if(!read_var_sized(a, &v, NULL)) {
                        return ARCHIVE_EOF;
                }

                if (v > UINT_MAX) {
                        archive_set_error(&a->archive,
                            ARCHIVE_ERRNO_FILE_FORMAT,
                            "Invalid volume number");
                        return ARCHIVE_FATAL;
                }

                rar->main.vol_no = (unsigned int) v;
        } else {
                rar->main.vol_no = 0;
        }

        if(rar->vol.expected_vol_no > 0 &&
                rar->main.vol_no != rar->vol.expected_vol_no)
        {
                /* Returning EOF instead of FATAL because of strange
                 * libarchive behavior. When opening multiple files via
                 * archive_read_open_filenames(), after reading up the whole
                 * last file, the __archive_read_ahead function wraps up to
                 * the first archive instead of returning EOF. */
                return ARCHIVE_EOF;
        }

        if(extra_data_size == 0) {
                /* Early return. */
                return ARCHIVE_OK;
        }

        if(!read_var_sized(a, &extra_field_size, NULL)) {
                return ARCHIVE_EOF;
        }

        if(!read_var_sized(a, &extra_field_id, NULL)) {
                return ARCHIVE_EOF;
        }

        if(extra_field_size == 0) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Invalid extra field size");
                return ARCHIVE_FATAL;
        }

        enum MAIN_EXTRA {
                // Just one attribute here.
                LOCATOR = 0x01,
        };

        switch(extra_field_id) {
                case LOCATOR:
                        ret = process_main_locator_extra_block(a, rar);
                        if(ret != ARCHIVE_OK) {
                                /* Error while parsing main locator extra
                                 * block. */
                                return ret;
                        }

                        break;
                default:
                        archive_set_error(&a->archive,
                            ARCHIVE_ERRNO_FILE_FORMAT,
                            "Unsupported extra type (0x%x)",
                            (int) extra_field_id);
                        return ARCHIVE_FATAL;
        }

        return ARCHIVE_OK;
}

static int skip_unprocessed_bytes(struct archive_read* a) {
        struct rar5* rar = get_context(a);
        int ret;

        if(rar->file.bytes_remaining) {
                /* Use different skipping method in block merging mode than in
                 * normal mode. If merge mode is active, rar5_read_data_skip
                 * can't be used, because it could allow recursive use of
                 * merge_block() * function, and this function doesn't support
                 * recursive use. */
                if(rar->merge_mode) {
                        /* Discard whole merged block. This is valid in solid
                         * mode as well, because the code will discard blocks
                         * only if those blocks are safe to discard (i.e.
                         * they're not FILE blocks).  */
                        ret = consume(a, rar->file.bytes_remaining);
                        if(ret != ARCHIVE_OK) {
                                return ret;
                        }
                        rar->file.bytes_remaining = 0;
                } else {
                        /* If we're not in merge mode, use safe skipping code.
                         * This will ensure we'll handle solid archives
                         * properly. */
                        ret = rar5_read_data_skip(a);
                        if(ret != ARCHIVE_OK) {
                                return ret;
                        }
                }
        }

        return ARCHIVE_OK;
}

static int scan_for_signature(struct archive_read* a);

/* Base block processing function. A 'base block' is a RARv5 header block
 * that tells the reader what kind of data is stored inside the block.
 *
 * From the birds-eye view a RAR file looks file this:
 *
 * <magic><base_block_1><base_block_2>...<base_block_n>
 *
 * There are a few types of base blocks. Those types are specified inside
 * the 'switch' statement in this function. For example purposes, I'll write
 * how a standard RARv5 file could look like here:
 *
 * <magic><MAIN><FILE><FILE><FILE><SERVICE><ENDARC>
 *
 * The structure above could describe an archive file with 3 files in it,
 * one service "QuickOpen" block (that is ignored by this parser), and an
 * end of file base block marker.
 *
 * If the file is stored in multiple archive files ("multiarchive"), it might
 * look like this:
 *
 * .part01.rar: <magic><MAIN><FILE><ENDARC>
 * .part02.rar: <magic><MAIN><FILE><ENDARC>
 * .part03.rar: <magic><MAIN><FILE><ENDARC>
 *
 * This example could describe 3 RAR files that contain ONE archived file.
 * Or it could describe 3 RAR files that contain 3 different files. Or 3
 * RAR files than contain 2 files. It all depends what metadata is stored in
 * the headers of <FILE> blocks.
 *
 * Each <FILE> block contains info about its size, the name of the file it's
 * storing inside, and whether this FILE block is a continuation block of
 * previous archive ('split before'), and is this FILE block should be
 * continued in another archive ('split after'). By parsing the 'split before'
 * and 'split after' flags, we're able to tell if multiple <FILE> base blocks
 * are describing one file, or multiple files (with the same filename, for
 * example).
 *
 * One thing to note is that if we're parsing the first <FILE> block, and
 * we see 'split after' flag, then we need to jump over to another <FILE>
 * block to be able to decompress rest of the data. To do this, we need
 * to skip the <ENDARC> block, then switch to another file, then skip the
 * <magic> block, <MAIN> block, and then we're standing on the proper
 * <FILE> block.
 */

static int process_base_block(struct archive_read* a,
    struct archive_entry* entry)
{
        struct rar5* rar = get_context(a);
        uint32_t hdr_crc, computed_crc;
        size_t raw_hdr_size = 0, hdr_size_len, hdr_size;
        size_t header_id = 0;
        size_t header_flags = 0;
        const uint8_t* p;
        int ret;

        /* Skip any unprocessed data for this file. */
        ret = skip_unprocessed_bytes(a);
        if(ret != ARCHIVE_OK)
                return ret;

        /* Read the expected CRC32 checksum. */
        if(!read_u32(a, &hdr_crc)) {
                return ARCHIVE_EOF;
        }

        /* Read header size. */
        if(!read_var_sized(a, &raw_hdr_size, &hdr_size_len)) {
                return ARCHIVE_EOF;
        }

        /* Sanity check, maximum header size for RAR5 is 2MB. */
        if(raw_hdr_size > (2 * 1024 * 1024)) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Base block header is too large");

                return ARCHIVE_FATAL;
        }

        hdr_size = raw_hdr_size + hdr_size_len;

        /* Read the whole header data into memory, maximum memory use here is
         * 2MB. */
        if(!read_ahead(a, hdr_size, &p)) {
                return ARCHIVE_EOF;
        }

        /* Verify the CRC32 of the header data. */
        computed_crc = (uint32_t) crc32(0, p, (int) hdr_size);
        if(computed_crc != hdr_crc) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Header CRC error");

                return ARCHIVE_FATAL;
        }

        /* If the checksum is OK, we proceed with parsing. */
        if(ARCHIVE_OK != consume(a, hdr_size_len)) {
                return ARCHIVE_EOF;
        }

        if(!read_var_sized(a, &header_id, NULL))
                return ARCHIVE_EOF;

        if(!read_var_sized(a, &header_flags, NULL))
                return ARCHIVE_EOF;

        rar->generic.split_after = (header_flags & HFL_SPLIT_AFTER) > 0;
        rar->generic.split_before = (header_flags & HFL_SPLIT_BEFORE) > 0;
        rar->generic.size = (int)hdr_size;
        rar->generic.last_header_id = (int)header_id;
        rar->main.endarc = 0;

        /* Those are possible header ids in RARv5. */
        enum HEADER_TYPE {
                HEAD_MARK    = 0x00, HEAD_MAIN  = 0x01, HEAD_FILE   = 0x02,
                HEAD_SERVICE = 0x03, HEAD_CRYPT = 0x04, HEAD_ENDARC = 0x05,
                HEAD_UNKNOWN = 0xff,
        };

        switch(header_id) {
                case HEAD_MAIN:
                        ret = process_head_main(a, rar, entry, header_flags);

                        /* Main header doesn't have any files in it, so it's
                         * pointless to return to the caller. Retry to next
                         * header, which should be HEAD_FILE/HEAD_SERVICE. */
                        if(ret == ARCHIVE_OK)
                                return ARCHIVE_RETRY;

                        return ret;
                case HEAD_SERVICE:
                        ret = process_head_service(a, rar, entry, header_flags);
                        return ret;
                case HEAD_FILE:
                        ret = process_head_file(a, rar, entry, header_flags);
                        return ret;
                case HEAD_CRYPT:
                        archive_set_error(&a->archive,
                            ARCHIVE_ERRNO_FILE_FORMAT,
                            "Encryption is not supported");
                        return ARCHIVE_FATAL;
                case HEAD_ENDARC:
                        rar->main.endarc = 1;

