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 /*
  37  * The algorihm used here is FastCDC (Fast Content-Defined Chunking)
  38  * https://www.usenix.org/conference/atc16/technical-sessions/presentation/xia
  39  */
  40
  41 static uint32_t geartab[256] = {
  42     0x67ed26b7, 0x32da500c, 0x53d0fee0, 0xce387dc7, 0xcd406d90, 0x2e83a4d4,
  43     0x9fc9a38d, 0xb67259dc, 0xca6b1722, 0x6d2ea08c, 0x235cea2e, 0x3149bb5f,
  44     0x1beda787, 0x2a6b77d5, 0x2f22d9ac, 0x91fc0544, 0xe413acfa, 0x5a30ff7a,
  45     0xad6fdde0, 0x444fd0f5, 0x7ad87864, 0x58c5ff05, 0x8d2ec336, 0x2371f853,
  46     0x550f8572, 0x6aa448dd, 0x7c9ddbcf, 0x95221e14, 0x2a82ec33, 0xcbec5a78,
  47     0xc6795a0d, 0x243995b7, 0x1c909a2f, 0x4fded51c, 0x635d334b, 0x0e2b9999,
  48     0x2702968d, 0x856de1d5, 0x3325d60e, 0xeb6a7502, 0xec2a9844, 0x0905835a,
  49     0xa1820375, 0xa4be5cab, 0x96a6c058, 0x2c2ccd70, 0xba40fce3, 0xd794c46b,
  50     0x8fbae83e, 0xc3aa7899, 0x3d3ff8ed, 0xa0d42b5b, 0x571c0c97, 0xd2811516,
  51     0xf7e7b96c, 0x4fd2fcbd, 0xe2fdec94, 0x282cc436, 0x78e8e95c, 0x80a3b613,
  52     0xcfbee20c, 0xd4a32d1c, 0x2a12ff13, 0x6af82936, 0xe5630258, 0x8efa6a98,
  53     0x294fb2d1, 0xdeb57086, 0x5f0fddb3, 0xeceda7ce, 0x4c87305f, 0x3a6d3307,
  54     0xe22d2942, 0x9d060217, 0x1e42ed02, 0xb6f63b52, 0x4367f39f, 0x055cf262,
  55     0x03a461b2, 0x5ef9e382, 0x386bc03a, 0x2a1e79c7, 0xf1a0058b, 0xd4d2dea9,
  56     0x56baf37d, 0x5daff6cc, 0xf03a951d, 0xaef7de45, 0xa8f4581e, 0x3960b555,
  57     0xffbfff6d, 0xbe702a23, 0x8f5b6d6f, 0x061739fb, 0x98696f47, 0x3fd596d4,
  58     0x151eac6b, 0xa9fcc4f5, 0x69181a12, 0x3ac5a107, 0xb5198fe7, 0x96bcb1da,
  59     0x1b5ddf8e, 0xc757d650, 0x65865c3a, 0x8fc0a41a, 0x87435536, 0x99eda6f2,
  60     0x41874794, 0x29cff4e8, 0xb70efd9a, 0x3103f6e7, 0x84d2453b, 0x15a450bd,
  61     0x74f49af1, 0x60f664b1, 0xa1c86935, 0xfdafbce1, 0xe36353e3, 0x5d9ba739,
  62     0xbc0559ba, 0x708b0054, 0xd41d808c, 0xb2f31723, 0x9027c41f, 0xf136d165,
  63     0xb5374b12, 0x9420a6ac, 0x273958b6, 0xe6c2fad0, 0xebdc1f21, 0xfb33af8b,
  64     0xc71c25cd, 0xe9a2d8e5, 0xbeb38a50, 0xbceb7cc2, 0x4e4e73f0, 0xcd6c251d,
  65     0xde4c032c, 0x4b04ac30, 0x725b8b21, 0x4eb8c33b, 0x20d07b75, 0x0567aa63,
  66     0xb56b2bb7, 0xc1f5fd3a, 0xcafd35ca, 0x470dd4da, 0xfe4f94cd, 0xfb8de424,
  67     0xe8dbcf40, 0xfe50a37a, 0x62db5b5d, 0xf32f4ab6, 0x2c4a8a51, 0x18473dc0,
  68     0xfe0cbb6e, 0xfe399efd, 0xdf34ecc9, 0x6ccd5055, 0x46097073, 0x139135c2,
