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ffmpeg/libavformat/avio.h
Andreas Rheinhardt 2a68d945cd avformat/avio: Constify data pointees of write callbacks 
They are currently non-const for reasons unknown, although
avio_write() accepts a const buffer.

Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2023-09-10 22:55:42 +02:00

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/*
* copyright (c) 2001 Fabrice Bellard
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVFORMAT_AVIO_H
#define AVFORMAT_AVIO_H
/**
* @file
* @ingroup lavf_io
* Buffered I/O operations
*/
#include <stdint.h>
#include <stdio.h>
#include "libavutil/attributes.h"
#include "libavutil/dict.h"
#include "libavutil/log.h"
#include "libavformat/version_major.h"
/**
* Seeking works like for a local file.
*/
#define AVIO_SEEKABLE_NORMAL (1 << 0)
/**
* Seeking by timestamp with avio_seek_time() is possible.
*/
#define AVIO_SEEKABLE_TIME (1 << 1)
/**
* Callback for checking whether to abort blocking functions.
* AVERROR_EXIT is returned in this case by the interrupted
* function. During blocking operations, callback is called with
* opaque as parameter. If the callback returns 1, the
* blocking operation will be aborted.
*
* No members can be added to this struct without a major bump, if
* new elements have been added after this struct in AVFormatContext
* or AVIOContext.
*/
typedef struct AVIOInterruptCB {
int (*callback)(void*);
void *opaque;
} AVIOInterruptCB;
/**
* Directory entry types.
*/
enum AVIODirEntryType {
AVIO_ENTRY_UNKNOWN,
AVIO_ENTRY_BLOCK_DEVICE,
AVIO_ENTRY_CHARACTER_DEVICE,
AVIO_ENTRY_DIRECTORY,
AVIO_ENTRY_NAMED_PIPE,
AVIO_ENTRY_SYMBOLIC_LINK,
AVIO_ENTRY_SOCKET,
AVIO_ENTRY_FILE,
AVIO_ENTRY_SERVER,
AVIO_ENTRY_SHARE,
AVIO_ENTRY_WORKGROUP,
};
/**
* Describes single entry of the directory.
*
* Only name and type fields are guaranteed be set.
* Rest of fields are protocol or/and platform dependent and might be unknown.
*/
typedef struct AVIODirEntry {
char *name; /**< Filename */
int type; /**< Type of the entry */
int utf8; /**< Set to 1 when name is encoded with UTF-8, 0 otherwise.
Name can be encoded with UTF-8 even though 0 is set. */
int64_t size; /**< File size in bytes, -1 if unknown. */
int64_t modification_timestamp; /**< Time of last modification in microseconds since unix
epoch, -1 if unknown. */
int64_t access_timestamp; /**< Time of last access in microseconds since unix epoch,
-1 if unknown. */
int64_t status_change_timestamp; /**< Time of last status change in microseconds since unix
epoch, -1 if unknown. */
int64_t user_id; /**< User ID of owner, -1 if unknown. */
int64_t group_id; /**< Group ID of owner, -1 if unknown. */
int64_t filemode; /**< Unix file mode, -1 if unknown. */
} AVIODirEntry;
#if FF_API_AVIODIRCONTEXT
typedef struct AVIODirContext {
struct URLContext *url_context;
} AVIODirContext;
#else
typedef struct AVIODirContext AVIODirContext;
#endif
/**
* Different data types that can be returned via the AVIO
* write_data_type callback.
*/
enum AVIODataMarkerType {
/**
* Header data; this needs to be present for the stream to be decodeable.
*/
AVIO_DATA_MARKER_HEADER,
/**
* A point in the output bytestream where a decoder can start decoding
* (i.e. a keyframe). A demuxer/decoder given the data flagged with
* AVIO_DATA_MARKER_HEADER, followed by any AVIO_DATA_MARKER_SYNC_POINT,
* should give decodeable results.
