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517 lines
21 KiB
C
517 lines
21 KiB
C
/*
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* AVOptions
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* copyright (c) 2005 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef AVUTIL_OPT_H
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#define AVUTIL_OPT_H
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/**
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* @file
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* AVOptions
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*/
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#include "rational.h"
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#include "avutil.h"
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#include "dict.h"
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#include "log.h"
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/**
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* @defgroup avoptions AVOptions
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* @ingroup lavu_data
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* @{
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* AVOptions provide a generic system to declare options on arbitrary structs
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* ("objects"). An option can have a help text, a type and a range of possible
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* values. Options may then be enumerated, read and written to.
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*
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* @section avoptions_implement Implementing AVOptions
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* This section describes how to add AVOptions capabilities to a struct.
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*
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* All AVOptions-related information is stored in an AVClass. Therefore
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* the first member of the struct must be a pointer to an AVClass describing it.
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* The option field of the AVClass must be set to a NULL-terminated static array
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* of AVOptions. Each AVOption must have a non-empty name, a type, a default
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* value and for number-type AVOptions also a range of allowed values. It must
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* also declare an offset in bytes from the start of the struct, where the field
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* associated with this AVOption is located. Other fields in the AVOption struct
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* should also be set when applicable, but are not required.
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*
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* The following example illustrates an AVOptions-enabled struct:
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* @code
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* typedef struct test_struct {
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* AVClass *class;
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* int int_opt;
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* char *str_opt;
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* uint8_t *bin_opt;
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* int bin_len;
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* } test_struct;
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*
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* static const AVOption options[] = {
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* { "test_int", "This is a test option of int type.", offsetof(test_struct, int_opt),
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* AV_OPT_TYPE_INT, { .i64 = -1 }, INT_MIN, INT_MAX },
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* { "test_str", "This is a test option of string type.", offsetof(test_struct, str_opt),
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* AV_OPT_TYPE_STRING },
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* { "test_bin", "This is a test option of binary type.", offsetof(test_struct, bin_opt),
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* AV_OPT_TYPE_BINARY },
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* { NULL },
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* };
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*
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* static const AVClass test_class = {
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* .class_name = "test class",
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* .item_name = av_default_item_name,
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* .option = options,
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* .version = LIBAVUTIL_VERSION_INT,
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* };
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* @endcode
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*
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* Next, when allocating your struct, you must ensure that the AVClass pointer
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* is set to the correct value. Then, av_opt_set_defaults() must be called to
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* initialize defaults. After that the struct is ready to be used with the
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* AVOptions API.
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*
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* When cleaning up, you may use the av_opt_free() function to automatically
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* free all the allocated string and binary options.
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*
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* Continuing with the above example:
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*
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* @code
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* test_struct *alloc_test_struct(void)
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* {
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* test_struct *ret = av_malloc(sizeof(*ret));
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* ret->class = &test_class;
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* av_opt_set_defaults(ret);
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* return ret;
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* }
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* void free_test_struct(test_struct **foo)
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* {
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* av_opt_free(*foo);
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* av_freep(foo);
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* }
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* @endcode
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*
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* @subsection avoptions_implement_nesting Nesting
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* It may happen that an AVOptions-enabled struct contains another
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* AVOptions-enabled struct as a member (e.g. AVCodecContext in
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* libavcodec exports generic options, while its priv_data field exports
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* codec-specific options). In such a case, it is possible to set up the
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* parent struct to export a child's options. To do that, simply
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* implement AVClass.child_next() and AVClass.child_class_next() in the
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* parent struct's AVClass.
