2 * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. The name of the author may not be used to endorse or promote products
13 * derived from this software without specific prior written permission.
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 #ifndef EVENT2_BUFFER_H_INCLUDED_
27 #define EVENT2_BUFFER_H_INCLUDED_
29 /** @file event2/buffer.h
31 Functions for buffering data for network sending or receiving.
33 An evbuffer can be used for preparing data before sending it to
34 the network or conversely for reading data from the network.
35 Evbuffers try to avoid memory copies as much as possible. As a
36 result, evbuffers can be used to pass data around without actually
37 incurring the overhead of copying the data.
39 A new evbuffer can be allocated with evbuffer_new(), and can be
40 freed with evbuffer_free(). Most users will be using evbuffers via
41 the bufferevent interface. To access a bufferevent's evbuffers, use
42 bufferevent_get_input() and bufferevent_get_output().
44 There are several guidelines for using evbuffers.
46 - if you already know how much data you are going to add as a result
47 of calling evbuffer_add() multiple times, it makes sense to use
48 evbuffer_expand() first to make sure that enough memory is allocated
51 - evbuffer_add_buffer() adds the contents of one buffer to the other
52 without incurring any unnecessary memory copies.
54 - evbuffer_add() and evbuffer_add_buffer() do not mix very well:
55 if you use them, you will wind up with fragmented memory in your
58 - For high-performance code, you may want to avoid copying data into and out
59 of buffers. You can skip the copy step by using
60 evbuffer_reserve_space()/evbuffer_commit_space() when writing into a
61 buffer, and evbuffer_peek() when reading.
63 In Libevent 2.0 and later, evbuffers are represented using a linked
64 list of memory chunks, with pointers to the first and last chunk in
67 As the contents of an evbuffer can be stored in multiple different
68 memory blocks, it cannot be accessed directly. Instead, evbuffer_pullup()
69 can be used to force a specified number of bytes to be contiguous. This
70 will cause memory reallocation and memory copies if the data is split
71 across multiple blocks. It is more efficient, however, to use
72 evbuffer_peek() if you don't require that the memory to be contiguous.
75 #include <event2/visibility.h>
81 #include <event2/event-config.h>
83 #ifdef EVENT__HAVE_SYS_TYPES_H
84 #include <sys/types.h>
86 #ifdef EVENT__HAVE_SYS_UIO_H
89 #include <event2/util.h>
92 An evbuffer is an opaque data type for efficiently buffering data to be
93 sent or received on the network.
95 @see event2/event.h for more information
98 #ifdef EVENT_IN_DOXYGEN_
104 Pointer to a position within an evbuffer.
106 Used when repeatedly searching through a buffer. Calling any function
107 that modifies or re-packs the buffer contents may invalidate all
108 evbuffer_ptrs for that buffer. Do not modify or contruct these values
109 except with evbuffer_ptr_set.
111 An evbuffer_ptr can represent any position from the start of a buffer up
112 to a position immediately after the end of a buffer.
114 @see evbuffer_ptr_set()
116 struct evbuffer_ptr {
119 /* Do not alter or rely on the values of fields: they are for internal
127 /** Describes a single extent of memory inside an evbuffer. Used for
128 direct-access functions.
130 @see evbuffer_reserve_space, evbuffer_commit_space, evbuffer_peek
132 #ifdef EVENT__HAVE_SYS_UIO_H
133 #define evbuffer_iovec iovec
134 /* Internal use -- defined only if we are using the native struct iovec */
135 #define EVBUFFER_IOVEC_IS_NATIVE_
137 struct evbuffer_iovec {
138 /** The start of the extent of memory. */
140 /** The length of the extent of memory. */
146 Allocate storage for a new evbuffer.
148 @return a pointer to a newly allocated evbuffer struct, or NULL if an error
152 struct evbuffer *evbuffer_new(void);
154 Deallocate storage for an evbuffer.
156 @param buf pointer to the evbuffer to be freed
159 void evbuffer_free(struct evbuffer *buf);
162 Enable locking on an evbuffer so that it can safely be used by multiple
163 threads at the same time.
165 NOTE: when locking is enabled, the lock will be held when callbacks are
166 invoked. This could result in deadlock if you aren't careful. Plan
169 @param buf An evbuffer to make lockable.
170 @param lock A lock object, or NULL if we should allocate our own.
171 @return 0 on success, -1 on failure.
