duckstation

opt.h (39585B)

---

 /*
  * AVOptions
  * copyright (c) 2005 Michael Niedermayer <michaelni@gmx.at>
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #ifndef AVUTIL_OPT_H
 #define AVUTIL_OPT_H
 
 /**
  * @file
  * AVOptions
  */
 
 #include "rational.h"
 #include "avutil.h"
 #include "channel_layout.h"
 #include "dict.h"
 #include "log.h"
 #include "pixfmt.h"
 #include "samplefmt.h"
 
 /**
  * @defgroup avoptions AVOptions
  * @ingroup lavu_data
  * @{
  * AVOptions provide a generic system to declare options on arbitrary structs
  * ("objects"). An option can have a help text, a type and a range of possible
  * values. Options may then be enumerated, read and written to.
  *
  * There are two modes of access to members of AVOption and its child structs.
  * One is called 'native access', and refers to access from the code that
  * declares the AVOption in question.  The other is 'foreign access', and refers
  * to access from other code.
  *
  * Certain struct members in this header are documented as 'native access only'
  * or similar - it means that only the code that declared the AVOption in
  * question is allowed to access the field. This allows us to extend the
  * semantics of those fields without breaking API compatibility.
  *
  * @section avoptions_implement Implementing AVOptions
  * This section describes how to add AVOptions capabilities to a struct.
  *
  * All AVOptions-related information is stored in an AVClass. Therefore
  * the first member of the struct should be a pointer to an AVClass describing it.
  * The option field of the AVClass must be set to a NULL-terminated static array
  * of AVOptions. Each AVOption must have a non-empty name, a type, a default
  * value and for number-type AVOptions also a range of allowed values. It must
  * also declare an offset in bytes from the start of the struct, where the field
  * associated with this AVOption is located. Other fields in the AVOption struct
  * should also be set when applicable, but are not required.
  *
  * The following example illustrates an AVOptions-enabled struct:
  * @code
  * typedef struct test_struct {
  *     const AVClass *class;
  *     int      int_opt;
  *     char    *str_opt;
  *     uint8_t *bin_opt;
  *     int      bin_len;
  * } test_struct;
  *
  * static const AVOption test_options[] = {
  *   { "test_int", "This is a test option of int type.", offsetof(test_struct, int_opt),
  *     AV_OPT_TYPE_INT, { .i64 = -1 }, INT_MIN, INT_MAX },
  *   { "test_str", "This is a test option of string type.", offsetof(test_struct, str_opt),
  *     AV_OPT_TYPE_STRING },
  *   { "test_bin", "This is a test option of binary type.", offsetof(test_struct, bin_opt),
  *     AV_OPT_TYPE_BINARY },
  *   { NULL },
  * };
  *
  * static const AVClass test_class = {
  *     .class_name = "test class",
  *     .item_name  = av_default_item_name,
  *     .option     = test_options,
  *     .version    = LIBAVUTIL_VERSION_INT,
  * };
  * @endcode
  *
  * Next, when allocating your struct, you must ensure that the AVClass pointer
  * is set to the correct value. Then, av_opt_set_defaults() can be called to
  * initialize defaults. After that the struct is ready to be used with the
  * AVOptions API.
  *
  * When cleaning up, you may use the av_opt_free() function to automatically
  * free all the allocated string and binary options.
  *
  * Continuing with the above example:
  *
  * @code
  * test_struct *alloc_test_struct(void)
  * {
  *     test_struct *ret = av_mallocz(sizeof(*ret));
  *     ret->class = &test_class;
  *     av_opt_set_defaults(ret);
  *     return ret;
  * }
  * void free_test_struct(test_struct **foo)
  * {
  *     av_opt_free(*foo);
  *     av_freep(foo);
  * }
  * @endcode
  *
  * @subsection avoptions_implement_nesting Nesting
  *      It may happen that an AVOptions-enabled struct contains another
  *      AVOptions-enabled struct as a member (e.g. AVCodecContext in
  *      libavcodec exports generic options, while its priv_data field exports
  *      codec-specific options). In such a case, it is possible to set up the
  *      parent struct to export a child's options. To do that, simply
  *      implement AVClass.child_next() and AVClass.child_class_iterate() in the
  *      parent struct's AVClass.
  *      Assuming that the test_struct from above now also contains a
  *      child_struct field:
  *
  *      @code
  *      typedef struct child_struct {
  *          AVClass *class;
  *          int flags_opt;
  *      } child_struct;
  *      static const AVOption child_opts[] = {
  *          { "test_flags", "This is a test option of flags type.",
  *            offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX },
  *          { NULL },