  69     0x721c76f6, 0x1c6a94b4, 0x6eee014d, 0x8a508e02, 0x3da538f5, 0x280d394f,
  70     0x5248a0c4, 0x3ce94c6c, 0x9a71ad3a, 0x8493dd05, 0xe43f0ab6, 0x18e4ed42,
  71     0x6c5c0e09, 0x42b06ec9, 0x8d330343, 0xa45b6f59, 0x2a573c0c, 0xd7fd3de6,
  72     0xeedeab68, 0x5c84dafc, 0xbbd1b1a8, 0xa3ce1ad1, 0x85b70bed, 0xb6add07f,
  73     0xa531309c, 0x8f8ab852, 0x564de332, 0xeac9ed0c, 0x73da402c, 0x3ec52761,
  74     0x43af2f4d, 0xd6ff45c8, 0x4c367462, 0xd553bd6a, 0x44724855, 0x3b2aa728,
  75     0x56e5eb65, 0xeaf16173, 0x33fa42ff, 0xd714bb5d, 0xfbd0a3b9, 0xaf517134,
  76     0x9416c8cd, 0x534cf94f, 0x548947c2, 0x34193569, 0x32f4389a, 0xfe7028bc,
  77     0xed73b1ed, 0x9db95770, 0x468e3922, 0x0440c3cd, 0x60059a62, 0x33504562,
  78     0x2b229fbd, 0x5174dca5, 0xf7028752, 0xd63c6aa8, 0x31276f38, 0x0646721c,
  79     0xb0191da8, 0xe00e6de0, 0x9eac1a6e, 0x9f7628a5, 0xed6c06ea, 0x0bb8af15,
  80     0xf119fb12, 0x38693c1c, 0x732bc0fe, 0x84953275, 0xb82ec888, 0x33a4f1b3,
  81     0x3099835e, 0x028a8782, 0x5fdd51d7, 0xc6c717b3, 0xb06caf71, 0x17c8c111,
  82     0x61bad754, 0x9fd03061, 0xe09df1af, 0x3bc9eb73, 0x85878413, 0x9889aaf2,
  83     0x3f5a9e46, 0x42c9f01f, 0x9984a4f4, 0xd5de43cc, 0xd294daed, 0xbecba2d2,
  84     0xf1f6e72c, 0x5551128a, 0x83af87e2, 0x6f0342ba,
  85 };
  86
  87 static uint64_t
  88 hashblk(const unsigned char *p, off_t n)
  89 {
  90         unsigned char buf[SHA1_DIGEST_LENGTH];
  91         uint64_t h;
  92         SHA1_CTX ctx;
  93         SHA1Init(&ctx);
  94         SHA1Update(&ctx, p, n);
  95         SHA1Final(buf, &ctx);
  96         memcpy(&h, buf, sizeof(h));
  97         return be64toh(h);
  98 }
  99
 100 static const struct got_error *
 101 addblk(struct got_delta_table *dt, FILE *f, off_t file_offset0, off_t len,
 102     off_t offset, uint64_t h)
 103 {
 104         const struct got_error *err = NULL;
 105         int i;
 106         uint8_t buf[GOT_DELTIFY_MAXCHUNK];
 107         uint8_t buf2[GOT_DELTIFY_MAXCHUNK];
 108         size_t r = 0;
 109
 110         if (len == 0)
 111                 return NULL;
 112
 113         i = h % dt->nalloc;
 114         while (dt->blocks[i].len != 0) {
 115                 /*
 116                  * Avoid adding duplicate blocks.
 117                  * NB: A matching hash is insufficient for detecting equality.
 118                  * The hash can only detect inequality.
