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avio.h
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1 /*
2  * copyright (c) 2001 Fabrice Bellard
3  *
4  * This file is part of FFmpeg.
5  *
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.
10  *
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.
15  *
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
19  */
20 #ifndef AVFORMAT_AVIO_H
21 #define AVFORMAT_AVIO_H
22 
23 /**
24  * @file
25  * @ingroup lavf_io
26  * Buffered I/O operations
27  */
28 
29 #include <stdint.h>
30 
31 #include "libavutil/common.h"
32 #include "libavutil/dict.h"
33 #include "libavutil/log.h"
34 
35 #include "libavformat/version.h"
36 
37 
38 #define AVIO_SEEKABLE_NORMAL 0x0001 /**< Seeking works like for a local file */
39 
40 /**
41  * Callback for checking whether to abort blocking functions.
42  * AVERROR_EXIT is returned in this case by the interrupted
43  * function. During blocking operations, callback is called with
44  * opaque as parameter. If the callback returns 1, the
45  * blocking operation will be aborted.
46  *
47  * No members can be added to this struct without a major bump, if
48  * new elements have been added after this struct in AVFormatContext
49  * or AVIOContext.
50  */
51 typedef struct AVIOInterruptCB {
52  int (*callback)(void*);
53  void *opaque;
55 
56 /**
57  * Bytestream IO Context.
58  * New fields can be added to the end with minor version bumps.
59  * Removal, reordering and changes to existing fields require a major
60  * version bump.
61  * sizeof(AVIOContext) must not be used outside libav*.
62  *
63  * @note None of the function pointers in AVIOContext should be called
64  * directly, they should only be set by the client application
65  * when implementing custom I/O. Normally these are set to the
66  * function pointers specified in avio_alloc_context()
67  */
68 typedef struct AVIOContext {
69  /**
70  * A class for private options.
71  *
72  * If this AVIOContext is created by avio_open2(), av_class is set and
73  * passes the options down to protocols.
74  *
75  * If this AVIOContext is manually allocated, then av_class may be set by
76  * the caller.
77  *
78  * warning -- this field can be NULL, be sure to not pass this AVIOContext
79  * to any av_opt_* functions in that case.
80  */
81  const AVClass *av_class;
82  unsigned char *buffer; /**< Start of the buffer. */
83  int buffer_size; /**< Maximum buffer size */
84  unsigned char *buf_ptr; /**< Current position in the buffer */
85  unsigned char *buf_end; /**< End of the data, may be less than
86  buffer+buffer_size if the read function returned
87  less data than requested, e.g. for streams where
88  no more data has been received yet. */
89  void *opaque; /**< A private pointer, passed to the read/write/seek/...
90  functions. */
91  int (*read_packet)(void *opaque, uint8_t *buf, int buf_size);
92  int (*write_packet)(void *opaque, uint8_t *buf, int buf_size);
93  int64_t (*seek)(void *opaque, int64_t offset, int whence);
94  int64_t pos; /**< position in the file of the current buffer */
95  int must_flush; /**< true if the next seek should flush */
96  int eof_reached; /**< true if eof reached */
97  int write_flag; /**< true if open for writing */
99  unsigned long checksum;
100  unsigned char *checksum_ptr;
101  unsigned long (*update_checksum)(unsigned long checksum, const uint8_t *buf, unsigned int size);
102  int error; /**< contains the error code or 0 if no error happened */
103  /**
104  * Pause or resume playback for network streaming protocols - e.g. MMS.
105  */
106  int (*read_pause)(void *opaque, int pause);
107  /**
108  * Seek to a given timestamp in stream with the specified stream_index.
109  * Needed for some network streaming protocols which don't support seeking
110  * to byte position.
111  */
112  int64_t (*read_seek)(void *opaque, int stream_index,
113  int64_t timestamp, int flags);
114  /**
115  * A combination of AVIO_SEEKABLE_ flags or 0 when the stream is not seekable.
116  */
117  int seekable;
118 
119  /**
120  * max filesize, used to limit allocations
121  * This field is internal to libavformat and access from outside is not allowed.
122  */
123  int64_t maxsize;
124 
125  /**
126  * avio_read and avio_write should if possible be satisfied directly
127  * instead of going through a buffer, and avio_seek will always
128  * call the underlying seek function directly.
129  */
130  int direct;
131 
132  /**
133  * Bytes read statistic
134  * This field is internal to libavformat and access from outside is not allowed.
135  */
136  int64_t bytes_read;
137 
138  /**
139  * seek statistic
140  * This field is internal to libavformat and access from outside is not allowed.
141  */
143 
144  /**
145  * writeout statistic
146  * This field is internal to libavformat and access from outside is not allowed.
