libevent (2.1.12)
1 /*
2 * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
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.
14 *
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.
25 */
26 #ifndef EVENT2_BUFFER_H_INCLUDED_
27 #define EVENT2_BUFFER_H_INCLUDED_
28
29 /** @file event2/buffer.h
30
31 Functions for buffering data for network sending or receiving.
32
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.
38
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().
43
44 There are several guidelines for using evbuffers.
45
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
49 before hand.
50
51 - evbuffer_add_buffer() adds the contents of one buffer to the other
52 without incurring any unnecessary memory copies.
53
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
56 buffer.
57
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.
62
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
65 the chain.
66
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.
73 */
74
75 #include <event2/visibility.h>
76
77 #ifdef __cplusplus
78 extern "C" {
79 #endif
80
81 #include <event2/event-config.h>
82 #include <stdarg.h>
83 #ifdef EVENT__HAVE_SYS_TYPES_H
84 #include <sys/types.h>
85 #endif
86 #ifdef EVENT__HAVE_SYS_UIO_H
87 #include <sys/uio.h>
88 #endif
89 #include <event2/util.h>
90
91 /**
92 An evbuffer is an opaque data type for efficiently buffering data to be
93 sent or received on the network.
94
95 @see event2/event.h for more information
96 */
97 struct evbuffer
98 #ifdef EVENT_IN_DOXYGEN_
99 {}
100 #endif
101 ;
102
103 /**
104 Pointer to a position within an evbuffer.
105
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.
110
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.
113
114 @see evbuffer_ptr_set()
115 */
116 struct evbuffer_ptr {
117 ev_ssize_t pos;
118
119 /* Do not alter or rely on the values of fields: they are for internal
120 * use */
121 struct {
122 void *chain;
123 size_t pos_in_chain;
124 } internal_;
125 };
126
127 /** Describes a single extent of memory inside an evbuffer. Used for
128 direct-access functions.
129
130 @see evbuffer_reserve_space, evbuffer_commit_space, evbuffer_peek
131 */
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_
136 #else
137 struct evbuffer_iovec {
138 /** The start of the extent of memory. */
139 void *iov_base;
140 /** The length of the extent of memory. */
141 size_t iov_len;
142 };
143 #endif
144
145 /**
146 Allocate storage for a new evbuffer.
147
148 @return a pointer to a newly allocated evbuffer struct, or NULL if an error
149 occurred
150 */
151 EVENT2_EXPORT_SYMBOL
152 struct evbuffer *evbuffer_new(void);
153 /**
154 Deallocate storage for an evbuffer.
155
156 @param buf pointer to the evbuffer to be freed
157 */
158 EVENT2_EXPORT_SYMBOL
159 void evbuffer_free(struct evbuffer *buf);
160
161 /**
162 Enable locking on an evbuffer so that it can safely be used by multiple
163 threads at the same time.
164
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
167 accordingly!
168
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.
172 */
173 EVENT2_EXPORT_SYMBOL
174 int evbuffer_enable_locking(struct evbuffer *buf, void *lock);
175
176 /**
177 Acquire the lock on an evbuffer. Has no effect if locking was not enabled
178 with evbuffer_enable_locking.
179 */
180 EVENT2_EXPORT_SYMBOL
181 void evbuffer_lock(struct evbuffer *buf);
182
183 /**
184 Release the lock on an evbuffer. Has no effect if locking was not enabled
185 with evbuffer_enable_locking.
186 */
187 EVENT2_EXPORT_SYMBOL
188 void evbuffer_unlock(struct evbuffer *buf);
189
190
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).
197 *
198 * Using this option allows the implementation to use sendfile-based
199 * operations for evbuffer_add_file(); see that function for more
200 * information.
201 *
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
204 * output buffer.
205 */
206 #define EVBUFFER_FLAG_DRAINS_TO_FD 1
207
208 /** Change the flags that are set for an evbuffer by adding more.
209 *
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.
214 */
215 EVENT2_EXPORT_SYMBOL
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.
218 *
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.
223 */
224 EVENT2_EXPORT_SYMBOL
225 int evbuffer_clear_flags(struct evbuffer *buf, ev_uint64_t flags);
226
227 /**
228 Returns the total number of bytes stored in the evbuffer
229
230 @param buf pointer to the evbuffer
231 @return the number of bytes stored in the evbuffer
232 */
233 EVENT2_EXPORT_SYMBOL
234 size_t evbuffer_get_length(const struct evbuffer *buf);
235
236 /**
237 Returns the number of contiguous available bytes in the first buffer chain.
238
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
242 avoided.
