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_
27 #define _EVENT2_BUFFER_H_
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 #ifdef __cplusplus
76 extern "C" {
77 #endif
78
79 #include <event2/event-config.h>
80 #include <stdarg.h>
81 #ifdef _EVENT_HAVE_SYS_TYPES_H
82 #include <sys/types.h>
83 #endif
84 #ifdef _EVENT_HAVE_SYS_UIO_H
85 #include <sys/uio.h>
86 #endif
87 #include <event2/util.h>
88
89 /**
90 An evbuffer is an opaque data type for efficiently buffering data to be
91 sent or received on the network.
92
93 @see event2/event.h for more information
94 */
95 struct evbuffer
96 #ifdef _EVENT_IN_DOXYGEN
97 {}
98 #endif
99 ;
100
101 /**
102 Pointer to a position within an evbuffer.
103
104 Used when repeatedly searching through a buffer. Calling any function
105 that modifies or re-packs the buffer contents may invalidate all
106 evbuffer_ptrs for that buffer. Do not modify these values except with
107 evbuffer_ptr_set.
108 */
109 struct evbuffer_ptr {
110 ev_ssize_t pos;
111
112 /* Do not alter the values of fields. */
113 struct {
114 void *chain;
115 size_t pos_in_chain;
116 } _internal;
117 };
118
119 /** Describes a single extent of memory inside an evbuffer. Used for
120 direct-access functions.
121
122 @see evbuffer_reserve_space, evbuffer_commit_space, evbuffer_peek
123 */
124 #ifdef _EVENT_HAVE_SYS_UIO_H
125 #define evbuffer_iovec iovec
126 /* Internal use -- defined only if we are using the native struct iovec */
127 #define _EVBUFFER_IOVEC_IS_NATIVE
128 #else
129 struct evbuffer_iovec {
130 /** The start of the extent of memory. */
131 void *iov_base;
132 /** The length of the extent of memory. */
133 size_t iov_len;
134 };
135 #endif
136
137 /**
138 Allocate storage for a new evbuffer.
139
140 @return a pointer to a newly allocated evbuffer struct, or NULL if an error
141 occurred
142 */
143 struct evbuffer *evbuffer_new(void);
144 /**
145 Deallocate storage for an evbuffer.
146
147 @param buf pointer to the evbuffer to be freed
148 */
149 void evbuffer_free(struct evbuffer *buf);
150
151 /**
152 Enable locking on an evbuffer so that it can safely be used by multiple
153 threads at the same time.
154
155 NOTE: when locking is enabled, the lock will be held when callbacks are
156 invoked. This could result in deadlock if you aren't careful. Plan
157 accordingly!
158
159 @param buf An evbuffer to make lockable.
160 @param lock A lock object, or NULL if we should allocate our own.
161 @return 0 on success, -1 on failure.
162 */
163 int evbuffer_enable_locking(struct evbuffer *buf, void *lock);
164
165 /**
166 Acquire the lock on an evbuffer. Has no effect if locking was not enabled
167 with evbuffer_enable_locking.
168 */
169 void evbuffer_lock(struct evbuffer *buf);
170
171 /**
172 Release the lock on an evbuffer. Has no effect if locking was not enabled
173 with evbuffer_enable_locking.
174 */
175 void evbuffer_unlock(struct evbuffer *buf);
176
177
178 /** If this flag is set, then we will not use evbuffer_peek(),
179 * evbuffer_remove(), evbuffer_remove_buffer(), and so on to read bytes
180 * from this buffer: we'll only take bytes out of this buffer by
181 * writing them to the network (as with evbuffer_write_atmost), by
182 * removing them without observing them (as with evbuffer_drain),
183 * or by copying them all out at once (as with evbuffer_add_buffer).
184 *
185 * Using this option allows the implementation to use sendfile-based
186 * operations for evbuffer_add_file(); see that function for more
187 * information.
188 *
189 * This flag is on by default for bufferevents that can take advantage
190 * of it; you should never actually need to set it on a bufferevent's
191 * output buffer.
192 */
193 #define EVBUFFER_FLAG_DRAINS_TO_FD 1
194
195 /** Change the flags that are set for an evbuffer by adding more.
