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use bob jenkins' hashword2 hash from lookup3.c for our string hash

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* libguile/hash.c (JENKINS_LOOKUP3_HASHWORD2, narrow_string_hash)
  (wide_string_hash, scm_string_hash, scm_i_string_hash)
  (scm_i_latin1_string_hash): Replace our lame string hash with Bob
  Jenkins' hash, treating each codepoint as a word, for the purposes of
  the algorithm.  There are probably more optimal hashes for our use
  cases.
  (scm_i_locale_string_hash): Remove optimization, as it wasn't used.
  (scm_i_utf8_string_hash): Add a specialized implementation for utf8.
  It's tricky but mostly just cut-and-paste.
This commit is contained in:
Andy Wingo 2011-10-25 23:46:17 +02:00
parent cd644b5424
commit 1a04d29db7
1 changed files with 141 additions and 62 deletions
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203
libguile/hash.c
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@ -45,103 +45,182 @@ extern double floor();
#endif
/* This hash function is originally from
http://burtleburtle.net/bob/c/lookup3.c by Bob Jenkins, May 2006,
Public Domain. No warranty. */
#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
#define mix(a,b,c) \
{ \
a -= c; a ^= rot(c, 4); c += b; \
b -= a; b ^= rot(a, 6); a += c; \
c -= b; c ^= rot(b, 8); b += a; \
a -= c; a ^= rot(c,16); c += b; \
b -= a; b ^= rot(a,19); a += c; \
c -= b; c ^= rot(b, 4); b += a; \
}
#define final(a,b,c) \
{ \
c ^= b; c -= rot(b,14); \
a ^= c; a -= rot(c,11); \
b ^= a; b -= rot(a,25); \
c ^= b; c -= rot(b,16); \
a ^= c; a -= rot(c,4); \
b ^= a; b -= rot(a,14); \
c ^= b; c -= rot(b,24); \
}
#define JENKINS_LOOKUP3_HASHWORD2(k, length, ret) \
do { \
scm_t_uint32 a, b, c; \
\
/* Set up the internal state. */ \
a = b = c = 0xdeadbeef + ((scm_t_uint32)(length<<2)) + 47; \
\
/* Handle most of the key. */ \
while (length > 3) \
{ \
a += k[0]; \
b += k[1]; \
c += k[2]; \
mix (a, b, c); \
length -= 3; \
k += 3; \
} \
\
/* Handle the last 3 elements. */ \
switch(length) /* All the case statements fall through. */ \
{ \
case 3 : c += k[2]; \
case 2 : b += k[1]; \
case 1 : a += k[0]; \
final (a, b, c); \
case 0: /* case 0: nothing left to add */ \
break; \
} \
\
if (sizeof (ret) == 8) \
ret = (((unsigned long) c) << 32) | b; \
else \
ret = c; \
} while (0)
static unsigned long
narrow_string_hash (const scm_t_uint8 *str, size_t len)
{
unsigned long ret;
JENKINS_LOOKUP3_HASHWORD2 (str, len, ret);
ret >>= 2; /* Ensure that it fits in a fixnum. */
return ret;
}
static unsigned long
wide_string_hash (const scm_t_wchar *str, size_t len)
{
unsigned long ret;
JENKINS_LOOKUP3_HASHWORD2 (str, len, ret);
ret >>= 2; /* Ensure that it fits in a fixnum. */
return ret;
}
unsigned long
scm_string_hash (const unsigned char *str, size_t len)
{
/* from suggestion at: */
/* http://srfi.schemers.org/srfi-13/mail-archive/msg00112.html */
unsigned long h = 0;
while (len-- > 0)
h = *str++ + h*37;
return h;
return narrow_string_hash (str, len);
}
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;
scm_remember_upto_here_1 (str);
return h;
if (scm_i_is_narrow_string (str))
return narrow_string_hash ((const scm_t_uint8 *) scm_i_string_chars (str),
len);
else
return wide_string_hash (scm_i_string_wide_chars (str), len);
}
unsigned long
scm_i_locale_string_hash (const char *str, size_t len)
{
#ifdef HAVE_WCHAR_H
mbstate_t state;
wchar_t c;
size_t byte_idx = 0, nbytes;
unsigned long h = 0;
if (len == (size_t) -1)
len = strlen (str);
while ((nbytes = mbrtowc (&c, str + byte_idx, len - byte_idx, &state)) > 0)
{
if (nbytes >= (size_t) -2)
/* Invalid input string; punt. */
return scm_i_string_hash (scm_from_locale_stringn (str, len));
h = (unsigned long) c + h * 37;
byte_idx += nbytes;
}
return h;
#else
return scm_i_string_hash (scm_from_locale_stringn (str, len));
#endif
}
unsigned long
scm_i_latin1_string_hash (const char *str, size_t len)
{
const scm_t_uint8 *ustr = (const scm_t_uint8 *) str;
size_t i = 0;
unsigned long h = 0;
if (len == (size_t) -1)
len = strlen (str);
for (; i < len; i++)
h = (unsigned long) ustr[i] + h * 37;
return h;
return narrow_string_hash ((const scm_t_uint8 *) str, len);
}
/* A tricky optimization, but probably worth it. */
unsigned long
scm_i_utf8_string_hash (const char *str, size_t len)
{
const scm_t_uint8 *ustr = (const scm_t_uint8 *) str;
size_t byte_idx = 0;
unsigned long h = 0;
const scm_t_uint8 *end, *ustr = (const scm_t_uint8 *) str;
unsigned long ret;
/* The length of the string in characters. This name corresponds to
Jenkins' original name. */
size_t length;
scm_t_uint32 a, b, c, u32;
if (len == (size_t) -1)
len = strlen (str);
while (byte_idx < len)
end = ustr + len;
if (u8_check (ustr, len) != NULL)
/* Invalid UTF-8; punt. */
return scm_i_string_hash (scm_from_utf8_stringn (str, len));
length = u8_strnlen (ustr, len);
/* Set up the internal state. */
a = b = c = 0xdeadbeef + ((scm_t_uint32)(length<<2)) + 47;
/* Handle most of the key. */
while (length > 3)
{
ucs4_t c;
int nbytes;
nbytes = u8_mbtouc (&c, ustr + byte_idx, len - byte_idx);
if (nbytes == 0)
break;
else if (nbytes < 0)
/* Bad UTF-8; punt. */
return scm_i_string_hash (scm_from_utf8_stringn (str, len));
h = (unsigned long) c + h * 37;
byte_idx += nbytes;
ustr += u8_mbtouc_unsafe (&u32, ustr, end - ustr);
a += u32;
ustr += u8_mbtouc_unsafe (&u32, ustr, end - ustr);
b += u32;
ustr += u8_mbtouc_unsafe (&u32, ustr, end - ustr);
c += u32;
mix (a, b, c);
length -= 3;
}
return h;
/* Handle the last 3 elements's. */
ustr += u8_mbtouc_unsafe (&u32, ustr, end - ustr);
a += u32;
if (--length)
{
ustr += u8_mbtouc_unsafe (&u32, ustr, end - ustr);
b += u32;
if (--length)
{
ustr += u8_mbtouc_unsafe (&u32, ustr, end - ustr);
c += u32;
}
}
final (a, b, c);
if (sizeof (unsigned long) == 8)
ret = (((unsigned long) c) << 32) | b;
else
ret = c;
ret >>= 2; /* Ensure that it fits in a fixnum. */
return ret;
}