3 * This file is part of FFmpeg.
5 * FFmpeg is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2.1 of the License, or (at your option) any later version.
10 * FFmpeg is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with FFmpeg; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 * Public dictionary API.
24 * AVDictionary is provided for compatibility with libav. It is both in
25 * implementation as well as API inefficient. It does not scale and is
26 * extremely slow with large dictionaries.
27 * It is recommended that new code uses our tree container from tree.c/h
28 * where applicable, which uses AVL trees to achieve O(log n) performance.
35 * @addtogroup lavu_dict AVDictionary
38 * @brief Simple key:value store
41 * Dictionaries are used for storing key:value pairs. To create
42 * an AVDictionary, simply pass an address of a NULL pointer to
43 * av_dict_set(). NULL can be used as an empty dictionary wherever
44 * a pointer to an AVDictionary is required.
45 * Use av_dict_get() to retrieve an entry or iterate over all
46 * entries and finally av_dict_free() to free the dictionary
47 * and all its contents.
50 AVDictionary *d = NULL; // "create" an empty dictionary
51 AVDictionaryEntry *t = NULL;
53 av_dict_set(&d, "foo", "bar", 0); // add an entry
55 char *k = av_strdup("key"); // if your strings are already allocated,
56 char *v = av_strdup("value"); // you can avoid copying them like this
57 av_dict_set(&d, k, v, AV_DICT_DONT_STRDUP_KEY | AV_DICT_DONT_STRDUP_VAL);
59 while (t = av_dict_get(d, "", t, AV_DICT_IGNORE_SUFFIX)) {
60 <....> // iterate over all entries in d
67 #define AV_DICT_MATCH_CASE 1 /**< Only get an entry with exact-case key match. Only relevant in av_dict_get(). */
68 #define AV_DICT_IGNORE_SUFFIX 2 /**< Return first entry in a dictionary whose first part corresponds to the search key,
69 ignoring the suffix of the found key string. Only relevant in av_dict_get(). */
70 #define AV_DICT_DONT_STRDUP_KEY 4 /**< Take ownership of a key that's been
71 allocated with av_malloc() or another memory allocation function. */
72 #define AV_DICT_DONT_STRDUP_VAL 8 /**< Take ownership of a value that's been
73 allocated with av_malloc() or another memory allocation function. */
74 #define AV_DICT_DONT_OVERWRITE 16 ///< Don't overwrite existing entries.
75 #define AV_DICT_APPEND 32 /**< If the entry already exists, append to it. Note that no
76 delimiter is added, the strings are simply concatenated. */
78 typedef struct AVDictionaryEntry {
83 typedef struct AVDictionary AVDictionary;
86 * Get a dictionary entry with matching key.
88 * The returned entry key or value must not be changed, or it will
89 * cause undefined behavior.
91 * To iterate through all the dictionary entries, you can set the matching key
92 * to the null string "" and set the AV_DICT_IGNORE_SUFFIX flag.
94 * @param prev Set to the previous matching element to find the next.
95 * If set to NULL the first matching element is returned.
96 * @param key matching key
97 * @param flags a collection of AV_DICT_* flags controlling how the entry is retrieved
98 * @return found entry or NULL in case no matching entry was found in the dictionary
101 av_dict_get(const AVDictionary *m, const char *key, const AVDictionaryEntry *prev, int flags);
104 * Get number of entries in dictionary.
106 * @param m dictionary
107 * @return number of entries in dictionary
109 int av_dict_count(const AVDictionary *m);
112 * Set the given entry in *pm, overwriting an existing entry.
114 * @param pm pointer to a pointer to a dictionary struct. If *pm is NULL
115 * a dictionary struct is allocated and put in *pm.
116 * @param key entry key to add to *pm (will be av_strduped depending on flags)
117 * @param value entry value to add to *pm (will be av_strduped depending on flags).
118 * Passing a NULL value will cause an existing entry to be deleted.
119 * @return >= 0 on success otherwise an error code <0
121 int av_dict_set(AVDictionary **pm, const char *key, const char *value, int flags);
124 * Parse the key/value pairs list and add the parsed entries to a dictionary.
126 * In case of failure, all the successfully set entries are stored in
127 * *pm. You may need to manually free the created dictionary.
129 * @param key_val_sep a 0-terminated list of characters used to separate
131 * @param pairs_sep a 0-terminated list of characters used to separate
132 * two pairs from each other
133 * @param flags flags to use when adding to dictionary.
134 * AV_DICT_DONT_STRDUP_KEY and AV_DICT_DONT_STRDUP_VAL
135 * are ignored since the key/value tokens will always
137 * @return 0 on success, negative AVERROR code on failure
139 int av_dict_parse_string(AVDictionary **pm, const char *str,
140 const char *key_val_sep, const char *pairs_sep,
144 * Copy entries from one AVDictionary struct into another.
145 * @param dst pointer to a pointer to a AVDictionary struct. If *dst is NULL,
146 * this function will allocate a struct for you and put it in *dst
147 * @param src pointer to source AVDictionary struct
148 * @param flags flags to use when setting entries in *dst
149 * @note metadata is read using the AV_DICT_IGNORE_SUFFIX flag
151 void av_dict_copy(AVDictionary **dst, const AVDictionary *src, int flags);
154 * Free all the memory allocated for an AVDictionary struct
155 * and all keys and values.
157 void av_dict_free(AVDictionary **m);
163 #endif /* AVUTIL_DICT_H */