147  */
149 
150  /**
151  * Original buffer size
152  * used internally after probing and ensure seekback to reset the buffer size
153  * This field is internal to libavformat and access from outside is not allowed.
154  */
156 } AVIOContext;
157 
158 /* unbuffered I/O */
159 
160 /**
161  * Return the name of the protocol that will handle the passed URL.
162  *
163  * NULL is returned if no protocol could be found for the given URL.
164  *
165  * @return Name of the protocol or NULL.
166  */
167 const char *avio_find_protocol_name(const char *url);
168 
169 /**
170  * Return AVIO_FLAG_* access flags corresponding to the access permissions
171  * of the resource in url, or a negative value corresponding to an
172  * AVERROR code in case of failure. The returned access flags are
173  * masked by the value in flags.
174  *
175  * @note This function is intrinsically unsafe, in the sense that the
176  * checked resource may change its existence or permission status from
177  * one call to another. Thus you should not trust the returned value,
178  * unless you are sure that no other processes are accessing the
179  * checked resource.
180  */
181 int avio_check(const char *url, int flags);
182 
183 /**
184  * Allocate and initialize an AVIOContext for buffered I/O. It must be later
185  * freed with av_free().
186  *
187  * @param buffer Memory block for input/output operations via AVIOContext.
188  * The buffer must be allocated with av_malloc() and friends.
189  * It may be freed and replaced with a new buffer by libavformat.
190  * AVIOContext.buffer holds the buffer currently in use,
191  * which must be later freed with av_free().
192  * @param buffer_size The buffer size is very important for performance.
193  * For protocols with fixed blocksize it should be set to this blocksize.
194  * For others a typical size is a cache page, e.g. 4kb.
195  * @param write_flag Set to 1 if the buffer should be writable, 0 otherwise.
196  * @param opaque An opaque pointer to user-specific data.
197  * @param read_packet A function for refilling the buffer, may be NULL.
198  * @param write_packet A function for writing the buffer contents, may be NULL.
199  * The function may not change the input buffers content.
200  * @param seek A function for seeking to specified byte position, may be NULL.
201  *
202  * @return Allocated AVIOContext or NULL on failure.
203  */
205  unsigned char *buffer,
206  int buffer_size,
207  int write_flag,
208  void *opaque,
209  int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
210  int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
211  int64_t (*seek)(void *opaque, int64_t offset, int whence));
212 
213 void avio_w8(AVIOContext *s, int b);
214 void avio_write(AVIOContext *s, const unsigned char *buf, int size);
215 void avio_wl64(AVIOContext *s, uint64_t val);
216 void avio_wb64(AVIOContext *s, uint64_t val);
217 void avio_wl32(AVIOContext *s, unsigned int val);
218 void avio_wb32(AVIOContext *s, unsigned int val);
219 void avio_wl24(AVIOContext *s, unsigned int val);
220 void avio_wb24(AVIOContext *s, unsigned int val);
221 void avio_wl16(AVIOContext *s, unsigned int val);
222 void avio_wb16(AVIOContext *s, unsigned int val);
223 
224 /**
225  * Write a NULL-terminated string.
226  * @return number of bytes written.
227  */
228 int avio_put_str(AVIOContext *s, const char *str);
229 
230 /**
231  * Convert an UTF-8 string to UTF-16LE and write it.
232  * @return number of bytes written.
233  */
234 int avio_put_str16le(AVIOContext *s, const char *str);
235 
236 /**
237  * Passing this as the "whence" parameter to a seek function causes it to
238  * return the filesize without seeking anywhere. Supporting this is optional.
239  * If it is not supported then the seek function will return <0.
240  */
241 #define AVSEEK_SIZE 0x10000
242 
243 /**
244  * Oring this flag as into the "whence" parameter to a seek function causes it to
245  * seek by any means (like reopening and linear reading) or other normally unreasonable
246  * means that can be extremely slow.
247  * This may be ignored by the seek code.
248  */
249 #define AVSEEK_FORCE 0x20000
250 
251 /**
252  * fseek() equivalent for AVIOContext.
253  * @return new position or AVERROR.
254  */
255 int64_t avio_seek(AVIOContext *s, int64_t offset, int whence);
256 
257 /**
258  * Skip given number of bytes forward
259  * @return new position or AVERROR.
260  */
261 int64_t avio_skip(AVIOContext *s, int64_t offset);
262 
263 /**
264  * ftell() equivalent for AVIOContext.
265  * @return position or AVERROR.
266  */
268 {
269  return avio_seek(s, 0, SEEK_CUR);
270 }
271 
272 /**
273  * Get the filesize.
274  * @return filesize or AVERROR
275  */
276 int64_t avio_size(AVIOContext *s);
277 
278 /**
279  * feof() equivalent for AVIOContext.