  *      };
  *      static const AVClass child_class = {
  *          .class_name = "child class",
  *          .item_name  = av_default_item_name,
  *          .option     = child_opts,
  *          .version    = LIBAVUTIL_VERSION_INT,
  *      };
  *
  *      void *child_next(void *obj, void *prev)
  *      {
  *          test_struct *t = obj;
  *          if (!prev && t->child_struct)
  *              return t->child_struct;
  *          return NULL
  *      }
  *      const AVClass child_class_iterate(void **iter)
  *      {
  *          const AVClass *c = *iter ? NULL : &child_class;
  *          *iter = (void*)(uintptr_t)c;
  *          return c;
  *      }
  *      @endcode
  *      Putting child_next() and child_class_iterate() as defined above into
  *      test_class will now make child_struct's options accessible through
  *      test_struct (again, proper setup as described above needs to be done on
  *      child_struct right after it is created).
  *
  *      From the above example it might not be clear why both child_next()
  *      and child_class_iterate() are needed. The distinction is that child_next()
  *      iterates over actually existing objects, while child_class_iterate()
  *      iterates over all possible child classes. E.g. if an AVCodecContext
  *      was initialized to use a codec which has private options, then its
  *      child_next() will return AVCodecContext.priv_data and finish
  *      iterating. OTOH child_class_iterate() on AVCodecContext.av_class will
  *      iterate over all available codecs with private options.
  *
  * @subsection avoptions_implement_named_constants Named constants
  *      It is possible to create named constants for options. Simply set the unit
  *      field of the option the constants should apply to a string and
  *      create the constants themselves as options of type AV_OPT_TYPE_CONST
  *      with their unit field set to the same string.
  *      Their default_val field should contain the value of the named
  *      constant.
  *      For example, to add some named constants for the test_flags option
  *      above, put the following into the child_opts array:
  *      @code
  *      { "test_flags", "This is a test option of flags type.",
  *        offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX, "test_unit" },
  *      { "flag1", "This is a flag with value 16", 0, AV_OPT_TYPE_CONST, { .i64 = 16 }, 0, 0, "test_unit" },
  *      @endcode
  *
  * @section avoptions_use Using AVOptions
  * This section deals with accessing options in an AVOptions-enabled struct.
  * Such structs in FFmpeg are e.g. AVCodecContext in libavcodec or
  * AVFormatContext in libavformat.
  *
  * @subsection avoptions_use_examine Examining AVOptions
  * The basic functions for examining options are av_opt_next(), which iterates
  * over all options defined for one object, and av_opt_find(), which searches
  * for an option with the given name.
  *
  * The situation is more complicated with nesting. An AVOptions-enabled struct
  * may have AVOptions-enabled children. Passing the AV_OPT_SEARCH_CHILDREN flag
  * to av_opt_find() will make the function search children recursively.
  *
  * For enumerating there are basically two cases. The first is when you want to
  * get all options that may potentially exist on the struct and its children
  * (e.g.  when constructing documentation). In that case you should call
  * av_opt_child_class_iterate() recursively on the parent struct's AVClass.  The
  * second case is when you have an already initialized struct with all its
  * children and you want to get all options that can be actually written or read
  * from it. In that case you should call av_opt_child_next() recursively (and
  * av_opt_next() on each result).
  *
  * @subsection avoptions_use_get_set Reading and writing AVOptions
  * When setting options, you often have a string read directly from the
  * user. In such a case, simply passing it to av_opt_set() is enough. For
  * non-string type options, av_opt_set() will parse the string according to the
  * option type.
  *
  * Similarly av_opt_get() will read any option type and convert it to a string
  * which will be returned. Do not forget that the string is allocated, so you
  * have to free it with av_free().
  *
  * In some cases it may be more convenient to put all options into an
  * AVDictionary and call av_opt_set_dict() on it. A specific case of this
  * are the format/codec open functions in lavf/lavc which take a dictionary
  * filled with option as a parameter. This makes it possible to set some options
  * that cannot be set otherwise, since e.g. the input file format is not known
  * before the file is actually opened.
  */
 
