Fix a comment.

[rsync/qnx.git] / match.c

/*
 * Block matching used by the file-transfer code.
 *
 * Copyright (C) 1996 Andrew Tridgell
 * Copyright (C) 1996 Paul Mackerras
 * Copyright (C) 2003-2009 Wayne Davison
 *
 * 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 3 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, visit the http://fsf.org website.
 */

#include "rsync.h"
#include "inums.h"

extern int checksum_seed;
extern int append_mode;
extern int checksum_len;

int updating_basis_file;
char sender_file_sum[MAX_DIGEST_LEN];

static int false_alarms;
static int hash_hits;
static int matches;
static int64 data_transfer;

static int total_false_alarms;
static int total_hash_hits;
static int total_matches;

extern struct stats stats;

#define TRADITIONAL_TABLESIZE (1<<16)

static uint32 tablesize;
static int32 *hash_table;

#define SUM2HASH2(s1,s2) (((s1) + (s2)) & 0xFFFF)
#define SUM2HASH(sum) SUM2HASH2((sum)&0xFFFF,(sum)>>16)

#define BIG_SUM2HASH(sum) ((sum)%tablesize)

static void build_hash_table(struct sum_struct *s)
{
        static uint32 alloc_size;
        int32 i;

        /* Dynamically calculate the hash table size so that the hash load
         * for big files is about 80%.  A number greater than the traditional
         * size must be odd or s2 will not be able to span the entire set. */
        tablesize = (uint32)(s->count/8) * 10 + 11;
        if (tablesize < TRADITIONAL_TABLESIZE)
                tablesize = TRADITIONAL_TABLESIZE;
        if (tablesize > alloc_size || tablesize < alloc_size - 16*1024) {
                if (hash_table)
                        free(hash_table);
                hash_table = new_array(int32, tablesize);
                if (!hash_table)
                        out_of_memory("build_hash_table");
                alloc_size = tablesize;
        }

        memset(hash_table, 0xFF, tablesize * sizeof hash_table[0]);

        if (tablesize == TRADITIONAL_TABLESIZE) {
                for (i = 0; i < s->count; i++) {
                        uint32 t = SUM2HASH(s->sums[i].sum1);
                        s->sums[i].chain = hash_table[t];
                        hash_table[t] = i;
                }
        } else {
                for (i = 0; i < s->count; i++) {
                        uint32 t = BIG_SUM2HASH(s->sums[i].sum1);
                        s->sums[i].chain = hash_table[t];
                        hash_table[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!
 *
 * If i >= 0, the number of a matched token.  If < 0, indicates we have
 * only literal data.  A -1 will send a 0-token-int too, and a -2 sends
 * only literal data, w/o any token-int. */
static void matched(int f, struct sum_struct *s, struct map_struct *buf,
                    OFF_T offset, int32 i)
{
        int32 n = (int32)(offset - last_match); /* max value: block_size (int32) */
        int32 j;

        if (DEBUG_GTE(DELTASUM, 2) && i >= 0) {
                rprintf(FINFO,
                        "match at %s last_match=%s j=%d len=%ld n=%ld\n",
                        big_num(offset), big_num(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 && INFO_GTE(PROGRESS, 1))
                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, aligned_offset, end;
        int32 k, want_i, aligned_i, backup;
        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 (DEBUG_GTE(DELTASUM, 2)) {
                rprintf(FINFO, "hash search b=%ld len=%s\n",
                        (long)s->blength, big_num(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 (DEBUG_GTE(DELTASUM, 3))
                rprintf(FINFO, "sum=%.8x k=%ld\n", sum, (long)k);

        offset = aligned_offset = aligned_i = 0;

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

        if (DEBUG_GTE(DELTASUM, 3)) {
                rprintf(FINFO, "hash search s->blength=%ld len=%s count=%s\n",
                        (long)s->blength, big_num(len), big_num(s->count));
        }

        do {
                int done_csum2 = 0;
                int32 i;

                if (DEBUG_GTE(DELTASUM, 4)) {
                        rprintf(FINFO, "offset=%s sum=%04x%04x\n",
                                big_num(offset), s2 & 0xFFFF, s1 & 0xFFFF);
                }

                if (tablesize == TRADITIONAL_TABLESIZE) {
                        if ((i = hash_table[SUM2HASH2(s1,s2)]) < 0)
                                goto null_hash;
                        sum = (s1 & 0xffff) | (s2 << 16);
                } else {
                        sum = (s1 & 0xffff) | (s2 << 16);
                        if ((i = hash_table[BIG_SUM2HASH(sum)]) < 0)
                                goto null_hash;
                }

                hash_hits++;
                do {
                        int32 l;