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* Assuming that the test_struct from above now also contains a
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* child_struct field:
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*
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* @code
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* typedef struct child_struct {
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* AVClass *class;
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* int flags_opt;
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* } child_struct;
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* static const AVOption child_opts[] = {
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* { "test_flags", "This is a test option of flags type.",
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* offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX },
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* { NULL },
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* };
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* static const AVClass child_class = {
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* .class_name = "child class",
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* .item_name = av_default_item_name,
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* .option = child_opts,
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* .version = LIBAVUTIL_VERSION_INT,
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* };
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*
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* void *child_next(void *obj, void *prev)
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* {
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* test_struct *t = obj;
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* if (!prev && t->child_struct)
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* return t->child_struct;
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* return NULL
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* }
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* const AVClass child_class_next(const AVClass *prev)
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* {
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* return prev ? NULL : &child_class;
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* }
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* @endcode
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* Putting child_next() and child_class_next() as defined above into
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* test_class will now make child_struct's options accessible through
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* test_struct (again, proper setup as described above needs to be done on
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* child_struct right after it is created).
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*
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* From the above example it might not be clear why both child_next()
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* and child_class_next() are needed. The distinction is that child_next()
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* iterates over actually existing objects, while child_class_next()
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* iterates over all possible child classes. E.g. if an AVCodecContext
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* was initialized to use a codec which has private options, then its
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* child_next() will return AVCodecContext.priv_data and finish
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* iterating. OTOH child_class_next() on AVCodecContext.av_class will
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* iterate over all available codecs with private options.
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*
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* @subsection avoptions_implement_named_constants Named constants
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* It is possible to create named constants for options. Simply set the unit
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* field of the option the constants should apply to to a string and
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* create the constants themselves as options of type AV_OPT_TYPE_CONST
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* with their unit field set to the same string.
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* Their default_val field should contain the value of the named
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* constant.
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* For example, to add some named constants for the test_flags option
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* above, put the following into the child_opts array:
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* @code
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* { "test_flags", "This is a test option of flags type.",
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* offsetof(child_struct, flags_opt), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX, "test_unit" },
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* { "flag1", "This is a flag with value 16", 0, AV_OPT_TYPE_CONST, { .i64 = 16 }, 0, 0, "test_unit" },
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* @endcode
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*
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* @section avoptions_use Using AVOptions
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* This section deals with accessing options in an AVOptions-enabled struct.
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* Such structs in Libav are e.g. AVCodecContext in libavcodec or
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* AVFormatContext in libavformat.
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*
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* @subsection avoptions_use_examine Examining AVOptions
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* The basic functions for examining options are av_opt_next(), which iterates
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* over all options defined for one object, and av_opt_find(), which searches
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* for an option with the given name.
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*
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* The situation is more complicated with nesting. An AVOptions-enabled struct
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* may have AVOptions-enabled children. Passing the AV_OPT_SEARCH_CHILDREN flag
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* to av_opt_find() will make the function search children recursively.
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*
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* For enumerating there are basically two cases. The first is when you want to
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* get all options that may potentially exist on the struct and its children
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* (e.g. when constructing documentation). In that case you should call
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* av_opt_child_class_next() recursively on the parent struct's AVClass. The
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* second case is when you have an already initialized struct with all its
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* children and you want to get all options that can be actually written or read
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* from it. In that case you should call av_opt_child_next() recursively (and
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* av_opt_next() on each result).
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*
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* @subsection avoptions_use_get_set Reading and writing AVOptions
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* When setting options, you often have a string read directly from the
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* user. In such a case, simply passing it to av_opt_set() is enough. For
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* non-string type options, av_opt_set() will parse the string according to the
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* option type.
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*
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* Similarly av_opt_get() will read any option type and convert it to a string
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* which will be returned. Do not forget that the string is allocated, so you
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* have to free it with av_free().
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*
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* In some cases it may be more convenient to put all options into an
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* AVDictionary and call av_opt_set_dict() on it. A specific case of this
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* are the format/codec open functions in lavf/lavc which take a dictionary
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* filled with option as a parameter. This allows to set some options
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* that cannot be set otherwise, since e.g. the input file format is not known
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* before the file is actually opened.