 119                  */
 120                 if (len == dt->blocks[i].len && h == dt->blocks[i].hash) {
 121                         if (r == 0) {
 122                                 if (fseeko(f, file_offset0 + offset, SEEK_SET) == -1)
 123                                         return got_error_from_errno("fseeko");
 124                                 r = fread(buf, 1, len, f);
 125                                 if (r != len) {
 126                                         if (!ferror(f))
 127                                                 return NULL;
 128                                         return got_ferror(f, GOT_ERR_IO);
 129                                 }
 130                         }
 131                         if (fseeko(f, file_offset0 + dt->blocks[i].offset,
 132                             SEEK_SET) == -1)
 133                                 return got_error_from_errno("fseeko");
 134                         if (fread(buf2, 1, len, f) != len)
 135                                 return got_ferror(f, GOT_ERR_IO);
 136                         if (memcmp(buf, buf2, len) == 0)
 137                                 return NULL;
 138                 }
 139
 140                 i = (i + 1) % dt->nalloc;
 141         }
 142         assert(dt->blocks[i].len == 0);
 143         dt->blocks[i].len = len;
 144         dt->blocks[i].offset = offset;
 145         dt->blocks[i].hash = h;
 146         dt->nblocks++;
 147         if (dt->nalloc < dt->nblocks + 64) {
 148                 struct got_delta_block *db;
 149                 size_t old_size = dt->nalloc;
 150                 db = dt->blocks;
 151                 dt->blocks = calloc(dt->nalloc + 64,
 152                     sizeof(struct got_delta_block));
 153                 if (dt->blocks == NULL) {
 154                         err = got_error_from_errno("calloc");
 155                         dt->blocks = db;
 156                         return err;
 157                 }
 158                 dt->nalloc += 64;
 159                 /*
 160                  * Recompute all block positions. Hash-based indices of blocks
 161                  * in the array depend on the allocated length of the array.
 162                  */
 163                 dt->nblocks = 0;
 164                 for (i = 0; i < old_size; i++) {
 165                         if (db[i].len == 0)
 166                                 continue;
 167                         err = addblk(dt, f, file_offset0, db[i].len,
 168                             db[i].offset, db[i].hash);
 169                         if (err)
 170                                 break;
 171                 }
 172                 free(db);
 173         }
 174
 175         return err;
 176 }
 177
 178 static const struct got_error *
 179 lookupblk(struct got_delta_block **block, struct got_delta_table *dt,
 180     unsigned char *p, off_t len, FILE *basefile, off_t basefile_offset0)
 181 {
 182         int i;
 183         uint64_t h;
 184         uint8_t buf[GOT_DELTIFY_MAXCHUNK];
 185         size_t r;
 186
 187         *block = NULL;
 188
 189         h = hashblk(p, len);
 190         for (i = h % dt->nalloc; dt->blocks[i].len != 0;
 191              i = (i + 1) % dt->nalloc) {
 192                 if (dt->blocks[i].hash != h ||
 193                     dt->blocks[i].len != len)
 194                         continue;
 195                 if (fseeko(basefile, basefile_offset0 + dt->blocks[i].offset,
 196                     SEEK_SET) == -1)
 197                         return got_error_from_errno("fseeko");
 198                 r = fread(buf, 1, len, basefile);
 199                 if (r != len)
 200                         return got_ferror(basefile, GOT_ERR_IO);
 201                 if (memcmp(p, buf, len) == 0) {
 202                         *block = &dt->blocks[i];
 203                         break;
 204                 }
 205         }
 206         return NULL;
 207 }
 208
 209 static const struct got_error *
 210 nextblk(uint8_t *buf, off_t *blocklen, FILE *f)
 211 {
 212         uint32_t gh;
 213         const unsigned char *p;
 214         size_t r;
 215         off_t pos = ftello(f);
 216
 217         *blocklen = 0;
 218
 219         r = fread(buf, 1, GOT_DELTIFY_MAXCHUNK, f);
 220         if (r == 0 && ferror(f))
 221                 return got_ferror(f, GOT_ERR_IO);
 222         if (r < GOT_DELTIFY_MINCHUNK)
