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opt.h
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1 /*
2  * AVOptions
3  * copyright (c) 2005 Michael Niedermayer <michaelni@gmx.at>
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #ifndef AVUTIL_OPT_H
23 #define AVUTIL_OPT_H
24 
25 /**
26  * @file
27  * AVOptions
28  */
29 
30 #include "rational.h"
31 #include "avutil.h"
32 #include "dict.h"
33 #include "log.h"
34 #include "pixfmt.h"
35 #include "samplefmt.h"
36 
37 /**
38  * @defgroup avoptions AVOptions
39  * @ingroup lavu_data
40  * @{
41  * AVOptions provide a generic system to declare options on arbitrary structs
42  * ("objects"). An option can have a help text, a type and a range of possible
43  * values. Options may then be enumerated, read and written to.
44  *
45  * @section avoptions_implement Implementing AVOptions
46  * This section describes how to add AVOptions capabilities to a struct.
47  *
48  * All AVOptions-related information is stored in an AVClass. Therefore
49  * the first member of the struct should be a pointer to an AVClass describing it.
50  * The option field of the AVClass must be set to a NULL-terminated static array
51  * of AVOptions. Each AVOption must have a non-empty name, a type, a default
52  * value and for number-type AVOptions also a range of allowed values. It must
53  * also declare an offset in bytes from the start of the struct, where the field
54  * associated with this AVOption is located. Other fields in the AVOption struct
55  * should also be set when applicable, but are not required.
56  *
57  * The following example illustrates an AVOptions-enabled struct:
58  * @code
59  * typedef struct test_struct {
60  * AVClass *class;
61  * int int_opt;
62  * char *str_opt;
63  * uint8_t *bin_opt;
64  * int bin_len;
65  * } test_struct;
66  *
67  * static const AVOption test_options[] = {
68  * { "test_int", "This is a test option of int type.", offsetof(test_struct, int_opt),
69  * AV_OPT_TYPE_INT, { .i64 = -1 }, INT_MIN, INT_MAX },
70  * { "test_str", "This is a test option of string type.", offsetof(test_struct, str_opt),
71  * AV_OPT_TYPE_STRING },
72  * { "test_bin", "This is a test option of binary type.", offsetof(test_struct, bin_opt),
73  * AV_OPT_TYPE_BINARY },
74  * { NULL },
75  * };
76  *
77  * static const AVClass test_class = {
78  * .class_name = "test class",
79  * .item_name = av_default_item_name,
80  * .option = test_options,
81  * .version = LIBAVUTIL_VERSION_INT,
82  * };
83  * @endcode
84  *
85  * Next, when allocating your struct, you must ensure that the AVClass pointer
86  * is set to the correct value. Then, av_opt_set_defaults() can be called to
87  * initialize defaults. After that the struct is ready to be used with the
88  * AVOptions API.
89  *
90  * When cleaning up, you may use the av_opt_free() function to automatically
91  * free all the allocated string and binary options.
92  *
93  * Continuing with the above example:
94  *
95  * @code
96  * test_struct *alloc_test_struct(void)
97  * {
98  * test_struct *ret = av_malloc(sizeof(*ret));
99  * ret->class = &test_class;
100  * av_opt_set_defaults(ret);
101  * return ret;
102  * }
103  * void free_test_struct(test_struct **foo)
104  * {
105  * av_opt_free(*foo);
106  * av_freep(foo);
107  * }
108  * @endcode
109  *
110  * @subsection avoptions_implement_nesting Nesting
111  * It may happen that an AVOptions-enabled struct contains another
112  * AVOptions-enabled struct as a member (e.g. AVCodecContext in
113  * libavcodec exports generic options, while its priv_data field exports
114  * codec-specific options). In such a case, it is possible to set up the
115  * parent struct to export a child's options. To do that, simply
116  * implement AVClass.child_next() and AVClass.child_class_next() in the
117  * parent struct's AVClass.
118  * Assuming that the test_struct from above now also contains a
119  * child_struct field:
120  *
121  * @code
122  * typedef struct child_struct {
123  * AVClass *class;
124  * int flags_opt;
125  * } child_struct;
126  * static const AVOption child_opts[] = {
127  * { "test_flags", "This is a test option of flags type.",
128  * offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX },
129  * { NULL },
130  * };
131  * static const AVClass child_class = {
132  * .class_name = "child class",
133  * .item_name = av_default_item_name,
134  * .option = child_opts,
135  * .version = LIBAVUTIL_VERSION_INT,
136  * };
137  *
138  * void *child_next(void *obj, void *prev)
139  * {
140  * test_struct *t = obj;
141  * if (!prev && t->child_struct)
142  * return t->child_struct;
143  * return NULL
144  * }
145  * const AVClass child_class_next(const AVClass *prev)
146  * {
147  * return prev ? NULL : &child_class;
148  * }
149  * @endcode
150  * Putting child_next() and child_class_next() as defined above into
151  * test_class will now make child_struct's options accessible through
152  * test_struct (again, proper setup as described above needs to be done on
153  * child_struct right after it is created).
