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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  * @param buffer_size The buffer size is very important for performance.
190  * For protocols with fixed blocksize it should be set to this blocksize.
191  * For others a typical size is a cache page, e.g. 4kb.
192  * @param write_flag Set to 1 if the buffer should be writable, 0 otherwise.
193  * @param opaque An opaque pointer to user-specific data.
194  * @param read_packet A function for refilling the buffer, may be NULL.
195  * @param write_packet A function for writing the buffer contents, may be NULL.
196  * The function may not change the input buffers content.
197  * @param seek A function for seeking to specified byte position, may be NULL.
198  *
199  * @return Allocated AVIOContext or NULL on failure.
200  */
202  unsigned char *buffer,
203  int buffer_size,
204  int write_flag,
205  void *opaque,
206  int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
207  int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
208  int64_t (*seek)(void *opaque, int64_t offset, int whence));
209 
210 void avio_w8(AVIOContext *s, int b);
211 void avio_write(AVIOContext *s, const unsigned char *buf, int size);
212 void avio_wl64(AVIOContext *s, uint64_t val);
213 void avio_wb64(AVIOContext *s, uint64_t val);
214 void avio_wl32(AVIOContext *s, unsigned int val);
215 void avio_wb32(AVIOContext *s, unsigned int val);
216 void avio_wl24(AVIOContext *s, unsigned int val);
217 void avio_wb24(AVIOContext *s, unsigned int val);
218 void avio_wl16(AVIOContext *s, unsigned int val);
219 void avio_wb16(AVIOContext *s, unsigned int val);
220 
221 /**
222  * Write a NULL-terminated string.
223  * @return number of bytes written.
224  */
225 int avio_put_str(AVIOContext *s, const char *str);
226 
227 /**
228  * Convert an UTF-8 string to UTF-16LE and write it.
229  * @return number of bytes written.
230  */
231 int avio_put_str16le(AVIOContext *s, const char *str);
232 
233 /**
234  * Passing this as the "whence" parameter to a seek function causes it to
235  * return the filesize without seeking anywhere. Supporting this is optional.
236  * If it is not supported then the seek function will return <0.
237  */
238 #define AVSEEK_SIZE 0x10000
239 
240 /**
241  * Oring this flag as into the "whence" parameter to a seek function causes it to
242  * seek by any means (like reopening and linear reading) or other normally unreasonable
243  * means that can be extremely slow.
244  * This may be ignored by the seek code.
245  */
246 #define AVSEEK_FORCE 0x20000
247 
248 /**
249  * fseek() equivalent for AVIOContext.
250  * @return new position or AVERROR.
251  */
252 int64_t avio_seek(AVIOContext *s, int64_t offset, int whence);
253 
254 /**
255  * Skip given number of bytes forward
256  * @return new position or AVERROR.
257  */
258 int64_t avio_skip(AVIOContext *s, int64_t offset);
259 
260 /**
261  * ftell() equivalent for AVIOContext.
262  * @return position or AVERROR.
263  */
265 {
266  return avio_seek(s, 0, SEEK_CUR);
267 }
268 
269 /**
270  * Get the filesize.
271  * @return filesize or AVERROR
272  */
273 int64_t avio_size(AVIOContext *s);
274 
275 /**
276  * feof() equivalent for AVIOContext.
277  * @return non zero if and only if end of file
278  */
279 int url_feof(AVIOContext *s);
280 
281 /** @warning currently size is limited */
282 int avio_printf(AVIOContext *s, const char *fmt, ...) av_printf_format(2, 3);
283 
284 /**
285  * Force flushing of buffered data to the output s.
286  *
287  * Force the buffered data to be immediately written to the output,
288  * without to wait to fill the internal buffer.
289  */
290 void avio_flush(AVIOContext *s);
291 
292 /**
293  * Read size bytes from AVIOContext into buf.