 enum AVOptionType{
     AV_OPT_TYPE_FLAGS = 1,
     AV_OPT_TYPE_INT,
     AV_OPT_TYPE_INT64,
     AV_OPT_TYPE_DOUBLE,
     AV_OPT_TYPE_FLOAT,
     AV_OPT_TYPE_STRING,
     AV_OPT_TYPE_RATIONAL,
     AV_OPT_TYPE_BINARY,  ///< offset must point to a pointer immediately followed by an int for the length
     AV_OPT_TYPE_DICT,
     AV_OPT_TYPE_UINT64,
     AV_OPT_TYPE_CONST,
     AV_OPT_TYPE_IMAGE_SIZE, ///< offset must point to two consecutive integers
     AV_OPT_TYPE_PIXEL_FMT,
     AV_OPT_TYPE_SAMPLE_FMT,
     AV_OPT_TYPE_VIDEO_RATE, ///< offset must point to AVRational
     AV_OPT_TYPE_DURATION,
     AV_OPT_TYPE_COLOR,
     AV_OPT_TYPE_BOOL,
     AV_OPT_TYPE_CHLAYOUT,
 
     /**
      * May be combined with another regular option type to declare an array
      * option.
      *
      * For array options, @ref AVOption.offset should refer to a pointer
      * corresponding to the option type. The pointer should be immediately
      * followed by an unsigned int that will store the number of elements in the
      * array.
      */
     AV_OPT_TYPE_FLAG_ARRAY = (1 << 16),
 };
 
 /**
  * A generic parameter which can be set by the user for muxing or encoding.
  */
 #define AV_OPT_FLAG_ENCODING_PARAM  (1 << 0)
 /**
  * A generic parameter which can be set by the user for demuxing or decoding.
  */
 #define AV_OPT_FLAG_DECODING_PARAM  (1 << 1)
 #define AV_OPT_FLAG_AUDIO_PARAM     (1 << 3)
 #define AV_OPT_FLAG_VIDEO_PARAM     (1 << 4)
 #define AV_OPT_FLAG_SUBTITLE_PARAM  (1 << 5)
 /**
  * The option is intended for exporting values to the caller.
  */
 #define AV_OPT_FLAG_EXPORT          (1 << 6)
 /**
  * The option may not be set through the AVOptions API, only read.
  * This flag only makes sense when AV_OPT_FLAG_EXPORT is also set.
  */
 #define AV_OPT_FLAG_READONLY        (1 << 7)
 /**
  * A generic parameter which can be set by the user for bit stream filtering.
  */
 #define AV_OPT_FLAG_BSF_PARAM       (1 << 8)
 
 /**
  * A generic parameter which can be set by the user at runtime.
  */
 #define AV_OPT_FLAG_RUNTIME_PARAM   (1 << 15)
 /**
  * A generic parameter which can be set by the user for filtering.
  */
 #define AV_OPT_FLAG_FILTERING_PARAM (1 << 16)
 /**
  * Set if option is deprecated, users should refer to AVOption.help text for
  * more information.
  */
 #define AV_OPT_FLAG_DEPRECATED      (1 << 17)
 /**
  * Set if option constants can also reside in child objects.
  */
 #define AV_OPT_FLAG_CHILD_CONSTS    (1 << 18)
 
 /**
  * May be set as default_val for AV_OPT_TYPE_FLAG_ARRAY options.
  */
 typedef struct AVOptionArrayDef {
     /**
      * Native access only.
      *
      * Default value of the option, as would be serialized by av_opt_get() (i.e.
      * using the value of sep as the separator).
      */
     const char         *def;
 
     /**
      * Minimum number of elements in the array. When this field is non-zero, def
      * must be non-NULL and contain at least this number of elements.
      */
     unsigned            size_min;
     /**
      * Maximum number of elements in the array, 0 when unlimited.
      */
     unsigned            size_max;
 
     /**
      * Separator between array elements in string representations of this
      * option, used by av_opt_set() and av_opt_get(). It must be a printable
      * ASCII character, excluding alphanumeric and the backslash. A comma is
      * used when sep=0.
      *
      * The separator and the backslash must be backslash-escaped in order to
      * appear in string representations of the option value.
      */
     char                sep;
 } AVOptionArrayDef;
 
 /**
  * AVOption
  */
 typedef struct AVOption {
     const char *name;
 
     /**
      * short English help text
      * @todo What about other languages?
      */
     const char *help;
 
     /**
      * Native access only.
      *
      * The offset relative to the context structure where the option
      * value is stored. It should be 0 for named constants.
      */
     int offset;
     enum AVOptionType type;
 
     /**
      * Native access only, except when documented otherwise.
      * the default value for scalar options
      */
     union {
         int64_t i64;
         double dbl;
         const char *str;
         /* TODO those are unused now */
         AVRational q;
 
         /**
          * Used for AV_OPT_TYPE_FLAG_ARRAY options. May be NULL.
          *
          * Foreign access to some members allowed, as noted in AVOptionArrayDef
          * documentation.
          */
         const AVOptionArrayDef *arr;
     } default_val;
     double min;                 ///< minimum valid value for the option
     double max;                 ///< maximum valid value for the option
 
     /**
      * A combination of AV_OPT_FLAG_*.
      */
     int flags;
 
     /**
      * The logical unit to which the option belongs. Non-constant
      * options and corresponding named constants share the same
      * unit. May be NULL.
      */
     const char *unit;
 } AVOption;
 