154  *
155  * From the above example it might not be clear why both child_next()
156  * and child_class_next() are needed. The distinction is that child_next()
157  * iterates over actually existing objects, while child_class_next()
158  * iterates over all possible child classes. E.g. if an AVCodecContext
159  * was initialized to use a codec which has private options, then its
160  * child_next() will return AVCodecContext.priv_data and finish
161  * iterating. OTOH child_class_next() on AVCodecContext.av_class will
162  * iterate over all available codecs with private options.
163  *
164  * @subsection avoptions_implement_named_constants Named constants
165  * It is possible to create named constants for options. Simply set the unit
166  * field of the option the constants should apply to a string and
167  * create the constants themselves as options of type AV_OPT_TYPE_CONST
168  * with their unit field set to the same string.
169  * Their default_val field should contain the value of the named
170  * constant.
171  * For example, to add some named constants for the test_flags option
172  * above, put the following into the child_opts array:
173  * @code
174  * { "test_flags", "This is a test option of flags type.",
175  * offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX, "test_unit" },
176  * { "flag1", "This is a flag with value 16", 0, AV_OPT_TYPE_CONST, { .i64 = 16 }, 0, 0, "test_unit" },
177  * @endcode
178  *
179  * @section avoptions_use Using AVOptions
180  * This section deals with accessing options in an AVOptions-enabled struct.
181  * Such structs in FFmpeg are e.g. AVCodecContext in libavcodec or
182  * AVFormatContext in libavformat.
183  *
184  * @subsection avoptions_use_examine Examining AVOptions
185  * The basic functions for examining options are av_opt_next(), which iterates
186  * over all options defined for one object, and av_opt_find(), which searches
187  * for an option with the given name.
188  *
189  * The situation is more complicated with nesting. An AVOptions-enabled struct
190  * may have AVOptions-enabled children. Passing the AV_OPT_SEARCH_CHILDREN flag
191  * to av_opt_find() will make the function search children recursively.
192  *
193  * For enumerating there are basically two cases. The first is when you want to
194  * get all options that may potentially exist on the struct and its children
195  * (e.g. when constructing documentation). In that case you should call
196  * av_opt_child_class_next() recursively on the parent struct's AVClass. The
197  * second case is when you have an already initialized struct with all its
198  * children and you want to get all options that can be actually written or read
199  * from it. In that case you should call av_opt_child_next() recursively (and
200  * av_opt_next() on each result).
201  *
202  * @subsection avoptions_use_get_set Reading and writing AVOptions
203  * When setting options, you often have a string read directly from the
204  * user. In such a case, simply passing it to av_opt_set() is enough. For
205  * non-string type options, av_opt_set() will parse the string according to the
206  * option type.
207  *
208  * Similarly av_opt_get() will read any option type and convert it to a string
209  * which will be returned. Do not forget that the string is allocated, so you
210  * have to free it with av_free().
211  *
212  * In some cases it may be more convenient to put all options into an
213  * AVDictionary and call av_opt_set_dict() on it. A specific case of this
214  * are the format/codec open functions in lavf/lavc which take a dictionary
215  * filled with option as a parameter. This allows to set some options
216  * that cannot be set otherwise, since e.g. the input file format is not known
217  * before the file is actually opened.
218  */
219 
228  AV_OPT_TYPE_BINARY, ///< offset must point to a pointer immediately followed by an int for the length
231  AV_OPT_TYPE_IMAGE_SIZE = MKBETAG('S','I','Z','E'), ///< offset must point to two consecutive integers
232  AV_OPT_TYPE_PIXEL_FMT = MKBETAG('P','F','M','T'),
233  AV_OPT_TYPE_SAMPLE_FMT = MKBETAG('S','F','M','T'),
234  AV_OPT_TYPE_VIDEO_RATE = MKBETAG('V','R','A','T'), ///< offset must point to AVRational
235  AV_OPT_TYPE_DURATION = MKBETAG('D','U','R',' '),
236  AV_OPT_TYPE_COLOR = MKBETAG('C','O','L','R'),
238 #if FF_API_OLD_AVOPTIONS
246  FF_OPT_TYPE_BINARY, ///< offset must point to a pointer immediately followed by an int for the length
248 #endif
249 };
250 
251 /**
252  * AVOption
253  */
254 typedef struct AVOption {
255  const char *name;
256 
257  /**
258  * short English help text
259  * @todo What about other languages?
