/*= -*- c-basic-offset: 4; indent-tabs-mode: nil; -*- * * librsync -- the library for network deltas * $Id$ * * Copyright (C) 1999, 2000, 2001 by Martin Pool <mbp@samba.org> * Copyright (C) 1996 by Andrew Tridgell * Copyright (C) 1996 by Paul Mackerras * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation; either version 2.1 of the License, 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 Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ #include <config_rsync.h> #include <assert.h> #include <stdlib.h> #include <stdio.h> #include "rsync.h" #include "checksum.h" /* This can possibly be used to restart the checksum system in the * case where we detected corruption. I'm not sure yet how to make * this useful in librsync. */ int checksum_seed = 0; /* * A simple 32 bit checksum that can be updated from either end * (inspired by Mark Adler's Adler-32 checksum) */ unsigned int rs_calc_weak_sum(void const *p, int len) { int i; unsigned s1, s2; unsigned char const *buf = (unsigned char const *) p; s1 = s2 = 0; for (i = 0; i < (len - 4); i += 4) { s2 += 4 * (s1 + buf[i]) + 3 * buf[i + 1] + 2 * buf[i + 2] + buf[i + 3] + 10 * RS_CHAR_OFFSET; s1 += (buf[i + 0] + buf[i + 1] + buf[i + 2] + buf[i + 3] + 4 * RS_CHAR_OFFSET); } for (; i < len; i++) { s1 += (buf[i] + RS_CHAR_OFFSET); s2 += s1; } return (s1 & 0xffff) + (s2 << 16); } /** * Calculate and store into SUM a strong MD4 checksum of the file * blocks seen so far. * * In plain rsync, the checksum is perturbed by a seed value. This is * used when retrying a failed transmission: we've discovered that the * hashes collided at some point, so we're going to try again with * different hashes to see if we can get it right. (Check tridge's * thesis for details and to see if that's correct.) * * Since we can't retry a web transaction I'm not sure if it's very * useful in rproxy. */ void rs_calc_strong_sum(void const *buf, size_t len, rs_strong_sum_t *sum) { rs_mdfour((unsigned char *) sum, buf, len); }