2 * copyright (c) 2001 Fabrice Bellard
4 * This file is part of FFmpeg.
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 #ifndef AVFORMAT_AVIO_H
21 #define AVFORMAT_AVIO_H
26 * Buffered I/O operations
31 #include "libavutil/common.h"
32 #include "libavutil/dict.h"
33 #include "libavutil/log.h"
35 #include "libavformat/version.h"
38 * Seeking works like for a local file.
40 #define AVIO_SEEKABLE_NORMAL (1 << 0)
43 * Seeking by timestamp with avio_seek_time() is possible.
45 #define AVIO_SEEKABLE_TIME (1 << 1)
48 * Callback for checking whether to abort blocking functions.
49 * AVERROR_EXIT is returned in this case by the interrupted
50 * function. During blocking operations, callback is called with
51 * opaque as parameter. If the callback returns 1, the
52 * blocking operation will be aborted.
54 * No members can be added to this struct without a major bump, if
55 * new elements have been added after this struct in AVFormatContext
58 typedef struct AVIOInterruptCB {
59 int (*callback)(void*);
64 * Directory entry types.
66 enum AVIODirEntryType {
68 AVIO_ENTRY_BLOCK_DEVICE,
69 AVIO_ENTRY_CHARACTER_DEVICE,
71 AVIO_ENTRY_NAMED_PIPE,
72 AVIO_ENTRY_SYMBOLIC_LINK,
81 * Describes single entry of the directory.
83 * Only name and type fields are guaranteed be set.
84 * Rest of fields are protocol or/and platform dependent and might be unknown.
86 typedef struct AVIODirEntry {
87 char *name; /**< Filename */
88 int type; /**< Type of the entry */
89 int utf8; /**< Set to 1 when name is encoded with UTF-8, 0 otherwise.
90 Name can be encoded with UTF-8 even though 0 is set. */
91 int64_t size; /**< File size in bytes, -1 if unknown. */
92 int64_t modification_timestamp; /**< Time of last modification in microseconds since unix
93 epoch, -1 if unknown. */
94 int64_t access_timestamp; /**< Time of last access in microseconds since unix epoch,
96 int64_t status_change_timestamp; /**< Time of last status change in microseconds since unix
97 epoch, -1 if unknown. */
98 int64_t user_id; /**< User ID of owner, -1 if unknown. */
99 int64_t group_id; /**< Group ID of owner, -1 if unknown. */
100 int64_t filemode; /**< Unix file mode, -1 if unknown. */
103 typedef struct AVIODirContext {
104 struct URLContext *url_context;
108 * Different data types that can be returned via the AVIO
109 * write_data_type callback.
111 enum AVIODataMarkerType {
113 * Header data; this needs to be present for the stream to be decodeable.
115 AVIO_DATA_MARKER_HEADER,
117 * A point in the output bytestream where a decoder can start decoding
118 * (i.e. a keyframe). A demuxer/decoder given the data flagged with
119 * AVIO_DATA_MARKER_HEADER, followed by any AVIO_DATA_MARKER_SYNC_POINT,
120 * should give decodeable results.
122 AVIO_DATA_MARKER_SYNC_POINT,
124 * A point in the output bytestream where a demuxer can start parsing
125 * (for non self synchronizing bytestream formats). That is, any
126 * non-keyframe packet start point.
128 AVIO_DATA_MARKER_BOUNDARY_POINT,
130 * This is any, unlabelled data. It can either be a muxer not marking
131 * any positions at all, it can be an actual boundary/sync point
132 * that the muxer chooses not to mark, or a later part of a packet/fragment
133 * that is cut into multiple write callbacks due to limited IO buffer size.
135 AVIO_DATA_MARKER_UNKNOWN,
137 * Trailer data, which doesn't contain actual content, but only for
138 * finalizing the output file.
140 AVIO_DATA_MARKER_TRAILER
144 * Bytestream IO Context.
145 * New fields can be added to the end with minor version bumps.
146 * Removal, reordering and changes to existing fields require a major
148 * sizeof(AVIOContext) must not be used outside libav*.
150 * @note None of the function pointers in AVIOContext should be called
151 * directly, they should only be set by the client application
152 * when implementing custom I/O. Normally these are set to the
153 * function pointers specified in avio_alloc_context()
155 typedef struct AVIOContext {
157 * A class for private options.
