git

1
#define USE_THE_REPOSITORY_VARIABLE
2

3
#include "git-compat-util.h"
4
#include "gettext.h"
5
#include "pack-revindex.h"
6
#include "object-file.h"
7
#include "object-store-ll.h"
8
#include "packfile.h"
9
#include "strbuf.h"
10
#include "trace2.h"
11
#include "parse.h"
12
#include "midx.h"
13
#include "csum-file.h"
14

15
struct revindex_entry {
16
	off_t offset;
17
	unsigned int nr;
18
};
19

20
/*
21
 * Pack index for existing packs give us easy access to the offsets into
22
 * corresponding pack file where each object's data starts, but the entries
23
 * do not store the size of the compressed representation (uncompressed
24
 * size is easily available by examining the pack entry header).  It is
25
 * also rather expensive to find the sha1 for an object given its offset.
26
 *
27
 * The pack index file is sorted by object name mapping to offset;
28
 * this revindex array is a list of offset/index_nr pairs
29
 * ordered by offset, so if you know the offset of an object, next offset
30
 * is where its packed representation ends and the index_nr can be used to
31
 * get the object sha1 from the main index.
32
 */
33

34
/*
35
 * This is a least-significant-digit radix sort.
36
 *
37
 * It sorts each of the "n" items in "entries" by its offset field. The "max"
38
 * parameter must be at least as large as the largest offset in the array,
39
 * and lets us quit the sort early.
40
 */
41
static void sort_revindex(struct revindex_entry *entries, unsigned n, off_t max)
42
{
43
	/*
44
	 * We use a "digit" size of 16 bits. That keeps our memory
45
	 * usage reasonable, and we can generally (for a 4G or smaller
46
	 * packfile) quit after two rounds of radix-sorting.
47
	 */
48
#define DIGIT_SIZE (16)
49
#define BUCKETS (1 << DIGIT_SIZE)
50
	/*
51
	 * We want to know the bucket that a[i] will go into when we are using
52
	 * the digit that is N bits from the (least significant) end.
53
	 */
54
#define BUCKET_FOR(a, i, bits) (((a)[(i)].offset >> (bits)) & (BUCKETS-1))
55

56
	/*
57
	 * We need O(n) temporary storage. Rather than do an extra copy of the
58
	 * partial results into "entries", we sort back and forth between the
59
	 * real array and temporary storage. In each iteration of the loop, we
60
	 * keep track of them with alias pointers, always sorting from "from"
61
	 * to "to".
62
	 */
63
	struct revindex_entry *tmp, *from, *to;
64
	int bits;
65
	unsigned *pos;
66

67
	ALLOC_ARRAY(pos, BUCKETS);
68
	ALLOC_ARRAY(tmp, n);
69
	from = entries;
70
	to = tmp;
71

72
	/*
73
	 * If (max >> bits) is zero, then we know that the radix digit we are
74
	 * on (and any higher) will be zero for all entries, and our loop will
75
	 * be a no-op, as everybody lands in the same zero-th bucket.
76
	 */
77
	for (bits = 0; max >> bits; bits += DIGIT_SIZE) {
78
		unsigned i;
79

80
		memset(pos, 0, BUCKETS * sizeof(*pos));
81

82
		/*
83
		 * We want pos[i] to store the index of the last element that
84
		 * will go in bucket "i" (actually one past the last element).
85
		 * To do this, we first count the items that will go in each
86
		 * bucket, which gives us a relative offset from the last
87
		 * bucket. We can then cumulatively add the index from the
88
		 * previous bucket to get the true index.
89
		 */
90
		for (i = 0; i < n; i++)
91
			pos[BUCKET_FOR(from, i, bits)]++;
92
		for (i = 1; i < BUCKETS; i++)
93
			pos[i] += pos[i-1];
94

95
		/*
96
		 * Now we can drop the elements into their correct buckets (in
97
		 * our temporary array).  We iterate the pos counter backwards
98
		 * to avoid using an extra index to count up. And since we are
99
		 * going backwards there, we must also go backwards through the
100
		 * array itself, to keep the sort stable.
101
		 *
102
		 * Note that we use an unsigned iterator to make sure we can
103
		 * handle 2^32-1 objects, even on a 32-bit system. But this
104
		 * means we cannot use the more obvious "i >= 0" loop condition
105
		 * for counting backwards, and must instead check for
106
		 * wrap-around with UINT_MAX.
107
		 */
108
		for (i = n - 1; i != UINT_MAX; i--)
109
			to[--pos[BUCKET_FOR(from, i, bits)]] = from[i];
110