174 int evbuffer_enable_locking(struct evbuffer *buf, void *lock);
177 Acquire the lock on an evbuffer. Has no effect if locking was not enabled
178 with evbuffer_enable_locking.
181 void evbuffer_lock(struct evbuffer *buf);
184 Release the lock on an evbuffer. Has no effect if locking was not enabled
185 with evbuffer_enable_locking.
188 void evbuffer_unlock(struct evbuffer *buf);
191 /** If this flag is set, then we will not use evbuffer_peek(),
192 * evbuffer_remove(), evbuffer_remove_buffer(), and so on to read bytes
193 * from this buffer: we'll only take bytes out of this buffer by
194 * writing them to the network (as with evbuffer_write_atmost), by
195 * removing them without observing them (as with evbuffer_drain),
196 * or by copying them all out at once (as with evbuffer_add_buffer).
198 * Using this option allows the implementation to use sendfile-based
199 * operations for evbuffer_add_file(); see that function for more
202 * This flag is on by default for bufferevents that can take advantage
203 * of it; you should never actually need to set it on a bufferevent's
206 #define EVBUFFER_FLAG_DRAINS_TO_FD 1
208 /** Change the flags that are set for an evbuffer by adding more.
210 * @param buffer the evbuffer that the callback is watching.
211 * @param cb the callback whose status we want to change.
212 * @param flags One or more EVBUFFER_FLAG_* options
213 * @return 0 on success, -1 on failure.
216 int evbuffer_set_flags(struct evbuffer *buf, ev_uint64_t flags);
217 /** Change the flags that are set for an evbuffer by removing some.
219 * @param buffer the evbuffer that the callback is watching.
220 * @param cb the callback whose status we want to change.
221 * @param flags One or more EVBUFFER_FLAG_* options
222 * @return 0 on success, -1 on failure.
225 int evbuffer_clear_flags(struct evbuffer *buf, ev_uint64_t flags);
228 Returns the total number of bytes stored in the evbuffer
230 @param buf pointer to the evbuffer
231 @return the number of bytes stored in the evbuffer
234 size_t evbuffer_get_length(const struct evbuffer *buf);
237 Returns the number of contiguous available bytes in the first buffer chain.
239 This is useful when processing data that might be split into multiple
240 chains, or that might all be in the first chain. Calls to
241 evbuffer_pullup() that cause reallocation and copying of data can thus be
244 @param buf pointer to the evbuffer
245 @return 0 if no data is available, otherwise the number of available bytes
246 in the first buffer chain.
249 size_t evbuffer_get_contiguous_space(const struct evbuffer *buf);
252 Expands the available space in an evbuffer.
254 Expands the available space in the evbuffer to at least datlen, so that
255 appending datlen additional bytes will not require any new allocations.
257 @param buf the evbuffer to be expanded
258 @param datlen the new minimum length requirement
259 @return 0 if successful, or -1 if an error occurred
262 int evbuffer_expand(struct evbuffer *buf, size_t datlen);
265 Reserves space in the last chain or chains of an evbuffer.
267 Makes space available in the last chain or chains of an evbuffer that can
268 be arbitrarily written to by a user. The space does not become
269 available for reading until it has been committed with
270 evbuffer_commit_space().
272 The space is made available as one or more extents, represented by
273 an initial pointer and a length. You can force the memory to be
274 available as only one extent. Allowing more extents, however, makes the
275 function more efficient.
277 Multiple subsequent calls to this function will make the same space
278 available until evbuffer_commit_space() has been called.
280 It is an error to do anything that moves around the buffer's internal
281 memory structures before committing the space.
283 NOTE: The code currently does not ever use more than two extents.
284 This may change in future versions.
286 @param buf the evbuffer in which to reserve space.
287 @param size how much space to make available, at minimum. The
288 total length of the extents may be greater than the requested
290 @param vec an array of one or more evbuffer_iovec structures to
291 hold pointers to the reserved extents of memory.
292 @param n_vec The length of the vec array. Must be at least 1;
294 @return the number of provided extents, or -1 on error.
295 @see evbuffer_commit_space()
299 evbuffer_reserve_space(struct evbuffer *buf, ev_ssize_t size,
300 struct evbuffer_iovec *vec, int n_vec);
303 Commits previously reserved space.
305 Commits some of the space previously reserved with
306 evbuffer_reserve_space(). It then becomes available for reading.