159 * If this AVIOContext is created by avio_open2(), av_class is set and
160 * passes the options down to protocols.
162 * If this AVIOContext is manually allocated, then av_class may be set by
165 * warning -- this field can be NULL, be sure to not pass this AVIOContext
166 * to any av_opt_* functions in that case.
168 const AVClass *av_class;
171 * The following shows the relationship between buffer, buf_ptr,
172 * buf_ptr_max, buf_end, buf_size, and pos, when reading and when writing
173 * (since AVIOContext is used for both):
175 **********************************************************************************
177 **********************************************************************************
180 * |---------------------------------------|
183 * buffer buf_ptr buf_end
184 * +---------------+-----------------------+
185 * |/ / / / / / / /|/ / / / / / /| |
186 * read buffer: |/ / consumed / | to be read /| |
187 * |/ / / / / / / /|/ / / / / / /| |
188 * +---------------+-----------------------+
191 * +-------------------------------------------+-----------------+
193 * +-------------------------------------------+-----------------+
196 **********************************************************************************
198 **********************************************************************************
201 * |--------------------------------------|
205 * buffer (buf_ptr) buf_end
206 * +-----------------------+--------------+
207 * |/ / / / / / / / / / / /| |
208 * write buffer: | / / to be flushed / / | |
209 * |/ / / / / / / / / / / /| |
210 * +-----------------------+--------------+
211 * buf_ptr can be in this
212 * due to a backward seek
215 * +-------------+----------------------------------------------+
217 * +-------------+----------------------------------------------+
220 unsigned char *buffer; /**< Start of the buffer. */
221 int buffer_size; /**< Maximum buffer size */
222 unsigned char *buf_ptr; /**< Current position in the buffer */
223 unsigned char *buf_end; /**< End of the data, may be less than
224 buffer+buffer_size if the read function returned
225 less data than requested, e.g. for streams where
226 no more data has been received yet. */
227 void *opaque; /**< A private pointer, passed to the read/write/seek/...
229 int (*read_packet)(void *opaque, uint8_t *buf, int buf_size);
230 int (*write_packet)(void *opaque, uint8_t *buf, int buf_size);
231 int64_t (*seek)(void *opaque, int64_t offset, int whence);
232 int64_t pos; /**< position in the file of the current buffer */
233 int must_flush; /**< unused */
234 int eof_reached; /**< true if eof reached */
235 int write_flag; /**< true if open for writing */
237 unsigned long checksum;
238 unsigned char *checksum_ptr;
239 unsigned long (*update_checksum)(unsigned long checksum, const uint8_t *buf, unsigned int size);
240 int error; /**< contains the error code or 0 if no error happened */
242 * Pause or resume playback for network streaming protocols - e.g. MMS.
244 int (*read_pause)(void *opaque, int pause);
246 * Seek to a given timestamp in stream with the specified stream_index.
247 * Needed for some network streaming protocols which don't support seeking
250 int64_t (*read_seek)(void *opaque, int stream_index,
251 int64_t timestamp, int flags);
253 * A combination of AVIO_SEEKABLE_ flags or 0 when the stream is not seekable.
258 * max filesize, used to limit allocations
259 * This field is internal to libavformat and access from outside is not allowed.
264 * avio_read and avio_write should if possible be satisfied directly
265 * instead of going through a buffer, and avio_seek will always
266 * call the underlying seek function directly.
271 * Bytes read statistic
272 * This field is internal to libavformat and access from outside is not allowed.
278 * This field is internal to libavformat and access from outside is not allowed.
284 * This field is internal to libavformat and access from outside is not allowed.
289 * Original buffer size
290 * used internally after probing and ensure seekback to reset the buffer size
291 * This field is internal to libavformat and access from outside is not allowed.
293 int orig_buffer_size;
296 * Threshold to favor readahead over seek.
297 * This is current internal only, do not use from outside.
299 int short_seek_threshold;
302 * ',' separated list of allowed protocols.
304 const char *protocol_whitelist;
307 * ',' separated list of disallowed protocols.
309 const char *protocol_blacklist;
312 * A callback that is used instead of write_packet.
