lib/deltify.c

   1 /*
   2  * Copyright (c) 2020 Ori Bernstein
   3  * Copyright (c) 2021 Stefan Sperling <stsp@openbsd.org>
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  */
  17
  18 #include <sys/types.h>
  19
  20 #include <assert.h>
  21 #include <errno.h>
  22 #include <limits.h>
  23 #include <stdint.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27
  28 #include "got_error.h"
  29
  30 #include "got_lib_deltify.h"
  31
  32 #ifndef MIN
  33 #define MIN(_a,_b) ((_a) < (_b) ? (_a) : (_b))
  34 #endif
  35
  36 static uint32_t geartab[] = {
  37     0x67ed26b7, 0x32da500c, 0x53d0fee0, 0xce387dc7, 0xcd406d90, 0x2e83a4d4,
  38     0x9fc9a38d, 0xb67259dc, 0xca6b1722, 0x6d2ea08c, 0x235cea2e, 0x3149bb5f,
  39     0x1beda787, 0x2a6b77d5, 0x2f22d9ac, 0x91fc0544, 0xe413acfa, 0x5a30ff7a,
  40     0xad6fdde0, 0x444fd0f5, 0x7ad87864, 0x58c5ff05, 0x8d2ec336, 0x2371f853,
  41     0x550f8572, 0x6aa448dd, 0x7c9ddbcf, 0x95221e14, 0x2a82ec33, 0xcbec5a78,
  42     0xc6795a0d, 0x243995b7, 0x1c909a2f, 0x4fded51c, 0x635d334b, 0x0e2b9999,
  43     0x2702968d, 0x856de1d5, 0x3325d60e, 0xeb6a7502, 0xec2a9844, 0x0905835a,
  44     0xa1820375, 0xa4be5cab, 0x96a6c058, 0x2c2ccd70, 0xba40fce3, 0xd794c46b,
  45     0x8fbae83e, 0xc3aa7899, 0x3d3ff8ed, 0xa0d42b5b, 0x571c0c97, 0xd2811516,
  46     0xf7e7b96c, 0x4fd2fcbd, 0xe2fdec94, 0x282cc436, 0x78e8e95c, 0x80a3b613,
  47     0xcfbee20c, 0xd4a32d1c, 0x2a12ff13, 0x6af82936, 0xe5630258, 0x8efa6a98,
  48     0x294fb2d1, 0xdeb57086, 0x5f0fddb3, 0xeceda7ce, 0x4c87305f, 0x3a6d3307,
  49     0xe22d2942, 0x9d060217, 0x1e42ed02, 0xb6f63b52, 0x4367f39f, 0x055cf262,
  50     0x03a461b2, 0x5ef9e382, 0x386bc03a, 0x2a1e79c7, 0xf1a0058b, 0xd4d2dea9,
  51     0x56baf37d, 0x5daff6cc, 0xf03a951d, 0xaef7de45, 0xa8f4581e, 0x3960b555,
  52     0xffbfff6d, 0xbe702a23, 0x8f5b6d6f, 0x061739fb, 0x98696f47, 0x3fd596d4,
  53     0x151eac6b, 0xa9fcc4f5, 0x69181a12, 0x3ac5a107, 0xb5198fe7, 0x96bcb1da,
  54     0x1b5ddf8e, 0xc757d650, 0x65865c3a, 0x8fc0a41a, 0x87435536, 0x99eda6f2,
  55     0x41874794, 0x29cff4e8, 0xb70efd9a, 0x3103f6e7, 0x84d2453b, 0x15a450bd,
  56     0x74f49af1, 0x60f664b1, 0xa1c86935, 0xfdafbce1, 0xe36353e3, 0x5d9ba739,
  57     0xbc0559ba, 0x708b0054, 0xd41d808c, 0xb2f31723, 0x9027c41f, 0xf136d165,
  58     0xb5374b12, 0x9420a6ac, 0x273958b6, 0xe6c2fad0, 0xebdc1f21, 0xfb33af8b,
  59     0xc71c25cd, 0xe9a2d8e5, 0xbeb38a50, 0xbceb7cc2, 0x4e4e73f0, 0xcd6c251d,
  60     0xde4c032c, 0x4b04ac30, 0x725b8b21, 0x4eb8c33b, 0x20d07b75, 0x0567aa63,
