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authorUlrich Drepper <drepper@redhat.com>2001-11-27 03:47:06 +0000
committerUlrich Drepper <drepper@redhat.com>2001-11-27 03:47:06 +0000
commit8e9b2075ba1d6ce2ab82c2eb2547e2c2ef3ecca8 (patch)
treede7fba86c989c6f7df1d6d7bac078813d0855fa3 /locale/programs/simple-hash.c
parentf4efd06825ba5fec62662be611d94335eff4f8f7 (diff)
downloadglibc-8e9b2075ba1d6ce2ab82c2eb2547e2c2ef3ecca8.tar.gz
Update.
2001-11-21 Bruno Haible <bruno@clisp.org> * charmaps/ISO-8859-16: Swap 0xa5 and 0xab entries.
Diffstat (limited to 'locale/programs/simple-hash.c')
-rw-r--r--locale/programs/simple-hash.c22
1 files changed, 10 insertions, 12 deletions
diff --git a/locale/programs/simple-hash.c b/locale/programs/simple-hash.c
index 35e32ca51e..9056fa0447 100644
--- a/locale/programs/simple-hash.c
+++ b/locale/programs/simple-hash.c
@@ -1,5 +1,5 @@
/* Implement simple hashing table with string based keys.
- Copyright (C) 1994, 1995, 1996, 1997, 2000 Free Software Foundation, Inc.
+ Copyright (C) 1994-1997, 2000, 2001 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, October 1994.
@@ -163,9 +163,11 @@ insert_entry_2 (htab, key, keylen, hval, idx, data)
}
++htab->filled;
- if (100 * htab->filled > 90 * htab->size)
+ if (100 * htab->filled > 75 * htab->size)
{
- /* Table is filled more than 90%. Resize the table. */
+ /* Table is filled more than 75%. Resize the table.
+ Experiments have shown that for best performance, this threshold
+ must lie between 40% and 85%. */
unsigned long int old_size = htab->size;
htab->size = next_prime (htab->size * 2);
@@ -346,22 +348,18 @@ compute_hashval (key, keylen)
size_t keylen;
{
size_t cnt;
- unsigned long int hval, g;
+ unsigned long int hval;
/* Compute the hash value for the given string. The algorithm
- is taken from [Aho,Sethi,Ullman]. */
+ is taken from [Aho,Sethi,Ullman], modified to reduce the number of
+ collisions for short strings with very varied bit patterns.
+ See http://www.clisp.org/haible/hashfunc.html. */
cnt = 0;
hval = keylen;
while (cnt < keylen)
{
- hval <<= 4;
+ hval = (hval << 9) | (hval >> (LONGBITS - 9));
hval += (unsigned long int) *(((char *) key) + cnt++);
- g = hval & ((unsigned long) 0xf << (LONGBITS - 4));
- if (g != 0)
- {
- hval ^= g >> (LONGBITS - 8);
- hval ^= g;
- }
}
return hval != 0 ? hval : ~((unsigned long) 0);
}