314 int (*write_data_type)(void *opaque, uint8_t *buf, int buf_size,
315 enum AVIODataMarkerType type, int64_t time);
317 * If set, don't call write_data_type separately for AVIO_DATA_MARKER_BOUNDARY_POINT,
318 * but ignore them and treat them as AVIO_DATA_MARKER_UNKNOWN (to avoid needlessly
319 * small chunks of data returned from the callback).
321 int ignore_boundary_point;
324 * Internal, not meant to be used from outside of AVIOContext.
326 enum AVIODataMarkerType current_type;
330 * A callback that is used instead of short_seek_threshold.
331 * This is current internal only, do not use from outside.
333 int (*short_seek_get)(void *opaque);
338 * Maximum reached position before a backward seek in the write buffer,
339 * used keeping track of already written data for a later flush.
341 unsigned char *buf_ptr_max;
345 * Return the name of the protocol that will handle the passed URL.
347 * NULL is returned if no protocol could be found for the given URL.
349 * @return Name of the protocol or NULL.
351 const char *avio_find_protocol_name(const char *url);
354 * Return AVIO_FLAG_* access flags corresponding to the access permissions
355 * of the resource in url, or a negative value corresponding to an
356 * AVERROR code in case of failure. The returned access flags are
357 * masked by the value in flags.
359 * @note This function is intrinsically unsafe, in the sense that the
360 * checked resource may change its existence or permission status from
361 * one call to another. Thus you should not trust the returned value,
362 * unless you are sure that no other processes are accessing the
365 int avio_check(const char *url, int flags);
368 * Move or rename a resource.
370 * @note url_src and url_dst should share the same protocol and authority.
372 * @param url_src url to resource to be moved
373 * @param url_dst new url to resource if the operation succeeded
374 * @return >=0 on success or negative on error.
376 int avpriv_io_move(const char *url_src, const char *url_dst);
381 * @param url resource to be deleted.
382 * @return >=0 on success or negative on error.
384 int avpriv_io_delete(const char *url);
387 * Open directory for reading.
389 * @param s directory read context. Pointer to a NULL pointer must be passed.
390 * @param url directory to be listed.
391 * @param options A dictionary filled with protocol-private options. On return
392 * this parameter will be destroyed and replaced with a dictionary
393 * containing options that were not found. May be NULL.
394 * @return >=0 on success or negative on error.
396 int avio_open_dir(AVIODirContext **s, const char *url, AVDictionary **options);
399 * Get next directory entry.
401 * Returned entry must be freed with avio_free_directory_entry(). In particular
402 * it may outlive AVIODirContext.
404 * @param s directory read context.
405 * @param[out] next next entry or NULL when no more entries.
406 * @return >=0 on success or negative on error. End of list is not considered an
409 int avio_read_dir(AVIODirContext *s, AVIODirEntry **next);
414 * @note Entries created using avio_read_dir() are not deleted and must be
415 * freeded with avio_free_directory_entry().
417 * @param s directory read context.
418 * @return >=0 on success or negative on error.
420 int avio_close_dir(AVIODirContext **s);
423 * Free entry allocated by avio_read_dir().
425 * @param entry entry to be freed.
427 void avio_free_directory_entry(AVIODirEntry **entry);
430 * Allocate and initialize an AVIOContext for buffered I/O. It must be later
431 * freed with av_free().
433 * @param buffer Memory block for input/output operations via AVIOContext.
434 * The buffer must be allocated with av_malloc() and friends.
435 * It may be freed and replaced with a new buffer by libavformat.
436 * AVIOContext.buffer holds the buffer currently in use,
437 * which must be later freed with av_free().
438 * @param buffer_size The buffer size is very important for performance.
439 * For protocols with fixed blocksize it should be set to this blocksize.
440 * For others a typical size is a cache page, e.g. 4kb.
441 * @param write_flag Set to 1 if the buffer should be writable, 0 otherwise.
442 * @param opaque An opaque pointer to user-specific data.
443 * @param read_packet A function for refilling the buffer, may be NULL.
444 * @param write_packet A function for writing the buffer contents, may be NULL.
445 * The function may not change the input buffers content.
446 * @param seek A function for seeking to specified byte position, may be NULL.
448 * @return Allocated AVIOContext or NULL on failure.