                        /* After encountering an end of file marker, we need
                         * to take into consideration if this archive is
                         * continued in another file (i.e. is it part01.rar:
                         * is there a part02.rar?) */
                        if(rar->main.volume) {
                                /* In case there is part02.rar, position the
                                 * read pointer in a proper place, so we can
                                 * resume parsing. */
                                ret = scan_for_signature(a);
                                if(ret == ARCHIVE_FATAL) {
                                        return ARCHIVE_EOF;
                                } else {
                                        if(rar->vol.expected_vol_no ==
                                            UINT_MAX) {
                                                archive_set_error(&a->archive,
                                                    ARCHIVE_ERRNO_FILE_FORMAT,
                                                    "Header error");
                                                        return ARCHIVE_FATAL;
                                        }

                                        rar->vol.expected_vol_no =
                                            rar->main.vol_no + 1;
                                        return ARCHIVE_OK;
                                }
                        } else {
                                return ARCHIVE_EOF;
                        }
                case HEAD_MARK:
                        return ARCHIVE_EOF;
                default:
                        if((header_flags & HFL_SKIP_IF_UNKNOWN) == 0) {
                                archive_set_error(&a->archive,
                                    ARCHIVE_ERRNO_FILE_FORMAT,
                                    "Header type error");
                                return ARCHIVE_FATAL;
                        } else {
                                /* If the block is marked as 'skip if unknown',
                                 * do as the flag says: skip the block
                                 * instead on failing on it. */
                                return ARCHIVE_RETRY;
                        }
        }

#if !defined WIN32
        // Not reached.
        archive_set_error(&a->archive, ARCHIVE_ERRNO_PROGRAMMER,
            "Internal unpacker error");
        return ARCHIVE_FATAL;
#endif
}

static int skip_base_block(struct archive_read* a) {
        int ret;
        struct rar5* rar = get_context(a);

        /* Create a new local archive_entry structure that will be operated on
         * by header reader; operations on this archive_entry will be discarded.
         */
        struct archive_entry* entry = archive_entry_new();
        ret = process_base_block(a, entry);

        /* Discard operations on this archive_entry structure. */
        archive_entry_free(entry);
        if(ret == ARCHIVE_FATAL)
                return ret;

        if(rar->generic.last_header_id == 2 && rar->generic.split_before > 0)
                return ARCHIVE_OK;

        if(ret == ARCHIVE_OK)
                return ARCHIVE_RETRY;
        else
                return ret;
}

static int rar5_read_header(struct archive_read *a,
    struct archive_entry *entry)
{
        struct rar5* rar = get_context(a);
        int ret;

        if(rar->header_initialized == 0) {
                init_header(a);
                rar->header_initialized = 1;
        }

        if(rar->skipped_magic == 0) {
                if(ARCHIVE_OK != consume(a, rar5_signature_size)) {
                        return ARCHIVE_EOF;
                }

                rar->skipped_magic = 1;
        }

        do {
                ret = process_base_block(a, entry);
        } while(ret == ARCHIVE_RETRY ||
                        (rar->main.endarc > 0 && ret == ARCHIVE_OK));

        return ret;
}

static void init_unpack(struct rar5* rar) {
        rar->file.calculated_crc32 = 0;
        if (rar->cstate.window_size)
                rar->cstate.window_mask = rar->cstate.window_size - 1;
        else
                rar->cstate.window_mask = 0;

        free(rar->cstate.window_buf);
        free(rar->cstate.filtered_buf);

        if(rar->cstate.window_size > 0) {
                rar->cstate.window_buf = calloc(1, rar->cstate.window_size);
                rar->cstate.filtered_buf = calloc(1, rar->cstate.window_size);
        } else {
                rar->cstate.window_buf = NULL;
                rar->cstate.filtered_buf = NULL;
        }

        rar->cstate.write_ptr = 0;
        rar->cstate.last_write_ptr = 0;

        memset(&rar->cstate.bd, 0, sizeof(rar->cstate.bd));
        memset(&rar->cstate.ld, 0, sizeof(rar->cstate.ld));
        memset(&rar->cstate.dd, 0, sizeof(rar->cstate.dd));
        memset(&rar->cstate.ldd, 0, sizeof(rar->cstate.ldd));
        memset(&rar->cstate.rd, 0, sizeof(rar->cstate.rd));
}

static void update_crc(struct rar5* rar, const uint8_t* p, size_t to_read) {
    int verify_crc;

        if(rar->skip_mode) {
#if defined CHECK_CRC_ON_SOLID_SKIP
                verify_crc = 1;
#else
                verify_crc = 0;
#endif
        } else
                verify_crc = 1;

        if(verify_crc) {
                /* Don't update CRC32 if the file doesn't have the
                 * `stored_crc32` info filled in. */
                if(rar->file.stored_crc32 > 0) {
                        rar->file.calculated_crc32 =
                                crc32(rar->file.calculated_crc32, p, to_read);
                }

                /* Check if the file uses an optional BLAKE2sp checksum
                 * algorithm. */
                if(rar->file.has_blake2 > 0) {
                        /* Return value of the `update` function is always 0,
                         * so we can explicitly ignore it here. */
                        (void) blake2sp_update(&rar->file.b2state, p, to_read);
                }
        }
}

static int create_decode_tables(uint8_t* bit_length,
    struct decode_table* table, int size)
{
        int code, upper_limit = 0, i, lc[16];
        uint32_t decode_pos_clone[rar5_countof(table->decode_pos)];
        ssize_t cur_len, quick_data_size;

        memset(&lc, 0, sizeof(lc));
        memset(table->decode_num, 0, sizeof(table->decode_num));
        table->size = size;
        table->quick_bits = size == HUFF_NC ? 10 : 7;

        for(i = 0; i < size; i++) {
                lc[bit_length[i] & 15]++;
        }

        lc[0] = 0;
        table->decode_pos[0] = 0;
        table->decode_len[0] = 0;

        for(i = 1; i < 16; i++) {
                upper_limit += lc[i];

                table->decode_len[i] = upper_limit << (16 - i);
                table->decode_pos[i] = table->decode_pos[i - 1] + lc[i - 1];

                upper_limit <<= 1;
        }

        memcpy(decode_pos_clone, table->decode_pos, sizeof(decode_pos_clone));

        for(i = 0; i < size; i++) {
                uint8_t clen = bit_length[i] & 15;
                if(clen > 0) {
                        int last_pos = decode_pos_clone[clen];
                        table->decode_num[last_pos] = i;
                        decode_pos_clone[clen]++;
                }
        }

        quick_data_size = (int64_t)1 << table->quick_bits;
        cur_len = 1;
        for(code = 0; code < quick_data_size; code++) {
                int bit_field = code << (16 - table->quick_bits);
                int dist, pos;

                while(cur_len < rar5_countof(table->decode_len) &&
                                bit_field >= table->decode_len[cur_len]) {
                        cur_len++;
                }

                table->quick_len[code] = (uint8_t) cur_len;

                dist = bit_field - table->decode_len[cur_len - 1];
                dist >>= (16 - cur_len);

                pos = table->decode_pos[cur_len & 15] + dist;
                if(cur_len < rar5_countof(table->decode_pos) && pos < size) {
                        table->quick_num[code] = table->decode_num[pos];
                } else {
                        table->quick_num[code] = 0;
                }
        }

        return ARCHIVE_OK;
}

static int decode_number(struct archive_read* a, struct decode_table* table,
    const uint8_t* p, uint16_t* num)
{
        int i, bits, dist;
        uint16_t bitfield;
        uint32_t pos;
        struct rar5* rar = get_context(a);

        if(ARCHIVE_OK != read_bits_16(rar, p, &bitfield)) {
                return ARCHIVE_EOF;
        }

        bitfield &= 0xfffe;

        if(bitfield < table->decode_len[table->quick_bits]) {
                int code = bitfield >> (16 - table->quick_bits);
                skip_bits(rar, table->quick_len[code]);
                *num = table->quick_num[code];
                return ARCHIVE_OK;
        }

        bits = 15;

        for(i = table->quick_bits + 1; i < 15; i++) {
                if(bitfield < table->decode_len[i]) {
                        bits = i;
                        break;
                }
        }

        skip_bits(rar, bits);

        dist = bitfield - table->decode_len[bits - 1];
        dist >>= (16 - bits);
        pos = table->decode_pos[bits] + dist;

        if(pos >= table->size)
                pos = 0;

