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[rsync.git] / match.c

/*
   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"

extern int verbose;
extern int am_server;
extern int do_progress;
extern int checksum_seed;

int updating_basis_file;

typedef unsigned short tag;

#define TABLESIZE (1<<16)
#define NULL_TAG (-1)

static int false_alarms;
static int tag_hits;
static int matches;
static int64 data_transfer;

static int total_false_alarms;
static int total_tag_hits;
static int total_matches;

extern struct stats stats;

struct target {
        tag t;
        int32 i;
};

static struct target *targets;

static int32 *tag_table;

#define gettag2(s1,s2) (((s1) + (s2)) & 0xFFFF)
#define gettag(sum) gettag2((sum)&0xFFFF,(sum)>>16)

static int compare_targets(struct target *t1,struct target *t2)
{
        return (int)t1->t - (int)t2->t;
}


static void build_hash_table(struct sum_struct *s)
{
        int32 i;

        if (!tag_table)
                tag_table = new_array(int32, TABLESIZE);

        targets = new_array(struct target, s->count);
        if (!tag_table || !targets)
                out_of_memory("build_hash_table");

        for (i = 0; i < s->count; i++) {
                targets[i].i = i;
                targets[i].t = gettag(s->sums[i].sum1);
        }

        qsort(targets,s->count,sizeof(targets[0]),(int (*)())compare_targets);

        for (i = 0; i < TABLESIZE; i++)
                tag_table[i] = NULL_TAG;

        for (i = s->count; i-- > 0; )
                tag_table[targets[i].t] = i;
}


static OFF_T last_match;


/**
 * Transmit a literal and/or match token.
 *
 * This delightfully-named function is called either when we find a
 * match and need to transmit all the unmatched data leading up to it,
 * or when we get bored of accumulating literal data and just need to
 * transmit it.  As a result of this second case, it is called even if
 * we have not matched at all!
 *
 * @param i If >0, the number of a matched token.  If 0, indicates we
 * have only literal data.
 **/
static void matched(int f, struct sum_struct *s, struct map_struct *buf,
                    OFF_T offset, int32 i)
{
        int32 n = offset - last_match; /* max value: block_size (int32) */
        int32 j;

        if (verbose > 2 && i >= 0) {
                rprintf(FINFO,
                        "match at %.0f last_match=%.0f j=%d len=%ld n=%ld\n",
                        (double)offset, (double)last_match, i,
                        (long)s->sums[i].len, (long)n);
        }

        send_token(f, i, buf, last_match, n, i < 0 ? 0 : s->sums[i].len);
        data_transfer += n;

        if (i >= 0) {
                stats.matched_data += s->sums[i].len;
                n += s->sums[i].len;
        }

        for (j = 0; j < n; j += CHUNK_SIZE) {
                int32 n1 = MIN(CHUNK_SIZE, n - j);
                sum_update(map_ptr(buf, last_match + j, n1), n1);
        }


        if (i >= 0)
                last_match = offset + s->sums[i].len;
        else
                last_match = offset;

        if (buf && do_progress)
                show_progress(last_match, buf->file_size);
}


static void hash_search(int f,struct sum_struct *s,
                        struct map_struct *buf, OFF_T len)
{
        OFF_T offset, end, backup;
        int32 k, want_i;
        char sum2[SUM_LENGTH];
        uint32 s1, s2, sum;
        int more;
        schar *map;

        /* want_i is used to encourage adjacent matches, allowing the RLL
         * coding of the output to work more efficiently. */
        want_i = 0;

        if (verbose > 2) {
                rprintf(FINFO, "hash search b=%ld len=%.0f\n",
                        (long)s->blength, (double)len);
        }

        k = (int32)MIN(len, (OFF_T)s->blength);

        map = (schar *)map_ptr(buf, 0, k);

        sum = get_checksum1((char *)map, k);
        s1 = sum & 0xFFFF;
        s2 = sum >> 16;
        if (verbose > 3)
                rprintf(FINFO, "sum=%.8x k=%ld\n", sum, (long)k);

        offset = 0;

        end = len + 1 - s->sums[s->count-1].len;

        if (verbose > 3) {
                rprintf(FINFO, "hash search s->blength=%ld len=%.0f count=%.0f\n",
                        (long)s->blength, (double)len, (double)s->count);
        }

        do {
                tag t = gettag2(s1,s2);
                int done_csum2 = 0;
                int32 j = tag_table[t];

                if (verbose > 4)
                        rprintf(FINFO,"offset=%.0f sum=%08x\n",(double)offset,sum);

                if (j == NULL_TAG)
                        goto null_tag;

                sum = (s1 & 0xffff) | (s2 << 16);
                tag_hits++;
                do {
                        int32 l, i = targets[j].i;

                        if (sum != s->sums[i].sum1)
                                continue;

                        /* also make sure the two blocks are the same length */
                        l = (int32)MIN((OFF_T)s->blength, len-offset);
                        if (l != s->sums[i].len)
                                continue;

                        /* in-place: ensure chunk's offset is either >= our
                         * offset or that the data didn't move. */
                        if (updating_basis_file && s->sums[i].offset < offset
                            && !(s->sums[i].flags & SUMFLG_SAME_OFFSET))
                                continue;

                        if (verbose > 3)
                                rprintf(FINFO,"potential match at %.0f target=%.0f %.0f sum=%08x\n",
                                        (double)offset,(double)j,(double)i,sum);

