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/*
Copyright (C) Slava Astashonok <sla@0n.ru>
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License.
$Id: hash.c,v 1.3.2.2.2.1 2005/01/29 19:30:41 sla Exp $
*/
#include <common.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>
#include <hash.h>
#ifdef HASH_TYPE_CRC
static uint16_t crc16_poly;
static uint8_t shuffle_table[256];
static uint16_t crc16_table[256];
uint16_t crc16(uint16_t crc, uint8_t val)
{
int i;
crc ^= val << 8;
for (i = 8; i--; )
crc = crc & 0x8000 ? (crc << 1) ^ crc16_poly : crc << 1;
return crc;
}
#endif
hash_t hash(void *p, int size)
{
/*
?FIXME?
Check for valid size (> 0)
*/
hash_t hash = 0;
#if defined HASH_TYPE_XOR && HASH_BITS == 16
if (size & 1) hash = *((uint8_t *) p++);
size >>= 1;
#endif
for (;size--;) {
#ifdef HASH_TYPE_XOR
hash ^= *((hash_t *) p++);
# if HASH_BITS == 16
p++;
# endif
#endif
#ifdef HASH_TYPE_CRC
hash = crc16_table[shuffle_table[*((uint8_t *) p++)] \
^ (hash >> 8)] ^ (hash << 8);
#endif
}
return hash;
}
void hash_init()
{
#ifdef HASH_TYPE_CRC
int rnd, i, j, m;
FILE *rnddev;
if ((rnddev = fopen(RNDDEV, "r"))) {
fcntl(fileno(rnddev), F_SETFL, \
fcntl(fileno(rnddev), F_GETFL) | O_NONBLOCK);
fread(&rnd, sizeof(rnd), 1, rnddev);
fclose(rnddev);
}
srand(time(NULL) ^ getpid() ^ rnd);
crc16_poly = rand() | 1;
for (i = 0; i < 256; i++) {
crc16_table[i] = crc16(0, i);
shuffle_table[i] = i;
}
for (i = 0; i < 256; i++) {
j = (int) (256.0 * rand() / (RAND_MAX + 1.0));
m = shuffle_table[i];
shuffle_table[i] = shuffle_table[j];
shuffle_table[j] = m;
}
#endif
}
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