450 AVIOContext *avio_alloc_context(
451 unsigned char *buffer,
455 int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
456 int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
457 int64_t (*seek)(void *opaque, int64_t offset, int whence));
459 void avio_w8(AVIOContext *s, int b);
460 void avio_write(AVIOContext *s, const unsigned char *buf, int size);
461 void avio_wl64(AVIOContext *s, uint64_t val);
462 void avio_wb64(AVIOContext *s, uint64_t val);
463 void avio_wl32(AVIOContext *s, unsigned int val);
464 void avio_wb32(AVIOContext *s, unsigned int val);
465 void avio_wl24(AVIOContext *s, unsigned int val);
466 void avio_wb24(AVIOContext *s, unsigned int val);
467 void avio_wl16(AVIOContext *s, unsigned int val);
468 void avio_wb16(AVIOContext *s, unsigned int val);
471 * Write a NULL-terminated string.
472 * @return number of bytes written.
474 int avio_put_str(AVIOContext *s, const char *str);
477 * Convert an UTF-8 string to UTF-16LE and write it.
478 * @param s the AVIOContext
479 * @param str NULL-terminated UTF-8 string
481 * @return number of bytes written.
483 int avio_put_str16le(AVIOContext *s, const char *str);
486 * Convert an UTF-8 string to UTF-16BE and write it.
487 * @param s the AVIOContext
488 * @param str NULL-terminated UTF-8 string
490 * @return number of bytes written.
492 int avio_put_str16be(AVIOContext *s, const char *str);
495 * Mark the written bytestream as a specific type.
497 * Zero-length ranges are omitted from the output.
499 * @param time the stream time the current bytestream pos corresponds to
500 * (in AV_TIME_BASE units), or AV_NOPTS_VALUE if unknown or not
502 * @param type the kind of data written starting at the current pos
504 void avio_write_marker(AVIOContext *s, int64_t time, enum AVIODataMarkerType type);
507 * ORing this as the "whence" parameter to a seek function causes it to
508 * return the filesize without seeking anywhere. Supporting this is optional.
509 * If it is not supported then the seek function will return <0.
511 #define AVSEEK_SIZE 0x10000
514 * Passing this flag as the "whence" parameter to a seek function causes it to
515 * seek by any means (like reopening and linear reading) or other normally unreasonable
516 * means that can be extremely slow.
517 * This may be ignored by the seek code.
519 #define AVSEEK_FORCE 0x20000
522 * fseek() equivalent for AVIOContext.
523 * @return new position or AVERROR.
525 int64_t avio_seek(AVIOContext *s, int64_t offset, int whence);
528 * Skip given number of bytes forward
529 * @return new position or AVERROR.
531 int64_t avio_skip(AVIOContext *s, int64_t offset);
534 * ftell() equivalent for AVIOContext.
535 * @return position or AVERROR.
537 static av_always_inline int64_t avio_tell(AVIOContext *s)
539 return avio_seek(s, 0, SEEK_CUR);
544 * @return filesize or AVERROR
546 int64_t avio_size(AVIOContext *s);
549 * feof() equivalent for AVIOContext.
550 * @return non zero if and only if end of file
552 int avio_feof(AVIOContext *s);
555 * @deprecated use avio_feof()
558 int url_feof(AVIOContext *s);
561 /** @warning Writes up to 4 KiB per call */
562 int avio_printf(AVIOContext *s, const char *fmt, ...) av_printf_format(2, 3);
565 * Force flushing of buffered data.
567 * For write streams, force the buffered data to be immediately written to the output,
568 * without to wait to fill the internal buffer.
570 * For read streams, discard all currently buffered data, and advance the
571 * reported file position to that of the underlying stream. This does not
572 * read new data, and does not perform any seeks.
574 void avio_flush(AVIOContext *s);
577 * Read size bytes from AVIOContext into buf.
578 * @return number of bytes read or AVERROR
580 int avio_read(AVIOContext *s, unsigned char *buf, int size);
583 * @name Functions for reading from AVIOContext
586 * @note return 0 if EOF, so you cannot use it if EOF handling is
589 int avio_r8 (AVIOContext *s);
590 unsigned int avio_rl16(AVIOContext *s);
591 unsigned int avio_rl24(AVIOContext *s);
592 unsigned int avio_rl32(AVIOContext *s);
593 uint64_t avio_rl64(AVIOContext *s);
594 unsigned int avio_rb16(AVIOContext *s);
595 unsigned int avio_rb24(AVIOContext *s);
596 unsigned int avio_rb32(AVIOContext *s);
597 uint64_t avio_rb64(AVIOContext *s);
603 * Read a string from pb into buf. The reading will terminate when either
604 * a NULL character was encountered, maxlen bytes have been read, or nothing
605 * more can be read from pb. The result is guaranteed to be NULL-terminated, it
606 * will be truncated if buf is too small.