243
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.
247 */
248 EVENT2_EXPORT_SYMBOL
249 size_t evbuffer_get_contiguous_space(const struct evbuffer *buf);
250
251 /**
252 Expands the available space in an evbuffer.
253
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.
256
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
260 */
261 EVENT2_EXPORT_SYMBOL
262 int evbuffer_expand(struct evbuffer *buf, size_t datlen);
263
264 /**
265 Reserves space in the last chain or chains of an evbuffer.
266
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().
271
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.
276
277 Multiple subsequent calls to this function will make the same space
278 available until evbuffer_commit_space() has been called.
279
280 It is an error to do anything that moves around the buffer's internal
281 memory structures before committing the space.
282
283 NOTE: The code currently does not ever use more than two extents.
284 This may change in future versions.
285
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
289 length.
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;
293 2 is more efficient.
294 @return the number of provided extents, or -1 on error.
295 @see evbuffer_commit_space()
296 */
297 EVENT2_EXPORT_SYMBOL
298 int
299 evbuffer_reserve_space(struct evbuffer *buf, ev_ssize_t size,
300 struct evbuffer_iovec *vec, int n_vec);
301
302 /**
303 Commits previously reserved space.
304
305 Commits some of the space previously reserved with
306 evbuffer_reserve_space(). It then becomes available for reading.
307
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.
311
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!
316
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()
322 */
323 EVENT2_EXPORT_SYMBOL
324 int evbuffer_commit_space(struct evbuffer *buf,
325 struct evbuffer_iovec *vec, int n_vecs);
326
327 /**
328 Append data to the end of an evbuffer.
329
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.
334 */
335 EVENT2_EXPORT_SYMBOL
336 int evbuffer_add(struct evbuffer *buf, const void *data, size_t datlen);
337
338
339 /**
340 Read data from an evbuffer and drain the bytes read.
341
342 If more bytes are requested than are available in the evbuffer, we
343 only extract as many bytes as were available.
344
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.
349 */
350 EVENT2_EXPORT_SYMBOL
351 int evbuffer_remove(struct evbuffer *buf, void *data, size_t datlen);
352
353 /**
354 Read data from an evbuffer, and leave the buffer unchanged.
355
356 If more bytes are requested than are available in the evbuffer, we
357 only extract as many bytes as were available.
358
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.
363 */
364 EVENT2_EXPORT_SYMBOL
365 ev_ssize_t evbuffer_copyout(struct evbuffer *buf, void *data_out, size_t datlen);
366
367 /**
368 Read data from the middle of an evbuffer, and leave the buffer unchanged.
369
370 If more bytes are requested than are available in the evbuffer, we
371 only extract as many bytes as were available.
372
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.
378 */
379 EVENT2_EXPORT_SYMBOL
380 ev_ssize_t evbuffer_copyout_from(struct evbuffer *buf, const struct evbuffer_ptr *pos, void *data_out, size_t datlen);
381
382 /**
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.
386
387 If more bytes are requested than are available in src, the src
388 buffer is drained completely.
389
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
394 */
395 EVENT2_EXPORT_SYMBOL
396 int evbuffer_remove_buffer(struct evbuffer *src, struct evbuffer *dst,
397 size_t datlen);
398
399 /** Used to tell evbuffer_readln what kind of line-ending to look for.
400 */
401 enum evbuffer_eol_style {
402 /** Any sequence of CR and LF characters is acceptable as an
403 * EOL.
404 *
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.
410 */
411 EVBUFFER_EOL_ANY,
412 /** An EOL is an LF, optionally preceded by a CR. This style is
413 * most useful for implementing text-based internet protocols. */
414 EVBUFFER_EOL_CRLF,
415 /** An EOL is a CR followed by an LF. */
416 EVBUFFER_EOL_CRLF_STRICT,
417 /** An EOL is a LF. */
418 EVBUFFER_EOL_LF,
419 /** An EOL is a NUL character (that is, a single byte with value 0) */
420 EVBUFFER_EOL_NUL
421 };
422
423 /**
424 * Read a single line from an evbuffer.
