Mysql源码学习——没那么简单的Hash(3)

初始化函数

   Hash初始化函数对外提供两个，my_hash_init和my_hash_init2，其区别即是否定义了growth_size（用于设置DYNAMIC_ARRAY的alloc_increment）。代码在mysys/hash.c中。

#define my_hash_init(A,B,C,D,E,F,G,H) \

          _my_hash_init(A,0,B,C,D,E,F,G,H)

#define my_hash_init2(A,B,C,D,E,F,G,H,I) \

          _my_hash_init(A,B,C,D,E,F,G,H,I)

/**

  @brief Initialize the hash

  @details

  Initialize the hash, by defining and giving valid values for

  its elements. The failure to allocate memory for the

  hash->array element will not result in a fatal failure. The

  dynamic array that is part of the hash will allocate memory

  as required during insertion.

  @param[in,out] hash         The hash that is initialized

  @param[in]     charset      The charater set information

  @param[in]     size         The hash size

  @param[in]     key_offest   The key offset for the hash

  @param[in]     key_length   The length of the key used in

                              the hash

  @param[in]     get_key      get the key for the hash

  @param[in]     free_element pointer to the function that

                              does cleanup

  @return        inidicates success or failure of initialization

    @retval 0 success

    @retval 1 failure

*/

my_bool

_my_hash_init(HASH *hash, uint growth_size, CHARSET_INFO *charset,

              ulong size, size_t key_offset, size_t key_length,

              my_hash_get_key get_key,

              void (*free_element)(void*), uint flags)