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_ */ 843