308 This function may return an error if the pointer in the extents do
309 not match those returned from evbuffer_reserve_space, or if data
310 has been added to the buffer since the space was reserved.
312 If you want to commit less data than you got reserved space for,
313 modify the iov_len pointer of the appropriate extent to a smaller
314 value. Note that you may have received more space than you
315 requested if it was available!
317 @param buf the evbuffer in which to reserve space.
318 @param vec one or two extents returned by evbuffer_reserve_space.
319 @param n_vecs the number of extents.
320 @return 0 on success, -1 on error
321 @see evbuffer_reserve_space()
324 int evbuffer_commit_space(struct evbuffer *buf,
325 struct evbuffer_iovec *vec, int n_vecs);
328 Append data to the end of an evbuffer.
330 @param buf the evbuffer to be appended to
331 @param data pointer to the beginning of the data buffer
332 @param datlen the number of bytes to be copied from the data buffer
333 @return 0 on success, -1 on failure.
336 int evbuffer_add(struct evbuffer *buf, const void *data, size_t datlen);
340 Read data from an evbuffer and drain the bytes read.
342 If more bytes are requested than are available in the evbuffer, we
343 only extract as many bytes as were available.
345 @param buf the evbuffer to be read from
346 @param data the destination buffer to store the result
347 @param datlen the maximum size of the destination buffer
348 @return the number of bytes read, or -1 if we can't drain the buffer.
351 int evbuffer_remove(struct evbuffer *buf, void *data, size_t datlen);
354 Read data from an evbuffer, and leave the buffer unchanged.
356 If more bytes are requested than are available in the evbuffer, we
357 only extract as many bytes as were available.
359 @param buf the evbuffer to be read from
360 @param data_out the destination buffer to store the result
361 @param datlen the maximum size of the destination buffer
362 @return the number of bytes read, or -1 if we can't drain the buffer.
365 ev_ssize_t evbuffer_copyout(struct evbuffer *buf, void *data_out, size_t datlen);
368 Read data from the middle of an evbuffer, and leave the buffer unchanged.
370 If more bytes are requested than are available in the evbuffer, we
371 only extract as many bytes as were available.
373 @param buf the evbuffer to be read from
374 @param pos the position to start reading from
375 @param data_out the destination buffer to store the result
376 @param datlen the maximum size of the destination buffer
377 @return the number of bytes read, or -1 if we can't drain the buffer.
380 ev_ssize_t evbuffer_copyout_from(struct evbuffer *buf, const struct evbuffer_ptr *pos, void *data_out, size_t datlen);
383 Read data from an evbuffer into another evbuffer, draining
384 the bytes from the source buffer. This function avoids copy
385 operations to the extent possible.
387 If more bytes are requested than are available in src, the src
388 buffer is drained completely.
390 @param src the evbuffer to be read from
391 @param dst the destination evbuffer to store the result into
392 @param datlen the maximum numbers of bytes to transfer
393 @return the number of bytes read
396 int evbuffer_remove_buffer(struct evbuffer *src, struct evbuffer *dst,
399 /** Used to tell evbuffer_readln what kind of line-ending to look for.
401 enum evbuffer_eol_style {
402 /** Any sequence of CR and LF characters is acceptable as an
405 * Note that this style can produce ambiguous results: the
406 * sequence "CRLF" will be treated as a single EOL if it is
407 * all in the buffer at once, but if you first read a CR from
408 * the network and later read an LF from the network, it will
409 * be treated as two EOLs.
412 /** An EOL is an LF, optionally preceded by a CR. This style is
413 * most useful for implementing text-based internet protocols. */
415 /** An EOL is a CR followed by an LF. */
416 EVBUFFER_EOL_CRLF_STRICT,
417 /** An EOL is a LF. */
419 /** An EOL is a NUL character (that is, a single byte with value 0) */
424 * Read a single line from an evbuffer.
426 * Reads a line terminated by an EOL as determined by the evbuffer_eol_style
427 * argument. Returns a newly allocated nul-terminated string; the caller must
428 * free the returned value. The EOL is not included in the returned string.
430 * @param buffer the evbuffer to read from
431 * @param n_read_out if non-NULL, points to a size_t that is set to the
432 * number of characters in the returned string. This is useful for
433 * strings that can contain NUL characters.
434 * @param eol_style the style of line-ending to use.