260  */
261  const char *help;
262 
263  /**
264  * The offset relative to the context structure where the option
265  * value is stored. It should be 0 for named constants.
266  */
267  int offset;
269 
270  /**
271  * the default value for scalar options
272  */
273  union {
274  int64_t i64;
275  double dbl;
276  const char *str;
277  /* TODO those are unused now */
279  } default_val;
280  double min; ///< minimum valid value for the option
281  double max; ///< maximum valid value for the option
282 
283  int flags;
284 #define AV_OPT_FLAG_ENCODING_PARAM 1 ///< a generic parameter which can be set by the user for muxing or encoding
285 #define AV_OPT_FLAG_DECODING_PARAM 2 ///< a generic parameter which can be set by the user for demuxing or decoding
286 #if FF_API_OPT_TYPE_METADATA
287 #define AV_OPT_FLAG_METADATA 4 ///< some data extracted or inserted into the file like title, comment, ...
288 #endif
289 #define AV_OPT_FLAG_AUDIO_PARAM 8
290 #define AV_OPT_FLAG_VIDEO_PARAM 16
291 #define AV_OPT_FLAG_SUBTITLE_PARAM 32
292 /**
293  * The option is inteded for exporting values to the caller.
294  */
295 #define AV_OPT_FLAG_EXPORT 64
296 /**
297  * The option may not be set through the AVOptions API, only read.
298  * This flag only makes sense when AV_OPT_FLAG_EXPORT is also set.
299  */
300 #define AV_OPT_FLAG_READONLY 128
301 #define AV_OPT_FLAG_FILTERING_PARAM (1<<16) ///< a generic parameter which can be set by the user for filtering
302 //FIXME think about enc-audio, ... style flags
303 
304  /**
305  * The logical unit to which the option belongs. Non-constant
306  * options and corresponding named constants share the same
307  * unit. May be NULL.
308  */
309  const char *unit;
310 } AVOption;
311 
312 /**
313  * A single allowed range of values, or a single allowed value.
314  */
315 typedef struct AVOptionRange {
316  const char *str;
317  /**
318  * Value range.
319  * For string ranges this represents the min/max length.
320  * For dimensions this represents the min/max pixel count or width/height in multi-component case.
321  */
323  /**
324  * Value's component range.
325  * For string this represents the unicode range for chars, 0-127 limits to ASCII.
326  */
328  /**
329  * Range flag.
330  * If set to 1 the struct encodes a range, if set to 0 a single value.
331  */
332  int is_range;
333 } AVOptionRange;
334 
335 /**
336  * List of AVOptionRange structs.
337  */
338 typedef struct AVOptionRanges {
339  /**
340  * Array of option ranges.
341  *
342  * Most of option types use just one component.
343  * Following describes multi-component option types:
344  *
345  * AV_OPT_TYPE_IMAGE_SIZE:
346  * component index 0: range of pixel count (width * height).
347  * component index 1: range of width.
348  * component index 2: range of height.
349  *
350  * @note To obtain multi-component version of this structure, user must
351  * provide AV_OPT_MULTI_COMPONENT_RANGE to av_opt_query_ranges or
352  * av_opt_query_ranges_default function.
353  *
354  * Multi-component range can be read as in following example:
355  *
356  * @code
357  * int range_index, component_index;
358  * AVOptionRanges *ranges;
359  * AVOptionRange *range[3]; //may require more than 3 in the future.
360  * av_opt_query_ranges(&ranges, obj, key, AV_OPT_MULTI_COMPONENT_RANGE);
361  * for (range_index = 0; range_index < ranges->nb_ranges; range_index++) {
362  * for (component_index = 0; component_index < ranges->nb_components; component_index++)
363  * range[component_index] = ranges->range[ranges->nb_ranges * component_index + range_index];
364  * //do something with range here.
365  * }
366  * av_opt_freep_ranges(&ranges);
367  * @endcode
368  */
370  /**
371  * Number of ranges per component.
372  */
374  /**
375  * Number of componentes.
376  */
379 
380 
381 #if FF_API_OLD_AVOPTIONS
382 /**
383  * Set the field of obj with the given name to value.