        *num = table->decode_num[pos];
        return ARCHIVE_OK;
}

/* Reads and parses Huffman tables from the beginning of the block. */
static int parse_tables(struct archive_read* a, struct rar5* rar,
    const uint8_t* p)
{
        int ret, value, i, w, idx = 0;
        uint8_t bit_length[HUFF_BC],
                table[HUFF_TABLE_SIZE],
                nibble_mask = 0xF0,
                nibble_shift = 4;

        enum { ESCAPE = 15 };

        /* The data for table generation is compressed using a simple RLE-like
         * algorithm when storing zeroes, so we need to unpack it first. */
        for(w = 0, i = 0; w < HUFF_BC;) {
                if(i >= rar->cstate.cur_block_size) {
                        /* Truncated data, can't continue. */
                        archive_set_error(&a->archive,
                            ARCHIVE_ERRNO_FILE_FORMAT,
                            "Truncated data in huffman tables");
                        return ARCHIVE_FATAL;
                }

                value = (p[i] & nibble_mask) >> nibble_shift;

                if(nibble_mask == 0x0F)
                        ++i;

                nibble_mask ^= 0xFF;
                nibble_shift ^= 4;

                /* Values smaller than 15 is data, so we write it directly.
                 * Value 15 is a flag telling us that we need to unpack more
                 * bytes. */
                if(value == ESCAPE) {
                        value = (p[i] & nibble_mask) >> nibble_shift;
                        if(nibble_mask == 0x0F)
                                ++i;
                        nibble_mask ^= 0xFF;
                        nibble_shift ^= 4;

                        if(value == 0) {
                                /* We sometimes need to write the actual value
                                 * of 15, so this case handles that. */
                                bit_length[w++] = ESCAPE;
                        } else {
                                int k;

                                /* Fill zeroes. */
                                for(k = 0; (k < value + 2) && (w < HUFF_BC);
                                    k++) {
                                        bit_length[w++] = 0;
                                }
                        }
                } else {
                        bit_length[w++] = value;
                }
        }

        rar->bits.in_addr = i;
        rar->bits.bit_addr = nibble_shift ^ 4;

        ret = create_decode_tables(bit_length, &rar->cstate.bd, HUFF_BC);
        if(ret != ARCHIVE_OK) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Decoding huffman tables failed");
                return ARCHIVE_FATAL;
        }

        for(i = 0; i < HUFF_TABLE_SIZE;) {
                uint16_t num;

                if((rar->bits.in_addr + 6) >= rar->cstate.cur_block_size) {
                        /* Truncated data, can't continue. */
                        archive_set_error(&a->archive,
                            ARCHIVE_ERRNO_FILE_FORMAT,
                            "Truncated data in huffman tables (#2)");
                        return ARCHIVE_FATAL;
                }

                ret = decode_number(a, &rar->cstate.bd, p, &num);
                if(ret != ARCHIVE_OK) {
                        archive_set_error(&a->archive,
                            ARCHIVE_ERRNO_FILE_FORMAT,
                            "Decoding huffman tables failed");
                        return ARCHIVE_FATAL;
                }

                if(num < 16) {
                        /* 0..15: store directly */
                        table[i] = (uint8_t) num;
                        i++;
                        continue;
                }

                if(num < 18) {
                        /* 16..17: repeat previous code */
                        uint16_t n;
                        if(ARCHIVE_OK != read_bits_16(rar, p, &n))
                                return ARCHIVE_EOF;

                        if(num == 16) {
                                n >>= 13;
                                n += 3;
                                skip_bits(rar, 3);
                        } else {
                                n >>= 9;
                                n += 11;
                                skip_bits(rar, 7);
                        }

                        if(i > 0) {
                                while(n-- > 0 && i < HUFF_TABLE_SIZE) {
                                        table[i] = table[i - 1];
                                        i++;
                                }
                        } else {
                                archive_set_error(&a->archive,
                                    ARCHIVE_ERRNO_FILE_FORMAT,
                                    "Unexpected error when decoding "
                                    "huffman tables");
                                return ARCHIVE_FATAL;
                        }

                        continue;
                }

                /* other codes: fill with zeroes `n` times */
                uint16_t n;
                if(ARCHIVE_OK != read_bits_16(rar, p, &n))
                        return ARCHIVE_EOF;

                if(num == 18) {
                        n >>= 13;
                        n += 3;
                        skip_bits(rar, 3);
                } else {
                        n >>= 9;
                        n += 11;
                        skip_bits(rar, 7);
                }

                while(n-- > 0 && i < HUFF_TABLE_SIZE)
                        table[i++] = 0;
        }

        ret = create_decode_tables(&table[idx], &rar->cstate.ld, HUFF_NC);
        if(ret != ARCHIVE_OK) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                     "Failed to create literal table");
                return ARCHIVE_FATAL;
        }

        idx += HUFF_NC;

        ret = create_decode_tables(&table[idx], &rar->cstate.dd, HUFF_DC);
        if(ret != ARCHIVE_OK) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Failed to create distance table");
                return ARCHIVE_FATAL;
        }

        idx += HUFF_DC;

        ret = create_decode_tables(&table[idx], &rar->cstate.ldd, HUFF_LDC);
        if(ret != ARCHIVE_OK) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Failed to create lower bits of distances table");
                return ARCHIVE_FATAL;
        }

        idx += HUFF_LDC;

        ret = create_decode_tables(&table[idx], &rar->cstate.rd, HUFF_RC);
        if(ret != ARCHIVE_OK) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Failed to create repeating distances table");
                return ARCHIVE_FATAL;
        }

        return ARCHIVE_OK;
}

/* Parses the block header, verifies its CRC byte, and saves the header
 * fields inside the `hdr` pointer. */
static int parse_block_header(struct archive_read* a, const uint8_t* p,
    ssize_t* block_size, struct compressed_block_header* hdr)
{
        memcpy(hdr, p, sizeof(struct compressed_block_header));

        if(bf_byte_count(hdr) > 2) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Unsupported block header size (was %d, max is 2)",
                    bf_byte_count(hdr));
                return ARCHIVE_FATAL;
        }

        /* This should probably use bit reader interface in order to be more
         * future-proof. */
        *block_size = 0;
        switch(bf_byte_count(hdr)) {
                /* 1-byte block size */
                case 0:
                        *block_size = *(const uint8_t*) &p[2];
                        break;

                /* 2-byte block size */
                case 1:
                        *block_size = archive_le16dec(&p[2]);
                        break;

                /* 3-byte block size */
                case 2:
                        *block_size = archive_le32dec(&p[2]);
                        *block_size &= 0x00FFFFFF;
                        break;

                /* Other block sizes are not supported. This case is not
                 * reached, because we have an 'if' guard before the switch
                 * that makes sure of it. */
                default:
                        return ARCHIVE_FATAL;
        }

        /* Verify the block header checksum. 0x5A is a magic value and is
         * always * constant. */
        uint8_t calculated_cksum = 0x5A
            ^ (uint8_t) hdr->block_flags_u8
            ^ (uint8_t) *block_size
            ^ (uint8_t) (*block_size >> 8)
            ^ (uint8_t) (*block_size >> 16);

        if(calculated_cksum != hdr->block_cksum) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Block checksum error: got 0x%x, expected 0x%x",
                    hdr->block_cksum, calculated_cksum);

                return ARCHIVE_FATAL;
        }

        return ARCHIVE_OK;
}

/* Convenience function used during filter processing. */
static int parse_filter_data(struct rar5* rar, const uint8_t* p,
    uint32_t* filter_data)
{
        int i, bytes;
        uint32_t data = 0;

        if(ARCHIVE_OK != read_consume_bits(rar, p, 2, &bytes))
                return ARCHIVE_EOF;

        bytes++;

        for(i = 0; i < bytes; i++) {
                uint16_t byte;

                if(ARCHIVE_OK != read_bits_16(rar, p, &byte)) {
                        return ARCHIVE_EOF;
                }

                /* Cast to uint32_t will ensure the shift operation will not
                 * produce undefined result. */
                data += ((uint32_t) byte >> 8) << (i * 8);
                skip_bits(rar, 8);
        }