280  * @return non zero if and only if end of file
281  */
282 int avio_feof(AVIOContext *s);
283 #if FF_API_URL_FEOF
284 /**
285  * @deprecated use avio_feof()
286  */
288 int url_feof(AVIOContext *s);
289 #endif
290 
291 /** @warning currently size is limited */
292 int avio_printf(AVIOContext *s, const char *fmt, ...) av_printf_format(2, 3);
293 
294 /**
295  * Force flushing of buffered data.
296  *
297  * For write streams, force the buffered data to be immediately written to the output,
298  * without to wait to fill the internal buffer.
299  *
300  * For read streams, discard all currently buffered data, and advance the
301  * reported file position to that of the underlying stream. This does not
302  * read new data, and does not perform any seeks.
303  */
304 void avio_flush(AVIOContext *s);
305 
306 /**
307  * Read size bytes from AVIOContext into buf.
308  * @return number of bytes read or AVERROR
309  */
310 int avio_read(AVIOContext *s, unsigned char *buf, int size);
311 
312 /**
313  * @name Functions for reading from AVIOContext
314  * @{
315  *
316  * @note return 0 if EOF, so you cannot use it if EOF handling is
317  * necessary
318  */
319 int avio_r8 (AVIOContext *s);
320 unsigned int avio_rl16(AVIOContext *s);
321 unsigned int avio_rl24(AVIOContext *s);
322 unsigned int avio_rl32(AVIOContext *s);
323 uint64_t avio_rl64(AVIOContext *s);
324 unsigned int avio_rb16(AVIOContext *s);
325 unsigned int avio_rb24(AVIOContext *s);
326 unsigned int avio_rb32(AVIOContext *s);
327 uint64_t avio_rb64(AVIOContext *s);
328 /**
329  * @}
330  */
331 
332 /**
333  * Read a string from pb into buf. The reading will terminate when either
334  * a NULL character was encountered, maxlen bytes have been read, or nothing
335  * more can be read from pb. The result is guaranteed to be NULL-terminated, it
336  * will be truncated if buf is too small.
337  * Note that the string is not interpreted or validated in any way, it
338  * might get truncated in the middle of a sequence for multi-byte encodings.
339  *
340  * @return number of bytes read (is always <= maxlen).
341  * If reading ends on EOF or error, the return value will be one more than
342  * bytes actually read.
343  */
344 int avio_get_str(AVIOContext *pb, int maxlen, char *buf, int buflen);
345 
346 /**
347  * Read a UTF-16 string from pb and convert it to UTF-8.
348  * The reading will terminate when either a null or invalid character was
349  * encountered or maxlen bytes have been read.
350  * @return number of bytes read (is always <= maxlen)
351  */
352 int avio_get_str16le(AVIOContext *pb, int maxlen, char *buf, int buflen);
353 int avio_get_str16be(AVIOContext *pb, int maxlen, char *buf, int buflen);
354 
355 
356 /**
357  * @name URL open modes
358  * The flags argument to avio_open must be one of the following
359  * constants, optionally ORed with other flags.
360  * @{
361  */
362 #define AVIO_FLAG_READ 1 /**< read-only */
363 #define AVIO_FLAG_WRITE 2 /**< write-only */
364 #define AVIO_FLAG_READ_WRITE (AVIO_FLAG_READ|AVIO_FLAG_WRITE) /**< read-write pseudo flag */
365 /**
366  * @}
367  */
368 
369 /**
370  * Use non-blocking mode.
371  * If this flag is set, operations on the context will return
372  * AVERROR(EAGAIN) if they can not be performed immediately.
373  * If this flag is not set, operations on the context will never return
374  * AVERROR(EAGAIN).
375  * Note that this flag does not affect the opening/connecting of the
376  * context. Connecting a protocol will always block if necessary (e.g. on
377  * network protocols) but never hang (e.g. on busy devices).
378  * Warning: non-blocking protocols is work-in-progress; this flag may be
379  * silently ignored.
380  */
381 #define AVIO_FLAG_NONBLOCK 8
382 
383 /**
384  * Use direct mode.
385  * avio_read and avio_write should if possible be satisfied directly
386  * instead of going through a buffer, and avio_seek will always
387  * call the underlying seek function directly.
388  */
389 #define AVIO_FLAG_DIRECT 0x8000
390 
391 /**
392  * Create and initialize a AVIOContext for accessing the
393  * resource indicated by url.
394  * @note When the resource indicated by url has been opened in
395  * read+write mode, the AVIOContext can be used only for writing.
396  *
397  * @param s Used to return the pointer to the created AVIOContext.
398  * In case of failure the pointed to value is set to NULL.
399  * @param url resource to access
400  * @param flags flags which control how the resource indicated by url
401  * is to be opened
402  * @return >= 0 in case of success, a negative value corresponding to an
403  * AVERROR code in case of failure
404  */
405 int avio_open(AVIOContext **s, const char *url, int flags);
406 
407 /**
408  * Create and initialize a AVIOContext for accessing the
409  * resource indicated by url.
