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match.c

Go to the documentation of this file.

/* 
   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 csum_length;

extern int verbose;
extern int am_server;

extern int remote_version;

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;
  int i;
};

static struct target *targets;

static int *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)
{
  int i;

  if (!tag_table)
    tag_table = (int *)malloc(sizeof(tag_table[0])*TABLESIZE);

  targets = (struct target *)malloc(sizeof(targets[0])*s->count);
  if (!tag_table || !targets) 
    out_of_memory("build_hash_table");

  for (i=0;i<(int) 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-1;i>=0;i--) {    
    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,int i)
{
        OFF_T n = offset - last_match;
        OFF_T j;

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

                if (i == -1) end_progress(buf->file_size);
        }
}


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

        /* last_i is used to encourage adjacent matches, allowing the RLL coding of the
           output to work more efficiently */
        last_i = -1;

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

        /* cast is to make s->n signed; it should always be reasonably
         * small */
        k = MIN(len, (OFF_T) s->n);
        
        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=%d\n", sum, k);
        
        offset = 0;
        
        end = len + 1 - s->sums[s->count-1].len;
        
        if (verbose > 3)
                rprintf(FINFO, "hash search s->n=%ld len=%.0f count=%ld\n",
                        (long) s->n, (double) len, (long) s->count);
        
        do {
                tag t = gettag2(s1,s2);
                int done_csum2 = 0;
                        
                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++;
                for (; j < (int) s->count && targets[j].t == t; j++) {
                        int l, i = targets[j].i;
                        
                        if (sum != s->sums[i].sum1) continue;
                        
                        /* also make sure the two blocks are the same length */
                        l = MIN(s->n,len-offset);
                        if (l != s->sums[i].len) continue;                      

                        if (verbose > 3)
                                rprintf(FINFO,"potential match at %.0f target=%d %d sum=%08x\n",
                                        (double)offset,j,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,csum_length) != 0) {
                                false_alarms++;
                                continue;
                        }

                        /* we've found a match, but now check to see
                           if last_i can hint at a better match */
                        for (j++; j < (int) s->count && targets[j].t == t; j++) {
                                int i2 = targets[j].i;
                                if (i2 == last_i + 1) {
                                        if (sum != s->sums[i2].sum1) break;
                                        if (memcmp(sum2,s->sums[i2].sum2,csum_length) != 0) break;
                                        /* we've found an adjacent match - the RLL coder 
                                           will be happy */
                                        i = i2;
                                        break;
                                }
                        }

                        last_i = i;
                        
                        matched(f,s,buf,offset,i);
                        offset += s->sums[i].len - 1;
                        k = MIN((len-offset), s->n);
                        map = (schar *)map_ptr(buf,offset,k);
                        sum = get_checksum1((char *)map, k);
                        s1 = sum & 0xFFFF;
                        s2 = sum >> 16;
                        matches++;
                        break;
                }
                
        null_tag:
                /* Trim off the first byte from the checksum */
                map = (schar *)map_ptr(buf,offset,k+1);
                s1 -= map[0] + CHAR_OFFSET;
                s2 -= k * (map[0]+CHAR_OFFSET);
                
                /* Add on the next byte (if there is one) to the checksum */
                if (k < (len-offset)) {
                        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 (offset > last_match &&
                    offset-last_match >= CHUNK_SIZE+s->n && 
                    (end-offset > CHUNK_SIZE)) {
                        matched(f,s,buf,offset - s->n, -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];
        extern int write_batch;  /*  dw */

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

        sum_init();

        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=0;j<(len-CHUNK_SIZE);j+=CHUNK_SIZE) {
                        int n1 = MIN(CHUNK_SIZE,(len-CHUNK_SIZE)-j);
                        matched(f,s,buf,j+n1,-2);
                }
                matched(f,s,buf,len,-1);
        }

        sum_end(file_sum);

        if (remote_version >= 14) {
                if (verbose > 2)
                        rprintf(FINFO,"sending file_sum\n");
                write_buf(f,file_sum,MD4_SUM_LENGTH);
                if (write_batch) /* dw */
                    write_batch_delta_file(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);
}

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