294  * @return number of bytes read or AVERROR
295  */
296 int avio_read(AVIOContext *s, unsigned char *buf, int size);
297 
298 /**
299  * @name Functions for reading from AVIOContext
300  * @{
301  *
302  * @note return 0 if EOF, so you cannot use it if EOF handling is
303  * necessary
304  */
305 int avio_r8 (AVIOContext *s);
306 unsigned int avio_rl16(AVIOContext *s);
307 unsigned int avio_rl24(AVIOContext *s);
308 unsigned int avio_rl32(AVIOContext *s);
309 uint64_t avio_rl64(AVIOContext *s);
310 unsigned int avio_rb16(AVIOContext *s);
311 unsigned int avio_rb24(AVIOContext *s);
312 unsigned int avio_rb32(AVIOContext *s);
313 uint64_t avio_rb64(AVIOContext *s);
314 /**
315  * @}
316  */
317 
318 /**
319  * Read a string from pb into buf. The reading will terminate when either
320  * a NULL character was encountered, maxlen bytes have been read, or nothing
321  * more can be read from pb. The result is guaranteed to be NULL-terminated, it
322  * will be truncated if buf is too small.
323  * Note that the string is not interpreted or validated in any way, it
324  * might get truncated in the middle of a sequence for multi-byte encodings.
325  *
326  * @return number of bytes read (is always <= maxlen).
327  * If reading ends on EOF or error, the return value will be one more than
328  * bytes actually read.
329  */
330 int avio_get_str(AVIOContext *pb, int maxlen, char *buf, int buflen);
331 
332 /**
333  * Read a UTF-16 string from pb and convert it to UTF-8.
334  * The reading will terminate when either a null or invalid character was
335  * encountered or maxlen bytes have been read.
336  * @return number of bytes read (is always <= maxlen)
337  */
338 int avio_get_str16le(AVIOContext *pb, int maxlen, char *buf, int buflen);
339 int avio_get_str16be(AVIOContext *pb, int maxlen, char *buf, int buflen);
340 
341 
342 /**
343  * @name URL open modes
344  * The flags argument to avio_open must be one of the following
345  * constants, optionally ORed with other flags.
346  * @{
347  */
348 #define AVIO_FLAG_READ 1 /**< read-only */
349 #define AVIO_FLAG_WRITE 2 /**< write-only */
350 #define AVIO_FLAG_READ_WRITE (AVIO_FLAG_READ|AVIO_FLAG_WRITE) /**< read-write pseudo flag */
351 /**
352  * @}
353  */
354 
355 /**
356  * Use non-blocking mode.
357  * If this flag is set, operations on the context will return
358  * AVERROR(EAGAIN) if they can not be performed immediately.
359  * If this flag is not set, operations on the context will never return
360  * AVERROR(EAGAIN).
361  * Note that this flag does not affect the opening/connecting of the
362  * context. Connecting a protocol will always block if necessary (e.g. on
363  * network protocols) but never hang (e.g. on busy devices).
364  * Warning: non-blocking protocols is work-in-progress; this flag may be
365  * silently ignored.
366  */
367 #define AVIO_FLAG_NONBLOCK 8
368 
369 /**
370  * Use direct mode.
371  * avio_read and avio_write should if possible be satisfied directly
372  * instead of going through a buffer, and avio_seek will always
373  * call the underlying seek function directly.
374  */
375 #define AVIO_FLAG_DIRECT 0x8000
376 
377 /**
378  * Create and initialize a AVIOContext for accessing the
379  * resource indicated by url.
380  * @note When the resource indicated by url has been opened in
381  * read+write mode, the AVIOContext can be used only for writing.
382  *
383  * @param s Used to return the pointer to the created AVIOContext.
384  * In case of failure the pointed to value is set to NULL.
385  * @param url resource to access
386  * @param flags flags which control how the resource indicated by url
387  * is to be opened
388  * @return >= 0 in case of success, a negative value corresponding to an
389  * AVERROR code in case of failure
390  */
391 int avio_open(AVIOContext **s, const char *url, int flags);
392 
393 /**
394  * Create and initialize a AVIOContext for accessing the
395  * resource indicated by url.
396  * @note When the resource indicated by url has been opened in
397  * read+write mode, the AVIOContext can be used only for writing.
398  *
399  * @param s Used to return the pointer to the created AVIOContext.
400  * In case of failure the pointed to value is set to NULL.
