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https://github.com/RsyncProject/rsync.git
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79 lines
1.8 KiB
C
79 lines
1.8 KiB
C
/*
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Copyright (C) Andrew Tridgell 1996
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Copyright (C) Paul Mackerras 1996
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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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., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include "rsync.h"
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/*
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a simple 32 bit checksum that can be upadted from either end
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(inspired by Mark Adler's Adler-32 checksum)
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*/
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uint32 get_checksum1(char *buf,int len)
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{
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int i;
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uint32 s1, s2;
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s1 = s2 = 0;
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for (i = 0; i < len; i++) {
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s1 += buf[i];
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s2 += s1;
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}
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return (s1 & 0xffff) + (s2 << 16);
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}
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void get_checksum2(char *buf,int len,char *sum)
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{
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char buf2[64];
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int i;
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MDstruct MD;
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MDbegin(&MD);
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for(i = 0; i + 64 <= len; i += 64) {
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bcopy(buf+i,buf2,64);
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MDupdate(&MD, buf2, 512);
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}
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bcopy(buf+i,buf2,len-i);
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MDupdate(&MD, buf2, (len-i)*8);
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SIVAL(sum,0,MD.buffer[0]);
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SIVAL(sum,4,MD.buffer[1]);
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SIVAL(sum,8,MD.buffer[2]);
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SIVAL(sum,12,MD.buffer[3]);
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}
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void file_checksum(char *fname,char *sum,off_t size)
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{
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char *buf;
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int fd;
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bzero(sum,SUM_LENGTH);
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fd = open(fname,O_RDONLY);
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if (fd == -1) return;
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buf = map_file(fd,size);
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if (!buf) {
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close(fd);
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return;
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}
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get_checksum2(buf,size,sum);
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close(fd);
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unmap_file(buf,size);
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}
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