match.c

   1 /*
   2  * Block matching used by the file-transfer code.
   3  *
   4  * Copyright (C) 1996 Andrew Tridgell
   5  * Copyright (C) 1996 Paul Mackerras
   6  * Copyright (C) 2003-2007 Wayne Davison
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 3 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, visit the http://fsf.org website.
  20  */
  21
  22 #include "rsync.h"
  23
  24 extern int verbose;
  25 extern int do_progress;
  26 extern int checksum_seed;
  27 extern int append_mode;
  28
  29 int updating_basis_file;
  30
  31 static int false_alarms;
  32 static int hash_hits;
  33 static int matches;
  34 static int64 data_transfer;
  35
  36 static int total_false_alarms;
  37 static int total_hash_hits;
  38 static int total_matches;
  39
  40 extern struct stats stats;
  41
  42 #define TRADITIONAL_TABLESIZE (1<<16)
  43
  44 static uint32 tablesize;
  45 static int32 *hash_table;
  46
  47 #define SUM2HASH2(s1,s2) (((s1) + (s2)) & 0xFFFF)
  48 #define SUM2HASH(sum) SUM2HASH2((sum)&0xFFFF,(sum)>>16)
  49
  50 #define BIG_SUM2HASH(sum) ((sum)%tablesize)
  51
  52 static void build_hash_table(struct sum_struct *s)
  53 {
  54         static uint32 alloc_size;
  55         int32 i;
  56
  57         /* Dynamically calculate the hash table size so that the hash load
  58          * for big files is about 80%.  A number greater than the traditional
  59          * size must be odd or s2 will not be able to span the entire set. */
  60         tablesize = (uint32)(s->count/8) * 10 + 11;
  61         if (tablesize < TRADITIONAL_TABLESIZE)
  62                 tablesize = TRADITIONAL_TABLESIZE;
  63         if (tablesize > alloc_size || tablesize < alloc_size - 16*1024) {
  64                 if (hash_table)
  65                         free(hash_table);
  66                 hash_table = new_array(int32, tablesize);
  67                 if (!hash_table)
  68                         out_of_memory("build_hash_table");
  69                 alloc_size = tablesize;
  70         }
  71
  72         memset(hash_table, 0xFF, tablesize * sizeof hash_table[0]);
  73
  74         if (tablesize == TRADITIONAL_TABLESIZE) {
  75                 for (i = 0; i < s->count; i++) {
  76                         uint32 t = SUM2HASH(s->sums[i].sum1);
  77                         s->sums[i].chain = hash_table[t];
  78                         hash_table[t] = i;
  79                 }
  80         } else {
  81                 for (i = 0; i < s->count; i++) {
  82                         uint32 t = BIG_SUM2HASH(s->sums[i].sum1);
  83                         s->sums[i].chain = hash_table[t];
  84                         hash_table[t] = i;
  85                 }
  86         }
  87 }
  88
  89
  90 static OFF_T last_match;
  91
  92
  93 /**
  94  * Transmit a literal and/or match token.
  95  *
  96  * This delightfully-named function is called either when we find a
  97  * match and need to transmit all the unmatched data leading up to it,
  98  * or when we get bored of accumulating literal data and just need to
  99  * transmit it.  As a result of this second case, it is called even if
 100  * we have not matched at all!
 101  *
 102  * @param i If >0, the number of a matched token.  If 0, indicates we
 103  * have only literal data.
 104  **/
 105 static void matched(int f, struct sum_struct *s, struct map_struct *buf,
 106                     OFF_T offset, int32 i)
 107 {
 108         int32 n = (int32)(offset - last_match); /* max value: block_size (int32) */
 109         int32 j;
 110
 111         if (verbose > 2 && i >= 0) {
 112                 rprintf(FINFO,
 113                         "match at %.0f last_match=%.0f j=%d len=%ld n=%ld\n",
 114                         (double)offset, (double)last_match, i,
 115                         (long)s->sums[i].len, (long)n);
 116         }
 117
 118         send_token(f, i, buf, last_match, n, i < 0 ? 0 : s->sums[i].len);
 119         data_transfer += n;
 120
 121         if (i >= 0) {
 122                 stats.matched_data += s->sums[i].len;
 123                 n += s->sums[i].len;
 124         }
 125
 126         for (j = 0; j < n; j += CHUNK_SIZE) {
 127                 int32 n1 = MIN(CHUNK_SIZE, n - j);
 128                 sum_update(map_ptr(buf, last_match + j, n1), n1);
 129         }
 130
 131         if (i >= 0)
 132                 last_match = offset + s->sums[i].len;
 133         else
 134                 last_match = offset;
 135
 136         if (buf && do_progress)
 137                 show_progress(last_match, buf->file_size);
 138 }
 139
 140
 141 static void hash_search(int f,struct sum_struct *s,
 142                         struct map_struct *buf, OFF_T len)
 143 {
 144         OFF_T offset, end;
 145         int32 k, want_i, backup;
 146         char sum2[SUM_LENGTH];
 147         uint32 s1, s2, sum;
 148         int more;
 149         schar *map;
 150
 151         /* want_i is used to encourage adjacent matches, allowing the RLL
 152          * coding of the output to work more efficiently. */
 153         want_i = 0;
 154
 155         if (verbose > 2) {
 156                 rprintf(FINFO, "hash search b=%ld len=%.0f\n",
 157                         (long)s->blength, (double)len);
 158         }
 159
 160         k = (int32)MIN(len, (OFF_T)s->blength);
 161
 162         map = (schar *)map_ptr(buf, 0, k);
 163
 164         sum = get_checksum1((char *)map, k);
 165         s1 = sum & 0xFFFF;
 166         s2 = sum >> 16;
 167         if (verbose > 3)