196 *
197 * @param buffer the evbuffer that the callback is watching.
198 * @param cb the callback whose status we want to change.
199 * @param flags One or more EVBUFFER_FLAG_* options
200 * @return 0 on success, -1 on failure.
201 */
202 int evbuffer_set_flags(struct evbuffer *buf, ev_uint64_t flags);
203 /** Change the flags that are set for an evbuffer by removing some.
204 *
205 * @param buffer the evbuffer that the callback is watching.
206 * @param cb the callback whose status we want to change.
207 * @param flags One or more EVBUFFER_FLAG_* options
208 * @return 0 on success, -1 on failure.
209 */
210 int evbuffer_clear_flags(struct evbuffer *buf, ev_uint64_t flags);
211
212 /**
213 Returns the total number of bytes stored in the evbuffer
214
215 @param buf pointer to the evbuffer
216 @return the number of bytes stored in the evbuffer
217 */
218 size_t evbuffer_get_length(const struct evbuffer *buf);
219
220 /**
221 Returns the number of contiguous available bytes in the first buffer chain.
222
223 This is useful when processing data that might be split into multiple
224 chains, or that might all be in the first chain. Calls to
225 evbuffer_pullup() that cause reallocation and copying of data can thus be
226 avoided.
227
228 @param buf pointer to the evbuffer
229 @return 0 if no data is available, otherwise the number of available bytes
230 in the first buffer chain.
231 */
232 size_t evbuffer_get_contiguous_space(const struct evbuffer *buf);
233
234 /**
235 Expands the available space in an evbuffer.
236
237 Expands the available space in the evbuffer to at least datlen, so that
238 appending datlen additional bytes will not require any new allocations.
239
240 @param buf the evbuffer to be expanded
241 @param datlen the new minimum length requirement
242 @return 0 if successful, or -1 if an error occurred
243 */
244 int evbuffer_expand(struct evbuffer *buf, size_t datlen);
245
246 /**
247 Reserves space in the last chain or chains of an evbuffer.
248
249 Makes space available in the last chain or chains of an evbuffer that can
250 be arbitrarily written to by a user. The space does not become
251 available for reading until it has been committed with
252 evbuffer_commit_space().
253
254 The space is made available as one or more extents, represented by
255 an initial pointer and a length. You can force the memory to be
256 available as only one extent. Allowing more extents, however, makes the
257 function more efficient.
258
259 Multiple subsequent calls to this function will make the same space
260 available until evbuffer_commit_space() has been called.
261
262 It is an error to do anything that moves around the buffer's internal
263 memory structures before committing the space.
264
265 NOTE: The code currently does not ever use more than two extents.
266 This may change in future versions.
267
268 @param buf the evbuffer in which to reserve space.
269 @param size how much space to make available, at minimum. The
270 total length of the extents may be greater than the requested
271 length.
272 @param vec an array of one or more evbuffer_iovec structures to
273 hold pointers to the reserved extents of memory.
274 @param n_vec The length of the vec array. Must be at least 1;
275 2 is more efficient.
276 @return the number of provided extents, or -1 on error.
277 @see evbuffer_commit_space()
278 */
279 int
280 evbuffer_reserve_space(struct evbuffer *buf, ev_ssize_t size,
281 struct evbuffer_iovec *vec, int n_vec);
282
283 /**
284 Commits previously reserved space.
285
286 Commits some of the space previously reserved with
287 evbuffer_reserve_space(). It then becomes available for reading.
288
289 This function may return an error if the pointer in the extents do
290 not match those returned from evbuffer_reserve_space, or if data
291 has been added to the buffer since the space was reserved.
292
293 If you want to commit less data than you got reserved space for,
294 modify the iov_len pointer of the appropriate extent to a smaller
295 value. Note that you may have received more space than you
296 requested if it was available!
297
298 @param buf the evbuffer in which to reserve space.
299 @param vec one or two extents returned by evbuffer_reserve_space.
300 @param n_vecs the number of extents.