*/
AVIO_DATA_MARKER_SYNC_POINT,
/**
* A point in the output bytestream where a demuxer can start parsing
* (for non self synchronizing bytestream formats). That is, any
* non-keyframe packet start point.
*/
AVIO_DATA_MARKER_BOUNDARY_POINT,
/**
* This is any, unlabelled data. It can either be a muxer not marking
* any positions at all, it can be an actual boundary/sync point
* that the muxer chooses not to mark, or a later part of a packet/fragment
* that is cut into multiple write callbacks due to limited IO buffer size.
*/
AVIO_DATA_MARKER_UNKNOWN,
/**
* Trailer data, which doesn't contain actual content, but only for
* finalizing the output file.
*/
AVIO_DATA_MARKER_TRAILER,
/**
* A point in the output bytestream where the underlying AVIOContext might
* flush the buffer depending on latency or buffering requirements. Typically
* means the end of a packet.
*/
AVIO_DATA_MARKER_FLUSH_POINT,
};
/**
* Bytestream IO Context.
* New public fields can be added with minor version bumps.
* Removal, reordering and changes to existing public fields require
* a major version bump.
* sizeof(AVIOContext) must not be used outside libav*.
*
* @note None of the function pointers in AVIOContext should be called
* directly, they should only be set by the client application
* when implementing custom I/O. Normally these are set to the
* function pointers specified in avio_alloc_context()
*/
typedef struct AVIOContext {
/**
* A class for private options.
*
* If this AVIOContext is created by avio_open2(), av_class is set and
* passes the options down to protocols.
*
* If this AVIOContext is manually allocated, then av_class may be set by
* the caller.
*
* warning -- this field can be NULL, be sure to not pass this AVIOContext
* to any av_opt_* functions in that case.
*/
const AVClass *av_class;
/*
* The following shows the relationship between buffer, buf_ptr,
* buf_ptr_max, buf_end, buf_size, and pos, when reading and when writing
* (since AVIOContext is used for both):
*
**********************************************************************************
* READING
**********************************************************************************
*
* | buffer_size |
* |---------------------------------------|
* | |
*
* buffer buf_ptr buf_end
* +---------------+-----------------------+
* |/ / / / / / / /|/ / / / / / /| |
* read buffer: |/ / consumed / | to be read /| |
* |/ / / / / / / /|/ / / / / / /| |
* +---------------+-----------------------+
*
* pos
* +-------------------------------------------+-----------------+
* input file: | | |
* +-------------------------------------------+-----------------+
*
*
**********************************************************************************
* WRITING
**********************************************************************************
*
* | buffer_size |
* |--------------------------------------|
* | |
*
* buf_ptr_max
* buffer (buf_ptr) buf_end
* +-----------------------+--------------+
* |/ / / / / / / / / / / /| |
* write buffer: | / / to be flushed / / | |
* |/ / / / / / / / / / / /| |
* +-----------------------+--------------+
* buf_ptr can be in this
* due to a backward seek
*
* pos
* +-------------+----------------------------------------------+
* output file: | | |
* +-------------+----------------------------------------------+
*
*/
unsigned char *buffer; /**< Start of the buffer. */
int buffer_size; /**< Maximum buffer size */
unsigned char *buf_ptr; /**< Current position in the buffer */
unsigned char *buf_end; /**< End of the data, may be less than
buffer+buffer_size if the read function returned
less data than requested, e.g. for streams where
no more data has been received yet. */
void *opaque; /**< A private pointer, passed to the read/write/seek/...
functions. */
int (*read_packet)(void *opaque, uint8_t *buf, int buf_size);
#if FF_API_AVIO_WRITE_NONCONST
int (*write_packet)(void *opaque, uint8_t *buf, int buf_size);
#else
int (*write_packet)(void *opaque, const uint8_t *buf, int buf_size);
#endif
int64_t (*seek)(void *opaque, int64_t offset, int whence);
int64_t pos; /**< position in the file of the current buffer */
int eof_reached; /**< true if was unable to read due to error or eof */
int error; /**< contains the error code or 0 if no error happened */
int write_flag; /**< true if open for writing */
int max_packet_size;
int min_packet_size; /**< Try to buffer at least this amount of data
before flushing it. */
unsigned long checksum;
unsigned char *checksum_ptr;
unsigned long (*update_checksum)(unsigned long checksum, const uint8_t *buf, unsigned int size);
/**
* Pause or resume playback for network streaming protocols - e.g. MMS.
