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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 #include "libavutil/bprint.h"
35 
36 #include "libavformat/version.h"
37 
38 
39 #define AVIO_SEEKABLE_NORMAL 0x0001 /**< Seeking works like for a local file */
40 
41 /**
42  * Callback for checking whether to abort blocking functions.
43  * AVERROR_EXIT is returned in this case by the interrupted
44  * function. During blocking operations, callback is called with
45  * opaque as parameter. If the callback returns 1, the
46  * blocking operation will be aborted.
47  *
48  * No members can be added to this struct without a major bump, if
49  * new elements have been added after this struct in AVFormatContext
50  * or AVIOContext.
51  */
52 typedef struct AVIOInterruptCB {
53  int (*callback)(void*);
54  void *opaque;
56 
57 /**
58  * Bytestream IO Context.
59  * New fields can be added to the end with minor version bumps.
60  * Removal, reordering and changes to existing fields require a major
61  * version bump.
62  * sizeof(AVIOContext) must not be used outside libav*.
63  *
64  * @note None of the function pointers in AVIOContext should be called
65  * directly, they should only be set by the client application
66  * when implementing custom I/O. Normally these are set to the
67  * function pointers specified in avio_alloc_context()
68  */
69 typedef struct AVIOContext {
70  /**
71  * A class for private options.
72  *
73  * If this AVIOContext is created by avio_open2(), av_class is set and
74  * passes the options down to protocols.
75  *
76  * If this AVIOContext is manually allocated, then av_class may be set by
77  * the caller.
78  *
79  * warning -- this field can be NULL, be sure to not pass this AVIOContext
80  * to any av_opt_* functions in that case.
81  */
82  const AVClass *av_class;
83  unsigned char *buffer; /**< Start of the buffer. */
84  int buffer_size; /**< Maximum buffer size */
85  unsigned char *buf_ptr; /**< Current position in the buffer */
86  unsigned char *buf_end; /**< End of the data, may be less than
87  buffer+buffer_size if the read function returned
88  less data than requested, e.g. for streams where
89  no more data has been received yet. */
90  void *opaque; /**< A private pointer, passed to the read/write/seek/...
91  functions. */
92  int (*read_packet)(void *opaque, uint8_t *buf, int buf_size);
93  int (*write_packet)(void *opaque, uint8_t *buf, int buf_size);
94  int64_t (*seek)(void *opaque, int64_t offset, int whence);
95  int64_t pos; /**< position in the file of the current buffer */
96  int must_flush; /**< true if the next seek should flush */
97  int eof_reached; /**< true if eof reached */
98  int write_flag; /**< true if open for writing */
100  unsigned long checksum;
101  unsigned char *checksum_ptr;
102  unsigned long (*update_checksum)(unsigned long checksum, const uint8_t *buf, unsigned int size);
103  int error; /**< contains the error code or 0 if no error happened */
104  /**
105  * Pause or resume playback for network streaming protocols - e.g. MMS.
106  */
107  int (*read_pause)(void *opaque, int pause);
108  /**
109  * Seek to a given timestamp in stream with the specified stream_index.
110  * Needed for some network streaming protocols which don't support seeking
111  * to byte position.
112  */
113  int64_t (*read_seek)(void *opaque, int stream_index,
114  int64_t timestamp, int flags);
115  /**
116  * A combination of AVIO_SEEKABLE_ flags or 0 when the stream is not seekable.
117  */
118  int seekable;
119 
120  /**
121  * max filesize, used to limit allocations
122  * This field is internal to libavformat and access from outside is not allowed.
123  */
124  int64_t maxsize;
125 
126  /**
127  * avio_read and avio_write should if possible be satisfied directly
128  * instead of going through a buffer, and avio_seek will always
129  * call the underlying seek function directly.
130  */
131  int direct;
132 
133  /**
134  * Bytes read statistic
135  * This field is internal to libavformat and access from outside is not allowed.
136  */
137  int64_t bytes_read;
138 
139  /**
140  * seek statistic
141  * This field is internal to libavformat and access from outside is not allowed.
142  */
144 
145  /**
146  * writeout statistic
147  * This field is internal to libavformat and access from outside is not allowed.
148  */
150 
151  /**
152  * Original buffer size
153  * used internally after probing and ensure seekback to reset the buffer size
154  * This field is internal to libavformat and access from outside is not allowed.
155  */
157 } AVIOContext;
158 
159 /* unbuffered I/O */
160 
161 /**
162  * Return the name of the protocol that will handle the passed URL.