401  * @param url resource to access
402  * @param flags flags which control how the resource indicated by url
403  * is to be opened
404  * @param int_cb an interrupt callback to be used at the protocols level
405  * @param options A dictionary filled with protocol-private options. On return
406  * this parameter will be destroyed and replaced with a dict containing options
407  * that were not found. May be NULL.
408  * @return >= 0 in case of success, a negative value corresponding to an
409  * AVERROR code in case of failure
410  */
411 int avio_open2(AVIOContext **s, const char *url, int flags,
413 
414 /**
415  * Close the resource accessed by the AVIOContext s and free it.
416  * This function can only be used if s was opened by avio_open().
417  *
418  * The internal buffer is automatically flushed before closing the
419  * resource.
420  *
421  * @return 0 on success, an AVERROR < 0 on error.
422  * @see avio_closep
423  */
424 int avio_close(AVIOContext *s);
425 
426 /**
427  * Close the resource accessed by the AVIOContext *s, free it
428  * and set the pointer pointing to it to NULL.
429  * This function can only be used if s was opened by avio_open().
430  *
431  * The internal buffer is automatically flushed before closing the
432  * resource.
433  *
434  * @return 0 on success, an AVERROR < 0 on error.
435  * @see avio_close
436  */
437 int avio_closep(AVIOContext **s);
438 
439 
440 /**
441  * Open a write only memory stream.
442  *
443  * @param s new IO context
444  * @return zero if no error.
445  */
447 
448 /**
449  * Return the written size and a pointer to the buffer. The buffer
450  * must be freed with av_free().
451  * Padding of FF_INPUT_BUFFER_PADDING_SIZE is added to the buffer.
452  *
453  * @param s IO context
454  * @param pbuffer pointer to a byte buffer
455  * @return the length of the byte buffer
456  */
457 int avio_close_dyn_buf(AVIOContext *s, uint8_t **pbuffer);
458 
459 /**
460  * Iterate through names of available protocols.
461  *
462  * @param opaque A private pointer representing current protocol.
463  * It must be a pointer to NULL on first iteration and will
464  * be updated by successive calls to avio_enum_protocols.
465  * @param output If set to 1, iterate over output protocols,
466  * otherwise over input protocols.
467  *
468  * @return A static string containing the name of current protocol or NULL
469  */
470 const char *avio_enum_protocols(void **opaque, int output);
471 
472 /**
473  * Pause and resume playing - only meaningful if using a network streaming
474  * protocol (e.g. MMS).
475  *
476  * @param h IO context from which to call the read_pause function pointer
477  * @param pause 1 for pause, 0 for resume
478  */
479 int avio_pause(AVIOContext *h, int pause);
480 
481 /**
482  * Seek to a given timestamp relative to some component stream.
483  * Only meaningful if using a network streaming protocol (e.g. MMS.).
484  *
485  * @param h IO context from which to call the seek function pointers
486  * @param stream_index The stream index that the timestamp is relative to.
487  * If stream_index is (-1) the timestamp should be in AV_TIME_BASE
488  * units from the beginning of the presentation.
489  * If a stream_index >= 0 is used and the protocol does not support
490  * seeking based on component streams, the call will fail.
491  * @param timestamp timestamp in AVStream.time_base units
492  * or if there is no stream specified then in AV_TIME_BASE units.
493  * @param flags Optional combination of AVSEEK_FLAG_BACKWARD, AVSEEK_FLAG_BYTE
494  * and AVSEEK_FLAG_ANY. The protocol may silently ignore
495  * AVSEEK_FLAG_BACKWARD and AVSEEK_FLAG_ANY, but AVSEEK_FLAG_BYTE will
496  * fail if used and not supported.
497  * @return >= 0 on success
498  * @see AVInputFormat::read_seek
499  */
500 int64_t avio_seek_time(AVIOContext *h, int stream_index,
501  int64_t timestamp, int flags);
502 
503 /**
504  * Read contents of h into print buffer, up to max_size bytes, or up to EOF.
505  *
506  * @return 0 for success (max_size bytes read or EOF reached), negative error
507  * code otherwise
508  */
509 int avio_read_to_bprint(AVIOContext *h, struct AVBPrint *pb, size_t max_size);
510 
511 #endif /* AVFORMAT_AVIO_H */