2 * Copyright (c) 2020 Ori Bernstein
3 * Copyright (c) 2021 Stefan Sperling <stsp@openbsd.org>
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.
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.
18 #include <sys/types.h>
28 #include "got_error.h"
30 #include "got_lib_deltify.h"
33 #define MIN(_a,_b) ((_a) < (_b) ? (_a) : (_b))
37 * The algorihm used here is FastCDC (Fast Content-Defined Chunking)
38 * https://www.usenix.org/conference/atc16/technical-sessions/presentation/xia
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,
88 hashblk(const unsigned char *p, off_t n)
90 unsigned char buf[SHA1_DIGEST_LENGTH];
94 SHA1Update(&ctx, p, n);
96 memcpy(&h, buf, sizeof(h));
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)
104 const struct got_error *err = NULL;
106 uint8_t buf[GOT_DELTIFY_MAXCHUNK];
107 uint8_t buf2[GOT_DELTIFY_MAXCHUNK];
114 while (dt->blocks[i].len != 0) {
116 * Avoid adding duplicate blocks.
117 * NB: A matching hash is insufficient for detecting equality.
118 * The hash can only detect inequality.
120 if (len == dt->blocks[i].len && h == dt->blocks[i].hash) {
122 if (fseeko(f, file_offset0 + offset, SEEK_SET) == -1)
123 return got_error_from_errno("fseeko");
124 r = fread(buf, 1, len, f);
128 return got_ferror(f, GOT_ERR_IO);
131 if (fseeko(f, file_offset0 + dt->blocks[i].offset,
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)
140 i = (i + 1) % dt->nalloc;
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;
147 if (dt->nalloc < dt->nblocks + 64) {
148 struct got_delta_block *db;
149 size_t old_size = dt->nalloc;
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");
160 * Recompute all block positions. Hash-based indices of blocks
161 * in the array depend on the allocated length of the array.
164 for (i = 0; i < old_size; i++) {
167 err = addblk(dt, f, file_offset0, db[i].len,
168 db[i].offset, db[i].hash);
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)
184 uint8_t buf[GOT_DELTIFY_MAXCHUNK];
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)
195 if (fseeko(basefile, basefile_offset0 + dt->blocks[i].offset,
197 return got_error_from_errno("fseeko");
198 r = fread(buf, 1, len, basefile);
200 return got_ferror(basefile, GOT_ERR_IO);
201 if (memcmp(p, buf, len) == 0) {
202 *block = &dt->blocks[i];
209 static const struct got_error *
210 nextblk(uint8_t *buf, off_t *blocklen, FILE *f)
213 const unsigned char *p;
215 off_t pos = ftello(f);
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 */
225 /* Got a deltifiable block. Find the split-point where it ends. */
226 p = buf + GOT_DELTIFY_MINCHUNK;
228 while (p != buf + r) {
229 gh = (gh << 1) + geartab[*p++];
230 if ((gh & GOT_DELTIFY_SPLITMASK) == 0)
234 *blocklen = (p - buf);
235 if (fseeko(f, pos + *blocklen, SEEK_SET) == -1)
236 return got_error_from_errno("fseeko");
241 const struct got_error *
242 got_deltify_init(struct got_delta_table **dt, FILE *f, off_t fileoffset,
245 const struct got_error *err = NULL;
247 const off_t offset0 = fileoffset;
249 *dt = calloc(1, sizeof(**dt));
251 return got_error_from_errno("calloc");
255 (*dt)->blocks = calloc((*dt)->nalloc, sizeof(struct got_delta_block));
256 if ((*dt)->blocks == NULL) {
257 err = got_error_from_errno("calloc");
261 if (fseeko(f, fileoffset, SEEK_SET) == -1)
262 return got_error_from_errno("fseeko");
264 while (fileoffset < filesize) {
265 uint8_t buf[GOT_DELTIFY_MAXCHUNK];
267 err = nextblk(buf, &blocklen, f);
272 h = hashblk(buf, blocklen);
273 err = addblk(*dt, f, offset0, blocklen,
274 fileoffset - offset0, h);
277 fileoffset += blocklen;
278 if (fseeko(f, fileoffset, SEEK_SET) == -1)
279 return got_error_from_errno("fseeko");
292 got_deltify_free(struct got_delta_table *dt)
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)
304 struct got_delta_instruction *d, *p;
306 if (*nalloc < *ndeltas + alloc_chunk_size) {
307 p = reallocarray(*deltas, *nalloc + alloc_chunk_size,
308 sizeof(struct got_delta_instruction));
310 return got_error_from_errno("reallocarray");
312 *nalloc += alloc_chunk_size;
315 d = &(*deltas)[*ndeltas - 1];
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)
326 uint8_t basebuf[GOT_DELTIFY_MAXCHUNK], buf[GOT_DELTIFY_MAXCHUNK];
330 if (fseeko(basefile, base_offset0 + block->offset + *blocklen,
332 return got_error_from_errno("fseeko");
334 while (buf_equal && *blocklen < (1 << 24) - 1) {
335 base_r = fread(basebuf, 1, sizeof(basebuf), basefile);
337 if (ferror(basefile))
338 return got_ferror(basefile, GOT_ERR_IO);
341 r = fread(buf, 1, sizeof(buf), f);
344 return got_ferror(f, GOT_ERR_IO);
347 for (i = 0; i < MIN(base_r, r); i++) {
348 if (buf[i] != basebuf[i]) {
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)
365 const struct got_error *err = NULL;
366 const off_t offset0 = fileoffset;
368 const size_t alloc_chunk_size = 64;
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.
378 if (fseeko(f, offset0, SEEK_SET) == -1)
379 return got_error_from_errno("fseeko");
381 *deltas = reallocarray(NULL, alloc_chunk_size,
382 sizeof(struct got_delta_instruction));
384 return got_error_from_errno("reallocarray");
385 nalloc = alloc_chunk_size;
387 while (fileoffset < filesize) {
388 uint8_t buf[GOT_DELTIFY_MAXCHUNK];
390 struct got_delta_block *block;
391 err = nextblk(buf, &blocklen, f);
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);
403 err = lookupblk(&block, dt, buf, blocklen, basefile,
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.
413 err = stretchblk(basefile, basefile_offset0, block,
414 f, filesize, &blocklen);
417 err = emitdelta(deltas, &nalloc, ndeltas,
418 alloc_chunk_size, 1, block->offset, blocklen);
424 * This block needs to be sourced from the file itself.
426 err = emitdelta(deltas, &nalloc, ndeltas,
427 alloc_chunk_size, 0, fileoffset - offset0, blocklen);
431 fileoffset += blocklen;
432 if (fseeko(f, fileoffset, SEEK_SET) == -1) {
433 err = got_error_from_errno("fseeko");