        *filter_data = data;
        return ARCHIVE_OK;
}

/* Function is used during sanity checking. */
static int is_valid_filter_block_start(struct rar5* rar,
    uint32_t start)
{
        const int64_t block_start = (ssize_t) start + rar->cstate.write_ptr;
        const int64_t last_bs = rar->cstate.last_block_start;
        const ssize_t last_bl = rar->cstate.last_block_length;

        if(last_bs == 0 || last_bl == 0) {
                /* We didn't have any filters yet, so accept this offset. */
                return 1;
        }

        if(block_start >= last_bs + last_bl) {
                /* Current offset is bigger than last block's end offset, so
                 * accept current offset. */
                return 1;
        }

        /* Any other case is not a normal situation and we should fail. */
        return 0;
}

/* The function will create a new filter, read its parameters from the input
 * stream and add it to the filter collection. */
static int parse_filter(struct archive_read* ar, const uint8_t* p) {
        uint32_t block_start, block_length;
        uint16_t filter_type;
        struct rar5* rar = get_context(ar);

        /* Read the parameters from the input stream. */
        if(ARCHIVE_OK != parse_filter_data(rar, p, &block_start))
                return ARCHIVE_EOF;

        if(ARCHIVE_OK != parse_filter_data(rar, p, &block_length))
                return ARCHIVE_EOF;

        if(ARCHIVE_OK != read_bits_16(rar, p, &filter_type))
                return ARCHIVE_EOF;

        filter_type >>= 13;
        skip_bits(rar, 3);

        /* Perform some sanity checks on this filter parameters. Note that we
         * allow only DELTA, E8/E9 and ARM filters here, because rest of
         * filters are not used in RARv5. */

        if(block_length < 4 ||
            block_length > 0x400000 ||
            filter_type > FILTER_ARM ||
            !is_valid_filter_block_start(rar, block_start))
        {
                archive_set_error(&ar->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Invalid filter encountered");
                return ARCHIVE_FATAL;
        }

        /* Allocate a new filter. */
        struct filter_info* filt = add_new_filter(rar);
        if(filt == NULL) {
                archive_set_error(&ar->archive, ENOMEM,
                    "Can't allocate memory for a filter descriptor.");
                return ARCHIVE_FATAL;
        }

        filt->type = filter_type;
        filt->block_start = rar->cstate.write_ptr + block_start;
        filt->block_length = block_length;

        rar->cstate.last_block_start = filt->block_start;
        rar->cstate.last_block_length = filt->block_length;

        /* Read some more data in case this is a DELTA filter. Other filter
         * types don't require any additional data over what was already
         * read. */
        if(filter_type == FILTER_DELTA) {
                int channels;

                if(ARCHIVE_OK != read_consume_bits(rar, p, 5, &channels))
                        return ARCHIVE_EOF;

                filt->channels = channels + 1;
        }

        return ARCHIVE_OK;
}

static int decode_code_length(struct rar5* rar, const uint8_t* p,
    uint16_t code)
{
        int lbits, length = 2;
        if(code < 8) {
                lbits = 0;
                length += code;
        } else {
                lbits = code / 4 - 1;
                length += (4 | (code & 3)) << lbits;
        }

        if(lbits > 0) {
                int add;

                if(ARCHIVE_OK != read_consume_bits(rar, p, lbits, &add))
                        return -1;

                length += add;
        }

        return length;
}

static int copy_string(struct archive_read* a, int len, int dist) {
        struct rar5* rar = get_context(a);
        const uint64_t cmask = rar->cstate.window_mask;
        const uint64_t write_ptr = rar->cstate.write_ptr +
            rar->cstate.solid_offset;
        int i;

        if (rar->cstate.window_buf == NULL)
                return ARCHIVE_FATAL;

        /* The unpacker spends most of the time in this function. It would be
         * a good idea to introduce some optimizations here.
         *
         * Just remember that this loop treats buffers that overlap differently
         * than buffers that do not overlap. This is why a simple memcpy(3)
         * call will not be enough. */

        for(i = 0; i < len; i++) {
                const ssize_t write_idx = (write_ptr + i) & cmask;
                const ssize_t read_idx = (write_ptr + i - dist) & cmask;
                rar->cstate.window_buf[write_idx] =
                    rar->cstate.window_buf[read_idx];
        }

        rar->cstate.write_ptr += len;
        return ARCHIVE_OK;
}

static int do_uncompress_block(struct archive_read* a, const uint8_t* p) {
        struct rar5* rar = get_context(a);
        uint16_t num;
        int ret;

        const uint64_t cmask = rar->cstate.window_mask;
        const struct compressed_block_header* hdr = &rar->last_block_hdr;
        const uint8_t bit_size = 1 + bf_bit_size(hdr);

        while(1) {
                if(rar->cstate.write_ptr - rar->cstate.last_write_ptr >
                    (rar->cstate.window_size >> 1)) {
                        /* Don't allow growing data by more than half of the
                         * window size at a time. In such case, break the loop;
                         *  next call to this function will continue processing
                         *  from this moment. */
                        break;
                }

                if(rar->bits.in_addr > rar->cstate.cur_block_size - 1 ||
                    (rar->bits.in_addr == rar->cstate.cur_block_size - 1 &&
                    rar->bits.bit_addr >= bit_size))
                {
                        /* If the program counter is here, it means the
                         * function has finished processing the block. */
                        rar->cstate.block_parsing_finished = 1;
                        break;
                }

                /* Decode the next literal. */
                if(ARCHIVE_OK != decode_number(a, &rar->cstate.ld, p, &num)) {
                        return ARCHIVE_EOF;
                }

                /* Num holds a decompression literal, or 'command code'.
                 *
                 * - Values lower than 256 are just bytes. Those codes
                 *   can be stored in the output buffer directly.
                 *
                 * - Code 256 defines a new filter, which is later used to 
                 *   ransform the data block accordingly to the filter type.
                 *   The data block needs to be fully uncompressed first.
                 *
                 * - Code bigger than 257 and smaller than 262 define
                 *   a repetition pattern that should be copied from
                 *   an already uncompressed chunk of data.
                 */

                if(num < 256) {
                        /* Directly store the byte. */
                        int64_t write_idx = rar->cstate.solid_offset +
                            rar->cstate.write_ptr++;

                        rar->cstate.window_buf[write_idx & cmask] =
                            (uint8_t) num;
                        continue;
                } else if(num >= 262) {
                        uint16_t dist_slot;
                        int len = decode_code_length(rar, p, num - 262),
                                dbits,
                                dist = 1;

                        if(len == -1) {
                                archive_set_error(&a->archive,
                                    ARCHIVE_ERRNO_PROGRAMMER,
                                    "Failed to decode the code length");

                                return ARCHIVE_FATAL;
                        }

                        if(ARCHIVE_OK != decode_number(a, &rar->cstate.dd, p,
                            &dist_slot))
                        {
                                archive_set_error(&a->archive,
                                    ARCHIVE_ERRNO_PROGRAMMER,
                                    "Failed to decode the distance slot");

                                return ARCHIVE_FATAL;
                        }

                        if(dist_slot < 4) {
                                dbits = 0;
                                dist += dist_slot;
                        } else {
                                dbits = dist_slot / 2 - 1;

                                /* Cast to uint32_t will make sure the shift
                                 * left operation won't produce undefined
                                 * result. Then, the uint32_t type will
                                 * be implicitly casted to int. */
                                dist += (uint32_t) (2 |
                                    (dist_slot & 1)) << dbits;
                        }

                        if(dbits > 0) {
                                if(dbits >= 4) {
                                        uint32_t add = 0;
                                        uint16_t low_dist;

                                        if(dbits > 4) {
                                                if(ARCHIVE_OK != read_bits_32(
                                                    rar, p, &add)) {
                                                        /* Return EOF if we
                                                         * can't read more
                                                         * data. */
                                                        return ARCHIVE_EOF;
                                                }

                                                skip_bits(rar, dbits - 4);
                                                add = (add >> (
                                                    36 - dbits)) << 4;
                                                dist += add;
                                        }

                                        if(ARCHIVE_OK != decode_number(a,
                                            &rar->cstate.ldd, p, &low_dist))
                                        {
                                                archive_set_error(&a->archive,
                                                    ARCHIVE_ERRNO_PROGRAMMER,
                                                    "Failed to decode the "
                                                    "distance slot");