*/
int (*read_pause)(void *opaque, int pause);
/**
* Seek to a given timestamp in stream with the specified stream_index.
* Needed for some network streaming protocols which don't support seeking
* to byte position.
*/
int64_t (*read_seek)(void *opaque, int stream_index,
int64_t timestamp, int flags);
/**
* A combination of AVIO_SEEKABLE_ flags or 0 when the stream is not seekable.
*/
int seekable;
/**
* avio_read and avio_write should if possible be satisfied directly
* instead of going through a buffer, and avio_seek will always
* call the underlying seek function directly.
*/
int direct;
/**
* ',' separated list of allowed protocols.
*/
const char *protocol_whitelist;
/**
* ',' separated list of disallowed protocols.
*/
const char *protocol_blacklist;
/**
* A callback that is used instead of write_packet.
*/
#if FF_API_AVIO_WRITE_NONCONST
int (*write_data_type)(void *opaque, uint8_t *buf, int buf_size,
enum AVIODataMarkerType type, int64_t time);
#else
int (*write_data_type)(void *opaque, const uint8_t *buf, int buf_size,
enum AVIODataMarkerType type, int64_t time);
#endif
/**
* If set, don't call write_data_type separately for AVIO_DATA_MARKER_BOUNDARY_POINT,
* but ignore them and treat them as AVIO_DATA_MARKER_UNKNOWN (to avoid needlessly
* small chunks of data returned from the callback).
*/
int ignore_boundary_point;
/**
* Maximum reached position before a backward seek in the write buffer,
* used keeping track of already written data for a later flush.
*/
unsigned char *buf_ptr_max;
/**
* Read-only statistic of bytes read for this AVIOContext.
*/
int64_t bytes_read;
/**
* Read-only statistic of bytes written for this AVIOContext.
*/
int64_t bytes_written;
} AVIOContext;
/**
* Return the name of the protocol that will handle the passed URL.
*
* NULL is returned if no protocol could be found for the given URL.
*
* @return Name of the protocol or NULL.
*/
const char *avio_find_protocol_name(const char *url);
/**
* Return AVIO_FLAG_* access flags corresponding to the access permissions
* of the resource in url, or a negative value corresponding to an
* AVERROR code in case of failure. The returned access flags are
* masked by the value in flags.
*
* @note This function is intrinsically unsafe, in the sense that the
* checked resource may change its existence or permission status from
* one call to another. Thus you should not trust the returned value,
* unless you are sure that no other processes are accessing the
* checked resource.
*/
int avio_check(const char *url, int flags);
/**
* Open directory for reading.
*
* @param s directory read context. Pointer to a NULL pointer must be passed.
* @param url directory to be listed.
* @param options A dictionary filled with protocol-private options. On return
* this parameter will be destroyed and replaced with a dictionary
* containing options that were not found. May be NULL.
* @return >=0 on success or negative on error.
*/
int avio_open_dir(AVIODirContext **s, const char *url, AVDictionary **options);
/**
* Get next directory entry.
*
* Returned entry must be freed with avio_free_directory_entry(). In particular
* it may outlive AVIODirContext.
*
* @param s directory read context.
* @param[out] next next entry or NULL when no more entries.
* @return >=0 on success or negative on error. End of list is not considered an
* error.
*/
int avio_read_dir(AVIODirContext *s, AVIODirEntry **next);
/**
* Close directory.
*
* @note Entries created using avio_read_dir() are not deleted and must be
* freeded with avio_free_directory_entry().
*
* @param s directory read context.
* @return >=0 on success or negative on error.