425 *
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.
429 *
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
436 */
437 EVENT2_EXPORT_SYMBOL
438 char *evbuffer_readln(struct evbuffer *buffer, size_t *n_read_out,
439 enum evbuffer_eol_style eol_style);
440
441 /**
442 Move all data from one evbuffer into another evbuffer.
443
444 This is a destructive add. The data from one buffer moves into
445 the other buffer. However, no unnecessary memory copies occur.
446
447 @param outbuf the output buffer
448 @param inbuf the input buffer
449 @return 0 if successful, or -1 if an error occurred
450
451 @see evbuffer_remove_buffer()
452 */
453 EVENT2_EXPORT_SYMBOL
454 int evbuffer_add_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf);
455
456 /**
457 Copy data from one evbuffer into another evbuffer.
458
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.
461
462 Note that buffers already containing buffer references can't be added
463 to other buffers.
464
465 @param outbuf the output buffer
466 @param inbuf the input buffer
467 @return 0 if successful, or -1 if an error occurred
468 */
469 EVENT2_EXPORT_SYMBOL
470 int evbuffer_add_buffer_reference(struct evbuffer *outbuf,
471 struct evbuffer *inbuf);
472
473 /**
474 A cleanup function for a piece of memory added to an evbuffer by
475 reference.
476
477 @see evbuffer_add_reference()
478 */
479 typedef void (*evbuffer_ref_cleanup_cb)(const void *data,
480 size_t datalen, void *extra);
481
482 /**
483 Reference memory into an evbuffer without copying.
484
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.
488
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
496 */
497 EVENT2_EXPORT_SYMBOL
498 int evbuffer_add_reference(struct evbuffer *outbuf,
499 const void *data, size_t datlen,
500 evbuffer_ref_cleanup_cb cleanupfn, void *cleanupfn_arg);
501
502 /**
503 Copy data from a file into the evbuffer for writing to a socket.
504
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).
509
510 The function owns the resulting file descriptor and will close it
511 when finished transferring data.
512
513 The results of using evbuffer_remove() or evbuffer_pullup() on
514 evbuffers whose data was added using this function are undefined.
515
516 For more fine-grained control, use evbuffer_add_file_segment.
517
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
524 */
525
526 EVENT2_EXPORT_SYMBOL
527 int evbuffer_add_file(struct evbuffer *outbuf, int fd, ev_off_t offset,
528 ev_off_t length);
529
530 /**
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
536 evbuffer.
537 */
538 struct evbuffer_file_segment;
539
540 /**
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.
544 */
545 #define EVBUF_FS_CLOSE_ON_FREE 0x01
546 /**
547 Flag for creating evbuffer_file_segment: Disable memory-map based
548 implementations.
549 */
550 #define EVBUF_FS_DISABLE_MMAP 0x02
551 /**
552 Flag for creating evbuffer_file_segment: Disable direct fd-to-fd
553 implementations (including sendfile and splice).
554
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
558 network.
559 */
560 #define EVBUF_FS_DISABLE_SENDFILE 0x04
561 /**
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
565 at a time.
566 */
567 #define EVBUF_FS_DISABLE_LOCKING 0x08
568
569 /**
570 A cleanup function for a evbuffer_file_segment added to an evbuffer
571 for reference.
572 */
573 typedef void (*evbuffer_file_segment_cleanup_cb)(
574 struct evbuffer_file_segment const* seg, int flags, void* arg);
575
576 /**
577 Create and return a new evbuffer_file_segment for reading data from a
578 file and sending it out via an evbuffer.
579
580 This function avoids unnecessary data copies between userland and
581 kernel. Where available, it uses sendfile or splice.
582
583 The file descriptor must not be closed so long as any evbuffer is using
584 this segment.
585
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.
590
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.
597 **/
598 EVENT2_EXPORT_SYMBOL
599 struct evbuffer_file_segment *evbuffer_file_segment_new(
600 int fd, ev_off_t offset, ev_off_t length, unsigned flags);
601
602 /**
603 Free an evbuffer_file_segment
604
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.
608 */
609 EVENT2_EXPORT_SYMBOL
610 void evbuffer_file_segment_free(struct evbuffer_file_segment *seg);
611
612 /**
613 Add cleanup callback and argument for the callback to an
614 evbuffer_file_segment.