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*/
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enum AVOptionType{
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AV_OPT_TYPE_FLAGS,
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AV_OPT_TYPE_INT,
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AV_OPT_TYPE_INT64,
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AV_OPT_TYPE_DOUBLE,
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AV_OPT_TYPE_FLOAT,
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AV_OPT_TYPE_STRING,
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AV_OPT_TYPE_RATIONAL,
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AV_OPT_TYPE_BINARY, ///< offset must point to a pointer immediately followed by an int for the length
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AV_OPT_TYPE_CONST = 128,
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};
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/**
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* AVOption
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*/
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typedef struct AVOption {
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const char *name;
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/**
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* short English help text
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* @todo What about other languages?
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*/
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const char *help;
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/**
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* The offset relative to the context structure where the option
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* value is stored. It should be 0 for named constants.
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*/
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int offset;
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enum AVOptionType type;
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/**
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* the default value for scalar options
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*/
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union {
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int64_t i64;
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double dbl;
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const char *str;
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/* TODO those are unused now */
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AVRational q;
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} default_val;
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double min; ///< minimum valid value for the option
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double max; ///< maximum valid value for the option
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int flags;
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#define AV_OPT_FLAG_ENCODING_PARAM 1 ///< a generic parameter which can be set by the user for muxing or encoding
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#define AV_OPT_FLAG_DECODING_PARAM 2 ///< a generic parameter which can be set by the user for demuxing or decoding
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#define AV_OPT_FLAG_METADATA 4 ///< some data extracted or inserted into the file like title, comment, ...
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#define AV_OPT_FLAG_AUDIO_PARAM 8
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#define AV_OPT_FLAG_VIDEO_PARAM 16
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#define AV_OPT_FLAG_SUBTITLE_PARAM 32
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//FIXME think about enc-audio, ... style flags
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/**
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* The logical unit to which the option belongs. Non-constant
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* options and corresponding named constants share the same
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* unit. May be NULL.
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*/
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const char *unit;
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} AVOption;
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/**
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* Show the obj options.
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*
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* @param req_flags requested flags for the options to show. Show only the
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* options for which it is opt->flags & req_flags.
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* @param rej_flags rejected flags for the options to show. Show only the
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* options for which it is !(opt->flags & req_flags).
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* @param av_log_obj log context to use for showing the options
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*/
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int av_opt_show2(void *obj, void *av_log_obj, int req_flags, int rej_flags);
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/**
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* Set the values of all AVOption fields to their default values.
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*
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* @param s an AVOption-enabled struct (its first member must be a pointer to AVClass)
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*/
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void av_opt_set_defaults(void *s);
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/**
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* Parse the key/value pairs list in opts. For each key/value pair
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* found, stores the value in the field in ctx that is named like the
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* key. ctx must be an AVClass context, storing is done using
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* AVOptions.
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*
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* @param key_val_sep a 0-terminated list of characters used to
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* separate key from value
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* @param pairs_sep a 0-terminated list of characters used to separate
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* two pairs from each other
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* @return the number of successfully set key/value pairs, or a negative
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* value corresponding to an AVERROR code in case of error:
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* AVERROR(EINVAL) if opts cannot be parsed,
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* the error code issued by av_set_string3() if a key/value pair
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* cannot be set
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*/
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int av_set_options_string(void *ctx, const char *opts,
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const char *key_val_sep, const char *pairs_sep);
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/**
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* Free all string and binary options in obj.
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*/
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void av_opt_free(void *obj);
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/**
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* Check whether a particular flag is set in a flags field.
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*
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* @param field_name the name of the flag field option
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* @param flag_name the name of the flag to check
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* @return non-zero if the flag is set, zero if the flag isn't set,
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* isn't of the right type, or the flags field doesn't exist.
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*/
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int av_opt_flag_is_set(void *obj, const char *field_name, const char *flag_name);
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/*
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* Set all the options from a given dictionary on an object.