301 @return 0 on success, -1 on error
302 @see evbuffer_reserve_space()
303 */
304 int evbuffer_commit_space(struct evbuffer *buf,
305 struct evbuffer_iovec *vec, int n_vecs);
306
307 /**
308 Append data to the end of an evbuffer.
309
310 @param buf the evbuffer to be appended to
311 @param data pointer to the beginning of the data buffer
312 @param datlen the number of bytes to be copied from the data buffer
313 @return 0 on success, -1 on failure.
314 */
315 int evbuffer_add(struct evbuffer *buf, const void *data, size_t datlen);
316
317
318 /**
319 Read data from an evbuffer and drain the bytes read.
320
321 If more bytes are requested than are available in the evbuffer, we
322 only extract as many bytes as were available.
323
324 @param buf the evbuffer to be read from
325 @param data the destination buffer to store the result
326 @param datlen the maximum size of the destination buffer
327 @return the number of bytes read, or -1 if we can't drain the buffer.
328 */
329 int evbuffer_remove(struct evbuffer *buf, void *data, size_t datlen);
330
331 /**
332 Read data from an evbuffer, and leave the buffer unchanged.
333
334 If more bytes are requested than are available in the evbuffer, we
335 only extract as many bytes as were available.
336
337 @param buf the evbuffer to be read from
338 @param data_out the destination buffer to store the result
339 @param datlen the maximum size of the destination buffer
340 @return the number of bytes read, or -1 if we can't drain the buffer.
341 */
342 ev_ssize_t evbuffer_copyout(struct evbuffer *buf, void *data_out, size_t datlen);
343
344 /**
345 Read data from an evbuffer into another evbuffer, draining
346 the bytes from the source buffer. This function avoids copy
347 operations to the extent possible.
348
349 If more bytes are requested than are available in src, the src
350 buffer is drained completely.
351
352 @param src the evbuffer to be read from
353 @param dst the destination evbuffer to store the result into
354 @param datlen the maximum numbers of bytes to transfer
355 @return the number of bytes read
356 */
357 int evbuffer_remove_buffer(struct evbuffer *src, struct evbuffer *dst,
358 size_t datlen);
359
360 /** Used to tell evbuffer_readln what kind of line-ending to look for.
361 */
362 enum evbuffer_eol_style {
363 /** Any sequence of CR and LF characters is acceptable as an
364 * EOL.
365 *
366 * Note that this style can produce ambiguous results: the
367 * sequence "CRLF" will be treated as a single EOL if it is
368 * all in the buffer at once, but if you first read a CR from
369 * the network and later read an LF from the network, it will
370 * be treated as two EOLs.
371 */
372 EVBUFFER_EOL_ANY,
373 /** An EOL is an LF, optionally preceded by a CR. This style is
374 * most useful for implementing text-based internet protocols. */
375 EVBUFFER_EOL_CRLF,
376 /** An EOL is a CR followed by an LF. */
377 EVBUFFER_EOL_CRLF_STRICT,
378 /** An EOL is a LF. */
379 EVBUFFER_EOL_LF
380 };
381
382 /**
383 * Read a single line from an evbuffer.
384 *
385 * Reads a line terminated by an EOL as determined by the evbuffer_eol_style
386 * argument. Returns a newly allocated nul-terminated string; the caller must
387 * free the returned value. The EOL is not included in the returned string.
388 *
389 * @param buffer the evbuffer to read from
390 * @param n_read_out if non-NULL, points to a size_t that is set to the
391 * number of characters in the returned string. This is useful for
392 * strings that can contain NUL characters.
393 * @param eol_style the style of line-ending to use.
394 * @return pointer to a single line, or NULL if an error occurred
395 */
396 char *evbuffer_readln(struct evbuffer *buffer, size_t *n_read_out,
397 enum evbuffer_eol_style eol_style);
398
399 /**
400 Move all data from one evbuffer into another evbuffer.
401
402 This is a destructive add. The data from one buffer moves into
403 the other buffer. However, no unnecessary memory copies occur.
404
405 @param outbuf the output buffer
406 @param inbuf the input buffer
407 @return 0 if successful, or -1 if an error occurred
408
409 @see evbuffer_remove_buffer()
410 */
411 int evbuffer_add_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf);
412
413 /**
414 A cleanup function for a piece of memory added to an evbuffer by
415 reference.