435 * @return pointer to a single line, or NULL if an error occurred
438 char *evbuffer_readln(struct evbuffer *buffer, size_t *n_read_out,
439 enum evbuffer_eol_style eol_style);
442 Move all data from one evbuffer into another evbuffer.
444 This is a destructive add. The data from one buffer moves into
445 the other buffer. However, no unnecessary memory copies occur.
447 @param outbuf the output buffer
448 @param inbuf the input buffer
449 @return 0 if successful, or -1 if an error occurred
451 @see evbuffer_remove_buffer()
454 int evbuffer_add_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf);
457 Copy data from one evbuffer into another evbuffer.
459 This is a non-destructive add. The data from one buffer is copied
460 into the other buffer. However, no unnecessary memory copies occur.
462 Note that buffers already containing buffer references can't be added
465 @param outbuf the output buffer
466 @param inbuf the input buffer
467 @return 0 if successful, or -1 if an error occurred
470 int evbuffer_add_buffer_reference(struct evbuffer *outbuf,
471 struct evbuffer *inbuf);
474 A cleanup function for a piece of memory added to an evbuffer by
477 @see evbuffer_add_reference()
479 typedef void (*evbuffer_ref_cleanup_cb)(const void *data,
480 size_t datalen, void *extra);
483 Reference memory into an evbuffer without copying.
485 The memory needs to remain valid until all the added data has been
486 read. This function keeps just a reference to the memory without
487 actually incurring the overhead of a copy.
489 @param outbuf the output buffer
490 @param data the memory to reference
491 @param datlen how memory to reference
492 @param cleanupfn callback to be invoked when the memory is no longer
493 referenced by this evbuffer.
494 @param cleanupfn_arg optional argument to the cleanup callback
495 @return 0 if successful, or -1 if an error occurred
498 int evbuffer_add_reference(struct evbuffer *outbuf,
499 const void *data, size_t datlen,
500 evbuffer_ref_cleanup_cb cleanupfn, void *cleanupfn_arg);
503 Copy data from a file into the evbuffer for writing to a socket.
505 This function avoids unnecessary data copies between userland and
506 kernel. If sendfile is available and the EVBUFFER_FLAG_DRAINS_TO_FD
507 flag is set, it uses those functions. Otherwise, it tries to use
508 mmap (or CreateFileMapping on Windows).
510 The function owns the resulting file descriptor and will close it
511 when finished transferring data.
513 The results of using evbuffer_remove() or evbuffer_pullup() on
514 evbuffers whose data was added using this function are undefined.
516 For more fine-grained control, use evbuffer_add_file_segment.
518 @param outbuf the output buffer
519 @param fd the file descriptor
520 @param offset the offset from which to read data
521 @param length how much data to read, or -1 to read as much as possible.
522 (-1 requires that 'fd' support fstat.)
523 @return 0 if successful, or -1 if an error occurred
527 int evbuffer_add_file(struct evbuffer *outbuf, int fd, ev_off_t offset,
531 An evbuffer_file_segment holds a reference to a range of a file --
532 possibly the whole file! -- for use in writing from an evbuffer to a
533 socket. It could be implemented with mmap, sendfile, splice, or (if all
534 else fails) by just pulling all the data into RAM. A single
535 evbuffer_file_segment can be added more than once, and to more than one
538 struct evbuffer_file_segment;
541 Flag for creating evbuffer_file_segment: If this flag is set, then when
542 the evbuffer_file_segment is freed and no longer in use by any
543 evbuffer, the underlying fd is closed.
545 #define EVBUF_FS_CLOSE_ON_FREE 0x01
547 Flag for creating evbuffer_file_segment: Disable memory-map based
550 #define EVBUF_FS_DISABLE_MMAP 0x02
552 Flag for creating evbuffer_file_segment: Disable direct fd-to-fd
553 implementations (including sendfile and splice).
555 You might want to use this option if data needs to be taken from the
556 evbuffer by any means other than writing it to the network: the sendfile
557 backend is fast, but it only works for sending files directly to the
560 #define EVBUF_FS_DISABLE_SENDFILE 0x04
562 Flag for creating evbuffer_file_segment: Do not allocate a lock for this
563 segment. If this option is set, then neither the segment nor any
564 evbuffer it is added to may ever be accessed from more than one thread
567 #define EVBUF_FS_DISABLE_LOCKING 0x08
570 A cleanup function for a evbuffer_file_segment added to an evbuffer
573 typedef void (*evbuffer_file_segment_cleanup_cb)(
574 struct evbuffer_file_segment const* seg, int flags, void* arg);
577 Create and return a new evbuffer_file_segment for reading data from a
578 file and sending it out via an evbuffer.