384  *
385  * @param[in] obj A struct whose first element is a pointer to an
386  * AVClass.
387  * @param[in] name the name of the field to set
388  * @param[in] val The value to set. If the field is not of a string
389  * type, then the given string is parsed.
390  * SI postfixes and some named scalars are supported.
391  * If the field is of a numeric type, it has to be a numeric or named
392  * scalar. Behavior with more than one scalar and +- infix operators
393  * is undefined.
394  * If the field is of a flags type, it has to be a sequence of numeric
395  * scalars or named flags separated by '+' or '-'. Prefixing a flag
396  * with '+' causes it to be set without affecting the other flags;
397  * similarly, '-' unsets a flag.
398  * @param[out] o_out if non-NULL put here a pointer to the AVOption
399  * found
400  * @param alloc this parameter is currently ignored
401  * @return 0 if the value has been set, or an AVERROR code in case of
402  * error:
403  * AVERROR_OPTION_NOT_FOUND if no matching option exists
404  * AVERROR(ERANGE) if the value is out of range
405  * AVERROR(EINVAL) if the value is not valid
406  * @deprecated use av_opt_set()
407  */
409 int av_set_string3(void *obj, const char *name, const char *val, int alloc, const AVOption **o_out);
410 
411 attribute_deprecated const AVOption *av_set_double(void *obj, const char *name, double n);
412 attribute_deprecated const AVOption *av_set_q(void *obj, const char *name, AVRational n);
413 attribute_deprecated const AVOption *av_set_int(void *obj, const char *name, int64_t n);
414 
415 double av_get_double(void *obj, const char *name, const AVOption **o_out);
416 AVRational av_get_q(void *obj, const char *name, const AVOption **o_out);
417 int64_t av_get_int(void *obj, const char *name, const AVOption **o_out);
418 attribute_deprecated const char *av_get_string(void *obj, const char *name, const AVOption **o_out, char *buf, int buf_len);
419 attribute_deprecated const AVOption *av_next_option(void *obj, const AVOption *last);
420 #endif
421 
422 /**
423  * Show the obj options.
424  *
425  * @param req_flags requested flags for the options to show. Show only the
426  * options for which it is opt->flags & req_flags.
427  * @param rej_flags rejected flags for the options to show. Show only the
428  * options for which it is !(opt->flags & req_flags).
429  * @param av_log_obj log context to use for showing the options
430  */
431 int av_opt_show2(void *obj, void *av_log_obj, int req_flags, int rej_flags);
432 
433 /**
434  * Set the values of all AVOption fields to their default values.
435  *
436  * @param s an AVOption-enabled struct (its first member must be a pointer to AVClass)
437  */
438 void av_opt_set_defaults(void *s);
439 
440 #if FF_API_OLD_AVOPTIONS
442 void av_opt_set_defaults2(void *s, int mask, int flags);
443 #endif
444 
445 /**
446  * Parse the key/value pairs list in opts. For each key/value pair
447  * found, stores the value in the field in ctx that is named like the
448  * key. ctx must be an AVClass context, storing is done using
449  * AVOptions.
450  *
451  * @param opts options string to parse, may be NULL
452  * @param key_val_sep a 0-terminated list of characters used to
453  * separate key from value
454  * @param pairs_sep a 0-terminated list of characters used to separate
455  * two pairs from each other
456  * @return the number of successfully set key/value pairs, or a negative
457  * value corresponding to an AVERROR code in case of error:
458  * AVERROR(EINVAL) if opts cannot be parsed,
459  * the error code issued by av_opt_set() if a key/value pair
460  * cannot be set
461  */
462 int av_set_options_string(void *ctx, const char *opts,
463  const char *key_val_sep, const char *pairs_sep);
464 
465 /**
466  * Parse the key-value pairs list in opts. For each key=value pair found,
467  * set the value of the corresponding option in ctx.
468  *
469  * @param ctx the AVClass object to set options on
470  * @param opts the options string, key-value pairs separated by a
471  * delimiter
472  * @param shorthand a NULL-terminated array of options names for shorthand
473  * notation: if the first field in opts has no key part,
474  * the key is taken from the first element of shorthand;
475  * then again for the second, etc., until either opts is
476  * finished, shorthand is finished or a named option is
477  * found; after that, all options must be named
478  * @param key_val_sep a 0-terminated list of characters used to separate
479  * key from value, for example '='
480  * @param pairs_sep a 0-terminated list of characters used to separate
481  * two pairs from each other, for example ':' or ','
482  * @return the number of successfully set key=value pairs, or a negative
483  * value corresponding to an AVERROR code in case of error:
484  * AVERROR(EINVAL) if opts cannot be parsed,
485  * the error code issued by av_set_string3() if a key/value pair
486  * cannot be set
487  *
488  * Options names must use only the following characters: a-z A-Z 0-9 - . / _
489  * Separators must use characters distinct from option names and from each
490  * other.