163  *
164  * NULL is returned if no protocol could be found for the given URL.
165  *
166  * @return Name of the protocol or NULL.
167  */
168 const char *avio_find_protocol_name(const char *url);
169 
170 /**
171  * Return AVIO_FLAG_* access flags corresponding to the access permissions
172  * of the resource in url, or a negative value corresponding to an
173  * AVERROR code in case of failure. The returned access flags are
174  * masked by the value in flags.
175  *
176  * @note This function is intrinsically unsafe, in the sense that the
177  * checked resource may change its existence or permission status from
178  * one call to another. Thus you should not trust the returned value,
179  * unless you are sure that no other processes are accessing the
180  * checked resource.
181  */
182 int avio_check(const char *url, int flags);
183 
184 /**
185  * Allocate and initialize an AVIOContext for buffered I/O. It must be later
186  * freed with av_free().
187  *
188  * @param buffer Memory block for input/output operations via AVIOContext.
189  * The buffer must be allocated with av_malloc() and friends.
190  * @param buffer_size The buffer size is very important for performance.
191  * For protocols with fixed blocksize it should be set to this blocksize.
192  * For others a typical size is a cache page, e.g. 4kb.
193  * @param write_flag Set to 1 if the buffer should be writable, 0 otherwise.
194  * @param opaque An opaque pointer to user-specific data.
195  * @param read_packet A function for refilling the buffer, may be NULL.
196  * @param write_packet A function for writing the buffer contents, may be NULL.
197  * The function may not change the input buffers content.
198  * @param seek A function for seeking to specified byte position, may be NULL.
199  *
200  * @return Allocated AVIOContext or NULL on failure.
201  */
203  unsigned char *buffer,
204  int buffer_size,
205  int write_flag,
206  void *opaque,
207  int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
208  int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
209  int64_t (*seek)(void *opaque, int64_t offset, int whence));
210 
211 void avio_w8(AVIOContext *s, int b);
212 void avio_write(AVIOContext *s, const unsigned char *buf, int size);
213 void avio_wl64(AVIOContext *s, uint64_t val);
214 void avio_wb64(AVIOContext *s, uint64_t val);
215 void avio_wl32(AVIOContext *s, unsigned int val);
216 void avio_wb32(AVIOContext *s, unsigned int val);
217 void avio_wl24(AVIOContext *s, unsigned int val);
218 void avio_wb24(AVIOContext *s, unsigned int val);
219 void avio_wl16(AVIOContext *s, unsigned int val);
220 void avio_wb16(AVIOContext *s, unsigned int val);
221 
222 /**
223  * Write a NULL-terminated string.
224  * @return number of bytes written.
225  */
226 int avio_put_str(AVIOContext *s, const char *str);
227 
228 /**
229  * Convert an UTF-8 string to UTF-16LE and write it.
230  * @return number of bytes written.
231  */
232 int avio_put_str16le(AVIOContext *s, const char *str);
233 
234 /**
235  * Passing this as the "whence" parameter to a seek function causes it to
236  * return the filesize without seeking anywhere. Supporting this is optional.
237  * If it is not supported then the seek function will return <0.
238  */
239 #define AVSEEK_SIZE 0x10000
240 
241 /**
242  * Oring this flag as into the "whence" parameter to a seek function causes it to
243  * seek by any means (like reopening and linear reading) or other normally unreasonable
244  * means that can be extremely slow.
245  * This may be ignored by the seek code.
246  */
247 #define AVSEEK_FORCE 0x20000
248 
249 /**
250  * fseek() equivalent for AVIOContext.
251  * @return new position or AVERROR.
252  */
253 int64_t avio_seek(AVIOContext *s, int64_t offset, int whence);
254 
255 /**
256  * Skip given number of bytes forward
257  * @return new position or AVERROR.
258  */
259 int64_t avio_skip(AVIOContext *s, int64_t offset);
260 
261 /**
262  * ftell() equivalent for AVIOContext.
263  * @return position or AVERROR.
264  */
266 {
267  return avio_seek(s, 0, SEEK_CUR);
268 }
269 
270 /**
271  * Get the filesize.
272  * @return filesize or AVERROR
273  */
274 int64_t avio_size(AVIOContext *s);
275 
276 /**
277  * feof() equivalent for AVIOContext.