111
		/*
112
		 * Now "to" contains the most sorted list, so we swap "from" and
113
		 * "to" for the next iteration.
114
		 */
115
		SWAP(from, to);
116
	}
117

118
	/*
119
	 * If we ended with our data in the original array, great. If not,
120
	 * we have to move it back from the temporary storage.
121
	 */
122
	if (from != entries)
123
		COPY_ARRAY(entries, tmp, n);
124
	free(tmp);
125
	free(pos);
126

127
#undef BUCKET_FOR
128
#undef BUCKETS
129
#undef DIGIT_SIZE
130
}
131

132
/*
133
 * Ordered list of offsets of objects in the pack.
134
 */
135
static void create_pack_revindex(struct packed_git *p)
136
{
137
	const unsigned num_ent = p->num_objects;
138
	unsigned i;
139
	const char *index = p->index_data;
140
	const unsigned hashsz = the_hash_algo->rawsz;
141

142
	ALLOC_ARRAY(p->revindex, num_ent + 1);
143
	index += 4 * 256;
144

145
	if (p->index_version > 1) {
146
		const uint32_t *off_32 =
147
			(uint32_t *)(index + 8 + (size_t)p->num_objects * (hashsz + 4));
148
		const uint32_t *off_64 = off_32 + p->num_objects;
149
		for (i = 0; i < num_ent; i++) {
150
			const uint32_t off = ntohl(*off_32++);
151
			if (!(off & 0x80000000)) {
152
				p->revindex[i].offset = off;
153
			} else {
154
				p->revindex[i].offset = get_be64(off_64);
155
				off_64 += 2;
156
			}
157
			p->revindex[i].nr = i;
158
		}
159
	} else {
160
		for (i = 0; i < num_ent; i++) {
161
			const uint32_t hl = *((uint32_t *)(index + (hashsz + 4) * i));
162
			p->revindex[i].offset = ntohl(hl);
163
			p->revindex[i].nr = i;
164
		}
165
	}
166

167
	/*
168
	 * This knows the pack format -- the hash trailer
169
	 * follows immediately after the last object data.
170
	 */
171
	p->revindex[num_ent].offset = p->pack_size - hashsz;
172
	p->revindex[num_ent].nr = -1;
173
	sort_revindex(p->revindex, num_ent, p->pack_size);
174
}
175

176
static int create_pack_revindex_in_memory(struct packed_git *p)
177
{
178
	if (git_env_bool(GIT_TEST_REV_INDEX_DIE_IN_MEMORY, 0))
179
		die("dying as requested by '%s'",
180
		    GIT_TEST_REV_INDEX_DIE_IN_MEMORY);
181
	if (open_pack_index(p))
182
		return -1;
183
	create_pack_revindex(p);
184
	return 0;
185
}
186

187
static char *pack_revindex_filename(struct packed_git *p)
188
{
189
	size_t len;
190
	if (!strip_suffix(p->pack_name, ".pack", &len))
191
		BUG("pack_name does not end in .pack");
192
	return xstrfmt("%.*s.rev", (int)len, p->pack_name);
193
}
194

195
#define RIDX_HEADER_SIZE (12)
196
#define RIDX_MIN_SIZE (RIDX_HEADER_SIZE + (2 * the_hash_algo->rawsz))
197

198
struct revindex_header {
199
	uint32_t signature;
200
	uint32_t version;
201
	uint32_t hash_id;
202
};
203

204
static int load_revindex_from_disk(char *revindex_name,
205
				   uint32_t num_objects,
206
				   const uint32_t **data_p, size_t *len_p)
207
{
208
	int fd, ret = 0;
209
	struct stat st;
210
	void *data = NULL;
211
	size_t revindex_size;
212
	struct revindex_header *hdr;
213

214
	if (git_env_bool(GIT_TEST_REV_INDEX_DIE_ON_DISK, 0))
215
		die("dying as requested by '%s'", GIT_TEST_REV_INDEX_DIE_ON_DISK);
216

