FFmpeg
 All Data Structures Namespaces 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 #include <stdint.h>
35 
36 #include "version.h"
37 
38 /**
39  * @addtogroup lavu_dict AVDictionary
40  * @ingroup lavu_data
41  *
42  * @brief Simple key:value store
43  *
44  * @{
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.
52  *
53  @code
54  AVDictionary *d = NULL; // "create" an empty dictionary
55  AVDictionaryEntry *t = NULL;
56 
57  av_dict_set(&d, "foo", "bar", 0); // add an entry
58 
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);
62 
63  while (t = av_dict_get(d, "", t, AV_DICT_IGNORE_SUFFIX)) {
64  <....> // iterate over all entries in d
65  }
66  av_dict_free(&d);
67  @endcode
68  *
69  */
70 
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. */
81 
82 typedef struct AVDictionaryEntry {
83  char *key;
84  char *value;
86 
87 typedef struct AVDictionary AVDictionary;
88 
89 /**
90  * Get a dictionary entry with matching key.
91  *
92  * The returned entry key or value must not be changed, or it will
93  * cause undefined behavior.
94  *
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.
97  *
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
103  */
105  const AVDictionaryEntry *prev, int flags);
106 
107 /**
108  * Get number of entries in dictionary.
109  *
110  * @param m dictionary
111  * @return number of entries in dictionary
112  */
113 int av_dict_count(const AVDictionary *m);
114 
115 /**
116  * Set the given entry in *pm, overwriting an existing entry.
117  *
118  * Note: If AV_DICT_DONT_STRDUP_KEY or AV_DICT_DONT_STRDUP_VAL is set,
119  * these arguments will be freed on error.
120  *
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
127  */
128 int av_dict_set(AVDictionary **pm, const char *key, const char *value, int flags);
129 
130 /**
131  * Convenience wrapper for av_dict_set that converts the value to a string
132  * and stores it.
133  *
134  * Note: If AV_DICT_DONT_STRDUP_KEY is set, key will be freed on error.
135  */
136 int av_dict_set_int(AVDictionary **pm, const char *key, int64_t value, int flags);
137 
138 /**
139  * Parse the key/value pairs list and add the parsed entries to a dictionary.
140  *
141  * In case of failure, all the successfully set entries are stored in
142  * *pm. You may need to manually free the created dictionary.
143  *
144  * @param key_val_sep a 0-terminated list of characters used to separate
145  * key from value
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
151  * be duplicated.
152  * @return 0 on success, negative AVERROR code on failure
153  */
154 int av_dict_parse_string(AVDictionary **pm, const char *str,
155  const char *key_val_sep, const char *pairs_sep,
156  int flags);
157 
158 /**
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
165  */
167 
168 /**
169  * Free all the memory allocated for an AVDictionary struct
170  * and all keys and values.
171  */
172 void av_dict_free(AVDictionary **m);
173 
174 /**
175  * Get dictionary entries as a string.
176  *
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 ('\').
180  *
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.
188  */
189 int av_dict_get_string(const AVDictionary *m, char **buffer,
190  const char key_val_sep, const char pairs_sep);
191 
192 /**
193  * @}
194  */
195 
196 #endif /* AVUTIL_DICT_H */