 168                 rprintf(FINFO, "sum=%.8x k=%ld\n", sum, (long)k);
 169
 170         offset = 0;
 171
 172         end = len + 1 - s->sums[s->count-1].len;
 173
 174         if (verbose > 3) {
 175                 rprintf(FINFO, "hash search s->blength=%ld len=%.0f count=%.0f\n",
 176                         (long)s->blength, (double)len, (double)s->count);
 177         }
 178
 179         do {
 180                 int done_csum2 = 0;
 181                 int32 i;
 182
 183                 if (verbose > 4) {
 184                         rprintf(FINFO, "offset=%.0f sum=%04x%04x\n",
 185                                 (double)offset, s2 & 0xFFFF, s1 & 0xFFFF);
 186                 }
 187
 188                 if (tablesize == TRADITIONAL_TABLESIZE) {
 189                         if ((i = hash_table[SUM2HASH2(s1,s2)]) < 0)
 190                                 goto null_hash;
 191                         sum = (s1 & 0xffff) | (s2 << 16);
 192                 } else {
 193                         sum = (s1 & 0xffff) | (s2 << 16);
 194                         if ((i = hash_table[BIG_SUM2HASH(sum)]) < 0)
 195                                 goto null_hash;
 196                 }
 197
 198                 hash_hits++;
 199                 do {
 200                         int32 l;
 201
 202                         if (sum != s->sums[i].sum1)
 203                                 continue;
 204
 205                         /* also make sure the two blocks are the same length */
 206                         l = (int32)MIN((OFF_T)s->blength, len-offset);
 207                         if (l != s->sums[i].len)
 208                                 continue;
 209
 210                         /* in-place: ensure chunk's offset is either >= our
 211                          * offset or that the data didn't move. */
 212                         if (updating_basis_file && s->sums[i].offset < offset
 213                             && !(s->sums[i].flags & SUMFLG_SAME_OFFSET))
 214                                 continue;
 215
 216                         if (verbose > 3) {
 217                                 rprintf(FINFO,
 218                                         "potential match at %.0f i=%ld sum=%08x\n",
 219                                         (double)offset, (long)i, sum);
 220                         }
 221
 222                         if (!done_csum2) {
 223                                 map = (schar *)map_ptr(buf,offset,l);
 224                                 get_checksum2((char *)map,l,sum2);
 225                                 done_csum2 = 1;
 226                         }
 227
 228                         if (memcmp(sum2,s->sums[i].sum2,s->s2length) != 0) {
 229                                 false_alarms++;
 230                                 continue;
 231                         }
 232
 233                         /* When updating in-place, the best possible match is
 234                          * one with an identical offset, so we prefer that over
 235                          * the following want_i optimization. */
 236                         if (updating_basis_file) {
 237                                 int32 i2;
 238                                 for (i2 = i; i2 >= 0; i2 = s->sums[i2].chain) {
 239                                         if (s->sums[i2].offset != offset)
 240                                                 continue;
 241                                         if (i2 != i) {
 242                                                 if (sum != s->sums[i2].sum1)
 243                                                         break;
 244                                                 if (memcmp(sum2, s->sums[i2].sum2,
 245                                                            s->s2length) != 0)
 246                                                         break;
 247                                                 i = i2;
 248                                         }
 249                                         /* This chunk was at the same offset on
 250                                          * both the sender and the receiver. */
 251                                         s->sums[i].flags |= SUMFLG_SAME_OFFSET;
 252                                         goto set_want_i;
 253                                 }
 254                         }
 255
 256                         /* we've found a match, but now check to see
 257                          * if want_i can hint at a better match. */
 258                         if (i != want_i && want_i < s->count
 259                             && (!updating_basis_file || s->sums[want_i].offset >= offset
 260                              || s->sums[want_i].flags & SUMFLG_SAME_OFFSET)
 261                             && sum == s->sums[want_i].sum1
 262                             && memcmp(sum2, s->sums[want_i].sum2, s->s2length) == 0) {
 263                                 /* we've found an adjacent match - the RLL coder
 264                                  * will be happy */
 265                                 i = want_i;
 266                         }
 267                     set_want_i:
 268                         want_i = i + 1;
 269
 270                         matched(f,s,buf,offset,i);
 271                         offset += s->sums[i].len - 1;
 272                         k = (int32)MIN((OFF_T)s->blength, len-offset);
 273                         map = (schar *)map_ptr(buf, offset, k);
 274                         sum = get_checksum1((char *)map, k);