410  * @note When the resource indicated by url has been opened in
411  * read+write mode, the AVIOContext can be used only for writing.
412  *
413  * @param s Used to return the pointer to the created AVIOContext.
414  * In case of failure the pointed to value is set to NULL.
415  * @param url resource to access
416  * @param flags flags which control how the resource indicated by url
417  * is to be opened
418  * @param int_cb an interrupt callback to be used at the protocols level
419  * @param options A dictionary filled with protocol-private options. On return
420  * this parameter will be destroyed and replaced with a dict containing options
421  * that were not found. May be NULL.
422  * @return >= 0 in case of success, a negative value corresponding to an
423  * AVERROR code in case of failure
424  */
425 int avio_open2(AVIOContext **s, const char *url, int flags,
427 
428 /**
429  * Close the resource accessed by the AVIOContext s and free it.
430  * This function can only be used if s was opened by avio_open().
431  *
432  * The internal buffer is automatically flushed before closing the
433  * resource.
434  *
435  * @return 0 on success, an AVERROR < 0 on error.
436  * @see avio_closep
437  */
438 int avio_close(AVIOContext *s);
439 
440 /**
441  * Close the resource accessed by the AVIOContext *s, free it
442  * and set the pointer pointing to it to NULL.
443  * This function can only be used if s was opened by avio_open().
444  *
445  * The internal buffer is automatically flushed before closing the
446  * resource.
447  *
448  * @return 0 on success, an AVERROR < 0 on error.
449  * @see avio_close
450  */
451 int avio_closep(AVIOContext **s);
452 
453 
454 /**
455  * Open a write only memory stream.
456  *
457  * @param s new IO context
458  * @return zero if no error.
459  */
461 
462 /**
463  * Return the written size and a pointer to the buffer. The buffer
464  * must be freed with av_free().
465  * Padding of FF_INPUT_BUFFER_PADDING_SIZE is added to the buffer.
466  *
467  * @param s IO context
468  * @param pbuffer pointer to a byte buffer
469  * @return the length of the byte buffer
470  */
471 int avio_close_dyn_buf(AVIOContext *s, uint8_t **pbuffer);
472 
473 /**
474  * Iterate through names of available protocols.
475  *
476  * @param opaque A private pointer representing current protocol.
477  * It must be a pointer to NULL on first iteration and will
478  * be updated by successive calls to avio_enum_protocols.
479  * @param output If set to 1, iterate over output protocols,
480  * otherwise over input protocols.
481  *
482  * @return A static string containing the name of current protocol or NULL
483  */
484 const char *avio_enum_protocols(void **opaque, int output);
485 
486 /**
487  * Pause and resume playing - only meaningful if using a network streaming
488  * protocol (e.g. MMS).
489  *
490  * @param h IO context from which to call the read_pause function pointer
491  * @param pause 1 for pause, 0 for resume
492  */
493 int avio_pause(AVIOContext *h, int pause);
494 
495 /**
496  * Seek to a given timestamp relative to some component stream.
497  * Only meaningful if using a network streaming protocol (e.g. MMS.).
498  *
499  * @param h IO context from which to call the seek function pointers
500  * @param stream_index The stream index that the timestamp is relative to.
501  * If stream_index is (-1) the timestamp should be in AV_TIME_BASE
502  * units from the beginning of the presentation.
503  * If a stream_index >= 0 is used and the protocol does not support
504  * seeking based on component streams, the call will fail.
505  * @param timestamp timestamp in AVStream.time_base units
506  * or if there is no stream specified then in AV_TIME_BASE units.
507  * @param flags Optional combination of AVSEEK_FLAG_BACKWARD, AVSEEK_FLAG_BYTE
508  * and AVSEEK_FLAG_ANY. The protocol may silently ignore
509  * AVSEEK_FLAG_BACKWARD and AVSEEK_FLAG_ANY, but AVSEEK_FLAG_BYTE will
510  * fail if used and not supported.
511  * @return >= 0 on success
512  * @see AVInputFormat::read_seek
513  */
514 int64_t avio_seek_time(AVIOContext *h, int stream_index,
515  int64_t timestamp, int flags);
516 
517 /* Avoid a warning. The header can not be included because it breaks c++. */
518 struct AVBPrint;
519 
520 /**
521  * Read contents of h into print buffer, up to max_size bytes, or up to EOF.
522  *
523  * @return 0 for success (max_size bytes read or EOF reached), negative error
524  * code otherwise
525  */
526 int avio_read_to_bprint(AVIOContext *h, struct AVBPrint *pb, size_t max_size);
527 
528 #endif /* AVFORMAT_AVIO_H */