 223                 return NULL; /* no more delta-worthy blocks left */
 224
 225         /* Got a deltifiable block. Find the split-point where it ends. */
 226         p = buf + GOT_DELTIFY_MINCHUNK;
 227         gh = 0;
 228         while (p != buf + r) {
 229                 gh = (gh << 1) + geartab[*p++];
 230                 if ((gh & GOT_DELTIFY_SPLITMASK) == 0)
 231                         break;
 232         }
 233
 234         *blocklen = (p - buf);
 235         if (fseeko(f, pos + *blocklen, SEEK_SET) == -1)
 236                 return got_error_from_errno("fseeko");
 237
 238         return NULL;
 239 }
 240
 241 const struct got_error *
 242 got_deltify_init(struct got_delta_table **dt, FILE *f, off_t fileoffset,
 243     off_t filesize)
 244 {
 245         const struct got_error *err = NULL;
 246         uint64_t h;
 247         const off_t offset0 = fileoffset;
 248
 249         *dt = calloc(1, sizeof(**dt));
 250         if (*dt == NULL)
 251                 return got_error_from_errno("calloc");
 252
 253         (*dt)->nblocks = 0;
 254         (*dt)->nalloc = 128;
 255         (*dt)->blocks = calloc((*dt)->nalloc, sizeof(struct got_delta_block));
 256         if ((*dt)->blocks == NULL) {
 257                 err = got_error_from_errno("calloc");
 258                 goto done;
 259         }
 260
 261         if (fseeko(f, fileoffset, SEEK_SET) == -1)
 262                 return got_error_from_errno("fseeko");
 263
 264         while (fileoffset < filesize) {
 265                 uint8_t buf[GOT_DELTIFY_MAXCHUNK];
 266                 off_t blocklen;
 267                 err = nextblk(buf, &blocklen, f);
 268                 if (err)
 269                         goto done;
 270                 if (blocklen == 0)
 271                         break;
 272                 h = hashblk(buf, blocklen);
 273                 err = addblk(*dt, f, offset0, blocklen,
 274                     fileoffset - offset0, h);
 275                 if (err)
 276                         goto done;
 277                 fileoffset += blocklen;
 278                 if (fseeko(f, fileoffset, SEEK_SET) == -1)
 279                         return got_error_from_errno("fseeko");
 280         }
 281 done:
 282         if (err) {
 283                 free((*dt)->blocks);
 284                 free(*dt);
 285                 *dt = NULL;
 286         }
 287
 288         return err;
 289 }
 290
 291 void
 292 got_deltify_free(struct got_delta_table *dt)
 293 {
 294         if (dt == NULL)
 295                 return;
 296         free(dt->blocks);
 297         free(dt);
 298 }
 299
 300 static const struct got_error *
 301 emitdelta(struct got_delta_instruction **deltas, size_t *nalloc, int *ndeltas,
 302     const size_t alloc_chunk_size, int copy, off_t offset, off_t len)
 303 {
 304         struct got_delta_instruction *d, *p;
 305
 306         if (*nalloc < *ndeltas + alloc_chunk_size) {
 307                 p = reallocarray(*deltas, *nalloc + alloc_chunk_size,
 308                     sizeof(struct got_delta_instruction));
 309                 if (p == NULL)
 310                         return got_error_from_errno("reallocarray");
 311                 *deltas = p;
 312                 *nalloc += alloc_chunk_size;
 313         }
 314         *ndeltas += 1;
 315         d = &(*deltas)[*ndeltas - 1];
 316         d->copy = copy;
 317         d->offset = offset;
 318         d->len = len;
 319         return NULL;
 320 }
 321
 322 static const struct got_error *
 323 stretchblk(FILE *basefile, off_t base_offset0, struct got_delta_block *block,
 324     FILE *f, off_t filesize, off_t *blocklen)
 325 {
 326         uint8_t basebuf[GOT_DELTIFY_MAXCHUNK], buf[GOT_DELTIFY_MAXCHUNK];
 327         size_t base_r, r, i;
 328         int buf_equal = 1;
 329
 330         if (fseeko(basefile, base_offset0 + block->offset + *blocklen,
 331             SEEK_SET) == -1)
 332                 return got_error_from_errno("fseeko");
 333
 334         while (buf_equal && *blocklen < (1 << 24) - 1) {
 335                 base_r = fread(basebuf, 1, sizeof(basebuf), basefile);
 336                 if (base_r == 0) {
 337                         if (ferror(basefile))
 338                                 return got_ferror(basefile, GOT_ERR_IO);
 339                         break;
 340                 }
 341                 r = fread(buf, 1, sizeof(buf), f);