615
616 The cleanup callback will be invoked when no more references to the
617 evbuffer_file_segment exist.
618 **/
619 EVENT2_EXPORT_SYMBOL
620 void evbuffer_file_segment_add_cleanup_cb(struct evbuffer_file_segment *seg,
621 evbuffer_file_segment_cleanup_cb cb, void* arg);
622
623 /**
624 Insert some or all of an evbuffer_file_segment at the end of an evbuffer
625
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.
632
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.
638
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.
644 */
645 EVENT2_EXPORT_SYMBOL
646 int evbuffer_add_file_segment(struct evbuffer *buf,
647 struct evbuffer_file_segment *seg, ev_off_t offset, ev_off_t length);
648
649 /**
650 Append a formatted string to the end of an evbuffer.
651
652 The string is formated as printf.
653
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.
658
659 @see evutil_printf(), evbuffer_add_vprintf()
660 */
661 EVENT2_EXPORT_SYMBOL
662 int evbuffer_add_printf(struct evbuffer *buf, const char *fmt, ...)
663 #ifdef __GNUC__
664 __attribute__((format(printf, 2, 3)))
665 #endif
666 ;
667
668 /**
669 Append a va_list formatted string to the end of an evbuffer.
670
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.
675 */
676 EVENT2_EXPORT_SYMBOL
677 int evbuffer_add_vprintf(struct evbuffer *buf, const char *fmt, va_list ap)
678 #ifdef __GNUC__
679 __attribute__((format(printf, 2, 0)))
680 #endif
681 ;
682
683
684 /**
685 Remove a specified number of bytes data from the beginning of an evbuffer.
686
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.
690 */
691 EVENT2_EXPORT_SYMBOL
692 int evbuffer_drain(struct evbuffer *buf, size_t len);
693
694
695 /**
696 Write the contents of an evbuffer to a file descriptor.
697
698 The evbuffer will be drained after the bytes have been successfully written.
699
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
703 @see evbuffer_read()
704 */
705 EVENT2_EXPORT_SYMBOL
706 int evbuffer_write(struct evbuffer *buffer, evutil_socket_t fd);
707
708 /**
709 Write some of the contents of an evbuffer to a file descriptor.
710
711 The evbuffer will be drained after the bytes have been successfully written.
712
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
718 @see evbuffer_read()
719 */
720 EVENT2_EXPORT_SYMBOL
721 int evbuffer_write_atmost(struct evbuffer *buffer, evutil_socket_t fd,
722 ev_ssize_t howmuch);
723
724 /**
725 Read from a file descriptor and store the result in an evbuffer.
726
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. If the given number is negative
730 or out of maximum bytes per one read, as many bytes as we can will be read.
731 @return the number of bytes read, or -1 if an error occurred
732 @see evbuffer_write()
733 */
734 EVENT2_EXPORT_SYMBOL
735 int evbuffer_read(struct evbuffer *buffer, evutil_socket_t fd, int howmuch);
736
737 /**
738 Search for a string within an evbuffer.
739
740 @param buffer the evbuffer to be searched
741 @param what the string to be searched for
742 @param len the length of the search string
743 @param start NULL or a pointer to a valid struct evbuffer_ptr.
744 @return a struct evbuffer_ptr whose 'pos' field has the offset of the
745 first occurrence of the string in the buffer after 'start'. The 'pos'
746 field of the result is -1 if the string was not found.
747 */
748 EVENT2_EXPORT_SYMBOL
749 struct evbuffer_ptr evbuffer_search(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start);
750
751 /**
752 Search for a string within part of an evbuffer.
753
754 @param buffer the evbuffer to be searched
755 @param what the string to be searched for
756 @param len the length of the search string
757 @param start NULL or a pointer to a valid struct evbuffer_ptr that
758 indicates where we should start searching.
759 @param end NULL or a pointer to a valid struct evbuffer_ptr that
760 indicates where we should stop searching.
761 @return a struct evbuffer_ptr whose 'pos' field has the offset of the
762 first occurrence of the string in the buffer after 'start'. The 'pos'
763 field of the result is -1 if the string was not found.