217
	fd = git_open(revindex_name);
218

219
	if (fd < 0) {
220
		/* "No file" means return 1. */
221
		ret = 1;
222
		goto cleanup;
223
	}
224
	if (fstat(fd, &st)) {
225
		ret = error_errno(_("failed to read %s"), revindex_name);
226
		goto cleanup;
227
	}
228

229
	revindex_size = xsize_t(st.st_size);
230

231
	if (revindex_size < RIDX_MIN_SIZE) {
232
		ret = error(_("reverse-index file %s is too small"), revindex_name);
233
		goto cleanup;
234
	}
235

236
	if (revindex_size - RIDX_MIN_SIZE != st_mult(sizeof(uint32_t), num_objects)) {
237
		ret = error(_("reverse-index file %s is corrupt"), revindex_name);
238
		goto cleanup;
239
	}
240

241
	data = xmmap(NULL, revindex_size, PROT_READ, MAP_PRIVATE, fd, 0);
242
	hdr = data;
243

244
	if (ntohl(hdr->signature) != RIDX_SIGNATURE) {
245
		ret = error(_("reverse-index file %s has unknown signature"), revindex_name);
246
		goto cleanup;
247
	}
248
	if (ntohl(hdr->version) != 1) {
249
		ret = error(_("reverse-index file %s has unsupported version %"PRIu32),
250
			    revindex_name, ntohl(hdr->version));
251
		goto cleanup;
252
	}
253
	if (!(ntohl(hdr->hash_id) == 1 || ntohl(hdr->hash_id) == 2)) {
254
		ret = error(_("reverse-index file %s has unsupported hash id %"PRIu32),
255
			    revindex_name, ntohl(hdr->hash_id));
256
		goto cleanup;
257
	}
258

259
cleanup:
260
	if (ret) {
261
		if (data)
262
			munmap(data, revindex_size);
263
	} else {
264
		*len_p = revindex_size;
265
		*data_p = (const uint32_t *)data;
266
	}
267

268
	if (fd >= 0)
269
		close(fd);
270
	return ret;
271
}
272

273
int load_pack_revindex_from_disk(struct packed_git *p)
274
{
275
	char *revindex_name;
276
	int ret;
277
	if (open_pack_index(p))
278
		return -1;
279

280
	revindex_name = pack_revindex_filename(p);
281

282
	ret = load_revindex_from_disk(revindex_name,
283
				      p->num_objects,
284
				      &p->revindex_map,
285
				      &p->revindex_size);
286
	if (ret)
287
		goto cleanup;
288

289
	p->revindex_data = (const uint32_t *)((const char *)p->revindex_map + RIDX_HEADER_SIZE);
290

291
cleanup:
292
	free(revindex_name);
293
	return ret;
294
}
295

296
int load_pack_revindex(struct repository *r, struct packed_git *p)
297
{
298
	if (p->revindex || p->revindex_data)
299
		return 0;
300

301
	prepare_repo_settings(r);
302

303
	if (r->settings.pack_read_reverse_index &&
304
	    !load_pack_revindex_from_disk(p))
305
		return 0;
306
	else if (!create_pack_revindex_in_memory(p))
307
		return 0;
308
	return -1;
309
}
310

311
/*
312
 * verify_pack_revindex verifies that the on-disk rev-index for the given
313
 * pack-file is the same that would be created if written from scratch.
314
 *
315
 * A negative number is returned on error.
316
 */
317
int verify_pack_revindex(struct packed_git *p)
318
{
319
	int res = 0;
320

321
	/* Do not bother checking if not initialized. */
322
	if (!p->revindex_map || !p->revindex_data)
323
		return res;
324

325
	if (!hashfile_checksum_valid((const unsigned char *)p->revindex_map, p->revindex_size)) {
326
		error(_("invalid checksum"));
327
		res = -1;
328
	}
329

330
	/* This may fail due to a broken .idx. */
331
	if (create_pack_revindex_in_memory(p))
332
		return res;
333

334
	for (size_t i = 0; i < p->num_objects; i++) {
335
		uint32_t nr = p->revindex[i].nr;
336
		uint32_t rev_val = get_be32(p->revindex_data + i);
337