 /**
  * A single allowed range of values, or a single allowed value.
  */
 typedef struct AVOptionRange {
     const char *str;
     /**
      * Value range.
      * For string ranges this represents the min/max length.
      * For dimensions this represents the min/max pixel count or width/height in multi-component case.
      */
     double value_min, value_max;
     /**
      * Value's component range.
      * For string this represents the unicode range for chars, 0-127 limits to ASCII.
      */
     double component_min, component_max;
     /**
      * Range flag.
      * If set to 1 the struct encodes a range, if set to 0 a single value.
      */
     int is_range;
 } AVOptionRange;
 
 /**
  * List of AVOptionRange structs.
  */
 typedef struct AVOptionRanges {
     /**
      * Array of option ranges.
      *
      * Most of option types use just one component.
      * Following describes multi-component option types:
      *
      * AV_OPT_TYPE_IMAGE_SIZE:
      * component index 0: range of pixel count (width * height).
      * component index 1: range of width.
      * component index 2: range of height.
      *
      * @note To obtain multi-component version of this structure, user must
      *       provide AV_OPT_MULTI_COMPONENT_RANGE to av_opt_query_ranges or
      *       av_opt_query_ranges_default function.
      *
      * Multi-component range can be read as in following example:
      *
      * @code
      * int range_index, component_index;
      * AVOptionRanges *ranges;
      * AVOptionRange *range[3]; //may require more than 3 in the future.
      * av_opt_query_ranges(&ranges, obj, key, AV_OPT_MULTI_COMPONENT_RANGE);
      * for (range_index = 0; range_index < ranges->nb_ranges; range_index++) {
      *     for (component_index = 0; component_index < ranges->nb_components; component_index++)
      *         range[component_index] = ranges->range[ranges->nb_ranges * component_index + range_index];
      *     //do something with range here.
      * }
      * av_opt_freep_ranges(&ranges);
      * @endcode
      */
     AVOptionRange **range;
     /**
      * Number of ranges per component.
      */
     int nb_ranges;
     /**
      * Number of componentes.
      */
     int nb_components;
 } AVOptionRanges;
 
 /**
  * @defgroup opt_mng AVOption (un)initialization and inspection.
  * @{
  */
 
 /**
  * Set the values of all AVOption fields to their default values.
  *
  * @param s an AVOption-enabled struct (its first member must be a pointer to AVClass)
  */
 void av_opt_set_defaults(void *s);
 
 /**
  * Set the values of all AVOption fields to their default values. Only these
  * AVOption fields for which (opt->flags & mask) == flags will have their
  * default applied to s.
  *
  * @param s an AVOption-enabled struct (its first member must be a pointer to AVClass)
  * @param mask combination of AV_OPT_FLAG_*
  * @param flags combination of AV_OPT_FLAG_*
  */
 void av_opt_set_defaults2(void *s, int mask, int flags);
 
 /**
  * Free all allocated objects in obj.
  */
 void av_opt_free(void *obj);
 
 /**
  * Iterate over all AVOptions belonging to obj.
  *
  * @param obj an AVOptions-enabled struct or a double pointer to an
  *            AVClass describing it.
  * @param prev result of the previous call to av_opt_next() on this object
  *             or NULL
  * @return next AVOption or NULL
  */
 const AVOption *av_opt_next(const void *obj, const AVOption *prev);
 
 /**
  * Iterate over AVOptions-enabled children of obj.
  *
  * @param prev result of a previous call to this function or NULL
  * @return next AVOptions-enabled child or NULL
  */
 void *av_opt_child_next(void *obj, void *prev);
 
 /**
  * Iterate over potential AVOptions-enabled children of parent.
  *
  * @param iter a pointer where iteration state is stored.
  * @return AVClass corresponding to next potential child or NULL
  */
 const AVClass *av_opt_child_class_iterate(const AVClass *parent, void **iter);
 
 #define AV_OPT_SEARCH_CHILDREN   (1 << 0) /**< Search in possible children of the
                                                given object first. */
 /**
  *  The obj passed to av_opt_find() is fake -- only a double pointer to AVClass
  *  instead of a required pointer to a struct containing AVClass. This is
  *  useful for searching for options without needing to allocate the corresponding
  *  object.
  */
 #define AV_OPT_SEARCH_FAKE_OBJ   (1 << 1)
 
 /**
  *  In av_opt_get, return NULL if the option has a pointer type and is set to NULL,
  *  rather than returning an empty string.
  */
 #define AV_OPT_ALLOW_NULL (1 << 2)
 
 /**
  *  Allows av_opt_query_ranges and av_opt_query_ranges_default to return more than
  *  one component for certain option types.
  *  @see AVOptionRanges for details.
  */
 #define AV_OPT_MULTI_COMPONENT_RANGE (1 << 12)
 
