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.
39 * @addtogroup lavu_dict AVDictionary
42 * @brief Simple key:value store
45 * Dictionaries are used for storing key:value pairs. To create
46 * an AVDictionary, simply pass an address of a NULL pointer to
47 * av_dict_set(). NULL can be used as an empty dictionary wherever
48 * a pointer to an AVDictionary is required.
49 * Use av_dict_get() to retrieve an entry or iterate over all
50 * entries and finally av_dict_free() to free the dictionary
51 * and all its contents.
54 AVDictionary *d = NULL; // "create" an empty dictionary
55 AVDictionaryEntry *t = NULL;
57 av_dict_set(&d, "foo", "bar", 0); // add an entry
59 char *k = av_strdup("key"); // if your strings are already allocated,
60 char *v = av_strdup("value"); // you can avoid copying them like this
61 av_dict_set(&d, k, v, AV_DICT_DONT_STRDUP_KEY | AV_DICT_DONT_STRDUP_VAL);
63 while (t = av_dict_get(d, "", t, AV_DICT_IGNORE_SUFFIX)) {
64 <....> // iterate over all entries in d
71 #define AV_DICT_MATCH_CASE 1 /**< Only get an entry with exact-case key match. Only relevant in av_dict_get(). */
72 #define AV_DICT_IGNORE_SUFFIX 2 /**< Return first entry in a dictionary whose first part corresponds to the search key,
73 ignoring the suffix of the found key string. Only relevant in av_dict_get(). */
74 #define AV_DICT_DONT_STRDUP_KEY 4 /**< Take ownership of a key that's been
75 allocated with av_malloc() or another memory allocation function. */
76 #define AV_DICT_DONT_STRDUP_VAL 8 /**< Take ownership of a value that's been
77 allocated with av_malloc() or another memory allocation function. */
78 #define AV_DICT_DONT_OVERWRITE 16 ///< Don't overwrite existing entries.
79 #define AV_DICT_APPEND 32 /**< If the entry already exists, append to it. Note that no
80 delimiter is added, the strings are simply concatenated. */
82 typedef struct AVDictionaryEntry {
87 typedef struct AVDictionary AVDictionary;
90 * Get a dictionary entry with matching key.
92 * The returned entry key or value must not be changed, or it will
93 * cause undefined behavior.
95 * To iterate through all the dictionary entries, you can set the matching key
96 * to the null string "" and set the AV_DICT_IGNORE_SUFFIX flag.
98 * @param prev Set to the previous matching element to find the next.
99 * If set to NULL the first matching element is returned.
100 * @param key matching key
101 * @param flags a collection of AV_DICT_* flags controlling how the entry is retrieved
102 * @return found entry or NULL in case no matching entry was found in the dictionary
104 AVDictionaryEntry *av_dict_get(const AVDictionary *m, const char *key,
105 const AVDictionaryEntry *prev, int flags);
108 * Get number of entries in dictionary.
110 * @param m dictionary
111 * @return number of entries in dictionary
113 int av_dict_count(const AVDictionary *m);
116 * Set the given entry in *pm, overwriting an existing entry.
118 * Note: If AV_DICT_DONT_STRDUP_KEY or AV_DICT_DONT_STRDUP_VAL is set,
119 * these arguments will be freed on error.
121 * @param pm pointer to a pointer to a dictionary struct. If *pm is NULL
122 * a dictionary struct is allocated and put in *pm.
123 * @param key entry key to add to *pm (will be av_strduped depending on flags)
124 * @param value entry value to add to *pm (will be av_strduped depending on flags).
125 * Passing a NULL value will cause an existing entry to be deleted.
126 * @return >= 0 on success otherwise an error code <0
128 int av_dict_set(AVDictionary **pm, const char *key, const char *value, int flags);
131 * Convenience wrapper for av_dict_set that converts the value to a string
134 * Note: If AV_DICT_DONT_STRDUP_KEY is set, key will be freed on error.
136 int av_dict_set_int(AVDictionary **pm, const char *key, int64_t value, int flags);
139 * Parse the key/value pairs list and add the parsed entries to a dictionary.
141 * In case of failure, all the successfully set entries are stored in
142 * *pm. You may need to manually free the created dictionary.
144 * @param key_val_sep a 0-terminated list of characters used to separate
146 * @param pairs_sep a 0-terminated list of characters used to separate
147 * two pairs from each other
148 * @param flags flags to use when adding to dictionary.
149 * AV_DICT_DONT_STRDUP_KEY and AV_DICT_DONT_STRDUP_VAL
150 * are ignored since the key/value tokens will always
152 * @return 0 on success, negative AVERROR code on failure
154 int av_dict_parse_string(AVDictionary **pm, const char *str,
155 const char *key_val_sep, const char *pairs_sep,
159 * Copy entries from one AVDictionary struct into another.
160 * @param dst pointer to a pointer to a AVDictionary struct. If *dst is NULL,
161 * this function will allocate a struct for you and put it in *dst
162 * @param src pointer to source AVDictionary struct
163 * @param flags flags to use when setting entries in *dst
164 * @note metadata is read using the AV_DICT_IGNORE_SUFFIX flag
166 void av_dict_copy(AVDictionary **dst, const AVDictionary *src, int flags);
169 * Free all the memory allocated for an AVDictionary struct
170 * and all keys and values.
172 void av_dict_free(AVDictionary **m);
175 * Get dictionary entries as a string.
177 * Create a string containing dictionary's entries.
178 * Such string may be passed back to av_dict_parse_string().
179 * @note String is escaped with backslashes ('\').
181 * @param[in] m dictionary
182 * @param[out] buffer Pointer to buffer that will be allocated with string containg entries.
183 * Buffer must be freed by the caller when is no longer needed.
184 * @param[in] key_val_sep character used to separate key from value
185 * @param[in] pairs_sep character used to separate two pairs from each other
186 * @return >= 0 on success, negative on error
187 * @warning Separators cannot be neither '\\' nor '\0'. They also cannot be the same.
189 int av_dict_get_string(const AVDictionary *m, char **buffer,
190 const char key_val_sep, const char pairs_sep);
196 #endif /* AVUTIL_DICT_H */