*/
int avio_close_dir(AVIODirContext **s);
/**
* Free entry allocated by avio_read_dir().
*
* @param entry entry to be freed.
*/
void avio_free_directory_entry(AVIODirEntry **entry);
/**
* Allocate and initialize an AVIOContext for buffered I/O. It must be later
* freed with avio_context_free().
*
* @param buffer Memory block for input/output operations via AVIOContext.
* The buffer must be allocated with av_malloc() and friends.
* It may be freed and replaced with a new buffer by libavformat.
* AVIOContext.buffer holds the buffer currently in use,
* which must be later freed with av_free().
* @param buffer_size The buffer size is very important for performance.
* For protocols with fixed blocksize it should be set to this blocksize.
* For others a typical size is a cache page, e.g. 4kb.
* @param write_flag Set to 1 if the buffer should be writable, 0 otherwise.
* @param opaque An opaque pointer to user-specific data.
* @param read_packet A function for refilling the buffer, may be NULL.
* For stream protocols, must never return 0 but rather
* a proper AVERROR code.
* @param write_packet A function for writing the buffer contents, may be NULL.
* The function may not change the input buffers content.
* @param seek A function for seeking to specified byte position, may be NULL.
*
* @return Allocated AVIOContext or NULL on failure.
*/
AVIOContext *avio_alloc_context(
unsigned char *buffer,
int buffer_size,
int write_flag,
void *opaque,
int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
#if FF_API_AVIO_WRITE_NONCONST
int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
#else
int (*write_packet)(void *opaque, const uint8_t *buf, int buf_size),
#endif
int64_t (*seek)(void *opaque, int64_t offset, int whence));
/**
* Free the supplied IO context and everything associated with it.
*
* @param s Double pointer to the IO context. This function will write NULL
* into s.
*/
void avio_context_free(AVIOContext **s);
void avio_w8(AVIOContext *s, int b);
void avio_write(AVIOContext *s, const unsigned char *buf, int size);
void avio_wl64(AVIOContext *s, uint64_t val);
void avio_wb64(AVIOContext *s, uint64_t val);
void avio_wl32(AVIOContext *s, unsigned int val);
void avio_wb32(AVIOContext *s, unsigned int val);
void avio_wl24(AVIOContext *s, unsigned int val);
void avio_wb24(AVIOContext *s, unsigned int val);
void avio_wl16(AVIOContext *s, unsigned int val);
void avio_wb16(AVIOContext *s, unsigned int val);
/**
* Write a NULL-terminated string.
* @return number of bytes written.
*/
int avio_put_str(AVIOContext *s, const char *str);
/**
* Convert an UTF-8 string to UTF-16LE and write it.
* @param s the AVIOContext
* @param str NULL-terminated UTF-8 string
*
* @return number of bytes written.
*/
int avio_put_str16le(AVIOContext *s, const char *str);
/**
* Convert an UTF-8 string to UTF-16BE and write it.
* @param s the AVIOContext
* @param str NULL-terminated UTF-8 string
*
* @return number of bytes written.
*/
int avio_put_str16be(AVIOContext *s, const char *str);
/**
* Mark the written bytestream as a specific type.
*
* Zero-length ranges are omitted from the output.
*
* @param s the AVIOContext
* @param time the stream time the current bytestream pos corresponds to
* (in AV_TIME_BASE units), or AV_NOPTS_VALUE if unknown or not
* applicable
* @param type the kind of data written starting at the current pos
*/
void avio_write_marker(AVIOContext *s, int64_t time, enum AVIODataMarkerType type);
/**
* ORing this as the "whence" parameter to a seek function causes it to
* return the filesize without seeking anywhere. Supporting this is optional.
* If it is not supported then the seek function will return <0.
*/
#define AVSEEK_SIZE 0x10000
/**
* Passing this flag as the "whence" parameter to a seek function causes it to
* seek by any means (like reopening and linear reading) or other normally unreasonable
* means that can be extremely slow.
* This may be ignored by the seek code.