                        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 (DEBUG_GTE(DELTASUM, 3)) {
                                rprintf(FINFO,
                                        "potential match at %s i=%ld sum=%08x\n",
                                        big_num(offset), (long)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 adjacent want_i optimization. */
                        if (updating_basis_file) {
                                /* All the generator's chunks start at blength boundaries. */
                                while (aligned_offset < offset) {
                                        aligned_offset += s->blength;
                                        aligned_i++;
                                }
                                if ((offset == aligned_offset
                                  || (sum == 0 && l == s->blength && aligned_offset + l <= len))
                                 && aligned_i < s->count) {
                                        if (i != aligned_i) {
                                                if (sum != s->sums[aligned_i].sum1
                                                 || l != s->sums[aligned_i].len
                                                 || memcmp(sum2, s->sums[aligned_i].sum2, s->s2length) != 0)
                                                        goto check_want_i;
                                                i = aligned_i;
                                        }
                                        if (offset != aligned_offset) {
                                                /* We've matched some zeros in a spot that is also zeros
                                                 * further along in the basis file, if we find zeros ahead
                                                 * in the sender's file, we'll output enough literal data
                                                 * to re-align with the basis file, and get back to seeking
                                                 * instead of writing. */
                                                backup = (int32)(aligned_offset - last_match);
                                                if (backup < 0)
                                                        backup = 0;
                                                map = (schar *)map_ptr(buf, aligned_offset - backup, l + backup)
                                                    + backup;
                                                sum = get_checksum1((char *)map, l);
                                                if (sum != s->sums[i].sum1)
                                                        goto check_want_i;
                                                get_checksum2((char *)map, l, sum2);
                                                if (memcmp(sum2, s->sums[i].sum2, s->s2length) != 0)
                                                        goto check_want_i;
                                                /* OK, we have a re-alignment match.  Bump the offset
                                                 * forward to the new match point. */
                                                offset = aligned_offset;
                                        }
                                        /* This identical chunk is in the same spot in the old and new file. */
                                        s->sums[i].flags |= SUMFLG_SAME_OFFSET;
                                        want_i = i;
                                }
                        }

                  check_want_i:
                        /* 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;
                        }
                        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 ((i = s->sums[i].chain) >= 0);

          null_hash:
                backup = (int32)(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)
{
        last_match = 0;
        false_alarms = 0;
        hash_hits = 0;
        matches = 0;
        data_transfer = 0;

        sum_init(checksum_seed);

        if (append_mode > 0) {
                if (append_mode == 2) {
                        OFF_T j = 0;
                        for (j = CHUNK_SIZE; j < s->flength; j += CHUNK_SIZE) {
                                if (buf && INFO_GTE(PROGRESS, 1))
                                        show_progress(last_match, buf->file_size);
                                sum_update(map_ptr(buf, last_match, CHUNK_SIZE),
                                           CHUNK_SIZE);
                                last_match = j;
                        }
                        if (last_match < s->flength) {
                                int32 n = (int32)(s->flength - last_match);
                                if (buf && INFO_GTE(PROGRESS, 1))
                                        show_progress(last_match, buf->file_size);
                                sum_update(map_ptr(buf, last_match, n), n);
                        }
                }
                last_match = s->flength;
                s->count = 0;
        }

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

                if (DEBUG_GTE(DELTASUM, 2))
                        rprintf(FINFO,"built hash table\n");

                hash_search(f, s, buf, len);

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

        if (sum_end(sender_file_sum) != checksum_len)
                overflow_exit("checksum_len"); /* Impossible... */

        /* If we had a read error, send a bad checksum.  We use all bits
         * off as long as the checksum doesn't happen to be that, in
         * which case we turn the last 0 bit into a 1. */
        if (buf && buf->status != 0) {
                int i;
                for (i = 0; i < checksum_len && sender_file_sum[i] == 0; i++) {}
                memset(sender_file_sum, 0, checksum_len);
                if (i == checksum_len)
                        sender_file_sum[i-1]++;
        }

        if (DEBUG_GTE(DELTASUM, 2))
                rprintf(FINFO,"sending file_sum\n");
        write_buf(f, sender_file_sum, checksum_len);

        if (DEBUG_GTE(DELTASUM, 2)) {
                rprintf(FINFO, "false_alarms=%d hash_hits=%d matches=%d\n",
                        false_alarms, hash_hits, matches);
        }

        total_hash_hits += hash_hits;
        total_false_alarms += false_alarms;
        total_matches += matches;
        stats.literal_data += data_transfer;
}

void match_report(void)
{
        if (!DEBUG_GTE(DELTASUM, 1))
                return;

        rprintf(FINFO,
                "total: matches=%d  hash_hits=%d  false_alarms=%d data=%s\n",
                total_matches, total_hash_hits, total_false_alarms,
                big_num(stats.literal_data));
}