416
417 @see evbuffer_add_reference()
418 */
419 typedef void (*evbuffer_ref_cleanup_cb)(const void *data,
420 size_t datalen, void *extra);
421
422 /**
423 Reference memory into an evbuffer without copying.
424
425 The memory needs to remain valid until all the added data has been
426 read. This function keeps just a reference to the memory without
427 actually incurring the overhead of a copy.
428
429 @param outbuf the output buffer
430 @param data the memory to reference
431 @param datlen how memory to reference
432 @param cleanupfn callback to be invoked when the memory is no longer
433 referenced by this evbuffer.
434 @param cleanupfn_arg optional argument to the cleanup callback
435 @return 0 if successful, or -1 if an error occurred
436 */
437 int evbuffer_add_reference(struct evbuffer *outbuf,
438 const void *data, size_t datlen,
439 evbuffer_ref_cleanup_cb cleanupfn, void *cleanupfn_arg);
440
441 /**
442 Copy data from a file into the evbuffer for writing to a socket.
443
444 This function avoids unnecessary data copies between userland and
445 kernel. If sendfile is available and the EVBUFFER_FLAG_DRAINS_TO_FD
446 flag is set, it uses those functions. Otherwise, it tries to use
447 mmap (or CreateFileMapping on Windows).
448
449 The function owns the resulting file descriptor and will close it
450 when finished transferring data.
451
452 The results of using evbuffer_remove() or evbuffer_pullup() on
453 evbuffers whose data was added using this function are undefined.
454
455 @param outbuf the output buffer
456 @param fd the file descriptor
457 @param offset the offset from which to read data
458 @param length how much data to read
459 @return 0 if successful, or -1 if an error occurred
460 */
461
462 int evbuffer_add_file(struct evbuffer *outbuf, int fd, ev_off_t offset,
463 ev_off_t length);
464
465 /**
466 Append a formatted string to the end of an evbuffer.
467
468 The string is formated as printf.
469
470 @param buf the evbuffer that will be appended to
471 @param fmt a format string
472 @param ... arguments that will be passed to printf(3)
473 @return The number of bytes added if successful, or -1 if an error occurred.
474
475 @see evutil_printf(), evbuffer_add_vprintf()
476 */
477 int evbuffer_add_printf(struct evbuffer *buf, const char *fmt, ...)
478 #ifdef __GNUC__
479 __attribute__((format(printf, 2, 3)))
480 #endif
481 ;
482
483 /**
484 Append a va_list formatted string to the end of an evbuffer.
485
486 @param buf the evbuffer that will be appended to
487 @param fmt a format string
488 @param ap a varargs va_list argument array that will be passed to vprintf(3)
489 @return The number of bytes added if successful, or -1 if an error occurred.
490 */
491 int evbuffer_add_vprintf(struct evbuffer *buf, const char *fmt, va_list ap)
492 #ifdef __GNUC__
493 __attribute__((format(printf, 2, 0)))
494 #endif
495 ;
496
497
498 /**
499 Remove a specified number of bytes data from the beginning of an evbuffer.
500
501 @param buf the evbuffer to be drained
502 @param len the number of bytes to drain from the beginning of the buffer
503 @return 0 on success, -1 on failure.
504 */
505 int evbuffer_drain(struct evbuffer *buf, size_t len);
506
507
508 /**
509 Write the contents of an evbuffer to a file descriptor.
510
511 The evbuffer will be drained after the bytes have been successfully written.
512
513 @param buffer the evbuffer to be written and drained
514 @param fd the file descriptor to be written to
515 @return the number of bytes written, or -1 if an error occurred
516 @see evbuffer_read()
517 */
518 int evbuffer_write(struct evbuffer *buffer, evutil_socket_t fd);
519
520 /**
521 Write some of the contents of an evbuffer to a file descriptor.
522
523 The evbuffer will be drained after the bytes have been successfully written.
524
525 @param buffer the evbuffer to be written and drained
526 @param fd the file descriptor to be written to
527 @param howmuch the largest allowable number of bytes to write, or -1
528 to write as many bytes as we can.