607 * Note that the string is not interpreted or validated in any way, it
608 * might get truncated in the middle of a sequence for multi-byte encodings.
610 * @return number of bytes read (is always <= maxlen).
611 * If reading ends on EOF or error, the return value will be one more than
612 * bytes actually read.
614 int avio_get_str(AVIOContext *pb, int maxlen, char *buf, int buflen);
617 * Read a UTF-16 string from pb and convert it to UTF-8.
618 * The reading will terminate when either a null or invalid character was
619 * encountered or maxlen bytes have been read.
620 * @return number of bytes read (is always <= maxlen)
622 int avio_get_str16le(AVIOContext *pb, int maxlen, char *buf, int buflen);
623 int avio_get_str16be(AVIOContext *pb, int maxlen, char *buf, int buflen);
627 * @name URL open modes
628 * The flags argument to avio_open must be one of the following
629 * constants, optionally ORed with other flags.
632 #define AVIO_FLAG_READ 1 /**< read-only */
633 #define AVIO_FLAG_WRITE 2 /**< write-only */
634 #define AVIO_FLAG_READ_WRITE (AVIO_FLAG_READ|AVIO_FLAG_WRITE) /**< read-write pseudo flag */
640 * Use non-blocking mode.
641 * If this flag is set, operations on the context will return
642 * AVERROR(EAGAIN) if they can not be performed immediately.
643 * If this flag is not set, operations on the context will never return
645 * Note that this flag does not affect the opening/connecting of the
646 * context. Connecting a protocol will always block if necessary (e.g. on
647 * network protocols) but never hang (e.g. on busy devices).
648 * Warning: non-blocking protocols is work-in-progress; this flag may be
651 #define AVIO_FLAG_NONBLOCK 8
655 * avio_read and avio_write should if possible be satisfied directly
656 * instead of going through a buffer, and avio_seek will always
657 * call the underlying seek function directly.
659 #define AVIO_FLAG_DIRECT 0x8000
662 * Create and initialize a AVIOContext for accessing the
663 * resource indicated by url.
664 * @note When the resource indicated by url has been opened in
665 * read+write mode, the AVIOContext can be used only for writing.
667 * @param s Used to return the pointer to the created AVIOContext.
668 * In case of failure the pointed to value is set to NULL.
669 * @param url resource to access
670 * @param flags flags which control how the resource indicated by url
672 * @return >= 0 in case of success, a negative value corresponding to an
673 * AVERROR code in case of failure
675 int avio_open(AVIOContext **s, const char *url, int flags);
678 * Create and initialize a AVIOContext for accessing the
679 * resource indicated by url.
680 * @note When the resource indicated by url has been opened in
681 * read+write mode, the AVIOContext can be used only for writing.
683 * @param s Used to return the pointer to the created AVIOContext.
684 * In case of failure the pointed to value is set to NULL.
685 * @param url resource to access
686 * @param flags flags which control how the resource indicated by url
688 * @param int_cb an interrupt callback to be used at the protocols level
689 * @param options A dictionary filled with protocol-private options. On return
690 * this parameter will be destroyed and replaced with a dict containing options
691 * that were not found. May be NULL.
692 * @return >= 0 in case of success, a negative value corresponding to an
693 * AVERROR code in case of failure
695 int avio_open2(AVIOContext **s, const char *url, int flags,
696 const AVIOInterruptCB *int_cb, AVDictionary **options);
699 * Close the resource accessed by the AVIOContext s and free it.
700 * This function can only be used if s was opened by avio_open().
702 * The internal buffer is automatically flushed before closing the
705 * @return 0 on success, an AVERROR < 0 on error.
708 int avio_close(AVIOContext *s);
711 * Close the resource accessed by the AVIOContext *s, free it
712 * and set the pointer pointing to it to NULL.
713 * This function can only be used if s was opened by avio_open().
715 * The internal buffer is automatically flushed before closing the
718 * @return 0 on success, an AVERROR < 0 on error.
