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/*
*
* Copyright (C) 1999 David Mazieres (dm@uun.org)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
*/
/* Faster generic_fls */
/* (c) 2002, D.Phillips and Sistina Software */
#include "rabinpoly.h"
#define MSB64 0x8000000000000000ULL
static inline unsigned fls8(unsigned n)
{
return n & 0xf0?
n & 0xc0? (n >> 7) + 7: (n >> 5) + 5:
n & 0x0c? (n >> 3) + 3: n - ((n + 1) >> 2);
}
static inline unsigned fls16(unsigned n)
{
return n & 0xff00? fls8(n >> 8) + 8: fls8(n);
}
static inline unsigned fls32(unsigned n)
{
return n & 0xffff0000? fls16(n >> 16) + 16: fls16(n);
}
static inline unsigned fls64(unsigned long long n) /* should be u64 */
{
return n & 0xffffffff00000000ULL? fls32(n >> 32) + 32: fls32(n);
}
static u_int64_t polymod (u_int64_t nh, u_int64_t nl, u_int64_t d);
static void polymult (u_int64_t *php, u_int64_t *plp,
u_int64_t x, u_int64_t y);
static u_int64_t polymmult (u_int64_t x, u_int64_t y, u_int64_t d);
static u_int64_t poly = 0xb15e234bd3792f63ull; // Actual polynomial
static u_int64_t T[256]; // Lookup table for mod
static int shift;
u_int64_t append8 (u_int64_t p, u_char m)
{ return ((p << 8) | m) ^ T[p >> shift];
}
static u_int64_t
polymod (u_int64_t nh, u_int64_t nl, u_int64_t d)
{ int i, k;
assert (d);
k = fls64 (d) - 1;
d <<= 63 - k;
if (nh) {
if (nh & MSB64)
nh ^= d;
for (i = 62; i >= 0; i--)
if (nh & 1ULL << i) {
nh ^= d >> (63 - i);
nl ^= d << (i + 1);
}
}
for (i = 63; i >= k; i--)
if (nl & 1ULL << i)
nl ^= d >> (63 - i);
return nl;
}
static void
polymult (u_int64_t *php, u_int64_t *plp, u_int64_t x, u_int64_t y)
{ int i;
u_int64_t ph = 0, pl = 0;
if (x & 1)
pl = y;
for (i = 1; i < 64; i++)
if (x & (1ULL << i)) {
ph ^= y >> (64 - i);
pl ^= y << i;
}
if (php)
*php = ph;
if (plp)
*plp = pl;
}
static u_int64_t
polymmult (u_int64_t x, u_int64_t y, u_int64_t d)
{
u_int64_t h, l;
polymult (&h, &l, x, y);
return polymod (h, l, d);
}
static int size = RABIN_WINDOW_SIZE;
static u_int64_t fingerprint = 0;
static int bufpos = -1;
static u_int64_t U[256];
static u_char buf[RABIN_WINDOW_SIZE];
void rabin_init ()
{ u_int64_t sizeshift = 1;
u_int64_t T1;
int xshift;
int i, j;
assert (poly >= 0x100);
xshift = fls64 (poly) - 1;
shift = xshift - 8;
T1 = polymod (0, 1ULL << xshift, poly);
for (j = 0; j < 256; j++)
T[j] = polymmult (j, T1, poly) | ((u_int64_t) j << xshift);
for (i = 1; i < size; i++)
sizeshift = append8 (sizeshift, 0);
for (i = 0; i < 256; i++)
U[i] = polymmult (i, sizeshift, poly);
bzero (buf, sizeof (buf));
}
void
rabin_reset ()
{ rabin_init();
fingerprint = 0;
bzero (buf, sizeof (buf));
}
u_int64_t
rabin_slide8 (u_char m)
{ u_char om;
if (++bufpos >= size) bufpos = 0;
om = buf[bufpos];
buf[bufpos] = m;
fingerprint = append8 (fingerprint ^ U[om], m);
return fingerprint;
}
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