491  */
492 int av_opt_set_from_string(void *ctx, const char *opts,
493  const char *const *shorthand,
494  const char *key_val_sep, const char *pairs_sep);
495 /**
496  * Free all allocated objects in obj.
497  */
498 void av_opt_free(void *obj);
499 
500 /**
501  * Check whether a particular flag is set in a flags field.
502  *
503  * @param field_name the name of the flag field option
504  * @param flag_name the name of the flag to check
505  * @return non-zero if the flag is set, zero if the flag isn't set,
506  * isn't of the right type, or the flags field doesn't exist.
507  */
508 int av_opt_flag_is_set(void *obj, const char *field_name, const char *flag_name);
509 
510 /**
511  * Set all the options from a given dictionary on an object.
512  *
513  * @param obj a struct whose first element is a pointer to AVClass
514  * @param options options to process. This dictionary will be freed and replaced
515  * by a new one containing all options not found in obj.
516  * Of course this new dictionary needs to be freed by caller
517  * with av_dict_free().
518  *
519  * @return 0 on success, a negative AVERROR if some option was found in obj,
520  * but could not be set.
521  *
522  * @see av_dict_copy()
523  */
524 int av_opt_set_dict(void *obj, struct AVDictionary **options);
525 
526 
527 /**
528  * Set all the options from a given dictionary on an object.
529  *
530  * @param obj a struct whose first element is a pointer to AVClass
531  * @param options options to process. This dictionary will be freed and replaced
532  * by a new one containing all options not found in obj.
533  * Of course this new dictionary needs to be freed by caller
534  * with av_dict_free().
535  * @param search_flags A combination of AV_OPT_SEARCH_*.
536  *
537  * @return 0 on success, a negative AVERROR if some option was found in obj,
538  * but could not be set.
539  *
540  * @see av_dict_copy()
541  */
542 int av_opt_set_dict2(void *obj, struct AVDictionary **options, int search_flags);
543 
544 /**
545  * Extract a key-value pair from the beginning of a string.
546  *
547  * @param ropts pointer to the options string, will be updated to
548  * point to the rest of the string (one of the pairs_sep
549  * or the final NUL)
550  * @param key_val_sep a 0-terminated list of characters used to separate
551  * key from value, for example '='
552  * @param pairs_sep a 0-terminated list of characters used to separate
553  * two pairs from each other, for example ':' or ','
554  * @param flags flags; see the AV_OPT_FLAG_* values below
555  * @param rkey parsed key; must be freed using av_free()
556  * @param rval parsed value; must be freed using av_free()
557  *
558  * @return >=0 for success, or a negative value corresponding to an
559  * AVERROR code in case of error; in particular:
560  * AVERROR(EINVAL) if no key is present
561  *
562  */
563 int av_opt_get_key_value(const char **ropts,
564  const char *key_val_sep, const char *pairs_sep,
565  unsigned flags,
566  char **rkey, char **rval);
567 
568 enum {
569 
570  /**
571  * Accept to parse a value without a key; the key will then be returned
572  * as NULL.
573  */
575 };
576 
577 /**
578  * @defgroup opt_eval_funcs Evaluating option strings
579  * @{
580  * This group of functions can be used to evaluate option strings
581  * and get numbers out of them. They do the same thing as av_opt_set(),
582  * except the result is written into the caller-supplied pointer.
583  *
584  * @param obj a struct whose first element is a pointer to AVClass.
585  * @param o an option for which the string is to be evaluated.
586  * @param val string to be evaluated.
587  * @param *_out value of the string will be written here.
588  *
589  * @return 0 on success, a negative number on failure.
590  */
591 int av_opt_eval_flags (void *obj, const AVOption *o, const char *val, int *flags_out);
592 int av_opt_eval_int (void *obj, const AVOption *o, const char *val, int *int_out);
593 int av_opt_eval_int64 (void *obj, const AVOption *o, const char *val, int64_t *int64_out);
594 int av_opt_eval_float (void *obj, const AVOption *o, const char *val, float *float_out);
595 int av_opt_eval_double(void *obj, const AVOption *o, const char *val, double *double_out);
596 int av_opt_eval_q (void *obj, const AVOption *o, const char *val, AVRational *q_out);
597 /**
598  * @}
599  */
600 
601 #define AV_OPT_SEARCH_CHILDREN 0x0001 /**< Search in possible children of the
602  given object first. */
603 /**
604  * The obj passed to av_opt_find() is fake -- only a double pointer to AVClass
605  * instead of a required pointer to a struct containing AVClass. This is
606  * useful for searching for options without needing to allocate the corresponding
607  * object.