764 */
765 EVENT2_EXPORT_SYMBOL
766 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);
767
768 /**
769 Defines how to adjust an evbuffer_ptr by evbuffer_ptr_set()
770
771 @see evbuffer_ptr_set() */
772 enum evbuffer_ptr_how {
773 /** Sets the pointer to the position; can be called on with an
774 uninitialized evbuffer_ptr. */
775 EVBUFFER_PTR_SET,
776 /** Advances the pointer by adding to the current position. */
777 EVBUFFER_PTR_ADD
778 };
779
780 /**
781 Sets the search pointer in the buffer to position.
782
783 There are two ways to use this function: you can call
784 evbuffer_ptr_set(buf, &pos, N, EVBUFFER_PTR_SET)
785 to move 'pos' to a position 'N' bytes after the start of the buffer, or
786 evbuffer_ptr_set(buf, &pos, N, EVBUFFER_PTR_ADD)
787 to move 'pos' forward by 'N' bytes.
788
789 If evbuffer_ptr is not initialized, this function can only be called
790 with EVBUFFER_PTR_SET.
791
792 An evbuffer_ptr can represent any position from the start of the buffer to
793 a position immediately after the end of the buffer.
794
795 @param buffer the evbuffer to be search
796 @param ptr a pointer to a struct evbuffer_ptr
797 @param position the position at which to start the next search
798 @param how determines how the pointer should be manipulated.
799 @returns 0 on success or -1 otherwise
800 */
801 EVENT2_EXPORT_SYMBOL
802 int
803 evbuffer_ptr_set(struct evbuffer *buffer, struct evbuffer_ptr *ptr,
804 size_t position, enum evbuffer_ptr_how how);
805
806 /**
807 Search for an end-of-line string within an evbuffer.
808
809 @param buffer the evbuffer to be searched
810 @param start NULL or a pointer to a valid struct evbuffer_ptr to start
811 searching at.
812 @param eol_len_out If non-NULL, the pointed-to value will be set to
813 the length of the end-of-line string.
814 @param eol_style The kind of EOL to look for; see evbuffer_readln() for
815 more information
816 @return a struct evbuffer_ptr whose 'pos' field has the offset of the
817 first occurrence EOL in the buffer after 'start'. The 'pos'
818 field of the result is -1 if the string was not found.
819 */
820 EVENT2_EXPORT_SYMBOL
821 struct evbuffer_ptr evbuffer_search_eol(struct evbuffer *buffer,
822 struct evbuffer_ptr *start, size_t *eol_len_out,
823 enum evbuffer_eol_style eol_style);
824
825 /** Function to peek at data inside an evbuffer without removing it or
826 copying it out.
827
828 Pointers to the data are returned by filling the 'vec_out' array
829 with pointers to one or more extents of data inside the buffer.
830
831 The total data in the extents that you get back may be more than
832 you requested (if there is more data last extent than you asked
833 for), or less (if you do not provide enough evbuffer_iovecs, or if
834 the buffer does not have as much data as you asked to see).
835
836 @param buffer the evbuffer to peek into,
837 @param len the number of bytes to try to peek. If len is negative, we
838 will try to fill as much of vec_out as we can. If len is negative
839 and vec_out is not provided, we return the number of evbuffer_iovecs
840 that would be needed to get all the data in the buffer.
841 @param start_at an evbuffer_ptr indicating the point at which we
842 should start looking for data. NULL means, "At the start of the
843 buffer."
844 @param vec_out an array of evbuffer_iovec
845 @param n_vec the length of vec_out. If 0, we only count how many
846 extents would be necessary to point to the requested amount of
847 data.
848 @return The number of extents needed. This may be less than n_vec
849 if we didn't need all the evbuffer_iovecs we were given, or more
850 than n_vec if we would need more to return all the data that was
851 requested.
852 */
853 EVENT2_EXPORT_SYMBOL
854 int evbuffer_peek(struct evbuffer *buffer, ev_ssize_t len,
855 struct evbuffer_ptr *start_at,
856 struct evbuffer_iovec *vec_out, int n_vec);
857
858
859 /** Structure passed to an evbuffer_cb_func evbuffer callback
860
861 @see evbuffer_cb_func, evbuffer_add_cb()
862 */
863 struct evbuffer_cb_info {
864 /** The number of bytes in this evbuffer when callbacks were last
865 * invoked. */
866 size_t orig_size;
867 /** The number of bytes added since callbacks were last invoked. */
868 size_t n_added;
869 /** The number of bytes removed since callbacks were last invoked. */
870 size_t n_deleted;
871 };
872
873 /** Type definition for a callback that is invoked whenever data is added or
874 removed from an evbuffer.
