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[svn] Name the source of the integer hash function.

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hniksic 2003-11-07 19:42:58 -08:00
parent d7e592d797
commit 85ff32caeb
1 changed files with 9 additions and 6 deletions
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15
src/hash.c
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@ -175,9 +175,7 @@ struct hash_table {
for (; NON_EMPTY (mp); mp = NEXT_MAPPING (mp, mappings, size)) for (; NON_EMPTY (mp); mp = NEXT_MAPPING (mp, mappings, size))
/* Return the position of KEY in hash table SIZE large, hash function /* Return the position of KEY in hash table SIZE large, hash function
being HASHFUN. #### Some implementations multiply HASHFUN's output being HASHFUN. */
with the table's "golden ratio" to get better spreading of keys.
I'm not sure if that is necessary with our hash functions. */
#define HASH_POSITION(key, hashfun, size) ((hashfun) (key) % size) #define HASH_POSITION(key, hashfun, size) ((hashfun) (key) % size)
/* Find a prime near, but greather than or equal to SIZE. Of course, /* Find a prime near, but greather than or equal to SIZE. Of course,
@ -639,9 +637,14 @@ make_nocase_string_hash_table (int items)
return hash_table_new (items, string_hash_nocase, string_cmp_nocase); return hash_table_new (items, string_hash_nocase, string_cmp_nocase);
} }
/* Hashing of pointers. Used for hash tables that are keyed by /* Hashing of numeric values, such as pointers and integers. Used for
pointer identity. (Common Lisp calls them EQ hash tables, and Java hash tables that are keyed by pointer identity. (Common Lisp calls
calls them IdentityHashMaps.) */ them EQ hash tables, and Java calls them IdentityHashMaps.)
This implementation is the Robert Jenkins' 32 bit Mix Function,
with a simple adaptation for 64-bit values. It offers excellent
spreading of values and doesn't need to know the hash table size to
work (unlike the very popular Knuth's multiplication hash). */
static unsigned long static unsigned long
ptrhash (const void *ptr) ptrhash (const void *ptr)