*/
#define AVSEEK_FORCE 0x20000
/**
* fseek() equivalent for AVIOContext.
* @return new position or AVERROR.
*/
int64_t avio_seek(AVIOContext *s, int64_t offset, int whence);
/**
* Skip given number of bytes forward
* @return new position or AVERROR.
*/
int64_t avio_skip(AVIOContext *s, int64_t offset);
/**
* ftell() equivalent for AVIOContext.
* @return position or AVERROR.
*/
static av_always_inline int64_t avio_tell(AVIOContext *s)
{
return avio_seek(s, 0, SEEK_CUR);
}
/**
* Get the filesize.
* @return filesize or AVERROR
*/
int64_t avio_size(AVIOContext *s);
/**
* Similar to feof() but also returns nonzero on read errors.
* @return non zero if and only if at end of file or a read error happened when reading.
*/
int avio_feof(AVIOContext *s);
/**
* Writes a formatted string to the context taking a va_list.
* @return number of bytes written, < 0 on error.
*/
int avio_vprintf(AVIOContext *s, const char *fmt, va_list ap);
/**
* Writes a formatted string to the context.
* @return number of bytes written, < 0 on error.
*/
int avio_printf(AVIOContext *s, const char *fmt, ...) av_printf_format(2, 3);
/**
* Write a NULL terminated array of strings to the context.
* Usually you don't need to use this function directly but its macro wrapper,
* avio_print.
*/
void avio_print_string_array(AVIOContext *s, const char *strings[]);
/**
* Write strings (const char *) to the context.
* This is a convenience macro around avio_print_string_array and it
* automatically creates the string array from the variable argument list.
* For simple string concatenations this function is more performant than using
* avio_printf since it does not need a temporary buffer.
*/
#define avio_print(s, ...) \
avio_print_string_array(s, (const char*[]){__VA_ARGS__, NULL})
/**
* Force flushing of buffered data.
*
* For write streams, force the buffered data to be immediately written to the output,
* without to wait to fill the internal buffer.
*
* For read streams, discard all currently buffered data, and advance the
* reported file position to that of the underlying stream. This does not
* read new data, and does not perform any seeks.
*/
void avio_flush(AVIOContext *s);
/**
* Read size bytes from AVIOContext into buf.
* @return number of bytes read or AVERROR
*/
int avio_read(AVIOContext *s, unsigned char *buf, int size);
/**
* Read size bytes from AVIOContext into buf. Unlike avio_read(), this is allowed
* to read fewer bytes than requested. The missing bytes can be read in the next
* call. This always tries to read at least 1 byte.
* Useful to reduce latency in certain cases.
* @return number of bytes read or AVERROR
*/
int avio_read_partial(AVIOContext *s, unsigned char *buf, int size);
/**
* @name Functions for reading from AVIOContext
* @{
*
* @note return 0 if EOF, so you cannot use it if EOF handling is
* necessary
*/
int avio_r8 (AVIOContext *s);
unsigned int avio_rl16(AVIOContext *s);
unsigned int avio_rl24(AVIOContext *s);
unsigned int avio_rl32(AVIOContext *s);
uint64_t avio_rl64(AVIOContext *s);
unsigned int avio_rb16(AVIOContext *s);
unsigned int avio_rb24(AVIOContext *s);
unsigned int avio_rb32(AVIOContext *s);
uint64_t avio_rb64(AVIOContext *s);
/**
* @}
*/
/**
* Read a string from pb into buf. The reading will terminate when either
* a NULL character was encountered, maxlen bytes have been read, or nothing
* more can be read from pb. The result is guaranteed to be NULL-terminated, it
* will be truncated if buf is too small.
* Note that the string is not interpreted or validated in any way, it
* might get truncated in the middle of a sequence for multi-byte encodings.
*
* @return number of bytes read (is always <= maxlen).
* If reading ends on EOF or error, the return value will be one more than
* bytes actually read.
*/
int avio_get_str(AVIOContext *pb, int maxlen, char *buf, int buflen);
/**
* Read a UTF-16 string from pb and convert it to UTF-8.