580 This function avoids unnecessary data copies between userland and
581 kernel. Where available, it uses sendfile or splice.
583 The file descriptor must not be closed so long as any evbuffer is using
586 The results of using evbuffer_remove() or evbuffer_pullup() or any other
587 function that reads bytes from an evbuffer on any evbuffer containing
588 the newly returned segment are undefined, unless you pass the
589 EVBUF_FS_DISABLE_SENDFILE flag to this function.
591 @param fd an open file to read from.
592 @param offset an index within the file at which to start reading
593 @param length how much data to read, or -1 to read as much as possible.
594 (-1 requires that 'fd' support fstat.)
595 @param flags any number of the EVBUF_FS_* flags
596 @return a new evbuffer_file_segment, or NULL on failure.
599 struct evbuffer_file_segment *evbuffer_file_segment_new(
600 int fd, ev_off_t offset, ev_off_t length, unsigned flags);
603 Free an evbuffer_file_segment
605 It is safe to call this function even if the segment has been added to
606 one or more evbuffers. The evbuffer_file_segment will not be freed
607 until no more references to it exist.
610 void evbuffer_file_segment_free(struct evbuffer_file_segment *seg);
613 Add cleanup callback and argument for the callback to an
614 evbuffer_file_segment.
616 The cleanup callback will be invoked when no more references to the
617 evbuffer_file_segment exist.
620 void evbuffer_file_segment_add_cleanup_cb(struct evbuffer_file_segment *seg,
621 evbuffer_file_segment_cleanup_cb cb, void* arg);
624 Insert some or all of an evbuffer_file_segment at the end of an evbuffer
626 Note that the offset and length parameters of this function have a
627 different meaning from those provided to evbuffer_file_segment_new: When
628 you create the segment, the offset is the offset _within the file_, and
629 the length is the length _of the segment_, whereas when you add a
630 segment to an evbuffer, the offset is _within the segment_ and the
631 length is the length of the _part of the segment you want to use.
633 In other words, if you have a 10 KiB file, and you create an
634 evbuffer_file_segment for it with offset 20 and length 1000, it will
635 refer to bytes 20..1019 inclusive. If you then pass this segment to
636 evbuffer_add_file_segment and specify an offset of 20 and a length of
637 50, you will be adding bytes 40..99 inclusive.
639 @param buf the evbuffer to append to
640 @param seg the segment to add
641 @param offset the offset within the segment to start from
642 @param length the amount of data to add, or -1 to add it all.
643 @return 0 on success, -1 on failure.
646 int evbuffer_add_file_segment(struct evbuffer *buf,
647 struct evbuffer_file_segment *seg, ev_off_t offset, ev_off_t length);
650 Append a formatted string to the end of an evbuffer.
652 The string is formated as printf.
654 @param buf the evbuffer that will be appended to
655 @param fmt a format string
656 @param ... arguments that will be passed to printf(3)
657 @return The number of bytes added if successful, or -1 if an error occurred.
659 @see evutil_printf(), evbuffer_add_vprintf()
662 int evbuffer_add_printf(struct evbuffer *buf, const char *fmt, ...)
664 __attribute__((format(printf, 2, 3)))
669 Append a va_list formatted string to the end of an evbuffer.
671 @param buf the evbuffer that will be appended to
672 @param fmt a format string
673 @param ap a varargs va_list argument array that will be passed to vprintf(3)
674 @return The number of bytes added if successful, or -1 if an error occurred.
677 int evbuffer_add_vprintf(struct evbuffer *buf, const char *fmt, va_list ap)
679 __attribute__((format(printf, 2, 0)))
685 Remove a specified number of bytes data from the beginning of an evbuffer.
687 @param buf the evbuffer to be drained
688 @param len the number of bytes to drain from the beginning of the buffer
689 @return 0 on success, -1 on failure.