 342                 if (r == 0) {
 343                         if (ferror(f))
 344                                 return got_ferror(f, GOT_ERR_IO);
 345                         break;
 346                 }
 347                 for (i = 0; i < MIN(base_r, r); i++) {
 348                         if (buf[i] != basebuf[i]) {
 349                                 buf_equal = 0;
 350                                 break;
 351                         }
 352                         (*blocklen)++;
 353                 }
 354         }
 355
 356         return NULL;
 357 }
 358
 359 const struct got_error *
 360 got_deltify(struct got_delta_instruction **deltas, int *ndeltas,
 361     FILE *f, off_t fileoffset, off_t filesize,
 362     struct got_delta_table *dt, FILE *basefile,
 363     off_t basefile_offset0, off_t basefile_size)
 364 {
 365         const struct got_error *err = NULL;
 366         const off_t offset0 = fileoffset;
 367         size_t nalloc = 0;
 368         const size_t alloc_chunk_size = 64;
 369
 370         *deltas = NULL;
 371         *ndeltas = 0;
 372
 373         /*
 374          * offset0 indicates where data to be deltified begins.
 375          * For example, we want to avoid deltifying a Git object header at
 376          * the beginning of the file.
 377          */
 378         if (fseeko(f, offset0, SEEK_SET) == -1)
 379                 return got_error_from_errno("fseeko");
 380
 381         *deltas = reallocarray(NULL, alloc_chunk_size,
 382             sizeof(struct got_delta_instruction));
 383         if (*deltas == NULL)
 384                 return got_error_from_errno("reallocarray");
 385         nalloc = alloc_chunk_size;
 386
 387         while (fileoffset < filesize) {
 388                 uint8_t buf[GOT_DELTIFY_MAXCHUNK];
 389                 off_t blocklen;
 390                 struct got_delta_block *block;
 391                 err = nextblk(buf, &blocklen, f);
 392                 if (err)
 393                         break;
 394                 if (blocklen == 0) {
 395                         /* Source remainder from the file itself. */
 396                         if (fileoffset < filesize) {
 397                                 err = emitdelta(deltas, &nalloc, ndeltas,
 398                                     alloc_chunk_size, 0, fileoffset - offset0,
 399                                     filesize - fileoffset);
 400                         }
 401                         break;
 402                 }
 403                 err = lookupblk(&block, dt, buf, blocklen, basefile,
 404                     basefile_offset0);
 405                 if (err)
 406                         break;
 407                 if (block != NULL) {
 408                         /*
 409                          * We have found a matching block in the delta base.
 410                          * Attempt to stretch the block as far as possible and
 411                          * generate a copy instruction.
 412                          */
 413                         err = stretchblk(basefile, basefile_offset0, block,
 414                             f, filesize, &blocklen);
 415                         if (err)
 416                                 break;
 417                         err = emitdelta(deltas, &nalloc, ndeltas,
 418                             alloc_chunk_size, 1, block->offset, blocklen);
 419                         if (err)
 420                                 break;
 421                 } else {
 422                         /*
 423                          * No match.
 424                          * This block needs to be sourced from the file itself.
 425                          */
 426                         err = emitdelta(deltas, &nalloc, ndeltas,
 427                             alloc_chunk_size, 0, fileoffset - offset0, blocklen);
 428                         if (err)
 429                                 break;
 430                 }
 431                 fileoffset += blocklen;
 432                 if (fseeko(f, fileoffset, SEEK_SET) == -1) {
 433                         err = got_error_from_errno("fseeko");
 434                         break;
 435                 }
 436         }
 437
 438         if (err) {
 439                 free(*deltas);
 440                 *deltas = NULL;
 441                 *ndeltas = 0;
 442         }
 443         return err;
 444 }