278  * @return non zero if and only if end of file
279  */
280 int url_feof(AVIOContext *s);
281 
282 /** @warning currently size is limited */
283 int avio_printf(AVIOContext *s, const char *fmt, ...) av_printf_format(2, 3);
284 
285 /**
286  * Force flushing of buffered data to the output s.
287  *
288  * Force the buffered data to be immediately written to the output,
289  * without to wait to fill the internal buffer.
290  */
291 void avio_flush(AVIOContext *s);
292 
293 /**
294  * Read size bytes from AVIOContext into buf.
295  * @return number of bytes read or AVERROR
296  */
297 int avio_read(AVIOContext *s, unsigned char *buf, int size);
298 
299 /**
300  * @name Functions for reading from AVIOContext
301  * @{
302  *
303  * @note return 0 if EOF, so you cannot use it if EOF handling is
304  * necessary
305  */
306 int avio_r8 (AVIOContext *s);
307 unsigned int avio_rl16(AVIOContext *s);
308 unsigned int avio_rl24(AVIOContext *s);
309 unsigned int avio_rl32(AVIOContext *s);
310 uint64_t avio_rl64(AVIOContext *s);
311 unsigned int avio_rb16(AVIOContext *s);
312 unsigned int avio_rb24(AVIOContext *s);
313 unsigned int avio_rb32(AVIOContext *s);
314 uint64_t avio_rb64(AVIOContext *s);
315 /**
316  * @}
317  */
318 
319 /**
320  * Read a string from pb into buf. The reading will terminate when either
321  * a NULL character was encountered, maxlen bytes have been read, or nothing
322  * more can be read from pb. The result is guaranteed to be NULL-terminated, it
323  * will be truncated if buf is too small.
324  * Note that the string is not interpreted or validated in any way, it
325  * might get truncated in the middle of a sequence for multi-byte encodings.
326  *
327  * @return number of bytes read (is always <= maxlen).
328  * If reading ends on EOF or error, the return value will be one more than
329  * bytes actually read.
330  */
331 int avio_get_str(AVIOContext *pb, int maxlen, char *buf, int buflen);
332 
333 /**
334  * Read a UTF-16 string from pb and convert it to UTF-8.
335  * The reading will terminate when either a null or invalid character was
336  * encountered or maxlen bytes have been read.
337  * @return number of bytes read (is always <= maxlen)
338  */
339 int avio_get_str16le(AVIOContext *pb, int maxlen, char *buf, int buflen);
340 int avio_get_str16be(AVIOContext *pb, int maxlen, char *buf, int buflen);
341 
342 
343 /**
344  * @name URL open modes
345  * The flags argument to avio_open must be one of the following
346  * constants, optionally ORed with other flags.
347  * @{
348  */
349 #define AVIO_FLAG_READ 1 /**< read-only */
350 #define AVIO_FLAG_WRITE 2 /**< write-only */
351 #define AVIO_FLAG_READ_WRITE (AVIO_FLAG_READ|AVIO_FLAG_WRITE) /**< read-write pseudo flag */
352 /**
353  * @}
354  */
355 
356 /**
357  * Use non-blocking mode.
358  * If this flag is set, operations on the context will return
359  * AVERROR(EAGAIN) if they can not be performed immediately.
360  * If this flag is not set, operations on the context will never return
361  * AVERROR(EAGAIN).
362  * Note that this flag does not affect the opening/connecting of the
363  * context. Connecting a protocol will always block if necessary (e.g. on
364  * network protocols) but never hang (e.g. on busy devices).
365  * Warning: non-blocking protocols is work-in-progress; this flag may be
366  * silently ignored.
367  */
368 #define AVIO_FLAG_NONBLOCK 8
369 
370 /**
371  * Use direct mode.
372  * avio_read and avio_write should if possible be satisfied directly
373  * instead of going through a buffer, and avio_seek will always
374  * call the underlying seek function directly.
375  */
376 #define AVIO_FLAG_DIRECT 0x8000
377 
378 /**
379  * Create and initialize a AVIOContext for accessing the
380  * resource indicated by url.
381  * @note When the resource indicated by url has been opened in
382  * read+write mode, the AVIOContext can be used only for writing.
383  *
384  * @param s Used to return the pointer to the created AVIOContext.
385  * In case of failure the pointed to value is set to NULL.
386  * @param url resource to access
387  * @param flags flags which control how the resource indicated by url
388  * is to be opened
389  * @return >= 0 in case of success, a negative value corresponding to an
390  * AVERROR code in case of failure
391  */
392 int avio_open(AVIOContext **s, const char *url, int flags);
393 
394 /**
395  * Create and initialize a AVIOContext for accessing the
396  * resource indicated by url.
