FFmpeg/libavformat/avio.h
Martin Storsjö db7968bff4 avio: Allow custom IO users to get labels for the output bytestream
This allows callers with avio write callbacks to get the bytestream
positions that correspond to keyframes, suitable for live streaming.

In the simplest form, a caller could expect that a header is written
to the bytestream during the avformat_write_header, and the data
output to the avio context during e.g. av_write_frame corresponds
exactly to the current packet passed in.

When combined with av_interleaved_write_frame, and with muxers that
do buffering (most muxers that do some sort of fragmenting or
clustering), the mapping from input data to bytestream positions
is nontrivial.

This allows callers to get directly information about what part
of the bytestream is what, without having to resort to assumptions
about the muxer behaviour.

One keyframe/fragment/block can still be split into multiple (if
they are larger than the aviocontext buffer), which would call
the callback with e.g. AVIO_DATA_MARKER_SYNC_POINT, followed by
AVIO_DATA_MARKER_UNKNOWN for the second time it is called with
the following data.

Signed-off-by: Martin Storsjö <martin@martin.st>
2016-05-18 10:36:45 +03:00

516 lines
18 KiB
C

/*
* copyright (c) 2001 Fabrice Bellard
*
* This file is part of Libav.
*
* Libav 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.
*
* Libav 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 Libav; 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 "libavutil/common.h"
#include "libavutil/dict.h"
#include "libavutil/log.h"
#include "libavformat/version.h"
#define AVIO_SEEKABLE_NORMAL 0x0001 /**< Seeking works like for a local file */
/**
* 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;
/**
* 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
};
/**
* Bytestream IO Context.
* New fields can be added to the end with minor version bumps.
* Removal, reordering and changes to existing 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;
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);
int (*write_packet)(void *opaque, uint8_t *buf, int buf_size);
int64_t (*seek)(void *opaque, int64_t offset, int whence);
int64_t pos; /**< position in the file of the current buffer */
int must_flush; /**< true if the next seek should flush */
int eof_reached; /**< true if eof reached */
int write_flag; /**< true if open for writing */
int max_packet_size;
unsigned long checksum;
unsigned char *checksum_ptr;
unsigned long (*update_checksum)(unsigned long checksum, const uint8_t *buf, unsigned int size);
int error; /**< contains the error code or 0 if no error happened */
/**
* 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;
/**
* A callback that is used instead of write_packet.
*/
int (*write_data_type)(void *opaque, uint8_t *buf, int buf_size,
enum AVIODataMarkerType type, int64_t time);
/**
* 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;
/**
* Internal, not meant to be used from outside of AVIOContext.
*/
enum AVIODataMarkerType current_type;
int64_t last_time;
} AVIOContext;
/**
* 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);
/**
* Allocate and initialize an AVIOContext for buffered I/O. It must be later
* freed with av_free().
*
* @param buffer Memory block for input/output operations via AVIOContext.
* The buffer must be allocated with av_malloc() and friends.
* @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.
* @param write_packet A function for writing the buffer contents, may be NULL.
* @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),
int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
int64_t (*seek)(void *opaque, int64_t offset, int whence));
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 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.
*/
static av_always_inline int64_t avio_skip(AVIOContext *s, int64_t offset)
{
return avio_seek(s, offset, SEEK_CUR);
}
/**
* 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);
/** @warning currently size is limited */
int avio_printf(AVIOContext *s, const char *fmt, ...) av_printf_format(2, 3);
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);
/**
* @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
/**
* 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 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);
/**
* 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 with ENOTSUP.
* @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 with ENOTSUP 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);
#endif /* AVFORMAT_AVIO_H */