 275                         s1 = sum & 0xFFFF;
 276                         s2 = sum >> 16;
 277                         matches++;
 278                         break;
 279                 } while ((i = s->sums[i].chain) >= 0);
 280
 281           null_hash:
 282                 backup = (int32)(offset - last_match);
 283                 /* We sometimes read 1 byte prior to last_match... */
 284                 if (backup < 0)
 285                         backup = 0;
 286
 287                 /* Trim off the first byte from the checksum */
 288                 more = offset + k < len;
 289                 map = (schar *)map_ptr(buf, offset - backup, k + more + backup)
 290                     + backup;
 291                 s1 -= map[0] + CHAR_OFFSET;
 292                 s2 -= k * (map[0]+CHAR_OFFSET);
 293
 294                 /* Add on the next byte (if there is one) to the checksum */
 295                 if (more) {
 296                         s1 += map[k] + CHAR_OFFSET;
 297                         s2 += s1;
 298                 } else
 299                         --k;
 300
 301                 /* By matching early we avoid re-reading the
 302                    data 3 times in the case where a token
 303                    match comes a long way after last
 304                    match. The 3 reads are caused by the
 305                    running match, the checksum update and the
 306                    literal send. */
 307                 if (backup >= s->blength+CHUNK_SIZE && end-offset > CHUNK_SIZE)
 308                         matched(f, s, buf, offset - s->blength, -2);
 309         } while (++offset < end);
 310
 311         matched(f, s, buf, len, -1);
 312         map_ptr(buf, len-1, 1);
 313 }
 314
 315
 316 /**
 317  * Scan through a origin file, looking for sections that match
 318  * checksums from the generator, and transmit either literal or token
 319  * data.
 320  *
 321  * Also calculates the MD4 checksum of the whole file, using the md
 322  * accumulator.  This is transmitted with the file as protection
 323  * against corruption on the wire.
 324  *
 325  * @param s Checksums received from the generator.  If <tt>s->count ==
 326  * 0</tt>, then there are actually no checksums for this file.
 327  *
 328  * @param len Length of the file to send.
 329  **/
 330 void match_sums(int f, struct sum_struct *s, struct map_struct *buf, OFF_T len)
 331 {
 332         char file_sum[MAX_DIGEST_LEN];
 333         int sum_len;
 334
 335         last_match = 0;
 336         false_alarms = 0;
 337         hash_hits = 0;
 338         matches = 0;
 339         data_transfer = 0;
 340
 341         sum_init(checksum_seed);
 342
 343         if (append_mode > 0) {
 344                 if (append_mode == 2) {
 345                         OFF_T j = 0;
 346                         for (j = CHUNK_SIZE; j < s->flength; j += CHUNK_SIZE) {
 347                                 if (buf && do_progress)
 348                                         show_progress(last_match, buf->file_size);
 349                                 sum_update(map_ptr(buf, last_match, CHUNK_SIZE),
 350                                            CHUNK_SIZE);
 351                                 last_match = j;
 352                         }
 353                         if (last_match < s->flength) {
 354                                 int32 n = (int32)(s->flength - last_match);
 355                                 if (buf && do_progress)
 356                                         show_progress(last_match, buf->file_size);
 357                                 sum_update(map_ptr(buf, last_match, n), n);
 358                         }
 359                 }
 360                 last_match = s->flength;
 361                 s->count = 0;
 362         }
 363
 364         if (len > 0 && s->count > 0) {
 365                 build_hash_table(s);
 366
 367                 if (verbose > 2)
 368                         rprintf(FINFO,"built hash table\n");
 369
 370                 hash_search(f, s, buf, len);
 371
 372                 if (verbose > 2)
 373                         rprintf(FINFO,"done hash search\n");
 374         } else {
 375                 OFF_T j;
 376                 /* by doing this in pieces we avoid too many seeks */
 377                 for (j = last_match + CHUNK_SIZE; j < len; j += CHUNK_SIZE)
 378                         matched(f, s, buf, j, -2);
 379                 matched(f, s, buf, len, -1);
 380         }
 381
 382         sum_len = sum_end(file_sum);
 383         /* If we had a read error, send a bad checksum. */
 384         if (buf && buf->status != 0)
 385                 file_sum[0]++;
 386
 387         if (verbose > 2)
 388                 rprintf(FINFO,"sending file_sum\n");
 389         write_buf(f, file_sum, sum_len);
 390
 391         if (verbose > 2)
 392                 rprintf(FINFO, "false_alarms=%d hash_hits=%d matches=%d\n",
 393                         false_alarms, hash_hits, matches);
 394
 395         total_hash_hits += hash_hits;
 396         total_false_alarms += false_alarms;
 397         total_matches += matches;
 398         stats.literal_data += data_transfer;
 399 }
 400
 401 void match_report(void)
 402 {
 403         if (verbose <= 1)
 404                 return;
 405
 406         rprintf(FINFO,
 407                 "total: matches=%d  hash_hits=%d  false_alarms=%d data=%.0f\n",
 408                 total_matches, total_hash_hits, total_false_alarms,
 409                 (double)stats.literal_data);
 410 }