contrib/xz/src/liblzma/simple/simple_coder.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       simple_coder.c
   4 /// \brief      Wrapper for simple filters
   5 ///
   6 /// Simple filters don't change the size of the data i.e. number of bytes
   7 /// in equals the number of bytes out.
   8 //
   9 //  Author:     Lasse Collin
  10 //
  11 //  This file has been put into the public domain.
  12 //  You can do whatever you want with this file.
  13 //
  14 ///////////////////////////////////////////////////////////////////////////////
  15
  16 #include "simple_private.h"
  17
  18
  19 /// Copied or encodes/decodes more data to out[].
  20 static lzma_ret
  21 copy_or_code(lzma_simple_coder *coder, const lzma_allocator *allocator,
  22                 const uint8_t *restrict in, size_t *restrict in_pos,
  23                 size_t in_size, uint8_t *restrict out,
  24                 size_t *restrict out_pos, size_t out_size, lzma_action action)
  25 {
  26         assert(!coder->end_was_reached);
  27
  28         if (coder->next.code == NULL) {
  29                 lzma_bufcpy(in, in_pos, in_size, out, out_pos, out_size);
  30
  31                 // Check if end of stream was reached.
  32                 if (coder->is_encoder && action == LZMA_FINISH
  33                                 && *in_pos == in_size)
  34                         coder->end_was_reached = true;
  35
  36         } else {
  37                 // Call the next coder in the chain to provide us some data.
  38                 const lzma_ret ret = coder->next.code(
  39                                 coder->next.coder, allocator,
  40                                 in, in_pos, in_size,
  41                                 out, out_pos, out_size, action);
  42
  43                 if (ret == LZMA_STREAM_END) {
  44                         assert(!coder->is_encoder
  45                                         || action == LZMA_FINISH);
  46                         coder->end_was_reached = true;
  47
  48                 } else if (ret != LZMA_OK) {
  49                         return ret;
  50                 }
  51         }
  52
  53         return LZMA_OK;
  54 }
  55
  56
  57 static size_t
  58 call_filter(lzma_simple_coder *coder, uint8_t *buffer, size_t size)
  59 {
  60         const size_t filtered = coder->filter(coder->simple,
  61                         coder->now_pos, coder->is_encoder,
  62                         buffer, size);
  63         coder->now_pos += filtered;
  64         return filtered;
  65 }
  66
  67
  68 static lzma_ret
  69 simple_code(void *coder_ptr, const lzma_allocator *allocator,
  70                 const uint8_t *restrict in, size_t *restrict in_pos,
  71                 size_t in_size, uint8_t *restrict out,
  72                 size_t *restrict out_pos, size_t out_size, lzma_action action)
  73 {
  74         lzma_simple_coder *coder = coder_ptr;
  75
  76         // TODO: Add partial support for LZMA_SYNC_FLUSH. We can support it
  77         // in cases when the filter is able to filter everything. With most
  78         // simple filters it can be done at offset that is a multiple of 2,
  79         // 4, or 16. With x86 filter, it needs good luck, and thus cannot
  80         // be made to work predictably.
  81         if (action == LZMA_SYNC_FLUSH)
  82                 return LZMA_OPTIONS_ERROR;
  83
  84         // Flush already filtered data from coder->buffer[] to out[].
  85         if (coder->pos < coder->filtered) {
  86                 lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
  87                                 out, out_pos, out_size);
  88
  89                 // If we couldn't flush all the filtered data, return to
  90                 // application immediately.
  91                 if (coder->pos < coder->filtered)
  92                         return LZMA_OK;
  93
  94                 if (coder->end_was_reached) {
  95                         assert(coder->filtered == coder->size);
  96                         return LZMA_STREAM_END;
  97                 }
  98         }
  99
 100         // If we get here, there is no filtered data left in the buffer.
 101         coder->filtered = 0;
 102
 103         assert(!coder->end_was_reached);
 104
 105         // If there is more output space left than there is unfiltered data
 106         // in coder->buffer[], flush coder->buffer[] to out[], and copy/code
 107         // more data to out[] hopefully filling it completely. Then filter
 108         // the data in out[]. This step is where most of the data gets
 109         // filtered if the buffer sizes used by the application are reasonable.
 110         const size_t out_avail = out_size - *out_pos;
 111         const size_t buf_avail = coder->size - coder->pos;
 112         if (out_avail > buf_avail || buf_avail == 0) {
 113                 // Store the old position so that we know from which byte
 114                 // to start filtering.
 115                 const size_t out_start = *out_pos;
 116
 117                 // Flush data from coder->buffer[] to out[], but don't reset
 118                 // coder->pos and coder->size yet. This way the coder can be
 119                 // restarted if the next filter in the chain returns e.g.
 120                 // LZMA_MEM_ERROR.
 121                 //
 122                 // Do the memcpy() conditionally because out can be NULL
 123                 // (in which case buf_avail is always 0). Calling memcpy()
 124                 // with a null-pointer is undefined even if the third
 125                 // argument is 0.
 126                 if (buf_avail > 0)
 127                         memcpy(out + *out_pos, coder->buffer + coder->pos,
 128                                         buf_avail);
 129
 130                 *out_pos += buf_avail;
 131
 132                 // Copy/Encode/Decode more data to out[].
 133                 {
 134                         const lzma_ret ret = copy_or_code(coder, allocator,
 135                                         in, in_pos, in_size,
 136                                         out, out_pos, out_size, action);
 137                         assert(ret != LZMA_STREAM_END);
 138                         if (ret != LZMA_OK)
 139                                 return ret;
 140                 }
 141
 142                 // Filter out[].