529 @return the number of bytes written, or -1 if an error occurred
530 @see evbuffer_read()
531 */
532 int evbuffer_write_atmost(struct evbuffer *buffer, evutil_socket_t fd,
533 ev_ssize_t howmuch);
534
535 /**
536 Read from a file descriptor and store the result in an evbuffer.
537
538 @param buffer the evbuffer to store the result
539 @param fd the file descriptor to read from
540 @param howmuch the number of bytes to be read
541 @return the number of bytes read, or -1 if an error occurred
542 @see evbuffer_write()
543 */
544 int evbuffer_read(struct evbuffer *buffer, evutil_socket_t fd, int howmuch);
545
546 /**
547 Search for a string within an evbuffer.
548
549 @param buffer the evbuffer to be searched
550 @param what the string to be searched for
551 @param len the length of the search string
552 @param start NULL or a pointer to a valid struct evbuffer_ptr.
553 @return a struct evbuffer_ptr whose 'pos' field has the offset of the
554 first occurrence of the string in the buffer after 'start'. The 'pos'
555 field of the result is -1 if the string was not found.
556 */
557 struct evbuffer_ptr evbuffer_search(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start);
558
559 /**
560 Search for a string within part of an evbuffer.
561
562 @param buffer the evbuffer to be searched
563 @param what the string to be searched for
564 @param len the length of the search string
565 @param start NULL or a pointer to a valid struct evbuffer_ptr that
566 indicates where we should start searching.
567 @param end NULL or a pointer to a valid struct evbuffer_ptr that
568 indicates where we should stop searching.
569 @return a struct evbuffer_ptr whose 'pos' field has the offset of the
570 first occurrence of the string in the buffer after 'start'. The 'pos'
571 field of the result is -1 if the string was not found.
572 */
573 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);
574
575 /**
576 Defines how to adjust an evbuffer_ptr by evbuffer_ptr_set()
577
578 @see evbuffer_ptr_set() */
579 enum evbuffer_ptr_how {
580 /** Sets the pointer to the position; can be called on with an
581 uninitialized evbuffer_ptr. */
582 EVBUFFER_PTR_SET,
583 /** Advances the pointer by adding to the current position. */
584 EVBUFFER_PTR_ADD
585 };
586
587 /**
588 Sets the search pointer in the buffer to position.
589
590 If evbuffer_ptr is not initialized. This function can only be called
591 with EVBUFFER_PTR_SET.
592
593 @param buffer the evbuffer to be search
594 @param ptr a pointer to a struct evbuffer_ptr
595 @param position the position at which to start the next search
596 @param how determines how the pointer should be manipulated.
597 @returns 0 on success or -1 otherwise
598 */
599 int
600 evbuffer_ptr_set(struct evbuffer *buffer, struct evbuffer_ptr *ptr,
601 size_t position, enum evbuffer_ptr_how how);
602
603 /**
604 Search for an end-of-line string within an evbuffer.
605
606 @param buffer the evbuffer to be searched
607 @param start NULL or a pointer to a valid struct evbuffer_ptr to start
608 searching at.
609 @param eol_len_out If non-NULL, the pointed-to value will be set to
610 the length of the end-of-line string.
611 @param eol_style The kind of EOL to look for; see evbuffer_readln() for
612 more information
613 @return a struct evbuffer_ptr whose 'pos' field has the offset of the
614 first occurrence EOL in the buffer after 'start'. The 'pos'
615 field of the result is -1 if the string was not found.
616 */
617 struct evbuffer_ptr evbuffer_search_eol(struct evbuffer *buffer,
618 struct evbuffer_ptr *start, size_t *eol_len_out,
619 enum evbuffer_eol_style eol_style);
620
621 /** Function to peek at data inside an evbuffer without removing it or
622 copying it out.
623
624 Pointers to the data are returned by filling the 'vec_out' array
625 with pointers to one or more extents of data inside the buffer.
626
627 The total data in the extents that you get back may be more than
628 you requested (if there is more data last extent than you asked
629 for), or less (if you do not provide enough evbuffer_iovecs, or if
630 the buffer does not have as much data as you asked to see).