692 int evbuffer_drain(struct evbuffer *buf, size_t len);
696 Write the contents of an evbuffer to a file descriptor.
698 The evbuffer will be drained after the bytes have been successfully written.
700 @param buffer the evbuffer to be written and drained
701 @param fd the file descriptor to be written to
702 @return the number of bytes written, or -1 if an error occurred
706 int evbuffer_write(struct evbuffer *buffer, evutil_socket_t fd);
709 Write some of the contents of an evbuffer to a file descriptor.
711 The evbuffer will be drained after the bytes have been successfully written.
713 @param buffer the evbuffer to be written and drained
714 @param fd the file descriptor to be written to
715 @param howmuch the largest allowable number of bytes to write, or -1
716 to write as many bytes as we can.
717 @return the number of bytes written, or -1 if an error occurred
721 int evbuffer_write_atmost(struct evbuffer *buffer, evutil_socket_t fd,
725 Read from a file descriptor and store the result in an evbuffer.
727 @param buffer the evbuffer to store the result
728 @param fd the file descriptor to read from
729 @param howmuch the number of bytes to be read
730 @return the number of bytes read, or -1 if an error occurred
731 @see evbuffer_write()
734 int evbuffer_read(struct evbuffer *buffer, evutil_socket_t fd, int howmuch);
737 Search for a string within an evbuffer.
739 @param buffer the evbuffer to be searched
740 @param what the string to be searched for
741 @param len the length of the search string
742 @param start NULL or a pointer to a valid struct evbuffer_ptr.
743 @return a struct evbuffer_ptr whose 'pos' field has the offset of the
744 first occurrence of the string in the buffer after 'start'. The 'pos'
745 field of the result is -1 if the string was not found.
748 struct evbuffer_ptr evbuffer_search(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start);
751 Search for a string within part of an evbuffer.
753 @param buffer the evbuffer to be searched
754 @param what the string to be searched for
755 @param len the length of the search string
756 @param start NULL or a pointer to a valid struct evbuffer_ptr that
757 indicates where we should start searching.
758 @param end NULL or a pointer to a valid struct evbuffer_ptr that
759 indicates where we should stop searching.
760 @return a struct evbuffer_ptr whose 'pos' field has the offset of the
761 first occurrence of the string in the buffer after 'start'. The 'pos'
762 field of the result is -1 if the string was not found.
765 struct evbuffer_ptr evbuffer_search_range(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start, const struct evbuffer_ptr *end);
768 Defines how to adjust an evbuffer_ptr by evbuffer_ptr_set()
770 @see evbuffer_ptr_set() */
771 enum evbuffer_ptr_how {
772 /** Sets the pointer to the position; can be called on with an
773 uninitialized evbuffer_ptr. */
775 /** Advances the pointer by adding to the current position. */
780 Sets the search pointer in the buffer to position.
782 There are two ways to use this function: you can call
783 evbuffer_ptr_set(buf, &pos, N, EVBUFFER_PTR_SET)
784 to move 'pos' to a position 'N' bytes after the start of the buffer, or
785 evbuffer_ptr_set(buf, &pos, N, EVBUFFER_PTR_ADD)
786 to move 'pos' forward by 'N' bytes.
788 If evbuffer_ptr is not initialized, this function can only be called
789 with EVBUFFER_PTR_SET.
791 An evbuffer_ptr can represent any position from the start of the buffer to
792 a position immediately after the end of the buffer.
794 @param buffer the evbuffer to be search
795 @param ptr a pointer to a struct evbuffer_ptr
796 @param position the position at which to start the next search
797 @param how determines how the pointer should be manipulated.
798 @returns 0 on success or -1 otherwise
802 evbuffer_ptr_set(struct evbuffer *buffer, struct evbuffer_ptr *ptr,
803 size_t position, enum evbuffer_ptr_how how);
806 Search for an end-of-line string within an evbuffer.
808 @param buffer the evbuffer to be searched
809 @param start NULL or a pointer to a valid struct evbuffer_ptr to start
811 @param eol_len_out If non-NULL, the pointed-to value will be set to
812 the length of the end-of-line string.
813 @param eol_style The kind of EOL to look for; see evbuffer_readln() for
815 @return a struct evbuffer_ptr whose 'pos' field has the offset of the
816 first occurrence EOL in the buffer after 'start'. The 'pos'
817 field of the result is -1 if the string was not found.
820 struct evbuffer_ptr evbuffer_search_eol(struct evbuffer *buffer,
821 struct evbuffer_ptr *start, size_t *eol_len_out,
822 enum evbuffer_eol_style eol_style);
824 /** Function to peek at data inside an evbuffer without removing it or
827 Pointers to the data are returned by filling the 'vec_out' array
828 with pointers to one or more extents of data inside the buffer.