                                                return ARCHIVE_FATAL;
                                        }

                                        if(dist >= INT_MAX - low_dist - 1) {
                                                /* This only happens in
                                                 * invalid archives. */
                                                archive_set_error(&a->archive,
                                                    ARCHIVE_ERRNO_FILE_FORMAT,
                                                    "Distance pointer "
                                                    "overflow");
                                                return ARCHIVE_FATAL;
                                        }

                                        dist += low_dist;
                                } else {
                                        /* dbits is one of [0,1,2,3] */
                                        int add;

                                        if(ARCHIVE_OK != read_consume_bits(rar,
                                             p, dbits, &add)) {
                                                /* Return EOF if we can't read
                                                 * more data. */
                                                return ARCHIVE_EOF;
                                        }

                                        dist += add;
                                }
                        }

                        if(dist > 0x100) {
                                len++;

                                if(dist > 0x2000) {
                                        len++;

                                        if(dist > 0x40000) {
                                                len++;
                                        }
                                }
                        }

                        dist_cache_push(rar, dist);
                        rar->cstate.last_len = len;

                        if(ARCHIVE_OK != copy_string(a, len, dist))
                                return ARCHIVE_FATAL;

                        continue;
                } else if(num == 256) {
                        /* Create a filter. */
                        ret = parse_filter(a, p);
                        if(ret != ARCHIVE_OK)
                                return ret;

                        continue;
                } else if(num == 257) {
                        if(rar->cstate.last_len != 0) {
                                if(ARCHIVE_OK != copy_string(a,
                                    rar->cstate.last_len,
                                    rar->cstate.dist_cache[0]))
                                {
                                        return ARCHIVE_FATAL;
                                }
                        }

                        continue;
                } else if(num < 262) {
                        const int idx = num - 258;
                        const int dist = dist_cache_touch(rar, idx);

                        uint16_t len_slot;
                        int len;

                        if(ARCHIVE_OK != decode_number(a, &rar->cstate.rd, p,
                            &len_slot)) {
                                return ARCHIVE_FATAL;
                        }

                        len = decode_code_length(rar, p, len_slot);
                        rar->cstate.last_len = len;

                        if(ARCHIVE_OK != copy_string(a, len, dist))
                                return ARCHIVE_FATAL;

                        continue;
                }

                /* The program counter shouldn't reach here. */
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Unsupported block code: 0x%x", num);

                return ARCHIVE_FATAL;
        }

        return ARCHIVE_OK;
}

/* Binary search for the RARv5 signature. */
static int scan_for_signature(struct archive_read* a) {
        const uint8_t* p;
        const int chunk_size = 512;
        ssize_t i;

        /* If we're here, it means we're on an 'unknown territory' data.
         * There's no indication what kind of data we're reading here.
         * It could be some text comment, any kind of binary data,
         * digital sign, dragons, etc.
         *
         * We want to find a valid RARv5 magic header inside this unknown
         * data. */

        /* Is it possible in libarchive to just skip everything until the
         * end of the file? If so, it would be a better approach than the
         * current implementation of this function. */

        while(1) {
                if(!read_ahead(a, chunk_size, &p))
                        return ARCHIVE_EOF;

                for(i = 0; i < chunk_size - rar5_signature_size; i++) {
                        if(memcmp(&p[i], rar5_signature,
                            rar5_signature_size) == 0) {
                                /* Consume the number of bytes we've used to
                                 * search for the signature, as well as the
                                 * number of bytes used by the signature
                                 * itself. After this we should be standing
                                 * on a valid base block header. */
                                (void) consume(a, i + rar5_signature_size);
                                return ARCHIVE_OK;
                        }
                }

                consume(a, chunk_size);
        }

        return ARCHIVE_FATAL;
}

/* This function will switch the multivolume archive file to another file,
 * i.e. from part03 to part 04. */
static int advance_multivolume(struct archive_read* a) {
        int lret;
        struct rar5* rar = get_context(a);

        /* A small state machine that will skip unnecessary data, needed to
         * switch from one multivolume to another. Such skipping is needed if
         * we want to be an stream-oriented (instead of file-oriented)
         * unpacker.
         *
         * The state machine starts with `rar->main.endarc` == 0. It also
         * assumes that current stream pointer points to some base block
         * header.
         *
         * The `endarc` field is being set when the base block parsing
         * function encounters the 'end of archive' marker.
         */

        while(1) {
                if(rar->main.endarc == 1) {
                        int looping = 1;

                        rar->main.endarc = 0;

                        while(looping) {
                                lret = skip_base_block(a);
                                switch(lret) {
                                        case ARCHIVE_RETRY:
                                                /* Continue looping. */
                                                break;
                                        case ARCHIVE_OK:
                                                /* Break loop. */
                                                looping = 0;
                                                break;
                                        default:
                                                /* Forward any errors to the
                                                 * caller. */
                                                return lret;
                                }
                        }

                        break;
                } else {
                        /* Skip current base block. In order to properly skip
                         * it, we really need to simply parse it and discard
                         * the results. */

                        lret = skip_base_block(a);
                        if(lret == ARCHIVE_FATAL || lret == ARCHIVE_FAILED)
                                return lret;

                        /* The `skip_base_block` function tells us if we
                         * should continue with skipping, or we should stop
                         * skipping. We're trying to skip everything up to
                         * a base FILE block. */

                        if(lret != ARCHIVE_RETRY) {
                                /* If there was an error during skipping, or we
                                 * have just skipped a FILE base block... */

                                if(rar->main.endarc == 0) {
                                        return lret;
                                } else {
                                        continue;
                                }
                        }
                }
        }

        return ARCHIVE_OK;
}

/* Merges the partial block from the first multivolume archive file, and
 * partial block from the second multivolume archive file. The result is
 * a chunk of memory containing the whole block, and the stream pointer
 * is advanced to the next block in the second multivolume archive file. */
static int merge_block(struct archive_read* a, ssize_t block_size,
    const uint8_t** p)
{
        struct rar5* rar = get_context(a);
        ssize_t cur_block_size, partial_offset = 0;
        const uint8_t* lp;
        int ret;

        if(rar->merge_mode) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_PROGRAMMER,
                    "Recursive merge is not allowed");

                return ARCHIVE_FATAL;
        }

        /* Set a flag that we're in the switching mode. */
        rar->cstate.switch_multivolume = 1;

        /* Reallocate the memory which will hold the whole block. */
        if(rar->vol.push_buf)
                free((void*) rar->vol.push_buf);

        /* Increasing the allocation block by 8 is due to bit reading functions,
         * which are using additional 2 or 4 bytes. Allocating the block size
         * by exact value would make bit reader perform reads from invalid
         * memory block when reading the last byte from the buffer. */
        rar->vol.push_buf = malloc(block_size + 8);
        if(!rar->vol.push_buf) {
                archive_set_error(&a->archive, ENOMEM,
                    "Can't allocate memory for a merge block buffer.");
                return ARCHIVE_FATAL;
        }

        /* Valgrind complains if the extension block for bit reader is not
         * initialized, so initialize it. */
        memset(&rar->vol.push_buf[block_size], 0, 8);

        /* A single block can span across multiple multivolume archive files,
         * so we use a loop here. This loop will consume enough multivolume
         * archive files until the whole block is read. */

        while(1) {
                /* Get the size of current block chunk in this multivolume
                 * archive file and read it. */
                cur_block_size = rar5_min(rar->file.bytes_remaining,
                    block_size - partial_offset);

                if(cur_block_size == 0) {
                        archive_set_error(&a->archive,
                            ARCHIVE_ERRNO_FILE_FORMAT,
                            "Encountered block size == 0 during block merge");
                        return ARCHIVE_FATAL;
                }

                if(!read_ahead(a, cur_block_size, &lp))
                        return ARCHIVE_EOF;

                /* Sanity check; there should never be a situation where this
                 * function reads more data than the block's size. */
                if(partial_offset + cur_block_size > block_size) {
                        archive_set_error(&a->archive,
                            ARCHIVE_ERRNO_PROGRAMMER,
                            "Consumed too much data when merging blocks.");
                        return ARCHIVE_FATAL;
                }

                /* Merge previous block chunk with current block chunk,
                 * or create first block chunk if this is our first
                 * iteration. */
                memcpy(&rar->vol.push_buf[partial_offset], lp, cur_block_size);