397  * @note When the resource indicated by url has been opened in
398  * read+write mode, the AVIOContext can be used only for writing.
399  *
400  * @param s Used to return the pointer to the created AVIOContext.
401  * In case of failure the pointed to value is set to NULL.
402  * @param url resource to access
403  * @param flags flags which control how the resource indicated by url
404  * is to be opened
405  * @param int_cb an interrupt callback to be used at the protocols level
406  * @param options A dictionary filled with protocol-private options. On return
407  * this parameter will be destroyed and replaced with a dict containing options
408  * that were not found. May be NULL.
409  * @return >= 0 in case of success, a negative value corresponding to an
410  * AVERROR code in case of failure
411  */
412 int avio_open2(AVIOContext **s, const char *url, int flags,
414 
415 /**
416  * Close the resource accessed by the AVIOContext s and free it.
417  * This function can only be used if s was opened by avio_open().
418  *
419  * The internal buffer is automatically flushed before closing the
420  * resource.
421  *
422  * @return 0 on success, an AVERROR < 0 on error.
423  * @see avio_closep
424  */
425 int avio_close(AVIOContext *s);
426 
427 /**
428  * Close the resource accessed by the AVIOContext *s, free it
429  * and set the pointer pointing to it to NULL.
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_close
437  */
438 int avio_closep(AVIOContext **s);
439 
440 
441 /**
442  * Open a write only memory stream.
443  *
444  * @param s new IO context
445  * @return zero if no error.
446  */
448 
449 /**
450  * Return the written size and a pointer to the buffer. The buffer
451  * must be freed with av_free().
452  * Padding of FF_INPUT_BUFFER_PADDING_SIZE is added to the buffer.
453  *
454  * @param s IO context
455  * @param pbuffer pointer to a byte buffer
456  * @return the length of the byte buffer
457  */
458 int avio_close_dyn_buf(AVIOContext *s, uint8_t **pbuffer);
459 
460 /**
461  * Iterate through names of available protocols.
462  *
463  * @param opaque A private pointer representing current protocol.
464  * It must be a pointer to NULL on first iteration and will
465  * be updated by successive calls to avio_enum_protocols.
466  * @param output If set to 1, iterate over output protocols,
467  * otherwise over input protocols.
468  *
469  * @return A static string containing the name of current protocol or NULL
470  */
471 const char *avio_enum_protocols(void **opaque, int output);
472 
473 /**
474  * Pause and resume playing - only meaningful if using a network streaming
475  * protocol (e.g. MMS).
476  *
477  * @param h IO context from which to call the read_pause function pointer
478  * @param pause 1 for pause, 0 for resume
479  */
480 int avio_pause(AVIOContext *h, int pause);
481 
482 /**
483  * Seek to a given timestamp relative to some component stream.
484  * Only meaningful if using a network streaming protocol (e.g. MMS.).
485  *
486  * @param h IO context from which to call the seek function pointers
487  * @param stream_index The stream index that the timestamp is relative to.
488  * If stream_index is (-1) the timestamp should be in AV_TIME_BASE
489  * units from the beginning of the presentation.
490  * If a stream_index >= 0 is used and the protocol does not support
491  * seeking based on component streams, the call will fail.
492  * @param timestamp timestamp in AVStream.time_base units
493  * or if there is no stream specified then in AV_TIME_BASE units.
494  * @param flags Optional combination of AVSEEK_FLAG_BACKWARD, AVSEEK_FLAG_BYTE
495  * and AVSEEK_FLAG_ANY. The protocol may silently ignore
496  * AVSEEK_FLAG_BACKWARD and AVSEEK_FLAG_ANY, but AVSEEK_FLAG_BYTE will
497  * fail if used and not supported.
498  * @return >= 0 on success
499  * @see AVInputFormat::read_seek
500  */
501 int64_t avio_seek_time(AVIOContext *h, int stream_index,
502  int64_t timestamp, int flags);
503 
504 /**
505  * Read contents of h into print buffer, up to max_size bytes, or up to EOF.
506  *
507  * @return 0 for success (max_size bytes read or EOF reached), negative error
508  * code otherwise
509  */
510 int avio_read_to_bprint(AVIOContext *h, AVBPrint *pb, size_t max_size);
511 
512 #endif /* AVFORMAT_AVIO_H */