  61     0xb56b2bb7, 0xc1f5fd3a, 0xcafd35ca, 0x470dd4da, 0xfe4f94cd, 0xfb8de424,
  62     0xe8dbcf40, 0xfe50a37a, 0x62db5b5d, 0xf32f4ab6, 0x2c4a8a51, 0x18473dc0,
  63     0xfe0cbb6e, 0xfe399efd, 0xdf34ecc9, 0x6ccd5055, 0x46097073, 0x139135c2,
  64     0x721c76f6, 0x1c6a94b4, 0x6eee014d, 0x8a508e02, 0x3da538f5, 0x280d394f,
  65     0x5248a0c4, 0x3ce94c6c, 0x9a71ad3a, 0x8493dd05, 0xe43f0ab6, 0x18e4ed42,
  66     0x6c5c0e09, 0x42b06ec9, 0x8d330343, 0xa45b6f59, 0x2a573c0c, 0xd7fd3de6,
  67     0xeedeab68, 0x5c84dafc, 0xbbd1b1a8, 0xa3ce1ad1, 0x85b70bed, 0xb6add07f,
  68     0xa531309c, 0x8f8ab852, 0x564de332, 0xeac9ed0c, 0x73da402c, 0x3ec52761,
  69     0x43af2f4d, 0xd6ff45c8, 0x4c367462, 0xd553bd6a, 0x44724855, 0x3b2aa728,
  70     0x56e5eb65, 0xeaf16173, 0x33fa42ff, 0xd714bb5d, 0xfbd0a3b9, 0xaf517134,
  71     0x9416c8cd, 0x534cf94f, 0x548947c2, 0x34193569, 0x32f4389a, 0xfe7028bc,
  72     0xed73b1ed, 0x9db95770, 0x468e3922, 0x0440c3cd, 0x60059a62, 0x33504562,
  73     0x2b229fbd, 0x5174dca5, 0xf7028752, 0xd63c6aa8, 0x31276f38, 0x0646721c,
  74     0xb0191da8, 0xe00e6de0, 0x9eac1a6e, 0x9f7628a5, 0xed6c06ea, 0x0bb8af15,
  75     0xf119fb12, 0x38693c1c, 0x732bc0fe, 0x84953275, 0xb82ec888, 0x33a4f1b3,
  76     0x3099835e, 0x028a8782, 0x5fdd51d7, 0xc6c717b3, 0xb06caf71, 0x17c8c111,
  77     0x61bad754, 0x9fd03061, 0xe09df1af, 0x3bc9eb73, 0x85878413, 0x9889aaf2,
  78     0x3f5a9e46, 0x42c9f01f, 0x9984a4f4, 0xd5de43cc, 0xd294daed, 0xbecba2d2,
  79     0xf1f6e72c, 0x5551128a, 0x83af87e2, 0x6f0342ba,
  80 };
  81
  82 static uint64_t
  83 hashblk(const unsigned char *p, off_t n)
  84 {
  85         unsigned char buf[SHA1_DIGEST_LENGTH];
  86         uint64_t h;
  87         SHA1_CTX ctx;
  88         SHA1Init(&ctx);
  89         SHA1Update(&ctx, p, n);
  90         SHA1Final(buf, &ctx);
  91         memcpy(&h, buf, sizeof(h));
  92         return be64toh(h);
  93 }
  94
  95 static const struct got_error *
  96 addblk(struct got_delta_table *dt, FILE *f, off_t file_offset0, off_t len,
  97     off_t offset, uint64_t h)
  98 {
  99         const struct got_error *err = NULL;
 100         int i;
 101         uint8_t buf[GOT_DELTIFY_MAXCHUNK];
 102         uint8_t buf2[GOT_DELTIFY_MAXCHUNK];
 103         size_t r = 0;
 104
 105         if (len == 0)
 106                 return NULL;
 107
 108         i = h % dt->nalloc;
 109         while (dt->blocks[i].len != 0) {
 110                 /*
 111                  * Avoid adding duplicate blocks.
 112                  * NB: A matching hash is insufficient for detecting equality.