631
632 @param buffer the evbuffer to peek into,
633 @param len the number of bytes to try to peek. If len is negative, we
634 will try to fill as much of vec_out as we can. If len is negative
635 and vec_out is not provided, we return the number of evbuffer_iovecs
636 that would be needed to get all the data in the buffer.
637 @param start_at an evbuffer_ptr indicating the point at which we
638 should start looking for data. NULL means, "At the start of the
639 buffer."
640 @param vec_out an array of evbuffer_iovec
641 @param n_vec the length of vec_out. If 0, we only count how many
642 extents would be necessary to point to the requested amount of
643 data.
644 @return The number of extents needed. This may be less than n_vec
645 if we didn't need all the evbuffer_iovecs we were given, or more
646 than n_vec if we would need more to return all the data that was
647 requested.
648 */
649 int evbuffer_peek(struct evbuffer *buffer, ev_ssize_t len,
650 struct evbuffer_ptr *start_at,
651 struct evbuffer_iovec *vec_out, int n_vec);
652
653
654 /** Structure passed to an evbuffer_cb_func evbuffer callback
655
656 @see evbuffer_cb_func, evbuffer_add_cb()
657 */
658 struct evbuffer_cb_info {
659 /** The number of bytes in this evbuffer when callbacks were last
660 * invoked. */
661 size_t orig_size;
662 /** The number of bytes added since callbacks were last invoked. */
663 size_t n_added;
664 /** The number of bytes removed since callbacks were last invoked. */
665 size_t n_deleted;
666 };
667
668 /** Type definition for a callback that is invoked whenever data is added or
669 removed from an evbuffer.
670
671 An evbuffer may have one or more callbacks set at a time. The order
672 in which they are executed is undefined.
673
674 A callback function may add more callbacks, or remove itself from the
675 list of callbacks, or add or remove data from the buffer. It may not
676 remove another callback from the list.
677
678 If a callback adds or removes data from the buffer or from another
679 buffer, this can cause a recursive invocation of your callback or
680 other callbacks. If you ask for an infinite loop, you might just get
681 one: watch out!
682
683 @param buffer the buffer whose size has changed
684 @param info a structure describing how the buffer changed.
685 @param arg a pointer to user data
686 */
687 typedef void (*evbuffer_cb_func)(struct evbuffer *buffer, const struct evbuffer_cb_info *info, void *arg);
688
689 struct evbuffer_cb_entry;
690 /** Add a new callback to an evbuffer.
691
692 Subsequent calls to evbuffer_add_cb() add new callbacks. To remove this
693 callback, call evbuffer_remove_cb or evbuffer_remove_cb_entry.
694
695 @param buffer the evbuffer to be monitored
696 @param cb the callback function to invoke when the evbuffer is modified,
697 or NULL to remove all callbacks.
698 @param cbarg an argument to be provided to the callback function
699 @return a handle to the callback on success, or NULL on failure.
700 */
701 struct evbuffer_cb_entry *evbuffer_add_cb(struct evbuffer *buffer, evbuffer_cb_func cb, void *cbarg);
702
703 /** Remove a callback from an evbuffer, given a handle returned from
704 evbuffer_add_cb.
705
706 Calling this function invalidates the handle.
707
708 @return 0 if a callback was removed, or -1 if no matching callback was
709 found.
710 */
711 int evbuffer_remove_cb_entry(struct evbuffer *buffer,
712 struct evbuffer_cb_entry *ent);
713
714 /** Remove a callback from an evbuffer, given the function and argument
715 used to add it.
716
717 @return 0 if a callback was removed, or -1 if no matching callback was
718 found.
719 */
720 int evbuffer_remove_cb(struct evbuffer *buffer, evbuffer_cb_func cb, void *cbarg);
721
722 /** If this flag is not set, then a callback is temporarily disabled, and
723 * should not be invoked.
724 *
725 * @see evbuffer_cb_set_flags(), evbuffer_cb_clear_flags()
726 */
727 #define EVBUFFER_CB_ENABLED 1
728
729 /** Change the flags that are set for a callback on a buffer by adding more.
730
731 @param buffer the evbuffer that the callback is watching.
732 @param cb the callback whose status we want to change.
733 @param flags EVBUFFER_CB_ENABLED to re-enable the callback.