338
		if (nr != rev_val) {
339
			error(_("invalid rev-index position at %"PRIu64": %"PRIu32" != %"PRIu32""),
340
			      (uint64_t)i, nr, rev_val);
341
			res = -1;
342
		}
343
	}
344

345
	return res;
346
}
347

348
static int can_use_midx_ridx_chunk(struct multi_pack_index *m)
349
{
350
	if (!m->chunk_revindex)
351
		return 0;
352
	if (m->chunk_revindex_len != st_mult(sizeof(uint32_t), m->num_objects)) {
353
		error(_("multi-pack-index reverse-index chunk is the wrong size"));
354
		return 0;
355
	}
356
	return 1;
357
}
358

359
int load_midx_revindex(struct multi_pack_index *m)
360
{
361
	struct strbuf revindex_name = STRBUF_INIT;
362
	int ret;
363

364
	if (m->revindex_data)
365
		return 0;
366

367
	if (can_use_midx_ridx_chunk(m)) {
368
		/*
369
		 * If the MIDX `m` has a `RIDX` chunk, then use its contents for
370
		 * the reverse index instead of trying to load a separate `.rev`
371
		 * file.
372
		 *
373
		 * Note that we do *not* set `m->revindex_map` here, since we do
374
		 * not want to accidentally call munmap() in the middle of the
375
		 * MIDX.
376
		 */
377
		trace2_data_string("load_midx_revindex", the_repository,
378
				   "source", "midx");
379
		m->revindex_data = (const uint32_t *)m->chunk_revindex;
380
		return 0;
381
	}
382

383
	trace2_data_string("load_midx_revindex", the_repository,
384
			   "source", "rev");
385

386
	get_midx_filename_ext(&revindex_name, m->object_dir,
387
			      get_midx_checksum(m), MIDX_EXT_REV);
388

389
	ret = load_revindex_from_disk(revindex_name.buf,
390
				      m->num_objects,
391
				      &m->revindex_map,
392
				      &m->revindex_len);
393
	if (ret)
394
		goto cleanup;
395

396
	m->revindex_data = (const uint32_t *)((const char *)m->revindex_map + RIDX_HEADER_SIZE);
397

398
cleanup:
399
	strbuf_release(&revindex_name);
400
	return ret;
401
}
402

403
int close_midx_revindex(struct multi_pack_index *m)
404
{
405
	if (!m || !m->revindex_map)
406
		return 0;
407

408
	munmap((void*)m->revindex_map, m->revindex_len);
409

410
	m->revindex_map = NULL;
411
	m->revindex_data = NULL;
412
	m->revindex_len = 0;
413

414
	return 0;
415
}
416

417
int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos)
418
{
419
	unsigned lo, hi;
420

421
	if (load_pack_revindex(the_repository, p) < 0)
422
		return -1;
423

424
	lo = 0;
425
	hi = p->num_objects + 1;
426

427
	do {
428
		const unsigned mi = lo + (hi - lo) / 2;
429
		off_t got = pack_pos_to_offset(p, mi);
430

431
		if (got == ofs) {
432
			*pos = mi;
433
			return 0;
434
		} else if (ofs < got)
435
			hi = mi;
436
		else
437
			lo = mi + 1;
438
	} while (lo < hi);
439

440
	error("bad offset for revindex");
441
	return -1;
442
}
443

444
uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos)
445
{
446
	if (!(p->revindex || p->revindex_data))
447
		BUG("pack_pos_to_index: reverse index not yet loaded");
448
	if (p->num_objects <= pos)
449
		BUG("pack_pos_to_index: out-of-bounds object at %"PRIu32, pos);
450

451
	if (p->revindex)
452
		return p->revindex[pos].nr;
453
	else
454
		return get_be32(p->revindex_data + pos);
455
}
456

457
off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos)
458
{
459
	if (!(p->revindex || p->revindex_data))
460
		BUG("pack_pos_to_index: reverse index not yet loaded");
461
	if (p->num_objects < pos)
462
		BUG("pack_pos_to_offset: out-of-bounds object at %"PRIu32, pos);
463

464
	if (p->revindex)
465
		return p->revindex[pos].offset;
466
	else if (pos == p->num_objects)
467
		return p->pack_size - the_hash_algo->rawsz;
468
	else
469
		return nth_packed_object_offset(p, pack_pos_to_index(p, pos));
470
}
471