721 int avio_closep(AVIOContext **s);
725 * Open a write only memory stream.
727 * @param s new IO context
728 * @return zero if no error.
730 int avio_open_dyn_buf(AVIOContext **s);
733 * Return the written size and a pointer to the buffer.
734 * The AVIOContext stream is left intact.
735 * The buffer must NOT be freed.
736 * No padding is added to the buffer.
738 * @param s IO context
739 * @param pbuffer pointer to a byte buffer
740 * @return the length of the byte buffer
742 int avio_get_dyn_buf(AVIOContext *s, uint8_t **pbuffer);
745 * Return the written size and a pointer to the buffer. The buffer
746 * must be freed with av_free().
747 * Padding of AV_INPUT_BUFFER_PADDING_SIZE is added to the buffer.
749 * @param s IO context
750 * @param pbuffer pointer to a byte buffer
751 * @return the length of the byte buffer
753 int avio_close_dyn_buf(AVIOContext *s, uint8_t **pbuffer);
756 * Iterate through names of available protocols.
758 * @param opaque A private pointer representing current protocol.
759 * It must be a pointer to NULL on first iteration and will
760 * be updated by successive calls to avio_enum_protocols.
761 * @param output If set to 1, iterate over output protocols,
762 * otherwise over input protocols.
764 * @return A static string containing the name of current protocol or NULL
766 const char *avio_enum_protocols(void **opaque, int output);
769 * Pause and resume playing - only meaningful if using a network streaming
770 * protocol (e.g. MMS).
772 * @param h IO context from which to call the read_pause function pointer
773 * @param pause 1 for pause, 0 for resume
775 int avio_pause(AVIOContext *h, int pause);
778 * Seek to a given timestamp relative to some component stream.
779 * Only meaningful if using a network streaming protocol (e.g. MMS.).
781 * @param h IO context from which to call the seek function pointers
782 * @param stream_index The stream index that the timestamp is relative to.
783 * If stream_index is (-1) the timestamp should be in AV_TIME_BASE
784 * units from the beginning of the presentation.
785 * If a stream_index >= 0 is used and the protocol does not support
786 * seeking based on component streams, the call will fail.
787 * @param timestamp timestamp in AVStream.time_base units
788 * or if there is no stream specified then in AV_TIME_BASE units.
789 * @param flags Optional combination of AVSEEK_FLAG_BACKWARD, AVSEEK_FLAG_BYTE
790 * and AVSEEK_FLAG_ANY. The protocol may silently ignore
791 * AVSEEK_FLAG_BACKWARD and AVSEEK_FLAG_ANY, but AVSEEK_FLAG_BYTE will
792 * fail if used and not supported.
793 * @return >= 0 on success
794 * @see AVInputFormat::read_seek
796 int64_t avio_seek_time(AVIOContext *h, int stream_index,
797 int64_t timestamp, int flags);
799 /* Avoid a warning. The header can not be included because it breaks c++. */
803 * Read contents of h into print buffer, up to max_size bytes, or up to EOF.
805 * @return 0 for success (max_size bytes read or EOF reached), negative error
808 int avio_read_to_bprint(AVIOContext *h, struct AVBPrint *pb, size_t max_size);
811 * Accept and allocate a client context on a server context.
812 * @param s the server context
813 * @param c the client context, must be unallocated
814 * @return >= 0 on success or a negative value corresponding
815 * to an AVERROR on failure
817 int avio_accept(AVIOContext *s, AVIOContext **c);
820 * Perform one step of the protocol handshake to accept a new client.
821 * This function must be called on a client returned by avio_accept() before
822 * using it as a read/write context.
823 * It is separate from avio_accept() because it may block.
824 * A step of the handshake is defined by places where the application may
825 * decide to change the proceedings.
826 * For example, on a protocol with a request header and a reply header, each
827 * one can constitute a step because the application may use the parameters
828 * from the request to change parameters in the reply; or each individual
829 * chunk of the request can constitute a step.
830 * If the handshake is already finished, avio_handshake() does nothing and
831 * returns 0 immediately.
833 * @param c the client context to perform the handshake on
834 * @return 0 on a complete and successful handshake
835 * > 0 if the handshake progressed, but is not complete
836 * < 0 for an AVERROR code
838 int avio_handshake(AVIOContext *c);
839 #endif /* AVFORMAT_AVIO_H */