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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 } AVIOContext;
150 
151 /* unbuffered I/O */
152 
153 /**
154  * Return AVIO_FLAG_* access flags corresponding to the access permissions
155  * of the resource in url, or a negative value corresponding to an
156  * AVERROR code in case of failure. The returned access flags are
157  * masked by the value in flags.
158  *
159  * @note This function is intrinsically unsafe, in the sense that the
160  * checked resource may change its existence or permission status from
161  * one call to another. Thus you should not trust the returned value,
162  * unless you are sure that no other processes are accessing the
163  * checked resource.
164  */
165 int avio_check(const char *url, int flags);
166 
167 /**
168  * Allocate and initialize an AVIOContext for buffered I/O. It must be later
169  * freed with av_free().
170  *
171  * @param buffer Memory block for input/output operations via AVIOContext.
172  * The buffer must be allocated with av_malloc() and friends.
173  * @param buffer_size The buffer size is very important for performance.
174  * For protocols with fixed blocksize it should be set to this blocksize.
175  * For others a typical size is a cache page, e.g. 4kb.
176  * @param write_flag Set to 1 if the buffer should be writable, 0 otherwise.
177  * @param opaque An opaque pointer to user-specific data.
178  * @param read_packet A function for refilling the buffer, may be NULL.
179  * @param write_packet A function for writing the buffer contents, may be NULL.
180  * The function may not change the input buffers content.
181  * @param seek A function for seeking to specified byte position, may be NULL.
182  *
183  * @return Allocated AVIOContext or NULL on failure.
184  */
186  unsigned char *buffer,
187  int buffer_size,
188  int write_flag,
189  void *opaque,
190  int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
191  int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
192  int64_t (*seek)(void *opaque, int64_t offset, int whence));
193 
194 void avio_w8(AVIOContext *s, int b);
195 void avio_write(AVIOContext *s, const unsigned char *buf, int size);
196 void avio_wl64(AVIOContext *s, uint64_t val);
197 void avio_wb64(AVIOContext *s, uint64_t val);
198 void avio_wl32(AVIOContext *s, unsigned int val);
199 void avio_wb32(AVIOContext *s, unsigned int val);
200 void avio_wl24(AVIOContext *s, unsigned int val);
201 void avio_wb24(AVIOContext *s, unsigned int val);
202 void avio_wl16(AVIOContext *s, unsigned int val);
203 void avio_wb16(AVIOContext *s, unsigned int val);
204 
205 /**
206  * Write a NULL-terminated string.
207  * @return number of bytes written.
208  */
209 int avio_put_str(AVIOContext *s, const char *str);
210 
211 /**
212  * Convert an UTF-8 string to UTF-16LE and write it.
213  * @return number of bytes written.
214  */
215 int avio_put_str16le(AVIOContext *s, const char *str);
216 
217 /**
218  * Passing this as the "whence" parameter to a seek function causes it to
219  * return the filesize without seeking anywhere. Supporting this is optional.
220  * If it is not supported then the seek function will return <0.
221  */
222 #define AVSEEK_SIZE 0x10000
223 
224 /**
225  * Oring this flag as into the "whence" parameter to a seek function causes it to
226  * seek by any means (like reopening and linear reading) or other normally unreasonable
227  * means that can be extremely slow.
228  * This may be ignored by the seek code.
229  */
230 #define AVSEEK_FORCE 0x20000
231 
232 /**
233  * fseek() equivalent for AVIOContext.
234  * @return new position or AVERROR.
235  */
236 int64_t avio_seek(AVIOContext *s, int64_t offset, int whence);
237 
238 /**
239  * Skip given number of bytes forward
240  * @return new position or AVERROR.
241  */
242 int64_t avio_skip(AVIOContext *s, int64_t offset);
243 
244 /**
245  * ftell() equivalent for AVIOContext.
246  * @return position or AVERROR.
247  */
249 {
250  return avio_seek(s, 0, SEEK_CUR);
251 }
252 
253 /**
254  * Get the filesize.
255  * @return filesize or AVERROR
256  */
257 int64_t avio_size(AVIOContext *s);
258 
259 /**
260  * feof() equivalent for AVIOContext.