830 The total data in the extents that you get back may be more than
831 you requested (if there is more data last extent than you asked
832 for), or less (if you do not provide enough evbuffer_iovecs, or if
833 the buffer does not have as much data as you asked to see).
835 @param buffer the evbuffer to peek into,
836 @param len the number of bytes to try to peek. If len is negative, we
837 will try to fill as much of vec_out as we can. If len is negative
838 and vec_out is not provided, we return the number of evbuffer_iovecs
839 that would be needed to get all the data in the buffer.
840 @param start_at an evbuffer_ptr indicating the point at which we
841 should start looking for data. NULL means, "At the start of the
843 @param vec_out an array of evbuffer_iovec
844 @param n_vec the length of vec_out. If 0, we only count how many
845 extents would be necessary to point to the requested amount of
847 @return The number of extents needed. This may be less than n_vec
848 if we didn't need all the evbuffer_iovecs we were given, or more
849 than n_vec if we would need more to return all the data that was
853 int evbuffer_peek(struct evbuffer *buffer, ev_ssize_t len,
854 struct evbuffer_ptr *start_at,
855 struct evbuffer_iovec *vec_out, int n_vec);
858 /** Structure passed to an evbuffer_cb_func evbuffer callback
860 @see evbuffer_cb_func, evbuffer_add_cb()
862 struct evbuffer_cb_info {
863 /** The number of bytes in this evbuffer when callbacks were last
866 /** The number of bytes added since callbacks were last invoked. */
868 /** The number of bytes removed since callbacks were last invoked. */
872 /** Type definition for a callback that is invoked whenever data is added or
873 removed from an evbuffer.
875 An evbuffer may have one or more callbacks set at a time. The order
876 in which they are executed is undefined.
878 A callback function may add more callbacks, or remove itself from the
879 list of callbacks, or add or remove data from the buffer. It may not
880 remove another callback from the list.
882 If a callback adds or removes data from the buffer or from another
883 buffer, this can cause a recursive invocation of your callback or
884 other callbacks. If you ask for an infinite loop, you might just get
887 @param buffer the buffer whose size has changed
888 @param info a structure describing how the buffer changed.
889 @param arg a pointer to user data
891 typedef void (*evbuffer_cb_func)(struct evbuffer *buffer, const struct evbuffer_cb_info *info, void *arg);
893 struct evbuffer_cb_entry;
894 /** Add a new callback to an evbuffer.
896 Subsequent calls to evbuffer_add_cb() add new callbacks. To remove this
897 callback, call evbuffer_remove_cb or evbuffer_remove_cb_entry.
899 @param buffer the evbuffer to be monitored
900 @param cb the callback function to invoke when the evbuffer is modified,
901 or NULL to remove all callbacks.
902 @param cbarg an argument to be provided to the callback function
903 @return a handle to the callback on success, or NULL on failure.
906 struct evbuffer_cb_entry *evbuffer_add_cb(struct evbuffer *buffer, evbuffer_cb_func cb, void *cbarg);
908 /** Remove a callback from an evbuffer, given a handle returned from
911 Calling this function invalidates the handle.
913 @return 0 if a callback was removed, or -1 if no matching callback was
917 int evbuffer_remove_cb_entry(struct evbuffer *buffer,
918 struct evbuffer_cb_entry *ent);
920 /** Remove a callback from an evbuffer, given the function and argument
923 @return 0 if a callback was removed, or -1 if no matching callback was
927 int evbuffer_remove_cb(struct evbuffer *buffer, evbuffer_cb_func cb, void *cbarg);
929 /** If this flag is not set, then a callback is temporarily disabled, and
930 * should not be invoked.
932 * @see evbuffer_cb_set_flags(), evbuffer_cb_clear_flags()
934 #define EVBUFFER_CB_ENABLED 1
936 /** Change the flags that are set for a callback on a buffer by adding more.
938 @param buffer the evbuffer that the callback is watching.
939 @param cb the callback whose status we want to change.
940 @param flags EVBUFFER_CB_ENABLED to re-enable the callback.
941 @return 0 on success, -1 on failure.
944 int evbuffer_cb_set_flags(struct evbuffer *buffer,
945 struct evbuffer_cb_entry *cb, ev_uint32_t flags);
947 /** Change the flags that are set for a callback on a buffer by removing some
949 @param buffer the evbuffer that the callback is watching.