 113                  * The hash can only detect inequality.
 114                  */
 115                 if (len == dt->blocks[i].len && h == dt->blocks[i].hash) {
 116                         if (r == 0) {
 117                                 if (fseeko(f, file_offset0 + offset, SEEK_SET) == -1)
 118                                         return got_error_from_errno("fseeko");
 119                                 r = fread(buf, 1, len, f);
 120                                 if (r != len) {
 121                                         if (!ferror(f))
 122                                                 return NULL;
 123                                         return got_ferror(f, GOT_ERR_IO);
 124                                 }
 125                         }
 126                         if (fseeko(f, file_offset0 + dt->blocks[i].offset,
 127                             SEEK_SET) == -1)
 128                                 return got_error_from_errno("fseeko");
 129                         if (fread(buf2, 1, len, f) != len)
 130                                 return got_ferror(f, GOT_ERR_IO);
 131                         if (memcmp(buf, buf2, len) == 0)
 132                                 return NULL;
 133                 }
 134
 135                 i = (i + 1) % dt->nalloc;
 136         }
 137         assert(dt->blocks[i].len == 0);
 138         dt->blocks[i].len = len;
 139         dt->blocks[i].offset = offset;
 140         dt->blocks[i].hash = h;
 141         dt->nblocks++;
 142         if (dt->nalloc < dt->nblocks + 64) {
 143                 struct got_delta_block *db;
 144                 size_t old_size = dt->nalloc;
 145                 db = dt->blocks;
 146                 dt->blocks = calloc(dt->nalloc + 64,
 147                     sizeof(struct got_delta_block));
 148                 if (dt->blocks == NULL) {
 149                         err = got_error_from_errno("calloc");
 150                         dt->blocks = db;
 151                         return err;
 152                 }
 153                 dt->nalloc += 64;
 154                 /*
 155                  * Recompute all block positions. Hash-based indices of blocks
 156                  * in the array depend on the allocated length of the array.
 157                  */
 158                 dt->nblocks = 0;
 159                 for (i = 0; i < old_size; i++) {
 160                         if (db[i].len == 0)
 161                                 continue;
 162                         err = addblk(dt, f, file_offset0, db[i].len,
 163                             db[i].offset, db[i].hash);
 164                         if (err)
 165                                 break;
 166                 }
 167                 free(db);
 168         }
 169
 170         return err;
 171 }
 172
 173 static const struct got_error *
 174 lookupblk(struct got_delta_block **block, struct got_delta_table *dt,
 175     unsigned char *p, off_t len, FILE *basefile, off_t basefile_offset0)
 176 {
 177         int i;
 178         uint64_t h;
 179         uint8_t buf[GOT_DELTIFY_MAXCHUNK];
 180         size_t r;
 181
 182         *block = NULL;
 183
 184         h = hashblk(p, len);
 185         for (i = h % dt->nalloc; dt->blocks[i].len != 0;
 186              i = (i + 1) % dt->nalloc) {
 187                 if (dt->blocks[i].hash != h ||
 188                     dt->blocks[i].len != len)
 189                         continue;
 190                 if (fseeko(basefile, basefile_offset0 + dt->blocks[i].offset,
 191                     SEEK_SET) == -1)
 192                         return got_error_from_errno("fseeko");
 193                 r = fread(buf, 1, len, basefile);
 194                 if (r != len)
 195                         return got_ferror(basefile, GOT_ERR_IO);
 196                 if (memcmp(p, buf, len) == 0) {
 197                         *block = &dt->blocks[i];
 198                         break;
 199                 }
 200         }
 201         return NULL;
 202 }
 203
 204 static const struct got_error *
 205 nextblk(uint8_t *buf, off_t *blocklen, FILE *f)
 206 {
 207         uint32_t gh;
 208         const unsigned char *p;
 209         size_t r;
 210         off_t pos = ftello(f);
 211
 212         *blocklen = 0;
 213
 214         r = fread(buf, 1, GOT_DELTIFY_MAXCHUNK, f);
 215         if (r == 0 && ferror(f))
 216                 return got_ferror(f, GOT_ERR_IO);