* The reading will terminate when either a null or invalid character was
* encountered or maxlen bytes have been read.
* @return number of bytes read (is always <= maxlen)
*/
int avio_get_str16le(AVIOContext *pb, int maxlen, char *buf, int buflen);
int avio_get_str16be(AVIOContext *pb, int maxlen, char *buf, int buflen);
/**
* @name URL open modes
* The flags argument to avio_open must be one of the following
* constants, optionally ORed with other flags.
* @{
*/
#define AVIO_FLAG_READ 1 /**< read-only */
#define AVIO_FLAG_WRITE 2 /**< write-only */
#define AVIO_FLAG_READ_WRITE (AVIO_FLAG_READ|AVIO_FLAG_WRITE) /**< read-write pseudo flag */
/**
* @}
*/
/**
* Use non-blocking mode.
* If this flag is set, operations on the context will return
* AVERROR(EAGAIN) if they can not be performed immediately.
* If this flag is not set, operations on the context will never return
* AVERROR(EAGAIN).
* Note that this flag does not affect the opening/connecting of the
* context. Connecting a protocol will always block if necessary (e.g. on
* network protocols) but never hang (e.g. on busy devices).
* Warning: non-blocking protocols is work-in-progress; this flag may be
* silently ignored.
*/
#define AVIO_FLAG_NONBLOCK 8
/**
* Use direct mode.
* avio_read and avio_write should if possible be satisfied directly
* instead of going through a buffer, and avio_seek will always
* call the underlying seek function directly.
*/
#define AVIO_FLAG_DIRECT 0x8000
/**
* Create and initialize a AVIOContext for accessing the
* resource indicated by url.
* @note When the resource indicated by url has been opened in
* read+write mode, the AVIOContext can be used only for writing.
*
* @param s Used to return the pointer to the created AVIOContext.
* In case of failure the pointed to value is set to NULL.
* @param url resource to access
* @param flags flags which control how the resource indicated by url
* is to be opened
* @return >= 0 in case of success, a negative value corresponding to an
* AVERROR code in case of failure
*/
int avio_open(AVIOContext **s, const char *url, int flags);
/**
* Create and initialize a AVIOContext for accessing the
* resource indicated by url.
* @note When the resource indicated by url has been opened in
* read+write mode, the AVIOContext can be used only for writing.
*
* @param s Used to return the pointer to the created AVIOContext.
* In case of failure the pointed to value is set to NULL.
* @param url resource to access
* @param flags flags which control how the resource indicated by url
* is to be opened
* @param int_cb an interrupt callback to be used at the protocols level
* @param options A dictionary filled with protocol-private options. On return
* this parameter will be destroyed and replaced with a dict containing options
* that were not found. May be NULL.
* @return >= 0 in case of success, a negative value corresponding to an
* AVERROR code in case of failure
*/
int avio_open2(AVIOContext **s, const char *url, int flags,
const AVIOInterruptCB *int_cb, AVDictionary **options);
/**
* Close the resource accessed by the AVIOContext s and free it.
* This function can only be used if s was opened by avio_open().
*
* The internal buffer is automatically flushed before closing the
* resource.
*
* @return 0 on success, an AVERROR < 0 on error.
* @see avio_closep
*/
int avio_close(AVIOContext *s);
/**
* Close the resource accessed by the AVIOContext *s, free it
* and set the pointer pointing to it to NULL.
* This function can only be used if s was opened by avio_open().
*
* The internal buffer is automatically flushed before closing the
* resource.
*
* @return 0 on success, an AVERROR < 0 on error.
* @see avio_close
*/
int avio_closep(AVIOContext **s);
/**
* Open a write only memory stream.
*
* @param s new IO context
* @return zero if no error.
*/
int avio_open_dyn_buf(AVIOContext **s);
/**
* Return the written size and a pointer to the buffer.
* The AVIOContext stream is left intact.
* The buffer must NOT be freed.
* No padding is added to the buffer.
