libavutil/dict.h

   1 /*
   2  * This file is part of Libav.
   3  *
   4  * Libav is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2.1 of the License, or (at your option) any later version.
   8  *
   9  * Libav is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with Libav; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  17  */
  18
  19 /**
  20  * @file
  21  * Public dictionary API.
  22  */
  23
  24 #ifndef AVUTIL_DICT_H
  25 #define AVUTIL_DICT_H
  26
  27 /**
  28  * @addtogroup lavu_dict AVDictionary
  29  * @ingroup lavu_data
  30  *
  31  * @brief Simple key:value store
  32  *
  33  * @{
  34  * Dictionaries are used for storing key:value pairs. To create
  35  * an AVDictionary, simply pass an address of a NULL pointer to
  36  * av_dict_set(). NULL can be used as an empty dictionary wherever
  37  * a pointer to an AVDictionary is required.
  38  * Use av_dict_get() to retrieve an entry or iterate over all
  39  * entries and finally av_dict_free() to free the dictionary
  40  * and all its contents.
  41  *
  42  @code
  43    AVDictionary *d = NULL;           // "create" an empty dictionary
  44    AVDictionaryEntry *t = NULL;
  45
  46    av_dict_set(&d, "foo", "bar", 0); // add an entry
  47
  48    char *k = av_strdup("key");       // if your strings are already allocated,
  49    char *v = av_strdup("value");     // you can avoid copying them like this
  50    av_dict_set(&d, k, v, AV_DICT_DONT_STRDUP_KEY | AV_DICT_DONT_STRDUP_VAL);
  51
  52    while (t = av_dict_get(d, "", t, AV_DICT_IGNORE_SUFFIX)) {
  53        <....>                             // iterate over all entries in d
  54    }
  55    av_dict_free(&d);
  56  @endcode
  57  */
  58
  59 #define AV_DICT_MATCH_CASE      1
  60 #define AV_DICT_IGNORE_SUFFIX   2
  61 #define AV_DICT_DONT_STRDUP_KEY 4   /**< Take ownership of a key that's been
  62                                          allocated with av_malloc() and children. */
  63 #define AV_DICT_DONT_STRDUP_VAL 8   /**< Take ownership of a value that's been
  64                                          allocated with av_malloc() and children. */
  65 #define AV_DICT_DONT_OVERWRITE 16   ///< Don't overwrite existing entries.
  66 #define AV_DICT_APPEND         32   /**< If the entry already exists, append to it.  Note that no
  67                                       delimiter is added, the strings are simply concatenated. */
  68
  69 typedef struct AVDictionaryEntry {
  70     char *key;
  71     char *value;
  72 } AVDictionaryEntry;
  73
  74 typedef struct AVDictionary AVDictionary;
  75
  76 /**
  77  * Get a dictionary entry with matching key.
  78  *
  79  * @param prev Set to the previous matching element to find the next.
  80  *             If set to NULL the first matching element is returned.
  81  * @param flags Allows case as well as suffix-insensitive comparisons.
  82  * @return Found entry or NULL, changing key or value leads to undefined behavior.
  83  */
  84 AVDictionaryEntry *av_dict_get(const AVDictionary *m, const char *key,
  85                                const AVDictionaryEntry *prev, int flags);
  86
  87 /**
  88  * Get number of entries in dictionary.
  89  *
  90  * @param m dictionary
  91  * @return  number of entries in dictionary
  92  */
  93 int av_dict_count(const AVDictionary *m);
  94
  95 /**
  96  * Set the given entry in *pm, overwriting an existing entry.
  97  *
  98  * @param pm pointer to a pointer to a dictionary struct. If *pm is NULL
  99  * a dictionary struct is allocated and put in *pm.
 100  * @param key entry key to add to *pm (will be av_strduped depending on flags)
 101  * @param value entry value to add to *pm (will be av_strduped depending on flags).
 102  *        Passing a NULL value will cause an existing entry to be deleted.
 103  * @return >= 0 on success otherwise an error code <0
 104  */
 105 int av_dict_set(AVDictionary **pm, const char *key, const char *value, int flags);
 106
 107 /**
 108  * Parse the key/value pairs list and add to a dictionary.
 109  *
 110  * @param key_val_sep  a 0-terminated list of characters used to separate
 111  *                     key from value
 112  * @param pairs_sep    a 0-terminated list of characters used to separate
 113  *                     two pairs from each other
 114  * @param flags        flags to use when adding to dictionary.
 115  *                     AV_DICT_DONT_STRDUP_KEY and AV_DICT_DONT_STRDUP_VAL
 116  *                     are ignored since the key/value tokens will always
 117  *                     be duplicated.
 118  * @return             0 on success, negative AVERROR code on failure
 119  */
 120 int av_dict_parse_string(AVDictionary **pm, const char *str,
 121                          const char *key_val_sep, const char *pairs_sep,
 122                          int flags);
 123
 124 /**
 125  * Copy entries from one AVDictionary struct into another.
 126  * @param dst pointer to a pointer to a AVDictionary struct. If *dst is NULL,
 127  *            this function will allocate a struct for you and put it in *dst
 128  * @param src pointer to source AVDictionary struct
 129  * @param flags flags to use when setting entries in *dst
 130  * @note metadata is read using the AV_DICT_IGNORE_SUFFIX flag
 131  * @return 0 on success, negative AVERROR code on failure. If dst was allocated
 132  *           by this function, callers should free the associated memory.
 133  */
 134 int av_dict_copy(AVDictionary **dst, const AVDictionary *src, int flags);
 135
 136 /**
 137  * Free all the memory allocated for an AVDictionary struct
 138  * and all keys and values.
 139  */
 140 void av_dict_free(AVDictionary **m);
 141
 142 /**
 143  * @}
 144  */
 145
 146 #endif /* AVUTIL_DICT_H */