608  */
609 #define AV_OPT_SEARCH_FAKE_OBJ 0x0002
610 
611 /**
612  * Allows av_opt_query_ranges and av_opt_query_ranges_default to return more than
613  * one component for certain option types.
614  * @see AVOptionRanges for details.
615  */
616 #define AV_OPT_MULTI_COMPONENT_RANGE 0x1000
617 
618 /**
619  * Look for an option in an object. Consider only options which
620  * have all the specified flags set.
621  *
622  * @param[in] obj A pointer to a struct whose first element is a
623  * pointer to an AVClass.
624  * Alternatively a double pointer to an AVClass, if
625  * AV_OPT_SEARCH_FAKE_OBJ search flag is set.
626  * @param[in] name The name of the option to look for.
627  * @param[in] unit When searching for named constants, name of the unit
628  * it belongs to.
629  * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
630  * @param search_flags A combination of AV_OPT_SEARCH_*.
631  *
632  * @return A pointer to the option found, or NULL if no option
633  * was found.
634  *
635  * @note Options found with AV_OPT_SEARCH_CHILDREN flag may not be settable
636  * directly with av_opt_set(). Use special calls which take an options
637  * AVDictionary (e.g. avformat_open_input()) to set options found with this
638  * flag.
639  */
640 const AVOption *av_opt_find(void *obj, const char *name, const char *unit,
641  int opt_flags, int search_flags);
642 
643 /**
644  * Look for an option in an object. Consider only options which
645  * have all the specified flags set.
646  *
647  * @param[in] obj A pointer to a struct whose first element is a
648  * pointer to an AVClass.
649  * Alternatively a double pointer to an AVClass, if
650  * AV_OPT_SEARCH_FAKE_OBJ search flag is set.
651  * @param[in] name The name of the option to look for.
652  * @param[in] unit When searching for named constants, name of the unit
653  * it belongs to.
654  * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
655  * @param search_flags A combination of AV_OPT_SEARCH_*.
656  * @param[out] target_obj if non-NULL, an object to which the option belongs will be
657  * written here. It may be different from obj if AV_OPT_SEARCH_CHILDREN is present
658  * in search_flags. This parameter is ignored if search_flags contain
659  * AV_OPT_SEARCH_FAKE_OBJ.
660  *
661  * @return A pointer to the option found, or NULL if no option
662  * was found.
663  */
664 const AVOption *av_opt_find2(void *obj, const char *name, const char *unit,
665  int opt_flags, int search_flags, void **target_obj);
666 
667 /**
668  * Iterate over all AVOptions belonging to obj.
669  *
670  * @param obj an AVOptions-enabled struct or a double pointer to an
671  * AVClass describing it.
672  * @param prev result of the previous call to av_opt_next() on this object
673  * or NULL
674  * @return next AVOption or NULL
675  */
676 const AVOption *av_opt_next(void *obj, const AVOption *prev);
677 
678 /**
679  * Iterate over AVOptions-enabled children of obj.
680  *
681  * @param prev result of a previous call to this function or NULL
682  * @return next AVOptions-enabled child or NULL
683  */
684 void *av_opt_child_next(void *obj, void *prev);
685 
686 /**
687  * Iterate over potential AVOptions-enabled children of parent.
688  *
689  * @param prev result of a previous call to this function or NULL
690  * @return AVClass corresponding to next potential child or NULL
691  */
692 const AVClass *av_opt_child_class_next(const AVClass *parent, const AVClass *prev);
693 
694 /**
695  * @defgroup opt_set_funcs Option setting functions
696  * @{
697  * Those functions set the field of obj with the given name to value.
698  *
699  * @param[in] obj A struct whose first element is a pointer to an AVClass.
700  * @param[in] name the name of the field to set
701  * @param[in] val The value to set. In case of av_opt_set() if the field is not
702  * of a string type, then the given string is parsed.
703  * SI postfixes and some named scalars are supported.
704  * If the field is of a numeric type, it has to be a numeric or named
705  * scalar. Behavior with more than one scalar and +- infix operators
706  * is undefined.