                /* Advance the stream read pointer by this block chunk size. */
                if(ARCHIVE_OK != consume(a, cur_block_size))
                        return ARCHIVE_EOF;

                /* Update the pointers. `partial_offset` contains information
                 * about the sum of merged block chunks. */
                partial_offset += cur_block_size;
                rar->file.bytes_remaining -= cur_block_size;

                /* If `partial_offset` is the same as `block_size`, this means
                 * we've merged all block chunks and we have a valid full
                 * block. */
                if(partial_offset == block_size) {
                        break;
                }

                /* If we don't have any bytes to read, this means we should
                 * switch to another multivolume archive file. */
                if(rar->file.bytes_remaining == 0) {
                        rar->merge_mode++;
                        ret = advance_multivolume(a);
                        rar->merge_mode--;
                        if(ret != ARCHIVE_OK) {
                                return ret;
                        }
                }
        }

        *p = rar->vol.push_buf;

        /* If we're here, we can resume unpacking by processing the block
         * pointed to by the `*p` memory pointer. */

        return ARCHIVE_OK;
}

static int process_block(struct archive_read* a) {
        const uint8_t* p;
        struct rar5* rar = get_context(a);
        int ret;

        /* If we don't have any data to be processed, this most probably means
         * we need to switch to the next volume. */
        if(rar->main.volume && rar->file.bytes_remaining == 0) {
                ret = advance_multivolume(a);
                if(ret != ARCHIVE_OK)
                        return ret;
        }

        if(rar->cstate.block_parsing_finished) {
                ssize_t block_size;

                /* The header size won't be bigger than 6 bytes. */
                if(!read_ahead(a, 6, &p)) {
                        /* Failed to prefetch data block header. */
                        return ARCHIVE_EOF;
                }

                /*
                 * Read block_size by parsing block header. Validate the header
                 * by calculating CRC byte stored inside the header. Size of
                 * the header is not constant (block size can be stored either
                 * in 1 or 2 bytes), that's why block size is left out from the
                 * `compressed_block_header` structure and returned by
                 * `parse_block_header` as the second argument. */

                ret = parse_block_header(a, p, &block_size,
                    &rar->last_block_hdr);
                if(ret != ARCHIVE_OK) {
                        return ret;
                }

                /* Skip block header. Next data is huffman tables,
                 * if present. */
                ssize_t to_skip = sizeof(struct compressed_block_header) +
                        bf_byte_count(&rar->last_block_hdr) + 1;

                if(ARCHIVE_OK != consume(a, to_skip))
                        return ARCHIVE_EOF;

                rar->file.bytes_remaining -= to_skip;

                /* The block size gives information about the whole block size,
                 * but the block could be stored in split form when using
                 * multi-volume archives. In this case, the block size will be
                 * bigger than the actual data stored in this file. Remaining
                 * part of the data will be in another file. */

                ssize_t cur_block_size =
                        rar5_min(rar->file.bytes_remaining, block_size);

                if(block_size > rar->file.bytes_remaining) {
                        /* If current blocks' size is bigger than our data
                         * size, this means we have a multivolume archive.
                         * In this case, skip all base headers until the end
                         * of the file, proceed to next "partXXX.rar" volume,
                         * find its signature, skip all headers up to the first
                         * FILE base header, and continue from there.
                         *
                         * Note that `merge_block` will update the `rar`
                         * context structure quite extensively. */

                        ret = merge_block(a, block_size, &p);
                        if(ret != ARCHIVE_OK) {
                                return ret;
                        }

                        cur_block_size = block_size;

                        /* Current stream pointer should be now directly
                         * *after* the block that spanned through multiple
                         * archive files. `p` pointer should have the data of
                         * the *whole* block (merged from partial blocks
                         * stored in multiple archives files). */
                } else {
                        rar->cstate.switch_multivolume = 0;

                        /* Read the whole block size into memory. This can take
                         * up to  8 megabytes of memory in theoretical cases.
                         * Might be worth to optimize this and use a standard
                         * chunk of 4kb's. */
                        if(!read_ahead(a, 4 + cur_block_size, &p)) {
                                /* Failed to prefetch block data. */
                                return ARCHIVE_EOF;
                        }
                }

                rar->cstate.block_buf = p;
                rar->cstate.cur_block_size = cur_block_size;
                rar->cstate.block_parsing_finished = 0;

                rar->bits.in_addr = 0;
                rar->bits.bit_addr = 0;

                if(bf_is_table_present(&rar->last_block_hdr)) {
                        /* Load Huffman tables. */
                        ret = parse_tables(a, rar, p);
                        if(ret != ARCHIVE_OK) {
                                /* Error during decompression of Huffman
                                 * tables. */
                                return ret;
                        }
                }
        } else {
                /* Block parsing not finished, reuse previous memory buffer. */
                p = rar->cstate.block_buf;
        }

        /* Uncompress the block, or a part of it, depending on how many bytes
         * will be generated by uncompressing the block.
         *
         * In case too many bytes will be generated, calling this function
         * again will resume the uncompression operation. */
        ret = do_uncompress_block(a, p);
        if(ret != ARCHIVE_OK) {
                return ret;
        }

        if(rar->cstate.block_parsing_finished &&
            rar->cstate.switch_multivolume == 0 &&
            rar->cstate.cur_block_size > 0)
        {
                /* If we're processing a normal block, consume the whole
                 * block. We can do this because we've already read the whole
                 * block to memory. */
                if(ARCHIVE_OK != consume(a, rar->cstate.cur_block_size))
                        return ARCHIVE_FATAL;

                rar->file.bytes_remaining -= rar->cstate.cur_block_size;
        } else if(rar->cstate.switch_multivolume) {
                /* Don't consume the block if we're doing multivolume
                 * processing. The volume switching function will consume
                 * the proper count of bytes instead. */
                rar->cstate.switch_multivolume = 0;
        }

        return ARCHIVE_OK;
}

/* Pops the `buf`, `size` and `offset` from the "data ready" stack.
 *
 * Returns ARCHIVE_OK when those arguments can be used, ARCHIVE_RETRY
 * when there is no data on the stack. */
static int use_data(struct rar5* rar, const void** buf, size_t* size,
    int64_t* offset)
{
        int i;

        for(i = 0; i < rar5_countof(rar->cstate.dready); i++) {
                struct data_ready *d = &rar->cstate.dready[i];

                if(d->used) {
                        if(buf)    *buf = d->buf;
                        if(size)   *size = d->size;
                        if(offset) *offset = d->offset;

                        d->used = 0;
                        return ARCHIVE_OK;
                }
        }

        return ARCHIVE_RETRY;
}

/* Pushes the `buf`, `size` and `offset` arguments to the rar->cstate.dready
 * FIFO stack. Those values will be popped from this stack by the `use_data`
 * function. */
static int push_data_ready(struct archive_read* a, struct rar5* rar,
    const uint8_t* buf, size_t size, int64_t offset)
{
        int i;

        /* Don't push if we're in skip mode. This is needed because solid
         * streams need full processing even if we're skipping data. After
         * fully processing the stream, we need to discard the generated bytes,
         * because we're interested only in the side effect: building up the
         * internal window circular buffer. This window buffer will be used
         * later during unpacking of requested data. */
        if(rar->skip_mode)
                return ARCHIVE_OK;

        /* Sanity check. */
        if(offset != rar->file.last_offset + rar->file.last_size) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_PROGRAMMER,
                    "Sanity check error: output stream is not continuous");
                return ARCHIVE_FATAL;
        }

        for(i = 0; i < rar5_countof(rar->cstate.dready); i++) {
                struct data_ready* d = &rar->cstate.dready[i];
                if(!d->used) {
                        d->used = 1;
                        d->buf = buf;
                        d->size = size;
                        d->offset = offset;

                        /* These fields are used only in sanity checking. */
                        rar->file.last_offset = offset;
                        rar->file.last_size = size;

                        /* Calculate the checksum of this new block before
                         * submitting data to libarchive's engine. */
                        update_crc(rar, d->buf, d->size);

                        return ARCHIVE_OK;
                }
        }

        /* Program counter will reach this code if the `rar->cstate.data_ready`
         * stack will be filled up so that no new entries will be allowed. The
         * code shouldn't allow such situation to occur. So we treat this case
         * as an internal error. */

        archive_set_error(&a->archive, ARCHIVE_ERRNO_PROGRAMMER,
            "Error: premature end of data_ready stack");
        return ARCHIVE_FATAL;
}