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*
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* @param obj a struct whose first element is a pointer to AVClass
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* @param options options to process. This dictionary will be freed and replaced
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* by a new one containing all options not found in obj.
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* Of course this new dictionary needs to be freed by caller
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* with av_dict_free().
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*
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* @return 0 on success, a negative AVERROR if some option was found in obj,
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* but could not be set.
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*
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* @see av_dict_copy()
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*/
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int av_opt_set_dict(void *obj, struct AVDictionary **options);
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/**
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* @defgroup opt_eval_funcs Evaluating option strings
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* @{
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* This group of functions can be used to evaluate option strings
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* and get numbers out of them. They do the same thing as av_opt_set(),
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* except the result is written into the caller-supplied pointer.
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*
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* @param obj a struct whose first element is a pointer to AVClass.
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* @param o an option for which the string is to be evaluated.
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* @param val string to be evaluated.
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* @param *_out value of the string will be written here.
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*
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* @return 0 on success, a negative number on failure.
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*/
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int av_opt_eval_flags (void *obj, const AVOption *o, const char *val, int *flags_out);
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int av_opt_eval_int (void *obj, const AVOption *o, const char *val, int *int_out);
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int av_opt_eval_int64 (void *obj, const AVOption *o, const char *val, int64_t *int64_out);
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int av_opt_eval_float (void *obj, const AVOption *o, const char *val, float *float_out);
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int av_opt_eval_double(void *obj, const AVOption *o, const char *val, double *double_out);
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int av_opt_eval_q (void *obj, const AVOption *o, const char *val, AVRational *q_out);
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/**
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* @}
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*/
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#define AV_OPT_SEARCH_CHILDREN 0x0001 /**< Search in possible children of the
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given object first. */
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/**
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* The obj passed to av_opt_find() is fake -- only a double pointer to AVClass
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* instead of a required pointer to a struct containing AVClass. This is
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* useful for searching for options without needing to allocate the corresponding
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* object.
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*/
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#define AV_OPT_SEARCH_FAKE_OBJ 0x0002
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/**
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* Look for an option in an object. Consider only options which
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* have all the specified flags set.
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*
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* @param[in] obj A pointer to a struct whose first element is a
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* pointer to an AVClass.
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* Alternatively a double pointer to an AVClass, if
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* AV_OPT_SEARCH_FAKE_OBJ search flag is set.
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* @param[in] name The name of the option to look for.
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* @param[in] unit When searching for named constants, name of the unit
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* it belongs to.
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* @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
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* @param search_flags A combination of AV_OPT_SEARCH_*.
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*
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* @return A pointer to the option found, or NULL if no option
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* was found.
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*
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* @note Options found with AV_OPT_SEARCH_CHILDREN flag may not be settable
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* directly with av_set_string3(). Use special calls which take an options
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* AVDictionary (e.g. avformat_open_input()) to set options found with this
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* flag.
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*/
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const AVOption *av_opt_find(void *obj, const char *name, const char *unit,
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int opt_flags, int search_flags);
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/**
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* Look for an option in an object. Consider only options which
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* have all the specified flags set.
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*
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* @param[in] obj A pointer to a struct whose first element is a
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* pointer to an AVClass.
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* Alternatively a double pointer to an AVClass, if
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* AV_OPT_SEARCH_FAKE_OBJ search flag is set.
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* @param[in] name The name of the option to look for.
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* @param[in] unit When searching for named constants, name of the unit
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* it belongs to.
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* @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
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* @param search_flags A combination of AV_OPT_SEARCH_*.
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* @param[out] target_obj if non-NULL, an object to which the option belongs will be
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* written here. It may be different from obj if AV_OPT_SEARCH_CHILDREN is present
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* in search_flags. This parameter is ignored if search_flags contain
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* AV_OPT_SEARCH_FAKE_OBJ.
