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hash: switch to simpler "fast algorithm" #173

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Oct 26, 2021
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hash: switch to simpler "fast algorithm" #173

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224 changes: 18 additions & 206 deletions src/hash/func.c
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,10 @@
#include <re_hash.h>


#define FNV1_32A_INIT UINT32_C(0x811c9dc5)
#define FNV_32_PRIME UINT32_C(0x01000193)


/**
* Calculate hash-value using "Jenkins One-at-a-time" hash algorithm.
*
Expand Down Expand Up @@ -136,207 +140,6 @@ uint32_t hash_joaat_pl_ci(const struct pl *pl)
}


/*
* My best guess at if you are big-endian or little-endian. This may
* need adjustment.
*/
#if (defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && \
__BYTE_ORDER == __LITTLE_ENDIAN) || \
(defined(i386) || defined(__i386__) || defined(__i486__) || \
defined(__i586__) || defined(__i686__) || \
defined(vax) || defined(MIPSEL))
# define HASH_LITTLE_ENDIAN 1
# define HASH_BIG_ENDIAN 0
#elif (defined(__BYTE_ORDER) && defined(__BIG_ENDIAN) && \
__BYTE_ORDER == __BIG_ENDIAN) || \
(defined(sparc) || defined(POWERPC) || \
defined(mc68000) || defined(sel))
# define HASH_LITTLE_ENDIAN 0
# define HASH_BIG_ENDIAN 1
#else
# define HASH_LITTLE_ENDIAN 0
# define HASH_BIG_ENDIAN 0
#endif

#define hashsize(n) ((uint32_t)1<<(n))
#define hashmask(n) (hashsize(n)-1)
#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); \
}


static uint32_t hashlittle( const void *key, size_t length, uint32_t initval)
{
uint32_t a,b,c;
union { const void *ptr; size_t i; } u;

/* Set up the internal state */
a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;

u.ptr = key;
if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
const uint32_t *k = (const uint32_t *)key;

while (length > 12) {
a += k[0];
b += k[1];
c += k[2];
mix(a,b,c);
length -= 12;
k += 3;
}

#ifndef VALGRIND
switch (length) {

case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
case 8 : b+=k[1]; a+=k[0]; break;
case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
case 6 : b+=k[1]&0xffff; a+=k[0]; break;
case 5 : b+=k[1]&0xff; a+=k[0]; break;
case 4 : a+=k[0]; break;
case 3 : a+=k[0]&0xffffff; break;
case 2 : a+=k[0]&0xffff; break;
case 1 : a+=k[0]&0xff; break;
case 0 : return c;
}

#else /* make valgrind happy */

const uint8_t *k8 = (const uint8_t *)k;
switch (length) {

case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
case 10: c+=((uint32_t)k8[9])<<8; /* fall through */
case 9 : c+=k8[8]; /* fall through */
case 8 : b+=k[1]; a+=k[0]; break;
case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
case 6 : b+=((uint32_t)k8[5])<<8; /* fall through */
case 5 : b+=k8[4]; /* fall through */
case 4 : a+=k[0]; break;
case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
case 2 : a+=((uint32_t)k8[1])<<8; /* fall through */
case 1 : a+=k8[0]; break;
case 0 : return c;
}

#endif /* !valgrind */

}
else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
const uint16_t *k = (const uint16_t *)key;
const uint8_t *k8;

while (length > 12) {
a += k[0] + (((uint32_t)k[1])<<16);
b += k[2] + (((uint32_t)k[3])<<16);
c += k[4] + (((uint32_t)k[5])<<16);
mix(a,b,c);
length -= 12;
k += 6;
}

k8 = (const uint8_t *)k;

switch (length) {

case 12: c+=k[4]+(((uint32_t)k[5])<<16);
b+=k[2]+(((uint32_t)k[3])<<16);
a+=k[0]+(((uint32_t)k[1])<<16);
break;
case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
case 10: c+=k[4];
b+=k[2]+(((uint32_t)k[3])<<16);
a+=k[0]+(((uint32_t)k[1])<<16);
break;
case 9 : c+=k8[8]; /* fall through */
case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
a+=k[0]+(((uint32_t)k[1])<<16);
break;
case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
case 6 : b+=k[2];
a+=k[0]+(((uint32_t)k[1])<<16);
break;
case 5 : b+=k8[4]; /* fall through */
case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
break;
case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
case 2 : a+=k[0];
break;
case 1 : a+=k8[0];
break;
case 0 : return c;
}
}
else {
const uint8_t *k = (const uint8_t *)key;

while (length > 12) {
a += k[0];
a += ((uint32_t)k[1])<<8;
a += ((uint32_t)k[2])<<16;
a += ((uint32_t)k[3])<<24;
b += k[4];
b += ((uint32_t)k[5])<<8;
b += ((uint32_t)k[6])<<16;
b += ((uint32_t)k[7])<<24;
c += k[8];
c += ((uint32_t)k[9])<<8;
c += ((uint32_t)k[10])<<16;
c += ((uint32_t)k[11])<<24;
mix(a,b,c);
length -= 12;
k += 12;
}

/* all the case statements fall through */
switch (length) {

case 12: c+=((uint32_t)k[11])<<24; /* fall through */
case 11: c+=((uint32_t)k[10])<<16; /* fall through */
case 10: c+=((uint32_t)k[9])<<8; /* fall through */
case 9 : c+=k[8]; /* fall through */
case 8 : b+=((uint32_t)k[7])<<24; /* fall through */
case 7 : b+=((uint32_t)k[6])<<16; /* fall through */
case 6 : b+=((uint32_t)k[5])<<8; /* fall through */
case 5 : b+=k[4]; /* fall through */
case 4 : a+=((uint32_t)k[3])<<24; /* fall through */
case 3 : a+=((uint32_t)k[2])<<16; /* fall through */
case 2 : a+=((uint32_t)k[1])<<8; /* fall through */
case 1 : a+=k[0];
break;
case 0 : return c;
}
}

final(a,b,c);
return c;
}


/**
* Calculate hash-value using fast hash algorithm.
*
Expand All @@ -347,12 +150,14 @@ static uint32_t hashlittle( const void *key, size_t length, uint32_t initval)
*/
uint32_t hash_fast(const char *k, size_t len)
{
static volatile int random_seed = 0x304a0012;
uint32_t h = FNV1_32A_INIT;

if (!k)
return 0;
while (len--) {
h ^= (uint32_t)*k++;
h *= FNV_32_PRIME;
}

return hashlittle(k, len, random_seed);
return h;
}


Expand All @@ -365,5 +170,12 @@ uint32_t hash_fast(const char *k, size_t len)
*/
uint32_t hash_fast_str(const char *str)
{
return hash_fast(str, str_len(str));
uint32_t h = FNV1_32A_INIT;

while (*str) {
h ^= (uint32_t)*str++;
h *= FNV_32_PRIME;
}

return h;
}