707  * If the field is of a flags type, it has to be a sequence of numeric
708  * scalars or named flags separated by '+' or '-'. Prefixing a flag
709  * with '+' causes it to be set without affecting the other flags;
710  * similarly, '-' unsets a flag.
711  * @param search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
712  * is passed here, then the option may be set on a child of obj.
713  *
714  * @return 0 if the value has been set, or an AVERROR code in case of
715  * error:
716  * AVERROR_OPTION_NOT_FOUND if no matching option exists
717  * AVERROR(ERANGE) if the value is out of range
718  * AVERROR(EINVAL) if the value is not valid
719  */
720 int av_opt_set (void *obj, const char *name, const char *val, int search_flags);
721 int av_opt_set_int (void *obj, const char *name, int64_t val, int search_flags);
722 int av_opt_set_double (void *obj, const char *name, double val, int search_flags);
723 int av_opt_set_q (void *obj, const char *name, AVRational val, int search_flags);
724 int av_opt_set_bin (void *obj, const char *name, const uint8_t *val, int size, int search_flags);
725 int av_opt_set_image_size(void *obj, const char *name, int w, int h, int search_flags);
726 int av_opt_set_pixel_fmt (void *obj, const char *name, enum AVPixelFormat fmt, int search_flags);
727 int av_opt_set_sample_fmt(void *obj, const char *name, enum AVSampleFormat fmt, int search_flags);
728 int av_opt_set_video_rate(void *obj, const char *name, AVRational val, int search_flags);
729 int av_opt_set_channel_layout(void *obj, const char *name, int64_t ch_layout, int search_flags);
730 /**
731  * @note Any old dictionary present is discarded and replaced with a copy of the new one. The
732  * caller still owns val is and responsible for freeing it.
733  */
734 int av_opt_set_dict_val(void *obj, const char *name, const AVDictionary *val, int search_flags);
735 
736 /**
737  * Set a binary option to an integer list.
738  *
739  * @param obj AVClass object to set options on
740  * @param name name of the binary option
741  * @param val pointer to an integer list (must have the correct type with
742  * regard to the contents of the list)
743  * @param term list terminator (usually 0 or -1)
744  * @param flags search flags
745  */
746 #define av_opt_set_int_list(obj, name, val, term, flags) \
747  (av_int_list_length(val, term) > INT_MAX / sizeof(*(val)) ? \
748  AVERROR(EINVAL) : \
749  av_opt_set_bin(obj, name, (const uint8_t *)(val), \
750  av_int_list_length(val, term) * sizeof(*(val)), flags))
751 
752 /**
753  * @}
754  */
755 
756 /**
757  * @defgroup opt_get_funcs Option getting functions
758  * @{
759  * Those functions get a value of the option with the given name from an object.
760  *
761  * @param[in] obj a struct whose first element is a pointer to an AVClass.
762  * @param[in] name name of the option to get.
763  * @param[in] search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
764  * is passed here, then the option may be found in a child of obj.
765  * @param[out] out_val value of the option will be written here
766  * @return >=0 on success, a negative error code otherwise
767  */
768 /**
769  * @note the returned string will be av_malloc()ed and must be av_free()ed by the caller
770  */
771 int av_opt_get (void *obj, const char *name, int search_flags, uint8_t **out_val);
772 int av_opt_get_int (void *obj, const char *name, int search_flags, int64_t *out_val);
773 int av_opt_get_double (void *obj, const char *name, int search_flags, double *out_val);
774 int av_opt_get_q (void *obj, const char *name, int search_flags, AVRational *out_val);
775 int av_opt_get_image_size(void *obj, const char *name, int search_flags, int *w_out, int *h_out);
776 int av_opt_get_pixel_fmt (void *obj, const char *name, int search_flags, enum AVPixelFormat *out_fmt);
777 int av_opt_get_sample_fmt(void *obj, const char *name, int search_flags, enum AVSampleFormat *out_fmt);
778 int av_opt_get_video_rate(void *obj, const char *name, int search_flags, AVRational *out_val);
779 int av_opt_get_channel_layout(void *obj, const char *name, int search_flags, int64_t *ch_layout);
780 /**
781  * @param[out] out_val The returned dictionary is a copy of the actual value and must
782  * be freed with av_dict_free() by the caller
783  */
784 int av_opt_get_dict_val(void *obj, const char *name, int search_flags, AVDictionary **out_val);
785 /**
786  * @}
787  */
788 /**
789  * Gets a pointer to the requested field in a struct.
