text: /*
   * 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 "dict.h"
  #include "log.h"
  #include "pixfmt.h"
  #include "samplefmt.h"
  #include "version.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.
   *
   * @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_next() 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_next(const AVClass *prev)
   *      {
   *          return prev ? NULL : &child_class;
   *      }
   *      @endcode
   *      Putting child_next() and child_class_next() 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_next() are needed. The distinction is that child_next()
   *      iterates over actually existing objects, while child_class_next()
   *      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_next() 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_next() 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,
      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_CONST = 128,
      AV_OPT_TYPE_IMAGE_SIZE = MKBETAG('S','I','Z','E'), ///< offset must point to two consecutive integers
      AV_OPT_TYPE_PIXEL_FMT  = MKBETAG('P','F','M','T'),
      AV_OPT_TYPE_SAMPLE_FMT = MKBETAG('S','F','M','T'),
      AV_OPT_TYPE_VIDEO_RATE = MKBETAG('V','R','A','T'), ///< offset must point to AVRational
      AV_OPT_TYPE_DURATION   = MKBETAG('D','U','R',' '),
      AV_OPT_TYPE_COLOR      = MKBETAG('C','O','L','R'),
      AV_OPT_TYPE_CHANNEL_LAYOUT = MKBETAG('C','H','L','A'),
  #if FF_API_OLD_AVOPTIONS
      FF_OPT_TYPE_FLAGS = 0,
      FF_OPT_TYPE_INT,
      FF_OPT_TYPE_INT64,
      FF_OPT_TYPE_DOUBLE,
      FF_OPT_TYPE_FLOAT,
      FF_OPT_TYPE_STRING,
      FF_OPT_TYPE_RATIONAL,
      FF_OPT_TYPE_BINARY,  ///< offset must point to a pointer immediately followed by an int for the length
      FF_OPT_TYPE_CONST=128,
  #endif
  };
  
  /**
   * AVOption
   */
  typedef struct AVOption
  {
      const char* name;
  
      /**
       * short English help text
       * @todo What about other languages?
       */
      const char* help;
  
      /**
       * 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;
  
      /**
       * the default value for scalar options
       */
      union
      {
          int64_t i64;
          double dbl;
          const char* str;
          /* TODO those are unused now */
          AVRational q;
      } default_val;
      double min;                 ///< minimum valid value for the option
      double max;                 ///< maximum valid value for the option
  
      int flags;
  #define AV_OPT_FLAG_ENCODING_PARAM  1   ///< a generic parameter which can be set by the user for muxing or encoding
  #define AV_OPT_FLAG_DECODING_PARAM  2   ///< a generic parameter which can be set by the user for demuxing or decoding
  #if FF_API_OPT_TYPE_METADATA
  #define AV_OPT_FLAG_METADATA        4   ///< some data extracted or inserted into the file like title, comment, ...
  #endif
  #define AV_OPT_FLAG_AUDIO_PARAM     8
  #define AV_OPT_FLAG_VIDEO_PARAM     16
  #define AV_OPT_FLAG_SUBTITLE_PARAM  32
      /**
       * The option is inteded for exporting values to the caller.
       */
  #define AV_OPT_FLAG_EXPORT          64
      /**
       * 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        128
  #define AV_OPT_FLAG_FILTERING_PARAM (1<<16) ///< a generic parameter which can be set by the user for filtering
  //FIXME think about enc-audio, ... style 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;
  
  
  #if FF_API_OLD_AVOPTIONS
  /**
   * 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. 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.
   * @param[out] o_out if non-NULL put here a pointer to the AVOption
   * found
   * @param alloc this parameter is currently ignored
   * @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
   * @deprecated use av_opt_set()
   */
  attribute_deprecated
  int av_set_string3(void* obj, const char* name, const char* val, int alloc, const AVOption** o_out);
  
  attribute_deprecated const AVOption* av_set_double(void* obj, const char* name, double n);
  attribute_deprecated const AVOption* av_set_q(void* obj, const char* name, AVRational n);
  attribute_deprecated const AVOption* av_set_int(void* obj, const char* name, int64_t n);
  
  attribute_deprecated
  double av_get_double(void* obj, const char* name, const AVOption** o_out);
  attribute_deprecated
  AVRational av_get_q(void* obj, const char* name, const AVOption** o_out);
  attribute_deprecated
  int64_t av_get_int(void* obj, const char* name, const AVOption** o_out);
  attribute_deprecated const char* av_get_string(void* obj, const char* name, const AVOption** o_out, char* buf, int buf_len);
  attribute_deprecated const AVOption* av_next_option(FF_CONST_AVUTIL55 void* obj, const AVOption* last);
  #endif
  
  /**
   * 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);
  
  /**
   * 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);
  
  /**
   * 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);
  /**
   * Free all allocated objects in obj.
   */
  void av_opt_free(void* obj);
  
  /**
   * 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);
  
  /**
   * 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);
  
  /**
   * 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_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);
  /**
   * @}
   */
  
  #define AV_OPT_SEARCH_CHILDREN   0x0001 /**< 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   0x0002
  
  /**
   *  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 0x1000
  
  /**
   * 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);
  
  /**
   * 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(FF_CONST_AVUTIL55 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 prev result of a previous call to this function or NULL
   * @return AVClass corresponding to next potential child or NULL
   */
  const AVClass* av_opt_child_class_next(const AVClass* parent, const AVClass* prev);
  
  /**
   * @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.
   * @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_channel_layout(void* obj, const char* name, int64_t ch_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_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
   */
  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_channel_layout(void* obj, const char* name, int search_flags, int64_t* ch_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);
  /**
   * @}
   */
  /**
   * 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);
  
  /**
   * 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);
  
  /**
   * Copy options from src object into dest object.
   *
   * 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.
   *
   * @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, FF_CONST_AVUTIL55 void* src);
  
  /**
   * 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);
  
  /**
   * 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);
  
  
  #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);
  /**
   * @}
   */
  
  #endif /* AVUTIL_OPT_H */
  