 /**
  * Look for an option in an object. Consider only options which
  * have all the specified flags set.
  *
  * @param[in] obj A pointer to a struct whose first element is a
  *                pointer to an AVClass.
  *                Alternatively a double pointer to an AVClass, if
  *                AV_OPT_SEARCH_FAKE_OBJ search flag is set.
  * @param[in] name The name of the option to look for.
  * @param[in] unit When searching for named constants, name of the unit
  *                 it belongs to.
  * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
  * @param search_flags A combination of AV_OPT_SEARCH_*.
  *
  * @return A pointer to the option found, or NULL if no option
  *         was found.
  *
  * @note Options found with AV_OPT_SEARCH_CHILDREN flag may not be settable
  * directly with av_opt_set(). Use special calls which take an options
  * AVDictionary (e.g. avformat_open_input()) to set options found with this
  * flag.
  */
 const AVOption *av_opt_find(void *obj, const char *name, const char *unit,
                             int opt_flags, int search_flags);
 
 /**
  * Look for an option in an object. Consider only options which
  * have all the specified flags set.
  *
  * @param[in] obj A pointer to a struct whose first element is a
  *                pointer to an AVClass.
  *                Alternatively a double pointer to an AVClass, if
  *                AV_OPT_SEARCH_FAKE_OBJ search flag is set.
  * @param[in] name The name of the option to look for.
  * @param[in] unit When searching for named constants, name of the unit
  *                 it belongs to.
  * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
  * @param search_flags A combination of AV_OPT_SEARCH_*.
  * @param[out] target_obj if non-NULL, an object to which the option belongs will be
  * written here. It may be different from obj if AV_OPT_SEARCH_CHILDREN is present
  * in search_flags. This parameter is ignored if search_flags contain
  * AV_OPT_SEARCH_FAKE_OBJ.
  *
  * @return A pointer to the option found, or NULL if no option
  *         was found.
  */
 const AVOption *av_opt_find2(void *obj, const char *name, const char *unit,
                              int opt_flags, int search_flags, void **target_obj);
 
 /**
  * Show the obj options.
  *
  * @param req_flags requested flags for the options to show. Show only the
  * options for which it is opt->flags & req_flags.
  * @param rej_flags rejected flags for the options to show. Show only the
  * options for which it is !(opt->flags & req_flags).
  * @param av_log_obj log context to use for showing the options
  */
 int av_opt_show2(void *obj, void *av_log_obj, int req_flags, int rej_flags);
 
 /**
  * Extract a key-value pair from the beginning of a string.
  *
  * @param ropts        pointer to the options string, will be updated to
  *                     point to the rest of the string (one of the pairs_sep
  *                     or the final NUL)
  * @param key_val_sep  a 0-terminated list of characters used to separate
  *                     key from value, for example '='
  * @param pairs_sep    a 0-terminated list of characters used to separate
  *                     two pairs from each other, for example ':' or ','
  * @param flags        flags; see the AV_OPT_FLAG_* values below
  * @param rkey         parsed key; must be freed using av_free()
  * @param rval         parsed value; must be freed using av_free()
  *
  * @return  >=0 for success, or a negative value corresponding to an
  *          AVERROR code in case of error; in particular:
  *          AVERROR(EINVAL) if no key is present
  *
  */
 int av_opt_get_key_value(const char **ropts,
                          const char *key_val_sep, const char *pairs_sep,
                          unsigned flags,
                          char **rkey, char **rval);
 
 enum {
 
     /**
      * Accept to parse a value without a key; the key will then be returned
      * as NULL.
      */
     AV_OPT_FLAG_IMPLICIT_KEY = 1,
 };
 
 /**
  * @}
  */
 
 /**
  * @defgroup opt_write Setting and modifying option values
  * @{
  */
 
 /**
  * Parse the key/value pairs list in opts. For each key/value pair
  * found, stores the value in the field in ctx that is named like the
  * key. ctx must be an AVClass context, storing is done using
  * AVOptions.
  *
  * @param opts options string to parse, may be NULL
  * @param key_val_sep a 0-terminated list of characters used to
  * separate key from value
  * @param pairs_sep a 0-terminated list of characters used to separate
  * two pairs from each other
  * @return the number of successfully set key/value pairs, or a negative
  * value corresponding to an AVERROR code in case of error:
  * AVERROR(EINVAL) if opts cannot be parsed,
  * the error code issued by av_opt_set() if a key/value pair
  * cannot be set
  */
 int av_set_options_string(void *ctx, const char *opts,
                           const char *key_val_sep, const char *pairs_sep);
 