790  * This function allows accessing a struct even when its fields are moved or
791  * renamed since the application making the access has been compiled,
792  *
793  * @returns a pointer to the field, it can be cast to the correct type and read
794  * or written to.
795  */
796 void *av_opt_ptr(const AVClass *avclass, void *obj, const char *name);
797 
798 /**
799  * Free an AVOptionRanges struct and set it to NULL.
800  */
801 void av_opt_freep_ranges(AVOptionRanges **ranges);
802 
803 /**
804  * Get a list of allowed ranges for the given option.
805  *
806  * The returned list may depend on other fields in obj like for example profile.
807  *
808  * @param flags is a bitmask of flags, undefined flags should not be set and should be ignored
809  * AV_OPT_SEARCH_FAKE_OBJ indicates that the obj is a double pointer to a AVClass instead of a full instance
810  * AV_OPT_MULTI_COMPONENT_RANGE indicates that function may return more than one component, @see AVOptionRanges
811  *
812  * The result must be freed with av_opt_freep_ranges.
813  *
814  * @return number of compontents returned on success, a negative errro code otherwise
815  */
816 int av_opt_query_ranges(AVOptionRanges **, void *obj, const char *key, int flags);
817 
818 /**
819  * Copy options from src object into dest object.
820  *
821  * Options that require memory allocation (e.g. string or binary) are malloc'ed in dest object.
822  * Original memory allocated for such options is freed unless both src and dest options points to the same memory.
823  *
824  * @param dest Object to copy from
825  * @param src Object to copy into
826  * @return 0 on success, negative on error
827  */
828 int av_opt_copy(void *dest, void *src);
829 
830 /**
831  * Get a default list of allowed ranges for the given option.
832  *
833  * This list is constructed without using the AVClass.query_ranges() callback
834  * and can be used as fallback from within the callback.
835  *
836  * @param flags is a bitmask of flags, undefined flags should not be set and should be ignored
837  * AV_OPT_SEARCH_FAKE_OBJ indicates that the obj is a double pointer to a AVClass instead of a full instance
838  * AV_OPT_MULTI_COMPONENT_RANGE indicates that function may return more than one component, @see AVOptionRanges
839  *
840  * The result must be freed with av_opt_free_ranges.
841  *
842  * @return number of compontents returned on success, a negative errro code otherwise
843  */
844 int av_opt_query_ranges_default(AVOptionRanges **, void *obj, const char *key, int flags);
845 
846 /**
847  * Check if given option is set to its default value.
848  *
849  * Options o must belong to the obj. This function must not be called to check child's options state.
850  * @see av_opt_is_set_to_default_by_name().
851  *
852  * @param obj AVClass object to check option on
853  * @param o option to be checked
854  * @return >0 when option is set to its default,
855  * 0 when option is not set its default,
856  * <0 on error
857  */
858 int av_opt_is_set_to_default(void *obj, const AVOption *o);
859 
860 /**
861  * Check if given option is set to its default value.
862  *
863  * @param obj AVClass object to check option on
864  * @param name option name
865  * @param search_flags combination of AV_OPT_SEARCH_*
866  * @return >0 when option is set to its default,
867  * 0 when option is not set its default,
868  * <0 on error
869  */
870 int av_opt_is_set_to_default_by_name(void *obj, const char *name, int search_flags);
871 
872 
873 #define AV_OPT_SERIALIZE_SKIP_DEFAULTS 0x00000001 ///< Serialize options that are not set to default values only.
874 #define AV_OPT_SERIALIZE_OPT_FLAGS_EXACT 0x00000002 ///< Serialize options that exactly match opt_flags only.
875 
876 /**
877  * Serialize object's options.
878  *
879  * Create a string containing object's serialized options.
880  * Such string may be passed back to av_opt_set_from_string() in order to restore option values.
881  *
882  * @param[in] obj AVClass object to serialize
883  * @param[in] opt_flags serialize options with all the specified flags set (AV_OPT_FLAG)
884  * @param[in] flags combination of AV_OPT_SERIALIZE_* flags
885  * @param[out] buffer Pointer to buffer that will be allocated with string containg serialized options.
886  * Buffer must be freed by the caller when is no longer needed.
887  * @param[in] key_val_sep character used to separate key from value
888  * @param[in] pairs_sep character used to separate two pairs from each other
889  * @return >= 0 on success, negative on error
890  */
891 int av_opt_serialize(void *obj, int opt_flags, int flags, char **buffer,
892  const char key_val_sep, const char pairs_sep);
893 /**
894  * @}
895  */
896 
897 #endif /* AVUTIL_OPT_H */