 217         if (r < GOT_DELTIFY_MINCHUNK)
 218                 return NULL; /* no more delta-worthy blocks left */
 219
 220         /* Got a deltifiable block. Find the split-point where it ends. */
 221         p = buf + GOT_DELTIFY_MINCHUNK;
 222         gh = 0;
 223         while (p != buf + r) {
 224                 gh = (gh << 1) + geartab[*p++];
 225                 if ((gh & GOT_DELTIFY_SPLITMASK) == 0)
 226                         break;
 227         }
 228
 229         *blocklen = (p - buf);
 230         if (fseeko(f, pos + *blocklen, SEEK_SET) == -1)
 231                 return got_error_from_errno("fseeko");
 232
 233         return NULL;
 234 }
 235
 236 const struct got_error *
 237 got_deltify_init(struct got_delta_table **dt, FILE *f, off_t fileoffset,
 238     off_t filesize)
 239 {
 240         const struct got_error *err = NULL;
 241         uint64_t h;
 242         const off_t offset0 = fileoffset;
 243
 244         *dt = calloc(1, sizeof(**dt));
 245         if (*dt == NULL)
 246                 return got_error_from_errno("calloc");
 247
 248         (*dt)->nblocks = 0;
 249         (*dt)->nalloc = 128;
 250         (*dt)->blocks = calloc((*dt)->nalloc, sizeof(struct got_delta_block));
 251         if ((*dt)->blocks == NULL) {
 252                 err = got_error_from_errno("calloc");
 253                 goto done;
 254         }
 255
 256         if (fseeko(f, fileoffset, SEEK_SET) == -1)
 257                 return got_error_from_errno("fseeko");
 258
 259         while (fileoffset < filesize) {
 260                 uint8_t buf[GOT_DELTIFY_MAXCHUNK];
 261                 off_t blocklen;
 262                 err = nextblk(buf, &blocklen, f);
 263                 if (err)
 264                         goto done;
 265                 if (blocklen == 0)
 266                         break;
 267                 h = hashblk(buf, blocklen);
 268                 err = addblk(*dt, f, offset0, blocklen,
 269                     fileoffset - offset0, h);
 270                 if (err)
 271                         goto done;
 272                 fileoffset += blocklen;
 273                 if (fseeko(f, fileoffset, SEEK_SET) == -1)
 274                         return got_error_from_errno("fseeko");
 275         }
 276 done:
 277         if (err) {
 278                 free((*dt)->blocks);
 279                 free(*dt);
 280                 *dt = NULL;
 281         }
 282
 283         return err;
 284 }
 285
 286 void
 287 got_deltify_free(struct got_delta_table *dt)
 288 {
 289         if (dt == NULL)
 290                 return;
 291         free(dt->blocks);
 292         free(dt);
 293 }
 294
 295 static const struct got_error *
 296 emitdelta(struct got_delta_instruction **deltas, size_t *nalloc, int *ndeltas,
 297     const size_t alloc_chunk_size, int copy, off_t offset, off_t len)
 298 {
 299         struct got_delta_instruction *d, *p;
 300
 301         if (*nalloc < *ndeltas + alloc_chunk_size) {
 302                 p = reallocarray(*deltas, *nalloc + alloc_chunk_size,
 303                     sizeof(struct got_delta_instruction));
 304                 if (p == NULL)
 305                         return got_error_from_errno("realloc");
 306                 *deltas = p;
 307                 *nalloc += alloc_chunk_size;
 308         }
 309         *ndeltas += 1;
 310         d = &(*deltas)[*ndeltas - 1];
 311         d->copy = copy;
 312         d->offset = offset;
 313         d->len = len;
 314         return NULL;
 315 }
 316
 317 static const struct got_error *
 318 stretchblk(FILE *basefile, off_t base_offset0, struct got_delta_block *block,
 319     FILE *f, off_t filesize, off_t *blocklen)
 320 {
 321         uint8_t basebuf[GOT_DELTIFY_MAXCHUNK], buf[GOT_DELTIFY_MAXCHUNK];
 322         size_t base_r, r, i;
 323         int buf_equal = 1;
 324
 325         if (fseeko(basefile, base_offset0 + block->offset + *blocklen,
 326             SEEK_SET) == -1)
 327                 return got_error_from_errno("fseeko");
 328
 329         while (buf_equal && *blocklen < (1 << 24) - 1) {
 330                 base_r = fread(basebuf, 1, sizeof(basebuf), basefile);
 331                 if (base_r == 0) {
 332                         if (ferror(basefile))
 333                                 return got_ferror(basefile, GOT_ERR_IO);
 334                         break;
 335                 }