875
876 An evbuffer may have one or more callbacks set at a time. The order
877 in which they are executed is undefined.
878
879 A callback function may add more callbacks, or remove itself from the
880 list of callbacks, or add or remove data from the buffer. It may not
881 remove another callback from the list.
882
883 If a callback adds or removes data from the buffer or from another
884 buffer, this can cause a recursive invocation of your callback or
885 other callbacks. If you ask for an infinite loop, you might just get
886 one: watch out!
887
888 @param buffer the buffer whose size has changed
889 @param info a structure describing how the buffer changed.
890 @param arg a pointer to user data
891 */
892 typedef void (*evbuffer_cb_func)(struct evbuffer *buffer, const struct evbuffer_cb_info *info, void *arg);
893
894 struct evbuffer_cb_entry;
895 /** Add a new callback to an evbuffer.
896
897 Subsequent calls to evbuffer_add_cb() add new callbacks. To remove this
898 callback, call evbuffer_remove_cb or evbuffer_remove_cb_entry.
899
900 @param buffer the evbuffer to be monitored
901 @param cb the callback function to invoke when the evbuffer is modified,
902 or NULL to remove all callbacks.
903 @param cbarg an argument to be provided to the callback function
904 @return a handle to the callback on success, or NULL on failure.
905 */
906 EVENT2_EXPORT_SYMBOL
907 struct evbuffer_cb_entry *evbuffer_add_cb(struct evbuffer *buffer, evbuffer_cb_func cb, void *cbarg);
908
909 /** Remove a callback from an evbuffer, given a handle returned from
910 evbuffer_add_cb.
911
912 Calling this function invalidates the handle.
913
914 @return 0 if a callback was removed, or -1 if no matching callback was
915 found.
916 */
917 EVENT2_EXPORT_SYMBOL
918 int evbuffer_remove_cb_entry(struct evbuffer *buffer,
919 struct evbuffer_cb_entry *ent);
920
921 /** Remove a callback from an evbuffer, given the function and argument
922 used to add it.
923
924 @return 0 if a callback was removed, or -1 if no matching callback was
925 found.
926 */
927 EVENT2_EXPORT_SYMBOL
928 int evbuffer_remove_cb(struct evbuffer *buffer, evbuffer_cb_func cb, void *cbarg);
929
930 /** If this flag is not set, then a callback is temporarily disabled, and
931 * should not be invoked.
932 *
933 * @see evbuffer_cb_set_flags(), evbuffer_cb_clear_flags()
934 */
935 #define EVBUFFER_CB_ENABLED 1
936
937 /** Change the flags that are set for a callback on a buffer by adding more.
938
939 @param buffer the evbuffer that the callback is watching.
940 @param cb the callback whose status we want to change.
941 @param flags EVBUFFER_CB_ENABLED to re-enable the callback.
942 @return 0 on success, -1 on failure.
943 */
944 EVENT2_EXPORT_SYMBOL
945 int evbuffer_cb_set_flags(struct evbuffer *buffer,
946 struct evbuffer_cb_entry *cb, ev_uint32_t flags);
947
948 /** Change the flags that are set for a callback on a buffer by removing some
949
950 @param buffer the evbuffer that the callback is watching.
951 @param cb the callback whose status we want to change.
952 @param flags EVBUFFER_CB_ENABLED to disable the callback.
953 @return 0 on success, -1 on failure.
954 */
955 EVENT2_EXPORT_SYMBOL
956 int evbuffer_cb_clear_flags(struct evbuffer *buffer,
957 struct evbuffer_cb_entry *cb, ev_uint32_t flags);
958
959 #if 0
960 /** Postpone calling a given callback until unsuspend is called later.
961
962 This is different from disabling the callback, since the callback will get
963 invoked later if the buffer size changes between now and when we unsuspend
964 it.
965
966 @param the buffer that the callback is watching.
967 @param cb the callback we want to suspend.
968 */
969 EVENT2_EXPORT_SYMBOL
970 void evbuffer_cb_suspend(struct evbuffer *buffer, struct evbuffer_cb_entry *cb);
971 /** Stop postponing a callback that we postponed with evbuffer_cb_suspend.
