FFmpeg
 All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
dict.h
Go to the documentation of this file.
1 /*
2  *
3  * This file is part of FFmpeg.
4  *
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.
9  *
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.
14  *
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
18  */
19 
20 /**
21  * @file
22  * Public dictionary API.
23  * @deprecated
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.
29  */
30 
31 #ifndef AVUTIL_DICT_H
32 #define AVUTIL_DICT_H
33 
34 /**
35  * @addtogroup lavu_dict AVDictionary
36  * @ingroup lavu_data
37  *
38  * @brief Simple key:value store
39  *
40  * @{
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.
48  *
49  * @code
50  * AVDictionary *d = NULL; // "create" an empty dictionary
51  * av_dict_set(&d, "foo", "bar", 0); // add an entry
52  *
53  * char *k = av_strdup("key"); // if your strings are already allocated,
54  * char *v = av_strdup("value"); // you can avoid copying them like this
55  * av_dict_set(&d, k, v, AV_DICT_DONT_STRDUP_KEY | AV_DICT_DONT_STRDUP_VAL);
56  *
57  * AVDictionaryEntry *t = NULL;
58  * while (t = av_dict_get(d, "", t, AV_DICT_IGNORE_SUFFIX)) {
59  * <....> // iterate over all entries in d
60  * }
61  *
62  * av_dict_free(&d);
63  * @endcode
64  *
65  */
66 
67 #define AV_DICT_MATCH_CASE 1
68 #define AV_DICT_IGNORE_SUFFIX 2
69 #define AV_DICT_DONT_STRDUP_KEY 4 /**< Take ownership of a key that's been
70  allocated with av_malloc() and children. */
71 #define AV_DICT_DONT_STRDUP_VAL 8 /**< Take ownership of a value that's been
72  allocated with av_malloc() and chilren. */
73 #define AV_DICT_DONT_OVERWRITE 16 ///< Don't overwrite existing entries.
74 #define AV_DICT_APPEND 32 /**< If the entry already exists, append to it. Note that no
75  delimiter is added, the strings are simply concatenated. */
76 
77 typedef struct AVDictionaryEntry {
78  char *key;
79  char *value;
81 
82 typedef struct AVDictionary AVDictionary;
83 
84 /**
85  * Get a dictionary entry with matching key.
86  *
87  * @param prev Set to the previous matching element to find the next.
88  * If set to NULL the first matching element is returned.
89  * @param flags Allows case as well as suffix-insensitive comparisons.
90  * @return Found entry or NULL, changing key or value leads to undefined behavior.
91  */
93 av_dict_get(AVDictionary *m, const char *key, const AVDictionaryEntry *prev, int flags);
94 
95 /**
96  * Get number of entries in dictionary.
97  *
98  * @param m dictionary
99  * @return number of entries in dictionary
100  */
101 int av_dict_count(const AVDictionary *m);
102 
103 /**
104  * Set the given entry in *pm, overwriting an existing entry.
105  *
106  * @param pm pointer to a pointer to a dictionary struct. If *pm is NULL
107  * a dictionary struct is allocated and put in *pm.
108  * @param key entry key to add to *pm (will be av_strduped depending on flags)
109  * @param value entry value to add to *pm (will be av_strduped depending on flags).
110  * Passing a NULL value will cause an existing entry to be deleted.
111  * @return >= 0 on success otherwise an error code <0
112  */
113 int av_dict_set(AVDictionary **pm, const char *key, const char *value, int flags);
114 
115 /**
116  * Parse the key/value pairs list and add to a dictionary.
117  *
118  * @param key_val_sep a 0-terminated list of characters used to separate
119  * key from value
120  * @param pairs_sep a 0-terminated list of characters used to separate
121  * two pairs from each other
122  * @param flags flags to use when adding to dictionary.
123  * AV_DICT_DONT_STRDUP_KEY and AV_DICT_DONT_STRDUP_VAL
124  * are ignored since the key/value tokens will always
125  * be duplicated.
126  * @return 0 on success, negative AVERROR code on failure
127  */
128 int av_dict_parse_string(AVDictionary **pm, const char *str,
129  const char *key_val_sep, const char *pairs_sep,
130  int flags);
131 
132 /**
133  * Copy entries from one AVDictionary struct into another.
134  * @param dst pointer to a pointer to a AVDictionary struct. If *dst is NULL,
135  * this function will allocate a struct for you and put it in *dst
136  * @param src pointer to source AVDictionary struct
137  * @param flags flags to use when setting entries in *dst
138  * @note metadata is read using the AV_DICT_IGNORE_SUFFIX flag
139  */
140 void av_dict_copy(AVDictionary **dst, AVDictionary *src, int flags);
141 
142 /**
143  * Free all the memory allocated for an AVDictionary struct
144  * and all keys and values.
145  */
146 void av_dict_free(AVDictionary **m);
147 
148 /**
149  * @}
150  */
151 
152 #endif /* AVUTIL_DICT_H */