 336                 r = fread(buf, 1, sizeof(buf), f);
 337                 if (r == 0) {
 338                         if (ferror(f))
 339                                 return got_ferror(f, GOT_ERR_IO);
 340                         break;
 341                 }
 342                 for (i = 0; i < MIN(base_r, r); i++) {
 343                         if (buf[i] != basebuf[i]) {
 344                                 buf_equal = 0;
 345                                 break;
 346                         }
 347                         (*blocklen)++;
 348                 }
 349         }
 350
 351         return NULL;
 352 }
 353
 354 const struct got_error *
 355 got_deltify(struct got_delta_instruction **deltas, int *ndeltas,
 356     FILE *f, off_t fileoffset, off_t filesize,
 357     struct got_delta_table *dt, FILE *basefile,
 358     off_t basefile_offset0, off_t basefile_size)
 359 {
 360         const struct got_error *err = NULL;
 361         const off_t offset0 = fileoffset;
 362         size_t nalloc = 0;
 363         const size_t alloc_chunk_size = 64;
 364
 365         *deltas = NULL;
 366         *ndeltas = 0;
 367
 368         /*
 369          * offset0 indicates where data to be deltified begins.
 370          * For example, we want to avoid deltifying a Git object header at
 371          * the beginning of the file.
 372          */
 373         if (fseeko(f, offset0, SEEK_SET) == -1)
 374                 return got_error_from_errno("fseeko");
 375
 376         *deltas = reallocarray(NULL, alloc_chunk_size,
 377             sizeof(struct got_delta_instruction));
 378         if (*deltas == NULL)
 379                 return got_error_from_errno("reallocarray");
 380         nalloc = alloc_chunk_size;
 381
 382         while (fileoffset < filesize) {
 383                 uint8_t buf[GOT_DELTIFY_MAXCHUNK];
 384                 off_t blocklen;
 385                 struct got_delta_block *block;
 386                 err = nextblk(buf, &blocklen, f);
 387                 if (err)
 388                         break;
 389                 if (blocklen == 0) {
 390                         /* Source remainder from the file itself. */
 391                         if (fileoffset < filesize) {
 392                                 err = emitdelta(deltas, &nalloc, ndeltas,
 393                                     alloc_chunk_size, 0, fileoffset - offset0,
 394                                     filesize - fileoffset);
 395                         }
 396                         break;
 397                 }
 398                 err = lookupblk(&block, dt, buf, blocklen, basefile,
 399                     basefile_offset0);
 400                 if (err)
 401                         break;
 402                 if (block != NULL) {
 403                         /*
 404                          * We have found a matching block in the delta base.
 405                          * Attempt to stretch the block as far as possible and
 406                          * generate a copy instruction.
 407                          */
 408                         err = stretchblk(basefile, basefile_offset0, block,
 409                             f, filesize, &blocklen);
 410                         if (err)
 411                                 break;
 412                         err = emitdelta(deltas, &nalloc, ndeltas,
 413                             alloc_chunk_size, 1, block->offset, blocklen);
 414                         if (err)
 415                                 break;
 416                 } else {
 417                         /*
 418                          * No match.
 419                          * This block needs to be sourced from the file itself.
 420                          */
 421                         err = emitdelta(deltas, &nalloc, ndeltas,
 422                             alloc_chunk_size, 0, fileoffset - offset0, blocklen);
 423                         if (err)
 424                                 break;
 425                 }
 426                 fileoffset += blocklen;
 427                 if (fseeko(f, fileoffset, SEEK_SET) == -1) {
 428                         err = got_error_from_errno("fseeko");
 429                         break;
 430                 }
 431         }
 432
 433         if (err) {
 434                 free(*deltas);
 435                 *deltas = NULL;
 436                 *ndeltas = 0;
 437         }
 438         return err;
 439 }