972
973 If data was added to or removed from the buffer while the callback was
974 suspended, the callback will get called once now.
975
976 @param the buffer that the callback is watching.
977 @param cb the callback we want to stop suspending.
978 */
979 EVENT2_EXPORT_SYMBOL
980 void evbuffer_cb_unsuspend(struct evbuffer *buffer, struct evbuffer_cb_entry *cb);
981 #endif
982
983 /**
984 Makes the data at the beginning of an evbuffer contiguous.
985
986 @param buf the evbuffer to make contiguous
987 @param size the number of bytes to make contiguous, or -1 to make the
988 entire buffer contiguous.
989 @return a pointer to the contiguous memory array, or NULL if param size
990 requested more data than is present in the buffer.
991 */
992
993 EVENT2_EXPORT_SYMBOL
994 unsigned char *evbuffer_pullup(struct evbuffer *buf, ev_ssize_t size);
995
996 /**
997 Prepends data to the beginning of the evbuffer
998
999 @param buf the evbuffer to which to prepend data
1000 @param data a pointer to the memory to prepend
1001 @param size the number of bytes to prepend
1002 @return 0 if successful, or -1 otherwise
1003 */
1004
1005 EVENT2_EXPORT_SYMBOL
1006 int evbuffer_prepend(struct evbuffer *buf, const void *data, size_t size);
1007
1008 /**
1009 Prepends all data from the src evbuffer to the beginning of the dst
1010 evbuffer.
1011
1012 @param dst the evbuffer to which to prepend data
1013 @param src the evbuffer to prepend; it will be emptied as a result
1014 @return 0 if successful, or -1 otherwise
1015 */
1016 EVENT2_EXPORT_SYMBOL
1017 int evbuffer_prepend_buffer(struct evbuffer *dst, struct evbuffer* src);
1018
1019 /**
1020 Prevent calls that modify an evbuffer from succeeding. A buffer may
1021 frozen at the front, at the back, or at both the front and the back.
1022
1023 If the front of a buffer is frozen, operations that drain data from
1024 the front of the buffer, or that prepend data to the buffer, will
1025 fail until it is unfrozen. If the back a buffer is frozen, operations
1026 that append data from the buffer will fail until it is unfrozen.
1027
1028 @param buf The buffer to freeze
1029 @param at_front If true, we freeze the front of the buffer. If false,
1030 we freeze the back.
1031 @return 0 on success, -1 on failure.
1032 */
1033 EVENT2_EXPORT_SYMBOL
1034 int evbuffer_freeze(struct evbuffer *buf, int at_front);
1035 /**
1036 Re-enable calls that modify an evbuffer.
1037
1038 @param buf The buffer to un-freeze
1039 @param at_front If true, we unfreeze the front of the buffer. If false,
1040 we unfreeze the back.
1041 @return 0 on success, -1 on failure.
1042 */
1043 EVENT2_EXPORT_SYMBOL
1044 int evbuffer_unfreeze(struct evbuffer *buf, int at_front);
1045
1046 struct event_base;
1047 /**
1048 Force all the callbacks on an evbuffer to be run, not immediately after
1049 the evbuffer is altered, but instead from inside the event loop.
1050
1051 This can be used to serialize all the callbacks to a single thread
1052 of execution.
1053 */
1054 EVENT2_EXPORT_SYMBOL
1055 int evbuffer_defer_callbacks(struct evbuffer *buffer, struct event_base *base);
1056
1057 /**
1058 Append data from 1 or more iovec's to an evbuffer
1059
1060 Calculates the number of bytes needed for an iovec structure and guarantees
1061 all data will fit into a single chain. Can be used in lieu of functionality
1062 which calls evbuffer_add() constantly before being used to increase
1063 performance.
1064
1065 @param buffer the destination buffer
1066 @param vec the source iovec
1067 @param n_vec the number of iovec structures.
1068 @return the number of bytes successfully written to the output buffer.
1069 */
1070 EVENT2_EXPORT_SYMBOL
1071 size_t evbuffer_add_iovec(struct evbuffer * buffer, struct evbuffer_iovec * vec, int n_vec);
1072
1073 #ifdef __cplusplus
1074 }
1075 #endif
1076
1077 #endif /* EVENT2_BUFFER_H_INCLUDED_ */
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