 /**
  * Parse the key-value pairs list in opts. For each key=value pair found,
  * set the value of the corresponding option in ctx.
  *
  * @param ctx          the AVClass object to set options on
  * @param opts         the options string, key-value pairs separated by a
  *                     delimiter
  * @param shorthand    a NULL-terminated array of options names for shorthand
  *                     notation: if the first field in opts has no key part,
  *                     the key is taken from the first element of shorthand;
  *                     then again for the second, etc., until either opts is
  *                     finished, shorthand is finished or a named option is
  *                     found; after that, all options must be named
  * @param key_val_sep  a 0-terminated list of characters used to separate
  *                     key from value, for example '='
  * @param pairs_sep    a 0-terminated list of characters used to separate
  *                     two pairs from each other, for example ':' or ','
  * @return  the number of successfully set key=value pairs, or a negative
  *          value corresponding to an AVERROR code in case of error:
  *          AVERROR(EINVAL) if opts cannot be parsed,
  *          the error code issued by av_set_string3() if a key/value pair
  *          cannot be set
  *
  * Options names must use only the following characters: a-z A-Z 0-9 - . / _
  * Separators must use characters distinct from option names and from each
  * other.
  */
 int av_opt_set_from_string(void *ctx, const char *opts,
                            const char *const *shorthand,
                            const char *key_val_sep, const char *pairs_sep);
 
 /**
  * Set all the options from a given dictionary on an object.
  *
  * @param obj a struct whose first element is a pointer to AVClass
  * @param options options to process. This dictionary will be freed and replaced
  *                by a new one containing all options not found in obj.
  *                Of course this new dictionary needs to be freed by caller
  *                with av_dict_free().
  *
  * @return 0 on success, a negative AVERROR if some option was found in obj,
  *         but could not be set.
  *
  * @see av_dict_copy()
  */
 int av_opt_set_dict(void *obj, struct AVDictionary **options);
 
 
 /**
  * Set all the options from a given dictionary on an object.
  *
  * @param obj a struct whose first element is a pointer to AVClass
  * @param options options to process. This dictionary will be freed and replaced
  *                by a new one containing all options not found in obj.
  *                Of course this new dictionary needs to be freed by caller
  *                with av_dict_free().
  * @param search_flags A combination of AV_OPT_SEARCH_*.
  *
  * @return 0 on success, a negative AVERROR if some option was found in obj,
  *         but could not be set.
  *
  * @see av_dict_copy()
  */
 int av_opt_set_dict2(void *obj, struct AVDictionary **options, int search_flags);
 
 /**
  * Copy options from src object into dest object.
  *
  * The underlying AVClass of both src and dest must coincide. The guarantee
  * below does not apply if this is not fulfilled.
  *
  * Options that require memory allocation (e.g. string or binary) are malloc'ed in dest object.
  * Original memory allocated for such options is freed unless both src and dest options points to the same memory.
  *
  * Even on error it is guaranteed that allocated options from src and dest
  * no longer alias each other afterwards; in particular calling av_opt_free()
  * on both src and dest is safe afterwards if dest has been memdup'ed from src.
  *
  * @param dest Object to copy from
  * @param src  Object to copy into
  * @return 0 on success, negative on error
  */
 int av_opt_copy(void *dest, const void *src);
 
 /**
  * @defgroup opt_set_funcs Option setting functions
  * @{
  * Those functions set the field of obj with the given name to value.
  *
  * @param[in] obj A struct whose first element is a pointer to an AVClass.
  * @param[in] name the name of the field to set
  * @param[in] val The value to set. In case of av_opt_set() if the field is not
  * of a string type, then the given string is parsed.
  * SI postfixes and some named scalars are supported.
  * If the field is of a numeric type, it has to be a numeric or named
  * scalar. Behavior with more than one scalar and +- infix operators
  * is undefined.
  * If the field is of a flags type, it has to be a sequence of numeric
  * scalars or named flags separated by '+' or '-'. Prefixing a flag
  * with '+' causes it to be set without affecting the other flags;
  * similarly, '-' unsets a flag.
  * If the field is of a dictionary type, it has to be a ':' separated list of
  * key=value parameters. Values containing ':' special characters must be
  * escaped.
  * @param search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
  * is passed here, then the option may be set on a child of obj.
  *
  * @return 0 if the value has been set, or an AVERROR code in case of
  * error:
  * AVERROR_OPTION_NOT_FOUND if no matching option exists
  * AVERROR(ERANGE) if the value is out of range
  * AVERROR(EINVAL) if the value is not valid
  */
 int av_opt_set         (void *obj, const char *name, const char *val, int search_flags);
 int av_opt_set_int     (void *obj, const char *name, int64_t     val, int search_flags);
 int av_opt_set_double  (void *obj, const char *name, double      val, int search_flags);
 int av_opt_set_q       (void *obj, const char *name, AVRational  val, int search_flags);
 int av_opt_set_bin     (void *obj, const char *name, const uint8_t *val, int size, int search_flags);
 int av_opt_set_image_size(void *obj, const char *name, int w, int h, int search_flags);
 int av_opt_set_pixel_fmt (void *obj, const char *name, enum AVPixelFormat fmt, int search_flags);
 int av_opt_set_sample_fmt(void *obj, const char *name, enum AVSampleFormat fmt, int search_flags);
 int av_opt_set_video_rate(void *obj, const char *name, AVRational val, int search_flags);
 int av_opt_set_chlayout(void *obj, const char *name, const AVChannelLayout *layout, int search_flags);
 /**
  * @note Any old dictionary present is discarded and replaced with a copy of the new one. The
  * caller still owns val is and responsible for freeing it.
  */
 int av_opt_set_dict_val(void *obj, const char *name, const AVDictionary *val, int search_flags);
 
