stasis-aries-wal/src/lladd/hash.c

122 lines
3.5 KiB
C
Raw Normal View History

#include <lladd/hash.h>
2006-05-24 02:19:04 +00:00
#include <assert.h>
//#include <stdio.h>
/**
@todo Make hash.c 32/64bit little/big-endian clean...
*/
2006-05-24 02:19:04 +00:00
#ifdef THOMAS_WANG_32
static int thomasWangs32BitMixFunction(int key)
{
key += ~(key << 15);
key ^= (key >> 10);
key += (key << 3);
key ^= (key >> 6);
key += ~(key << 11);
key ^= (key >> 16);
return key;
}
2006-05-24 02:19:04 +00:00
#else
#ifdef THOMAS_WANG_64
2006-05-24 02:19:04 +00:00
static unsigned long thomasWangs64BitMixFunction(unsigned long key)
{
key += ~(key << 32L);
key ^= (key >> 22L);
key += ~(key << 13L);
key ^= (key >> 8L);
key += (key << 3L);
key ^= (key >> 15L);
key += ~(key << 27L);
key ^= (key >> 31L);
return key;
}
2006-05-24 02:19:04 +00:00
#endif
#endif
unsigned int max_bucket(unsigned char tableBits, unsigned int nextExtension) {
unsigned int oldTableLength = twoToThe(tableBits - 1);
return oldTableLength + nextExtension - 1;
}
void hashGetParamsForSize(unsigned int desiredSize,
unsigned char * tableBits, unsigned int* nextExtension) {
*tableBits = logBase2(desiredSize)+1;
*nextExtension = ((desiredSize) - twoToThe(*tableBits-1));
}
unsigned int hash(const void * val, long val_length,
unsigned char tableBits, unsigned int nextExtension) {
// Calculate the hash value as it was before this round of splitting.
unsigned int oldTableLength = twoToThe(tableBits - 1);
unsigned int unmixed = crc32(val, val_length, (unsigned int)-1);
unsigned int ret = unmixed & (oldTableLength - 1);
// If the hash value is before the point in this round where we've split,
// use the new value instead. (The new value may be the same as the
// old value.)
if(ret < nextExtension) { /* Might be too low. */
unsigned int tableLength = twoToThe(tableBits);
ret = unmixed & (tableLength - 1);
}
// printf("ret = %d, bits = %d, nextExt = %d\n", ret, tableBits, nextExtension);
// fflush(stdout);
// assert(ret >= 0 && ret < nextExtension - 1);
return ret;
}
2006-05-24 02:19:04 +00:00
static const char LogTable256[] =
{
0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7
};
/*Taken from
http://graphics.stanford.edu/~seander/bithacks.html
@todo extend to handle unsigned long (this will mean 64bit on 64bit
platforms; need compiler macro to test for sizeof(long), test
harness to compare logBase2Slow's output with logBase2's output,
etc...)
*/
2006-05-24 02:19:04 +00:00
unsigned int logBase2(unsigned int v) {
unsigned int r = 0; // r will be lg(v)
register unsigned int t, tt; // temporaries
if ((tt = v >> 16))
{
r = (t = v >> 24) ? 24 + LogTable256[t] : 16 + LogTable256[tt & 0xFF];
}
else
{
r = (t = v >> 8) ? 8 + LogTable256[t] : LogTable256[v];
}
return r;
}
unsigned long logBase2Slow(unsigned long v) {
unsigned long r = 0; // r will be lg(v)
while (v >>= 1) // unroll for more speed...
{
r++;
}
return r;
}