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