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dict.h
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3  * This file is part of FFmpeg.
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6  * modify it under the terms of the GNU Lesser General Public
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13  * Lesser General Public License for more details.
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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 "version.h"
35 
36 /**
37  * @addtogroup lavu_dict AVDictionary
38  * @ingroup lavu_data
39  *
40  * @brief Simple key:value store
41  *
42  * @{
43  * Dictionaries are used for storing key:value pairs. To create
44  * an AVDictionary, simply pass an address of a NULL pointer to
45  * av_dict_set(). NULL can be used as an empty dictionary wherever
46  * a pointer to an AVDictionary is required.
47  * Use av_dict_get() to retrieve an entry or iterate over all
48  * entries and finally av_dict_free() to free the dictionary
49  * and all its contents.
50  *
51  @code
52  AVDictionary *d = NULL; // "create" an empty dictionary
53  AVDictionaryEntry *t = NULL;
54 
55  av_dict_set(&d, "foo", "bar", 0); // add an entry
56 
57  char *k = av_strdup("key"); // if your strings are already allocated,
58  char *v = av_strdup("value"); // you can avoid copying them like this
59  av_dict_set(&d, k, v, AV_DICT_DONT_STRDUP_KEY | AV_DICT_DONT_STRDUP_VAL);
60 
61  while (t = av_dict_get(d, "", t, AV_DICT_IGNORE_SUFFIX)) {
62  <....> // iterate over all entries in d
63  }
64  av_dict_free(&d);
65  @endcode
66  *
67  */
68 
69 #define AV_DICT_MATCH_CASE 1 /**< Only get an entry with exact-case key match. Only relevant in av_dict_get(). */
70 #define AV_DICT_IGNORE_SUFFIX 2 /**< Return first entry in a dictionary whose first part corresponds to the search key,
71  ignoring the suffix of the found key string. Only relevant in av_dict_get(). */
72 #define AV_DICT_DONT_STRDUP_KEY 4 /**< Take ownership of a key that's been
73  allocated with av_malloc() or another memory allocation function. */
74 #define AV_DICT_DONT_STRDUP_VAL 8 /**< Take ownership of a value that's been
75  allocated with av_malloc() or another memory allocation function. */
76 #define AV_DICT_DONT_OVERWRITE 16 ///< Don't overwrite existing entries.
77 #define AV_DICT_APPEND 32 /**< If the entry already exists, append to it. Note that no
78  delimiter is added, the strings are simply concatenated. */
79 
80 typedef struct AVDictionaryEntry {
81  char *key;
82  char *value;
84 
85 typedef struct AVDictionary AVDictionary;
86 
87 /**
88  * Get a dictionary entry with matching key.
89  *
90  * The returned entry key or value must not be changed, or it will
91  * cause undefined behavior.
92  *
93  * To iterate through all the dictionary entries, you can set the matching key
94  * to the null string "" and set the AV_DICT_IGNORE_SUFFIX flag.
95  *
96  * @param prev Set to the previous matching element to find the next.
97  * If set to NULL the first matching element is returned.
98  * @param key matching key
99  * @param flags a collection of AV_DICT_* flags controlling how the entry is retrieved
100  * @return found entry or NULL in case no matching entry was found in the dictionary
101  */
103  const AVDictionaryEntry *prev, int flags);
104 
105 /**
106  * Get number of entries in dictionary.
107  *
108  * @param m dictionary
109  * @return number of entries in dictionary
110  */
111 int av_dict_count(const AVDictionary *m);
112 
113 /**
114  * Set the given entry in *pm, overwriting an existing entry.
115  *
116  * @param pm pointer to a pointer to a dictionary struct. If *pm is NULL
117  * a dictionary struct is allocated and put in *pm.
118  * @param key entry key to add to *pm (will be av_strduped depending on flags)
119  * @param value entry value to add to *pm (will be av_strduped depending on flags).
120  * Passing a NULL value will cause an existing entry to be deleted.
121  * @return >= 0 on success otherwise an error code <0
122  */
123 int av_dict_set(AVDictionary **pm, const char *key, const char *value, int flags);
124 
125 /**
126  * Parse the key/value pairs list and add the parsed entries to a dictionary.
127  *
128  * In case of failure, all the successfully set entries are stored in
129  * *pm. You may need to manually free the created dictionary.
130  *
131  * @param key_val_sep a 0-terminated list of characters used to separate
132  * key from value
133  * @param pairs_sep a 0-terminated list of characters used to separate
134  * two pairs from each other
135  * @param flags flags to use when adding to dictionary.
136  * AV_DICT_DONT_STRDUP_KEY and AV_DICT_DONT_STRDUP_VAL
137  * are ignored since the key/value tokens will always
138  * be duplicated.
139  * @return 0 on success, negative AVERROR code on failure
140  */
141 int av_dict_parse_string(AVDictionary **pm, const char *str,
142  const char *key_val_sep, const char *pairs_sep,
143  int flags);
144 
145 /**
146  * Copy entries from one AVDictionary struct into another.
147  * @param dst pointer to a pointer to a AVDictionary struct. If *dst is NULL,
148  * this function will allocate a struct for you and put it in *dst
149  * @param src pointer to source AVDictionary struct
150  * @param flags flags to use when setting entries in *dst
151  * @note metadata is read using the AV_DICT_IGNORE_SUFFIX flag
152  */
154 
155 /**
156  * Free all the memory allocated for an AVDictionary struct
157  * and all keys and values.
158  */
159 void av_dict_free(AVDictionary **m);
160 
161 /**
162  * @}
163  */
164 
165 #endif /* AVUTIL_DICT_H */