 /**
  * Set a binary option to an integer list.
  *
  * @param obj    AVClass object to set options on
  * @param name   name of the binary option
  * @param val    pointer to an integer list (must have the correct type with
  *               regard to the contents of the list)
  * @param term   list terminator (usually 0 or -1)
  * @param flags  search flags
  */
 #define av_opt_set_int_list(obj, name, val, term, flags) \
     (av_int_list_length(val, term) > INT_MAX / sizeof(*(val)) ? \
      AVERROR(EINVAL) : \
      av_opt_set_bin(obj, name, (const uint8_t *)(val), \
                     av_int_list_length(val, term) * sizeof(*(val)), flags))
 
 /**
  * @}
  * @}
  */
 
 /**
  * @defgroup opt_read Reading option values
  * @{
  */
 
 /**
  * @defgroup opt_get_funcs Option getting functions
  * @{
  * Those functions get a value of the option with the given name from an object.
  *
  * @param[in] obj a struct whose first element is a pointer to an AVClass.
  * @param[in] name name of the option to get.
  * @param[in] search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
  * is passed here, then the option may be found in a child of obj.
  * @param[out] out_val value of the option will be written here
  * @return >=0 on success, a negative error code otherwise
  */
 /**
  * @note the returned string will be av_malloc()ed and must be av_free()ed by the caller
  *
  * @note if AV_OPT_ALLOW_NULL is set in search_flags in av_opt_get, and the
  * option is of type AV_OPT_TYPE_STRING, AV_OPT_TYPE_BINARY or AV_OPT_TYPE_DICT
  * and is set to NULL, *out_val will be set to NULL instead of an allocated
  * empty string.
  */
 int av_opt_get         (void *obj, const char *name, int search_flags, uint8_t   **out_val);
 int av_opt_get_int     (void *obj, const char *name, int search_flags, int64_t    *out_val);
 int av_opt_get_double  (void *obj, const char *name, int search_flags, double     *out_val);
 int av_opt_get_q       (void *obj, const char *name, int search_flags, AVRational *out_val);
 int av_opt_get_image_size(void *obj, const char *name, int search_flags, int *w_out, int *h_out);
 int av_opt_get_pixel_fmt (void *obj, const char *name, int search_flags, enum AVPixelFormat *out_fmt);
 int av_opt_get_sample_fmt(void *obj, const char *name, int search_flags, enum AVSampleFormat *out_fmt);
 int av_opt_get_video_rate(void *obj, const char *name, int search_flags, AVRational *out_val);
 int av_opt_get_chlayout(void *obj, const char *name, int search_flags, AVChannelLayout *layout);
 /**
  * @param[out] out_val The returned dictionary is a copy of the actual value and must
  * be freed with av_dict_free() by the caller
  */
 int av_opt_get_dict_val(void *obj, const char *name, int search_flags, AVDictionary **out_val);
 /**
  * @}
  */
 
 /**
  * @defgroup opt_eval_funcs Evaluating option strings
  * @{
  * This group of functions can be used to evaluate option strings
  * and get numbers out of them. They do the same thing as av_opt_set(),
  * except the result is written into the caller-supplied pointer.
  *
  * @param obj a struct whose first element is a pointer to AVClass.
  * @param o an option for which the string is to be evaluated.
  * @param val string to be evaluated.
  * @param *_out value of the string will be written here.
  *
  * @return 0 on success, a negative number on failure.
  */
 int av_opt_eval_flags (void *obj, const AVOption *o, const char *val, int        *flags_out);
 int av_opt_eval_int   (void *obj, const AVOption *o, const char *val, int        *int_out);
 int av_opt_eval_int64 (void *obj, const AVOption *o, const char *val, int64_t    *int64_out);
 int av_opt_eval_float (void *obj, const AVOption *o, const char *val, float      *float_out);
 int av_opt_eval_double(void *obj, const AVOption *o, const char *val, double     *double_out);
 int av_opt_eval_q     (void *obj, const AVOption *o, const char *val, AVRational *q_out);
 /**
  * @}
  */
 