734 @return 0 on success, -1 on failure.
735 */
736 int evbuffer_cb_set_flags(struct evbuffer *buffer,
737 struct evbuffer_cb_entry *cb, ev_uint32_t flags);
738
739 /** Change the flags that are set for a callback on a buffer by removing some
740
741 @param buffer the evbuffer that the callback is watching.
742 @param cb the callback whose status we want to change.
743 @param flags EVBUFFER_CB_ENABLED to disable the callback.
744 @return 0 on success, -1 on failure.
745 */
746 int evbuffer_cb_clear_flags(struct evbuffer *buffer,
747 struct evbuffer_cb_entry *cb, ev_uint32_t flags);
748
749 #if 0
750 /** Postpone calling a given callback until unsuspend is called later.
751
752 This is different from disabling the callback, since the callback will get
753 invoked later if the buffer size changes between now and when we unsuspend
754 it.
755
756 @param the buffer that the callback is watching.
757 @param cb the callback we want to suspend.
758 */
759 void evbuffer_cb_suspend(struct evbuffer *buffer, struct evbuffer_cb_entry *cb);
760 /** Stop postponing a callback that we postponed with evbuffer_cb_suspend.
761
762 If data was added to or removed from the buffer while the callback was
763 suspended, the callback will get called once now.
764
765 @param the buffer that the callback is watching.
766 @param cb the callback we want to stop suspending.
767 */
768 void evbuffer_cb_unsuspend(struct evbuffer *buffer, struct evbuffer_cb_entry *cb);
769 #endif
770
771 /**
772 Makes the data at the beginning of an evbuffer contiguous.
773
774 @param buf the evbuffer to make contiguous
775 @param size the number of bytes to make contiguous, or -1 to make the
776 entire buffer contiguous.
777 @return a pointer to the contiguous memory array
778 */
779
780 unsigned char *evbuffer_pullup(struct evbuffer *buf, ev_ssize_t size);
781
782 /**
783 Prepends data to the beginning of the evbuffer
784
785 @param buf the evbuffer to which to prepend data
786 @param data a pointer to the memory to prepend
787 @param size the number of bytes to prepend
788 @return 0 if successful, or -1 otherwise
789 */
790
791 int evbuffer_prepend(struct evbuffer *buf, const void *data, size_t size);
792
793 /**
794 Prepends all data from the src evbuffer to the beginning of the dst
795 evbuffer.
796
797 @param dst the evbuffer to which to prepend data
798 @param src the evbuffer to prepend; it will be emptied as a result
799 @return 0 if successful, or -1 otherwise
800 */
801 int evbuffer_prepend_buffer(struct evbuffer *dst, struct evbuffer* src);
802
803 /**
804 Prevent calls that modify an evbuffer from succeeding. A buffer may
805 frozen at the front, at the back, or at both the front and the back.
806
807 If the front of a buffer is frozen, operations that drain data from
808 the front of the buffer, or that prepend data to the buffer, will
809 fail until it is unfrozen. If the back a buffer is frozen, operations
810 that append data from the buffer will fail until it is unfrozen.
811
812 @param buf The buffer to freeze
813 @param at_front If true, we freeze the front of the buffer. If false,
814 we freeze the back.
815 @return 0 on success, -1 on failure.
816 */
817 int evbuffer_freeze(struct evbuffer *buf, int at_front);
818 /**
819 Re-enable calls that modify an evbuffer.
820
821 @param buf The buffer to un-freeze
822 @param at_front If true, we unfreeze the front of the buffer. If false,
823 we unfreeze the back.
824 @return 0 on success, -1 on failure.
825 */
826 int evbuffer_unfreeze(struct evbuffer *buf, int at_front);
827
828 struct event_base;
829 /**
830 Force all the callbacks on an evbuffer to be run, not immediately after
831 the evbuffer is altered, but instead from inside the event loop.
832
833 This can be used to serialize all the callbacks to a single thread
834 of execution.
835 */
836 int evbuffer_defer_callbacks(struct evbuffer *buffer, struct event_base *base);
837
838 #ifdef __cplusplus
839 }
840 #endif
841
842 #endif /* _EVENT2_BUFFER_H_ */