950 @param cb the callback whose status we want to change.
951 @param flags EVBUFFER_CB_ENABLED to disable the callback.
952 @return 0 on success, -1 on failure.
955 int evbuffer_cb_clear_flags(struct evbuffer *buffer,
956 struct evbuffer_cb_entry *cb, ev_uint32_t flags);
959 /** Postpone calling a given callback until unsuspend is called later.
961 This is different from disabling the callback, since the callback will get
962 invoked later if the buffer size changes between now and when we unsuspend
965 @param the buffer that the callback is watching.
966 @param cb the callback we want to suspend.
969 void evbuffer_cb_suspend(struct evbuffer *buffer, struct evbuffer_cb_entry *cb);
970 /** Stop postponing a callback that we postponed with evbuffer_cb_suspend.
972 If data was added to or removed from the buffer while the callback was
973 suspended, the callback will get called once now.
975 @param the buffer that the callback is watching.
976 @param cb the callback we want to stop suspending.
979 void evbuffer_cb_unsuspend(struct evbuffer *buffer, struct evbuffer_cb_entry *cb);
983 Makes the data at the beginning of an evbuffer contiguous.
985 @param buf the evbuffer to make contiguous
986 @param size the number of bytes to make contiguous, or -1 to make the
987 entire buffer contiguous.
988 @return a pointer to the contiguous memory array, or NULL if param size
989 requested more data than is present in the buffer.
993 unsigned char *evbuffer_pullup(struct evbuffer *buf, ev_ssize_t size);
996 Prepends data to the beginning of the evbuffer
998 @param buf the evbuffer to which to prepend data
999 @param data a pointer to the memory to prepend
1000 @param size the number of bytes to prepend
1001 @return 0 if successful, or -1 otherwise
1004 EVENT2_EXPORT_SYMBOL
1005 int evbuffer_prepend(struct evbuffer *buf, const void *data, size_t size);
1008 Prepends all data from the src evbuffer to the beginning of the dst
1011 @param dst the evbuffer to which to prepend data
1012 @param src the evbuffer to prepend; it will be emptied as a result
1013 @return 0 if successful, or -1 otherwise
1015 EVENT2_EXPORT_SYMBOL
1016 int evbuffer_prepend_buffer(struct evbuffer *dst, struct evbuffer* src);
1019 Prevent calls that modify an evbuffer from succeeding. A buffer may
1020 frozen at the front, at the back, or at both the front and the back.
1022 If the front of a buffer is frozen, operations that drain data from
1023 the front of the buffer, or that prepend data to the buffer, will
1024 fail until it is unfrozen. If the back a buffer is frozen, operations
1025 that append data from the buffer will fail until it is unfrozen.
1027 @param buf The buffer to freeze
1028 @param at_front If true, we freeze the front of the buffer. If false,
1030 @return 0 on success, -1 on failure.
1032 EVENT2_EXPORT_SYMBOL
1033 int evbuffer_freeze(struct evbuffer *buf, int at_front);
1035 Re-enable calls that modify an evbuffer.
1037 @param buf The buffer to un-freeze
1038 @param at_front If true, we unfreeze the front of the buffer. If false,
1039 we unfreeze the back.
1040 @return 0 on success, -1 on failure.
1042 EVENT2_EXPORT_SYMBOL
1043 int evbuffer_unfreeze(struct evbuffer *buf, int at_front);
1047 Force all the callbacks on an evbuffer to be run, not immediately after
1048 the evbuffer is altered, but instead from inside the event loop.
1050 This can be used to serialize all the callbacks to a single thread
1053 EVENT2_EXPORT_SYMBOL
1054 int evbuffer_defer_callbacks(struct evbuffer *buffer, struct event_base *base);
1057 Append data from 1 or more iovec's to an evbuffer
1059 Calculates the number of bytes needed for an iovec structure and guarantees
1060 all data will fit into a single chain. Can be used in lieu of functionality
1061 which calls evbuffer_add() constantly before being used to increase
1064 @param buffer the destination buffer
1065 @param vec the source iovec
1066 @param n_vec the number of iovec structures.
1067 @return the number of bytes successfully written to the output buffer.
1069 EVENT2_EXPORT_SYMBOL
1070 size_t evbuffer_add_iovec(struct evbuffer * buffer, struct evbuffer_iovec * vec, int n_vec);
1076 #endif /* EVENT2_BUFFER_H_INCLUDED_ */