 /**
  * Gets a pointer to the requested field in a struct.
  * This function allows accessing a struct even when its fields are moved or
  * renamed since the application making the access has been compiled,
  *
  * @returns a pointer to the field, it can be cast to the correct type and read
  *          or written to.
  */
 void *av_opt_ptr(const AVClass *avclass, void *obj, const char *name);
 
 /**
  * Check if given option is set to its default value.
  *
  * Options o must belong to the obj. This function must not be called to check child's options state.
  * @see av_opt_is_set_to_default_by_name().
  *
  * @param obj  AVClass object to check option on
  * @param o    option to be checked
  * @return     >0 when option is set to its default,
  *              0 when option is not set its default,
  *             <0 on error
  */
 int av_opt_is_set_to_default(void *obj, const AVOption *o);
 
 /**
  * Check if given option is set to its default value.
  *
  * @param obj          AVClass object to check option on
  * @param name         option name
  * @param search_flags combination of AV_OPT_SEARCH_*
  * @return             >0 when option is set to its default,
  *                     0 when option is not set its default,
  *                     <0 on error
  */
 int av_opt_is_set_to_default_by_name(void *obj, const char *name, int search_flags);
 
 /**
  * Check whether a particular flag is set in a flags field.
  *
  * @param field_name the name of the flag field option
  * @param flag_name the name of the flag to check
  * @return non-zero if the flag is set, zero if the flag isn't set,
  *         isn't of the right type, or the flags field doesn't exist.
  */
 int av_opt_flag_is_set(void *obj, const char *field_name, const char *flag_name);
 
 #define AV_OPT_SERIALIZE_SKIP_DEFAULTS              0x00000001  ///< Serialize options that are not set to default values only.
 #define AV_OPT_SERIALIZE_OPT_FLAGS_EXACT            0x00000002  ///< Serialize options that exactly match opt_flags only.
 
 /**
  * Serialize object's options.
  *
  * Create a string containing object's serialized options.
  * Such string may be passed back to av_opt_set_from_string() in order to restore option values.
  * A key/value or pairs separator occurring in the serialized value or
  * name string are escaped through the av_escape() function.
  *
  * @param[in]  obj           AVClass object to serialize
  * @param[in]  opt_flags     serialize options with all the specified flags set (AV_OPT_FLAG)
  * @param[in]  flags         combination of AV_OPT_SERIALIZE_* flags
  * @param[out] buffer        Pointer to buffer that will be allocated with string containg serialized options.
  *                           Buffer must be freed by the caller when is no longer needed.
  * @param[in]  key_val_sep   character used to separate key from value
  * @param[in]  pairs_sep     character used to separate two pairs from each other
  * @return                   >= 0 on success, negative on error
  * @warning Separators cannot be neither '\\' nor '\0'. They also cannot be the same.
  */
 int av_opt_serialize(void *obj, int opt_flags, int flags, char **buffer,
                      const char key_val_sep, const char pairs_sep);
 
 /**
  * @}
  */
 
 /**
  * Free an AVOptionRanges struct and set it to NULL.
  */
 void av_opt_freep_ranges(AVOptionRanges **ranges);
 
 /**
  * Get a list of allowed ranges for the given option.
  *
  * The returned list may depend on other fields in obj like for example profile.
  *
  * @param flags is a bitmask of flags, undefined flags should not be set and should be ignored
  *              AV_OPT_SEARCH_FAKE_OBJ indicates that the obj is a double pointer to a AVClass instead of a full instance
  *              AV_OPT_MULTI_COMPONENT_RANGE indicates that function may return more than one component, @see AVOptionRanges
  *
  * The result must be freed with av_opt_freep_ranges.
  *
  * @return number of compontents returned on success, a negative errro code otherwise
  */
 int av_opt_query_ranges(AVOptionRanges **, void *obj, const char *key, int flags);
 
 /**
  * Get a default list of allowed ranges for the given option.
  *
  * This list is constructed without using the AVClass.query_ranges() callback
  * and can be used as fallback from within the callback.
  *
  * @param flags is a bitmask of flags, undefined flags should not be set and should be ignored
  *              AV_OPT_SEARCH_FAKE_OBJ indicates that the obj is a double pointer to a AVClass instead of a full instance
  *              AV_OPT_MULTI_COMPONENT_RANGE indicates that function may return more than one component, @see AVOptionRanges
  *
  * The result must be freed with av_opt_free_ranges.
  *
  * @return number of compontents returned on success, a negative errro code otherwise
  */
 int av_opt_query_ranges_default(AVOptionRanges **, void *obj, const char *key, int flags);
 
 /**
  * @}
  */
 
 #endif /* AVUTIL_OPT_H */