261  * @return non zero if and only if end of file
262  */
263 int url_feof(AVIOContext *s);
264 
265 /** @warning currently size is limited */
266 int avio_printf(AVIOContext *s, const char *fmt, ...) av_printf_format(2, 3);
267 
268 /**
269  * Force flushing of buffered data to the output s.
270  *
271  * Force the buffered data to be immediately written to the output,
272  * without to wait to fill the internal buffer.
273  */
274 void avio_flush(AVIOContext *s);
275 
276 /**
277  * Read size bytes from AVIOContext into buf.
278  * @return number of bytes read or AVERROR
279  */
280 int avio_read(AVIOContext *s, unsigned char *buf, int size);
281 
282 /**
283  * @name Functions for reading from AVIOContext
284  * @{
285  *
286  * @note return 0 if EOF, so you cannot use it if EOF handling is
287  * necessary
288  */
289 int avio_r8 (AVIOContext *s);
290 unsigned int avio_rl16(AVIOContext *s);
291 unsigned int avio_rl24(AVIOContext *s);
292 unsigned int avio_rl32(AVIOContext *s);
293 uint64_t avio_rl64(AVIOContext *s);
294 unsigned int avio_rb16(AVIOContext *s);
295 unsigned int avio_rb24(AVIOContext *s);
296 unsigned int avio_rb32(AVIOContext *s);
297 uint64_t avio_rb64(AVIOContext *s);
298 /**
299  * @}
300  */
301 
302 /**
303  * Read a string from pb into buf. The reading will terminate when either
304  * a NULL character was encountered, maxlen bytes have been read, or nothing
305  * more can be read from pb. The result is guaranteed to be NULL-terminated, it
306  * will be truncated if buf is too small.
307  * Note that the string is not interpreted or validated in any way, it
308  * might get truncated in the middle of a sequence for multi-byte encodings.
309  *
310  * @return number of bytes read (is always <= maxlen).
311  * If reading ends on EOF or error, the return value will be one more than
312  * bytes actually read.
313  */
314 int avio_get_str(AVIOContext *pb, int maxlen, char *buf, int buflen);
315 
316 /**
317  * Read a UTF-16 string from pb and convert it to UTF-8.
318  * The reading will terminate when either a null or invalid character was
319  * encountered or maxlen bytes have been read.
320  * @return number of bytes read (is always <= maxlen)
321  */
322 int avio_get_str16le(AVIOContext *pb, int maxlen, char *buf, int buflen);
323 int avio_get_str16be(AVIOContext *pb, int maxlen, char *buf, int buflen);
324 
325 
326 /**
327  * @name URL open modes
328  * The flags argument to avio_open must be one of the following
329  * constants, optionally ORed with other flags.
330  * @{
331  */
332 #define AVIO_FLAG_READ 1 /**< read-only */
333 #define AVIO_FLAG_WRITE 2 /**< write-only */
334 #define AVIO_FLAG_READ_WRITE (AVIO_FLAG_READ|AVIO_FLAG_WRITE) /**< read-write pseudo flag */
335 /**
336  * @}
337  */
338 
339 /**
340  * Use non-blocking mode.
341  * If this flag is set, operations on the context will return
342  * AVERROR(EAGAIN) if they can not be performed immediately.
343  * If this flag is not set, operations on the context will never return
344  * AVERROR(EAGAIN).
345  * Note that this flag does not affect the opening/connecting of the
346  * context. Connecting a protocol will always block if necessary (e.g. on
347  * network protocols) but never hang (e.g. on busy devices).
348  * Warning: non-blocking protocols is work-in-progress; this flag may be
349  * silently ignored.
350  */
351 #define AVIO_FLAG_NONBLOCK 8
352 
353 /**
354  * Use direct mode.
355  * avio_read and avio_write should if possible be satisfied directly
356  * instead of going through a buffer, and avio_seek will always
357  * call the underlying seek function directly.
358  */
359 #define AVIO_FLAG_DIRECT 0x8000
360 
361 /**
362  * Create and initialize a AVIOContext for accessing the
363  * resource indicated by url.
364  * @note When the resource indicated by url has been opened in
365  * read+write mode, the AVIOContext can be used only for writing.
366  *
367  * @param s Used to return the pointer to the created AVIOContext.
368  * In case of failure the pointed to value is set to NULL.