*
* @param s IO context
* @param pbuffer pointer to a byte buffer
* @return the length of the byte buffer
*/
int avio_get_dyn_buf(AVIOContext *s, uint8_t **pbuffer);
/**
* Return the written size and a pointer to the buffer. The buffer
* must be freed with av_free().
* Padding of AV_INPUT_BUFFER_PADDING_SIZE is added to the buffer.
*
* @param s IO context
* @param pbuffer pointer to a byte buffer
* @return the length of the byte buffer
*/
int avio_close_dyn_buf(AVIOContext *s, uint8_t **pbuffer);
/**
* Iterate through names of available protocols.
*
* @param opaque A private pointer representing current protocol.
* It must be a pointer to NULL on first iteration and will
* be updated by successive calls to avio_enum_protocols.
* @param output If set to 1, iterate over output protocols,
* otherwise over input protocols.
*
* @return A static string containing the name of current protocol or NULL
*/
const char *avio_enum_protocols(void **opaque, int output);
/**
* Get AVClass by names of available protocols.
*
* @return A AVClass of input protocol name or NULL
*/
const AVClass *avio_protocol_get_class(const char *name);
/**
* Pause and resume playing - only meaningful if using a network streaming
* protocol (e.g. MMS).
*
* @param h IO context from which to call the read_pause function pointer
* @param pause 1 for pause, 0 for resume
*/
int avio_pause(AVIOContext *h, int pause);
/**
* Seek to a given timestamp relative to some component stream.
* Only meaningful if using a network streaming protocol (e.g. MMS.).
*
* @param h IO context from which to call the seek function pointers
* @param stream_index The stream index that the timestamp is relative to.
* If stream_index is (-1) the timestamp should be in AV_TIME_BASE
* units from the beginning of the presentation.
* If a stream_index >= 0 is used and the protocol does not support
* seeking based on component streams, the call will fail.
* @param timestamp timestamp in AVStream.time_base units
* or if there is no stream specified then in AV_TIME_BASE units.
* @param flags Optional combination of AVSEEK_FLAG_BACKWARD, AVSEEK_FLAG_BYTE
* and AVSEEK_FLAG_ANY. The protocol may silently ignore
* AVSEEK_FLAG_BACKWARD and AVSEEK_FLAG_ANY, but AVSEEK_FLAG_BYTE will
* fail if used and not supported.
* @return >= 0 on success
* @see AVInputFormat::read_seek
*/
int64_t avio_seek_time(AVIOContext *h, int stream_index,
int64_t timestamp, int flags);
/* Avoid a warning. The header can not be included because it breaks c++. */
struct AVBPrint;
/**
* Read contents of h into print buffer, up to max_size bytes, or up to EOF.
*
* @return 0 for success (max_size bytes read or EOF reached), negative error
* code otherwise
*/
int avio_read_to_bprint(AVIOContext *h, struct AVBPrint *pb, size_t max_size);
/**
* Accept and allocate a client context on a server context.
* @param s the server context
* @param c the client context, must be unallocated
* @return >= 0 on success or a negative value corresponding
* to an AVERROR on failure
*/
int avio_accept(AVIOContext *s, AVIOContext **c);
/**
* Perform one step of the protocol handshake to accept a new client.
* This function must be called on a client returned by avio_accept() before
* using it as a read/write context.
* It is separate from avio_accept() because it may block.
* A step of the handshake is defined by places where the application may
* decide to change the proceedings.
* For example, on a protocol with a request header and a reply header, each
* one can constitute a step because the application may use the parameters
* from the request to change parameters in the reply; or each individual
* chunk of the request can constitute a step.
* If the handshake is already finished, avio_handshake() does nothing and
* returns 0 immediately.
*
* @param c the client context to perform the handshake on
* @return 0 on a complete and successful handshake
* > 0 if the handshake progressed, but is not complete
* < 0 for an AVERROR code
*/
int avio_handshake(AVIOContext *c);
#endif /* AVFORMAT_AVIO_H */
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