                        if (!done_csum2) {
                                map = (schar *)map_ptr(buf,offset,l);
                                get_checksum2((char *)map,l,sum2);
                                done_csum2 = 1;
                        }

                        if (memcmp(sum2,s->sums[i].sum2,s->s2length) != 0) {
                                false_alarms++;
                                continue;
                        }

                        /* When updating in-place, the best possible match is
                         * one with an identical offset, so we prefer that over
                         * the following want_i optimization. */
                        if (updating_basis_file) {
                                do {
                                        int32 i2 = targets[j].i;
                                        if (s->sums[i2].offset != offset)
                                                continue;
                                        if (i2 != i) {
                                                if (sum != s->sums[i2].sum1)
                                                        break;
                                                if (memcmp(sum2, s->sums[i2].sum2,
                                                           s->s2length) != 0)
                                                        break;
                                                i = i2;
                                        }
                                        /* This chunk was at the same offset on
                                         * both the sender and the receiver. */
                                        s->sums[i].flags |= SUMFLG_SAME_OFFSET;
                                        goto set_want_i;
                                } while (++j < s->count && targets[j].t == t);
                        }

                        /* we've found a match, but now check to see
                         * if want_i can hint at a better match. */
                        if (i != want_i && want_i < s->count
                            && (!updating_basis_file || s->sums[want_i].offset >= offset
                             || s->sums[want_i].flags & SUMFLG_SAME_OFFSET)
                            && sum == s->sums[want_i].sum1
                            && memcmp(sum2, s->sums[want_i].sum2, s->s2length) == 0) {
                                /* we've found an adjacent match - the RLL coder
                                 * will be happy */
                                i = want_i;
                        }
                    set_want_i:
                        want_i = i + 1;

                        matched(f,s,buf,offset,i);
                        offset += s->sums[i].len - 1;
                        k = (int32)MIN((OFF_T)s->blength, len-offset);
                        map = (schar *)map_ptr(buf, offset, k);
                        sum = get_checksum1((char *)map, k);
                        s1 = sum & 0xFFFF;
                        s2 = sum >> 16;
                        matches++;
                        break;
                } while (++j < s->count && targets[j].t == t);

        null_tag:
                backup = offset - last_match;
                /* We sometimes read 1 byte prior to last_match... */
                if (backup < 0)
                        backup = 0;

                /* Trim off the first byte from the checksum */
                more = offset + k < len;
                map = (schar *)map_ptr(buf, offset - backup, k + more + backup)
                    + backup;
                s1 -= map[0] + CHAR_OFFSET;
                s2 -= k * (map[0]+CHAR_OFFSET);

                /* Add on the next byte (if there is one) to the checksum */
                if (more) {
                        s1 += map[k] + CHAR_OFFSET;
                        s2 += s1;
                } else
                        --k;

                /* By matching early we avoid re-reading the
                   data 3 times in the case where a token
                   match comes a long way after last
                   match. The 3 reads are caused by the
                   running match, the checksum update and the
                   literal send. */
                if (backup >= s->blength+CHUNK_SIZE && end-offset > CHUNK_SIZE)
                        matched(f, s, buf, offset - s->blength, -2);
        } while (++offset < end);

        matched(f, s, buf, len, -1);
        map_ptr(buf, len-1, 1);
}


/**
 * Scan through a origin file, looking for sections that match
 * checksums from the generator, and transmit either literal or token
 * data.
 *
 * Also calculates the MD4 checksum of the whole file, using the md
 * accumulator.  This is transmitted with the file as protection
 * against corruption on the wire.
 *
 * @param s Checksums received from the generator.  If <tt>s->count ==
 * 0</tt>, then there are actually no checksums for this file.
 *
 * @param len Length of the file to send.
 **/
void match_sums(int f, struct sum_struct *s, struct map_struct *buf, OFF_T len)
{
        char file_sum[MD4_SUM_LENGTH];

        last_match = 0;
        false_alarms = 0;
        tag_hits = 0;
        matches = 0;
        data_transfer = 0;

        sum_init(checksum_seed);

        if (len > 0 && s->count > 0) {
                build_hash_table(s);

                if (verbose > 2)
                        rprintf(FINFO,"built hash table\n");

                hash_search(f,s,buf,len);

                if (verbose > 2)
                        rprintf(FINFO,"done hash search\n");
        } else {
                OFF_T j;
                /* by doing this in pieces we avoid too many seeks */
                for (j = CHUNK_SIZE; j < len; j += CHUNK_SIZE)
                        matched(f, s, buf, j, -2);
                matched(f, s, buf, len, -1);
        }

        sum_end(file_sum);
        /* If we had a read error, send a bad checksum. */
        if (buf && buf->status != 0)
                file_sum[0]++;

        if (verbose > 2)
                rprintf(FINFO,"sending file_sum\n");
        write_buf(f,file_sum,MD4_SUM_LENGTH);

        if (targets) {
                free(targets);
                targets=NULL;
        }

        if (verbose > 2)
                rprintf(FINFO, "false_alarms=%d tag_hits=%d matches=%d\n",
                        false_alarms, tag_hits, matches);

        total_tag_hits += tag_hits;
        total_false_alarms += false_alarms;
        total_matches += matches;
        stats.literal_data += data_transfer;
}

void match_report(void)
{
        if (verbose <= 1)
                return;

        rprintf(FINFO,
                "total: matches=%d  tag_hits=%d  false_alarms=%d data=%.0f\n",
                total_matches,total_tag_hits,
                total_false_alarms,
                (double)stats.literal_data);
}