369  * @param flags flags which control how the resource indicated by url
370  * is to be opened
371  * @return 0 in case of success, a negative value corresponding to an
372  * AVERROR code in case of failure
373  */
374 int avio_open(AVIOContext **s, const char *url, int flags);
375 
376 /**
377  * Create and initialize a AVIOContext for accessing the
378  * resource indicated by url.
379  * @note When the resource indicated by url has been opened in
380  * read+write mode, the AVIOContext can be used only for writing.
381  *
382  * @param s Used to return the pointer to the created AVIOContext.
383  * In case of failure the pointed to value is set to NULL.
384  * @param flags flags which control how the resource indicated by url
385  * is to be opened
386  * @param int_cb an interrupt callback to be used at the protocols level
387  * @param options A dictionary filled with protocol-private options. On return
388  * this parameter will be destroyed and replaced with a dict containing options
389  * that were not found. May be NULL.
390  * @return 0 in case of success, a negative value corresponding to an
391  * AVERROR code in case of failure
392  */
393 int avio_open2(AVIOContext **s, const char *url, int flags,
395 
396 /**
397  * Close the resource accessed by the AVIOContext s and free it.
398  * This function can only be used if s was opened by avio_open().
399  *
400  * The internal buffer is automatically flushed before closing the
401  * resource.
402  *
403  * @return 0 on success, an AVERROR < 0 on error.
404  * @see avio_closep
405  */
406 int avio_close(AVIOContext *s);
407 
408 /**
409  * Close the resource accessed by the AVIOContext *s, free it
410  * and set the pointer pointing to it to NULL.
411  * This function can only be used if s was opened by avio_open().
412  *
413  * The internal buffer is automatically flushed before closing the
414  * resource.
415  *
416  * @return 0 on success, an AVERROR < 0 on error.
417  * @see avio_close
418  */
419 int avio_closep(AVIOContext **s);
420 
421 
422 /**
423  * Open a write only memory stream.
424  *
425  * @param s new IO context
426  * @return zero if no error.
427  */
429 
430 /**
431  * Return the written size and a pointer to the buffer. The buffer
432  * must be freed with av_free().
433  * Padding of FF_INPUT_BUFFER_PADDING_SIZE is added to the buffer.
434  *
435  * @param s IO context
436  * @param pbuffer pointer to a byte buffer
437  * @return the length of the byte buffer
438  */
439 int avio_close_dyn_buf(AVIOContext *s, uint8_t **pbuffer);
440 
441 /**
442  * Iterate through names of available protocols.
443  *
444  * @param opaque A private pointer representing current protocol.
445  * It must be a pointer to NULL on first iteration and will
446  * be updated by successive calls to avio_enum_protocols.
447  * @param output If set to 1, iterate over output protocols,
448  * otherwise over input protocols.
449  *
450  * @return A static string containing the name of current protocol or NULL
451  */
452 const char *avio_enum_protocols(void **opaque, int output);
453 
454 /**
455  * Pause and resume playing - only meaningful if using a network streaming
456  * protocol (e.g. MMS).
457  * @param pause 1 for pause, 0 for resume
458  */
459 int avio_pause(AVIOContext *h, int pause);
460 
461 /**
462  * Seek to a given timestamp relative to some component stream.
463  * Only meaningful if using a network streaming protocol (e.g. MMS.).
464  * @param stream_index The stream index that the timestamp is relative to.
465  * If stream_index is (-1) the timestamp should be in AV_TIME_BASE
466  * units from the beginning of the presentation.
467  * If a stream_index >= 0 is used and the protocol does not support
468  * seeking based on component streams, the call will fail.
469  * @param timestamp timestamp in AVStream.time_base units
470  * or if there is no stream specified then in AV_TIME_BASE units.
471  * @param flags Optional combination of AVSEEK_FLAG_BACKWARD, AVSEEK_FLAG_BYTE
472  * and AVSEEK_FLAG_ANY. The protocol may silently ignore
473  * AVSEEK_FLAG_BACKWARD and AVSEEK_FLAG_ANY, but AVSEEK_FLAG_BYTE will
474  * fail if used and not supported.
475  * @return >= 0 on success
476  * @see AVInputFormat::read_seek
477  */
478 int64_t avio_seek_time(AVIOContext *h, int stream_index,
479  int64_t timestamp, int flags);
480 
481 #endif /* AVFORMAT_AVIO_H */