 143                 const size_t size = *out_pos - out_start;
 144                 const size_t filtered = call_filter(
 145                                 coder, out + out_start, size);
 146
 147                 const size_t unfiltered = size - filtered;
 148                 assert(unfiltered <= coder->allocated / 2);
 149
 150                 // Now we can update coder->pos and coder->size, because
 151                 // the next coder in the chain (if any) was successful.
 152                 coder->pos = 0;
 153                 coder->size = unfiltered;
 154
 155                 if (coder->end_was_reached) {
 156                         // The last byte has been copied to out[] already.
 157                         // They are left as is.
 158                         coder->size = 0;
 159
 160                 } else if (unfiltered > 0) {
 161                         // There is unfiltered data left in out[]. Copy it to
 162                         // coder->buffer[] and rewind *out_pos appropriately.
 163                         *out_pos -= unfiltered;
 164                         memcpy(coder->buffer, out + *out_pos, unfiltered);
 165                 }
 166         } else if (coder->pos > 0) {
 167                 memmove(coder->buffer, coder->buffer + coder->pos, buf_avail);
 168                 coder->size -= coder->pos;
 169                 coder->pos = 0;
 170         }
 171
 172         assert(coder->pos == 0);
 173
 174         // If coder->buffer[] isn't empty, try to fill it by copying/decoding
 175         // more data. Then filter coder->buffer[] and copy the successfully
 176         // filtered data to out[]. It is probable, that some filtered and
 177         // unfiltered data will be left to coder->buffer[].
 178         if (coder->size > 0) {
 179                 {
 180                         const lzma_ret ret = copy_or_code(coder, allocator,
 181                                         in, in_pos, in_size,
 182                                         coder->buffer, &coder->size,
 183                                         coder->allocated, action);
 184                         assert(ret != LZMA_STREAM_END);
 185                         if (ret != LZMA_OK)
 186                                 return ret;
 187                 }
 188
 189                 coder->filtered = call_filter(
 190                                 coder, coder->buffer, coder->size);
 191
 192                 // Everything is considered to be filtered if coder->buffer[]
 193                 // contains the last bytes of the data.
 194                 if (coder->end_was_reached)
 195                         coder->filtered = coder->size;
 196
 197                 // Flush as much as possible.
 198                 lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
 199                                 out, out_pos, out_size);
 200         }
 201
 202         // Check if we got everything done.
 203         if (coder->end_was_reached && coder->pos == coder->size)
 204                 return LZMA_STREAM_END;
 205
 206         return LZMA_OK;
 207 }
 208
 209
 210 static void
 211 simple_coder_end(void *coder_ptr, const lzma_allocator *allocator)
 212 {
 213         lzma_simple_coder *coder = coder_ptr;
 214         lzma_next_end(&coder->next, allocator);
 215         lzma_free(coder->simple, allocator);
 216         lzma_free(coder, allocator);
 217         return;
 218 }
 219
 220
 221 static lzma_ret
 222 simple_coder_update(void *coder_ptr, const lzma_allocator *allocator,
 223                 const lzma_filter *filters_null lzma_attribute((__unused__)),
 224                 const lzma_filter *reversed_filters)
 225 {
 226         lzma_simple_coder *coder = coder_ptr;
 227
 228         // No update support, just call the next filter in the chain.
 229         return lzma_next_filter_update(
 230                         &coder->next, allocator, reversed_filters + 1);
 231 }
 232
 233
 234 extern lzma_ret
 235 lzma_simple_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 236                 const lzma_filter_info *filters,
 237                 size_t (*filter)(void *simple, uint32_t now_pos,
 238                         bool is_encoder, uint8_t *buffer, size_t size),
 239                 size_t simple_size, size_t unfiltered_max,
 240                 uint32_t alignment, bool is_encoder)
 241 {
 242         // Allocate memory for the lzma_simple_coder structure if needed.
 243         lzma_simple_coder *coder = next->coder;
 244         if (coder == NULL) {
 245                 // Here we allocate space also for the temporary buffer. We
 246                 // need twice the size of unfiltered_max, because then it
 247                 // is always possible to filter at least unfiltered_max bytes
 248                 // more data in coder->buffer[] if it can be filled completely.
 249                 coder = lzma_alloc(sizeof(lzma_simple_coder)
 250                                 + 2 * unfiltered_max, allocator);
 251                 if (coder == NULL)
 252                         return LZMA_MEM_ERROR;
 253
 254                 next->coder = coder;
 255                 next->code = &simple_code;
 256                 next->end = &simple_coder_end;
 257                 next->update = &simple_coder_update;
 258
 259                 coder->next = LZMA_NEXT_CODER_INIT;
 260                 coder->filter = filter;
 261                 coder->allocated = 2 * unfiltered_max;
 262
 263                 // Allocate memory for filter-specific data structure.
 264                 if (simple_size > 0) {
 265                         coder->simple = lzma_alloc(simple_size, allocator);
 266                         if (coder->simple == NULL)
 267                                 return LZMA_MEM_ERROR;
 268                 } else {
 269                         coder->simple = NULL;
 270                 }
 271         }
 272
 273         if (filters[0].options != NULL) {
 274                 const lzma_options_bcj *simple = filters[0].options;
 275                 coder->now_pos = simple->start_offset;
 276                 if (coder->now_pos & (alignment - 1))
 277                         return LZMA_OPTIONS_ERROR;
 278         } else {
 279                 coder->now_pos = 0;
 280         }
 281
 282         // Reset variables.
 283         coder->is_encoder = is_encoder;
 284         coder->end_was_reached = false;
 285         coder->pos = 0;
 286         coder->filtered = 0;
 287         coder->size = 0;
 288
 289         return lzma_next_filter_init(&coder->next, allocator, filters + 1);
 290 }