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*
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* @return A pointer to the option found, or NULL if no option
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* was found.
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*/
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const AVOption *av_opt_find2(void *obj, const char *name, const char *unit,
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int opt_flags, int search_flags, void **target_obj);
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/**
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* Iterate over all AVOptions belonging to obj.
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*
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* @param obj an AVOptions-enabled struct or a double pointer to an
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* AVClass describing it.
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* @param prev result of the previous call to av_opt_next() on this object
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* or NULL
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* @return next AVOption or NULL
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*/
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const AVOption *av_opt_next(void *obj, const AVOption *prev);
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/**
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* Iterate over AVOptions-enabled children of obj.
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*
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* @param prev result of a previous call to this function or NULL
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* @return next AVOptions-enabled child or NULL
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*/
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void *av_opt_child_next(void *obj, void *prev);
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/**
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* Iterate over potential AVOptions-enabled children of parent.
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*
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* @param prev result of a previous call to this function or NULL
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* @return AVClass corresponding to next potential child or NULL
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*/
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const AVClass *av_opt_child_class_next(const AVClass *parent, const AVClass *prev);
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/**
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* @defgroup opt_set_funcs Option setting functions
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* @{
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* Those functions set the field of obj with the given name to value.
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*
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* @param[in] obj A struct whose first element is a pointer to an AVClass.
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* @param[in] name the name of the field to set
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* @param[in] val The value to set. In case of av_opt_set() if the field is not
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* of a string type, then the given string is parsed.
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* SI postfixes and some named scalars are supported.
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* If the field is of a numeric type, it has to be a numeric or named
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* scalar. Behavior with more than one scalar and +- infix operators
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* is undefined.
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* If the field is of a flags type, it has to be a sequence of numeric
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* scalars or named flags separated by '+' or '-'. Prefixing a flag
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* with '+' causes it to be set without affecting the other flags;
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* similarly, '-' unsets a flag.
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* @param search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
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* is passed here, then the option may be set on a child of obj.
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*
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* @return 0 if the value has been set, or an AVERROR code in case of
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* error:
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* AVERROR_OPTION_NOT_FOUND if no matching option exists
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* AVERROR(ERANGE) if the value is out of range
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* AVERROR(EINVAL) if the value is not valid
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*/
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int av_opt_set (void *obj, const char *name, const char *val, int search_flags);
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int av_opt_set_int (void *obj, const char *name, int64_t val, int search_flags);
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int av_opt_set_double(void *obj, const char *name, double val, int search_flags);
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int av_opt_set_q (void *obj, const char *name, AVRational val, int search_flags);
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int av_opt_set_bin (void *obj, const char *name, const uint8_t *val, int size, int search_flags);
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/**
|
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* @}
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*/
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/**
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* @defgroup opt_get_funcs Option getting functions
|
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* @{
|
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* Those functions get a value of the option with the given name from an object.
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*
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* @param[in] obj a struct whose first element is a pointer to an AVClass.
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* @param[in] name name of the option to get.
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* @param[in] search_flags flags passed to av_opt_find2. I.e. if AV_OPT_SEARCH_CHILDREN
|
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* is passed here, then the option may be found in a child of obj.
|
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* @param[out] out_val value of the option will be written here
|
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* @return 0 on success, a negative error code otherwise
|
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*/
|
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/**
|
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* @note the returned string will av_malloc()ed and must be av_free()ed by the caller
|
|
*/
|
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int av_opt_get (void *obj, const char *name, int search_flags, uint8_t **out_val);
|
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int av_opt_get_int (void *obj, const char *name, int search_flags, int64_t *out_val);
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int av_opt_get_double(void *obj, const char *name, int search_flags, double *out_val);
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int av_opt_get_q (void *obj, const char *name, int search_flags, AVRational *out_val);
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/**
|
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* @}
|
|
* @}
|
|
*/
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#endif /* AVUTIL_OPT_H */
|