/* This function uncompresses the data that is stored in the <FILE> base
 * block.
 *
 * The FILE base block looks like this:
 *
 * <header><huffman tables><block_1><block_2>...<block_n>
 *
 * The <header> is a block header, that is parsed in parse_block_header().
 * It's a "compressed_block_header" structure, containing metadata needed
 * to know when we should stop looking for more <block_n> blocks.
 *
 * <huffman tables> contain data needed to set up the huffman tables, needed
 * for the actual decompression.
 *
 * Each <block_n> consists of series of literals:
 *
 * <literal><literal><literal>...<literal>
 *
 * Those literals generate the uncompression data. They operate on a circular
 * buffer, sometimes writing raw data into it, sometimes referencing
 * some previous data inside this buffer, and sometimes declaring a filter
 * that will need to be executed on the data stored in the circular buffer.
 * It all depends on the literal that is used.
 *
 * Sometimes blocks produce output data, sometimes they don't. For example, for
 * some huge files that use lots of filters, sometimes a block is filled with
 * only filter declaration literals. Such blocks won't produce any data in the
 * circular buffer.
 *
 * Sometimes blocks will produce 4 bytes of data, and sometimes 1 megabyte,
 * because a literal can reference previously decompressed data. For example,
 * there can be a literal that says: 'append a byte 0xFE here', and after
 * it another literal can say 'append 1 megabyte of data from circular buffer
 * offset 0x12345'. This is how RAR format handles compressing repeated
 * patterns.
 *
 * The RAR compressor creates those literals and the actual efficiency of
 * compression depends on what those literals are. The literals can also
 * be seen as a kind of a non-turing-complete virtual machine that simply
 * tells the decompressor what it should do.
 * */

static int do_uncompress_file(struct archive_read* a) {
        struct rar5* rar = get_context(a);
        int ret;
        int64_t max_end_pos;

        if(!rar->cstate.initialized) {
                /* Don't perform full context reinitialization if we're
                 * processing a solid archive. */
                if(!rar->main.solid || !rar->cstate.window_buf) {
                        init_unpack(rar);
                }

                rar->cstate.initialized = 1;
        }

        if(rar->cstate.all_filters_applied == 1) {
                /* We use while(1) here, but standard case allows for just 1
                 * iteration. The loop will iterate if process_block() didn't
                 * generate any data at all. This can happen if the block
                 * contains only filter definitions (this is common in big
                 * files). */
                while(1) {
                        ret = process_block(a);
                        if(ret == ARCHIVE_EOF || ret == ARCHIVE_FATAL)
                                return ret;

                        if(rar->cstate.last_write_ptr ==
                            rar->cstate.write_ptr) {
                                /* The block didn't generate any new data,
                                 * so just process a new block. */
                                continue;
                        }

                        /* The block has generated some new data, so break
                         * the loop. */
                        break;
                }
        }

        /* Try to run filters. If filters won't be applied, it means that
         * insufficient data was generated. */
        ret = apply_filters(a);
        if(ret == ARCHIVE_RETRY) {
                return ARCHIVE_OK;
        } else if(ret == ARCHIVE_FATAL) {
                return ARCHIVE_FATAL;
        }

        /* If apply_filters() will return ARCHIVE_OK, we can continue here. */

        if(cdeque_size(&rar->cstate.filters) > 0) {
                /* Check if we can write something before hitting first
                 * filter. */
                struct filter_info* flt;

                /* Get the block_start offset from the first filter. */
                if(CDE_OK != cdeque_front(&rar->cstate.filters,
                    cdeque_filter_p(&flt)))
                {
                        archive_set_error(&a->archive,
                            ARCHIVE_ERRNO_PROGRAMMER,
                            "Can't read first filter");
                        return ARCHIVE_FATAL;
                }

                max_end_pos = rar5_min(flt->block_start,
                    rar->cstate.write_ptr);
        } else {
                /* There are no filters defined, or all filters were applied.
                 * This means we can just store the data without any
                 * postprocessing. */
                max_end_pos = rar->cstate.write_ptr;
        }

        if(max_end_pos == rar->cstate.last_write_ptr) {
                /* We can't write anything yet. The block uncompression
                 * function did not generate enough data, and no filter can be
                 * applied. At the same time we don't have any data that can be
                 *  stored without filter postprocessing. This means we need to
                 *  wait for more data to be generated, so we can apply the
                 * filters.
                 *
                 * Signal the caller that we need more data to be able to do
                 * anything.
                 */
                return ARCHIVE_RETRY;
        } else {
                /* We can write the data before hitting the first filter.
                 * So let's do it. The push_window_data() function will
                 * effectively return the selected data block to the user
                 * application. */
                push_window_data(a, rar, rar->cstate.last_write_ptr,
                    max_end_pos);
                rar->cstate.last_write_ptr = max_end_pos;
        }

        return ARCHIVE_OK;
}

static int uncompress_file(struct archive_read* a) {
        int ret;

        while(1) {
                /* Sometimes the uncompression function will return a
                 * 'retry' signal. If this will happen, we have to retry
                 * the function. */
                ret = do_uncompress_file(a);
                if(ret != ARCHIVE_RETRY)
                        return ret;
        }
}


static int do_unstore_file(struct archive_read* a,
    struct rar5* rar, const void** buf, size_t* size, int64_t* offset)
{
        const uint8_t* p;

        if(rar->file.bytes_remaining == 0 && rar->main.volume > 0 &&
            rar->generic.split_after > 0)
        {
                int ret;

                rar->cstate.switch_multivolume = 1;
                ret = advance_multivolume(a);
                rar->cstate.switch_multivolume = 0;

                if(ret != ARCHIVE_OK) {
                        /* Failed to advance to next multivolume archive
                         * file. */
                        return ret;
                }
        }

        size_t to_read = rar5_min(rar->file.bytes_remaining, 64 * 1024);
        if(to_read == 0) {
                return ARCHIVE_EOF;
        }

        if(!read_ahead(a, to_read, &p)) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "I/O error when unstoring file");
                return ARCHIVE_FATAL;
        }

        if(ARCHIVE_OK != consume(a, to_read)) {
                return ARCHIVE_EOF;
        }

        if(buf)    *buf = p;
        if(size)   *size = to_read;
        if(offset) *offset = rar->cstate.last_unstore_ptr;

        rar->file.bytes_remaining -= to_read;
        rar->cstate.last_unstore_ptr += to_read;

        update_crc(rar, p, to_read);
        return ARCHIVE_OK;
}

static int do_unpack(struct archive_read* a, struct rar5* rar,
    const void** buf, size_t* size, int64_t* offset)
{
        enum COMPRESSION_METHOD {
                STORE = 0, FASTEST = 1, FAST = 2, NORMAL = 3, GOOD = 4,
                BEST = 5
        };

        if(rar->file.service > 0) {
                return do_unstore_file(a, rar, buf, size, offset);
        } else {
                switch(rar->cstate.method) {
                        case STORE:
                                return do_unstore_file(a, rar, buf, size,
                                    offset);
                        case FASTEST:
                                /* fallthrough */
                        case FAST:
                                /* fallthrough */
                        case NORMAL:
                                /* fallthrough */
                        case GOOD:
                                /* fallthrough */
                        case BEST:
                                return uncompress_file(a);
                        default:
                                archive_set_error(&a->archive,
                                    ARCHIVE_ERRNO_FILE_FORMAT,
                                    "Compression method not supported: 0x%x",
                                    rar->cstate.method);

                                return ARCHIVE_FATAL;
                }
        }

#if !defined WIN32
        /* Not reached. */
        return ARCHIVE_OK;
#endif
}

static int verify_checksums(struct archive_read* a) {
        int verify_crc;
        struct rar5* rar = get_context(a);

        /* Check checksums only when actually unpacking the data. There's no
         * need to calculate checksum when we're skipping data in solid archives
         * (skipping in solid archives is the same thing as unpacking compressed
         * data and discarding the result). */

        if(!rar->skip_mode) {
                /* Always check checksums if we're not in skip mode */
                verify_crc = 1;
        } else {
                /* We can override the logic above with a compile-time option
                 * NO_CRC_ON_SOLID_SKIP. This option is used during debugging,
                 * and it will check checksums of unpacked data even when
                 * we're skipping it. */

