checksum.c

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/*
   Copyright (C) Andrew Tridgell 1996
   Copyright (C) Paul Mackerras 1996

   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 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 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "rsync.h"

int csum_length=2; /* initial value */

#define CSUM_CHUNK 64

extern int checksum_seed;
extern int protocol_version;

/*
  a simple 32 bit checksum that can be upadted from either end
  (inspired by Mark Adler's Adler-32 checksum)
  */
uint32 get_checksum1(char *buf1, int32 len)
{
    int32 i;
    uint32 s1, s2;
    schar *buf = (schar *)buf1;

    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*CHAR_OFFSET;
        s1 += (buf[i+0] + buf[i+1] + buf[i+2] + buf[i+3] + 4*CHAR_OFFSET);
    }
    for (; i < len; i++) {
        s1 += (buf[i]+CHAR_OFFSET); s2 += s1;
    }
    return (s1 & 0xffff) + (s2 << 16);
}


void get_checksum2(char *buf, int32 len, char *sum)
{
        int32 i;
        static char *buf1;
        static int32 len1;
        struct mdfour m;

        if (len > len1) {
                if (buf1)
                        free(buf1);
                buf1 = new_array(char, len+4);
                len1 = len;
                if (!buf1)
                        out_of_memory("get_checksum2");
        }

        mdfour_begin(&m);

        memcpy(buf1,buf,len);
        if (checksum_seed) {
                SIVAL(buf1,len,checksum_seed);
                len += 4;
        }

        for(i = 0; i + CSUM_CHUNK <= len; i += CSUM_CHUNK) {
                mdfour_update(&m, (uchar *)(buf1+i), CSUM_CHUNK);
        }
        /*
         * Prior to version 27 an incorrect MD4 checksum was computed
         * by failing to call mdfour_tail() for block sizes that
         * are multiples of 64.  This is fixed by calling mdfour_update()
         * even when there are no more bytes.
         */
        if (len - i > 0 || protocol_version >= 27) {
                mdfour_update(&m, (uchar *)(buf1+i), (len-i));
        }

        mdfour_result(&m, (uchar *)sum);
}


void file_checksum(char *fname,char *sum,OFF_T size)
{
        OFF_T i;
        struct map_struct *buf;
        int fd;
        OFF_T len = size;
        struct mdfour m;

        memset(sum,0,MD4_SUM_LENGTH);

        fd = do_open(fname, O_RDONLY, 0);
        if (fd == -1)
                return;

        buf = map_file(fd, size, MAX_MAP_SIZE, CSUM_CHUNK);

        mdfour_begin(&m);

        for(i = 0; i + CSUM_CHUNK <= len; i += CSUM_CHUNK) {
                mdfour_update(&m, (uchar *)map_ptr(buf, i, CSUM_CHUNK),
                              CSUM_CHUNK);
        }

        /* Prior to version 27 an incorrect MD4 checksum was computed
         * by failing to call mdfour_tail() for block sizes that
         * are multiples of 64.  This is fixed by calling mdfour_update()
         * even when there are no more bytes. */
        if (len - i > 0 || protocol_version >= 27)
                mdfour_update(&m, (uchar *)map_ptr(buf, i, len-i), len-i);

        mdfour_result(&m, (uchar *)sum);

        close(fd);
        unmap_file(buf);
}


static int32 sumresidue;
static char sumrbuf[CSUM_CHUNK];
static struct mdfour md;

void sum_init(int seed)
{
        char s[4];
        mdfour_begin(&md);
        sumresidue = 0;
        SIVAL(s, 0, seed);
        sum_update(s, 4);
}

/**
 * Feed data into an MD4 accumulator, md.  The results may be
 * retrieved using sum_end().  md is used for different purposes at
 * different points during execution.
 *
 * @todo Perhaps get rid of md and just pass in the address each time.
 * Very slightly clearer and slower.
 **/
void sum_update(char *p, int32 len)
{
        if (len + sumresidue < CSUM_CHUNK) {
                memcpy(sumrbuf + sumresidue, p, len);
                sumresidue += len;
                return;
        }

        if (sumresidue) {
                int32 i = CSUM_CHUNK - sumresidue;
                memcpy(sumrbuf + sumresidue, p, i);
                mdfour_update(&md, (uchar *)sumrbuf, CSUM_CHUNK);
                len -= i;
                p += i;
        }

        while (len >= CSUM_CHUNK) {
                mdfour_update(&md, (uchar *)p, CSUM_CHUNK);
                len -= CSUM_CHUNK;
                p += CSUM_CHUNK;
        }

        sumresidue = len;
        if (sumresidue)
                memcpy(sumrbuf, p, sumresidue);
}

void sum_end(char *sum)
{
        if (sumresidue || protocol_version >= 27)
                mdfour_update(&md, (uchar *)sumrbuf, sumresidue);

        mdfour_result(&md, (uchar *)sum);
}

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