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g_str_hash: switch to using DJB hash

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This is the same as what we were already doing with 2 changes:

  - use an initial value of 5381 instead of 0

  - multiply by 33 in each round instead of 31
This commit is contained in:
Ryan Lortie 2010-11-17 12:19:54 -05:00
parent f50a99e782
commit 354d655ba8
1 changed files with 12 additions and 6 deletions
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18
glib/gstring.c
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@ -121,20 +121,26 @@ g_str_equal (gconstpointer v1,
* @v: a string key * @v: a string key
* *
* Converts a string to a hash value. * Converts a string to a hash value.
* It can be passed to g_hash_table_new() as the @hash_func *
* parameter, when using strings as keys in a #GHashTable. * This function implements the widely used "djb" hash apparently posted
* by Daniel Bernstein to comp.lang.c some time ago. The 32 bit
* unsigned hash value starts at 5381 and for each byte 'c' in the
* string, is updated: <literal>hash = hash * 33 + c</literal>. This
* function uses the signed value of each byte.
*
* It can be passed to g_hash_table_new() as the @hash_func parameter,
* when using strings as keys in a #GHashTable.
* *
* Returns: a hash value corresponding to the key * Returns: a hash value corresponding to the key
*/ **/
guint guint
g_str_hash (gconstpointer v) g_str_hash (gconstpointer v)
{ {
/* 31 bit hash function */
const signed char *p; const signed char *p;
guint32 h = 0; guint32 h = 5381;
for (p = v; *p != '\0'; p++) for (p = v; *p != '\0'; p++)
h = (h << 5) - h + *p; h = (h << 5) + h + *p;
return h; return h;
} }