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Optimize 'string-hash'.

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This yields a 50% improvement on the "narrow string" benchmark of
'hash.bm', 41% on "wide string", and 76% on "long string".

* libguile/hash.c (scm_i_string_hash): Rewrite to avoid
  'scm_i_string_ref' calls.
This commit is contained in:
Ludovic Courtès 2015-01-11 22:40:07 +01:00
parent 87a8b56f8c
commit 01a301d1b6
1 changed files with 19 additions and 4 deletions
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23
libguile/hash.c
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@ -63,15 +63,30 @@ scm_string_hash (const unsigned char *str, size_t len)
#endif
unsigned long
unsigned long
scm_i_string_hash (SCM str)
{
size_t len = scm_i_string_length (str);
size_t i = 0;
unsigned long h = 0;
while (len-- > 0)
h = (unsigned long) scm_i_string_ref (str, i++) + h * 37;
const void *data;
data = scm_i_string_data (str);
if (scm_i_is_narrow_string (str))
{
const unsigned char *ndata = data;
for (i = 0; i < len; i++)
h = (unsigned long) ndata[i] + h * 37;
}
else
{
const scm_t_wchar *wdata = data;
for (i = 0; i < len; i++)
h = (unsigned long) wdata[i] + h * 37;
}
scm_remember_upto_here_1 (str);
return h;