472
uint32_t pack_pos_to_midx(struct multi_pack_index *m, uint32_t pos)
473
{
474
	if (!m->revindex_data)
475
		BUG("pack_pos_to_midx: reverse index not yet loaded");
476
	if (m->num_objects <= pos)
477
		BUG("pack_pos_to_midx: out-of-bounds object at %"PRIu32, pos);
478
	return get_be32(m->revindex_data + pos);
479
}
480

481
struct midx_pack_key {
482
	uint32_t pack;
483
	off_t offset;
484

485
	uint32_t preferred_pack;
486
	struct multi_pack_index *midx;
487
};
488

489
static int midx_pack_order_cmp(const void *va, const void *vb)
490
{
491
	const struct midx_pack_key *key = va;
492
	struct multi_pack_index *midx = key->midx;
493

494
	uint32_t versus = pack_pos_to_midx(midx, (uint32_t*)vb - (const uint32_t *)midx->revindex_data);
495
	uint32_t versus_pack = nth_midxed_pack_int_id(midx, versus);
496
	off_t versus_offset;
497

498
	uint32_t key_preferred = key->pack == key->preferred_pack;
499
	uint32_t versus_preferred = versus_pack == key->preferred_pack;
500

501
	/*
502
	 * First, compare the preferred-ness, noting that the preferred pack
503
	 * comes first.
504
	 */
505
	if (key_preferred && !versus_preferred)
506
		return -1;
507
	else if (!key_preferred && versus_preferred)
508
		return 1;
509

510
	/* Then, break ties first by comparing the pack IDs. */
511
	if (key->pack < versus_pack)
512
		return -1;
513
	else if (key->pack > versus_pack)
514
		return 1;
515

516
	/* Finally, break ties by comparing offsets within a pack. */
517
	versus_offset = nth_midxed_offset(midx, versus);
518
	if (key->offset < versus_offset)
519
		return -1;
520
	else if (key->offset > versus_offset)
521
		return 1;
522

523
	return 0;
524
}
525

526
static int midx_key_to_pack_pos(struct multi_pack_index *m,
527
				struct midx_pack_key *key,
528
				uint32_t *pos)
529
{
530
	uint32_t *found;
531

532
	if (key->pack >= m->num_packs)
533
		BUG("MIDX pack lookup out of bounds (%"PRIu32" >= %"PRIu32")",
534
		    key->pack, m->num_packs);
535
	/*
536
	 * The preferred pack sorts first, so determine its identifier by
537
	 * looking at the first object in pseudo-pack order.
538
	 *
539
	 * Note that if no --preferred-pack is explicitly given when writing a
540
	 * multi-pack index, then whichever pack has the lowest identifier
541
	 * implicitly is preferred (and includes all its objects, since ties are
542
	 * broken first by pack identifier).
543
	 */
544
	if (midx_preferred_pack(key->midx, &key->preferred_pack) < 0)
545
		return error(_("could not determine preferred pack"));
546

547
	found = bsearch(key, m->revindex_data, m->num_objects,
548
			sizeof(*m->revindex_data),
549
			midx_pack_order_cmp);
550

551
	if (!found)
552
		return -1;
553

554
	*pos = found - m->revindex_data;
555
	return 0;
556
}
557

558
int midx_to_pack_pos(struct multi_pack_index *m, uint32_t at, uint32_t *pos)
559
{
560
	struct midx_pack_key key;
561

562
	if (!m->revindex_data)
563
		BUG("midx_to_pack_pos: reverse index not yet loaded");
564
	if (m->num_objects <= at)
565
		BUG("midx_to_pack_pos: out-of-bounds object at %"PRIu32, at);
566

567
	key.pack = nth_midxed_pack_int_id(m, at);
568
	key.offset = nth_midxed_offset(m, at);
569
	key.midx = m;
570

571
	return midx_key_to_pack_pos(m, &key, pos);
572
}
573

574
int midx_pair_to_pack_pos(struct multi_pack_index *m, uint32_t pack_int_id,
575
			  off_t ofs, uint32_t *pos)
576
{
577
	struct midx_pack_key key = {
578
		.pack = pack_int_id,
579
		.offset = ofs,
580
		.midx = m,
581
	};
582
	return midx_key_to_pack_pos(m, &key, pos);
583
}
584