#if defined CHECK_CRC_ON_SOLID_SKIP
                /* Debug case */
                verify_crc = 1;
#else
                /* Normal case */
                verify_crc = 0;
#endif
        }

        if(verify_crc) {
                /* During unpacking, on each unpacked block we're calling the
                 * update_crc() function. Since we are here, the unpacking
                 * process is already over and we can check if calculated
                 * checksum (CRC32 or BLAKE2sp) is the same as what is stored
                 * in the archive. */
                if(rar->file.stored_crc32 > 0) {
                        /* Check CRC32 only when the file contains a CRC32
                         * value for this file. */

                        if(rar->file.calculated_crc32 !=
                            rar->file.stored_crc32) {
                                /* Checksums do not match; the unpacked file
                                 * is corrupted. */

                                DEBUG_CODE {
                                        printf("Checksum error: CRC32 "
                                            "(was: %08x, expected: %08x)\n",
                                            rar->file.calculated_crc32,
                                            rar->file.stored_crc32);
                                }

#ifndef DONT_FAIL_ON_CRC_ERROR
                                archive_set_error(&a->archive,
                                    ARCHIVE_ERRNO_FILE_FORMAT,
                                    "Checksum error: CRC32");
                                return ARCHIVE_FATAL;
#endif
                        } else {
                                DEBUG_CODE {
                                        printf("Checksum OK: CRC32 "
                                            "(%08x/%08x)\n",
                                            rar->file.stored_crc32,
                                            rar->file.calculated_crc32);
                                }
                        }
                }

                if(rar->file.has_blake2 > 0) {
                        /* BLAKE2sp is an optional checksum algorithm that is
                         * added to RARv5 archives when using the `-htb` switch
                         *  during creation of archive.
                         *
                         * We now finalize the hash calculation by calling the
                         * `final` function. This will generate the final hash
                         * value we can use to compare it with the BLAKE2sp
                         * checksum that is stored in the archive.
                         *
                         * The return value of this `final` function is not
                         * very helpful, as it guards only against improper use.
                         * This is why we're explicitly ignoring it. */

                        uint8_t b2_buf[32];
                        (void) blake2sp_final(&rar->file.b2state, b2_buf, 32);

                        if(memcmp(&rar->file.blake2sp, b2_buf, 32) != 0) {
#ifndef DONT_FAIL_ON_CRC_ERROR
                                archive_set_error(&a->archive,
                                    ARCHIVE_ERRNO_FILE_FORMAT,
                                    "Checksum error: BLAKE2");

                                return ARCHIVE_FATAL;
#endif
                        }
                }
        }

        /* Finalization for this file has been successfully completed. */
        return ARCHIVE_OK;
}

static int verify_global_checksums(struct archive_read* a) {
        return verify_checksums(a);
}

static int rar5_read_data(struct archive_read *a, const void **buff,
    size_t *size, int64_t *offset) {
        int ret;
        struct rar5* rar = get_context(a);

        if(rar->file.dir > 0) {
                /* Don't process any data if this file entry was declared
                 * as a directory. This is needed, because entries marked as
                 * directory doesn't have any dictionary buffer allocated, so
                 * it's impossible to perform any decompression. */
                archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
                    "Can't decompress an entry marked as a directory");
                return ARCHIVE_FAILED;
        }

        if(!rar->skip_mode && (rar->cstate.last_write_ptr > rar->file.unpacked_size)) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_PROGRAMMER,
                    "Unpacker has written too many bytes");
                return ARCHIVE_FATAL;
        }

        ret = use_data(rar, buff, size, offset);
        if(ret == ARCHIVE_OK) {
                return ret;
        }

        if(rar->file.eof == 1) {
                return ARCHIVE_EOF;
        }

        ret = do_unpack(a, rar, buff, size, offset);
        if(ret != ARCHIVE_OK) {
                return ret;
        }

        if(rar->file.bytes_remaining == 0 &&
                        rar->cstate.last_write_ptr == rar->file.unpacked_size)
        {
                /* If all bytes of current file were processed, run
                 * finalization.
                 *
                 * Finalization will check checksum against proper values. If
                 * some of the checksums will not match, we'll return an error
                 * value in the last `archive_read_data` call to signal an error
                 * to the user. */

                rar->file.eof = 1;
                return verify_global_checksums(a);
        }

        return ARCHIVE_OK;
}

static int rar5_read_data_skip(struct archive_read *a) {
        struct rar5* rar = get_context(a);

        if(rar->main.solid) {
                /* In solid archives, instead of skipping the data, we need to
                 * extract it, and dispose the result. The side effect of this
                 * operation will be setting up the initial window buffer state
                 * needed to be able to extract the selected file. */

                int ret;

                /* Make sure to process all blocks in the compressed stream. */
                while(rar->file.bytes_remaining > 0) {
                        /* Setting the "skip mode" will allow us to skip
                         * checksum checks during data skipping. Checking the
                         * checksum of skipped data isn't really necessary and
                         * it's only slowing things down.
                         *
                         * This is incremented instead of setting to 1 because
                         * this data skipping function can be called
                         * recursively. */
                        rar->skip_mode++;

                        /* We're disposing 1 block of data, so we use triple
                         * NULLs in arguments. */
                        ret = rar5_read_data(a, NULL, NULL, NULL);

                        /* Turn off "skip mode". */
                        rar->skip_mode--;

                        if(ret < 0) {
                                /* Propagate any potential error conditions
                                 * to the caller. */
                                return ret;
                        }
                }
        } else {
                /* In standard archives, we can just jump over the compressed
                 * stream. Each file in non-solid archives starts from an empty
                 * window buffer. */

                if(ARCHIVE_OK != consume(a, rar->file.bytes_remaining)) {
                        return ARCHIVE_FATAL;
                }

                rar->file.bytes_remaining = 0;
        }

        return ARCHIVE_OK;
}

static int64_t rar5_seek_data(struct archive_read *a, int64_t offset,
    int whence)
{
        (void) a;
        (void) offset;
        (void) whence;

        /* We're a streaming unpacker, and we don't support seeking. */

        return ARCHIVE_FATAL;
}

static int rar5_cleanup(struct archive_read *a) {
        struct rar5* rar = get_context(a);

        free(rar->cstate.window_buf);
        free(rar->cstate.filtered_buf);

        free(rar->vol.push_buf);

        free_filters(rar);
        cdeque_free(&rar->cstate.filters);

        free(rar);
        a->format->data = NULL;

        return ARCHIVE_OK;
}

static int rar5_capabilities(struct archive_read * a) {
        (void) a;
        return 0;
}

static int rar5_has_encrypted_entries(struct archive_read *_a) {
        (void) _a;

        /* Unsupported for now. */
        return ARCHIVE_READ_FORMAT_ENCRYPTION_UNSUPPORTED;
}

static int rar5_init(struct rar5* rar) {
        ssize_t i;

        memset(rar, 0, sizeof(struct rar5));

        /* Decrypt the magic signature pattern. Check the comment near the
         * `rar5_signature` symbol to read the rationale behind this. */

        if(rar5_signature[0] == 243) {
                for(i = 0; i < rar5_signature_size; i++) {
                        rar5_signature[i] ^= 0xA1;
                }
        }

        if(CDE_OK != cdeque_init(&rar->cstate.filters, 8192))
                return ARCHIVE_FATAL;

        return ARCHIVE_OK;
}

int archive_read_support_format_rar5(struct archive *_a) {
        struct archive_read* ar;
        int ret;
        struct rar5* rar;

        if(ARCHIVE_OK != (ret = get_archive_read(_a, &ar)))
                return ret;

        rar = malloc(sizeof(*rar));
        if(rar == NULL) {
                archive_set_error(&ar->archive, ENOMEM,
                    "Can't allocate rar5 data");
                return ARCHIVE_FATAL;
        }

        if(ARCHIVE_OK != rar5_init(rar)) {
                archive_set_error(&ar->archive, ENOMEM,
                    "Can't allocate rar5 filter buffer");
                return ARCHIVE_FATAL;
        }

        ret = __archive_read_register_format(ar,
            rar,
            "rar5",
            rar5_bid,
            rar5_options,
            rar5_read_header,
            rar5_read_data,
            rar5_read_data_skip,
            rar5_seek_data,
            rar5_cleanup,
            rar5_capabilities,
            rar5_has_encrypted_entries);

        if(ret != ARCHIVE_OK) {
                (void) rar5_cleanup(ar);
        }

        return ret;
}