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1 | #include "git-compat-util.h" | |
2 | #include "gettext.h" | |
3 | #include "pack-revindex.h" | |
4 | #include "object-file.h" | |
5 | #include "object-store-ll.h" | |
6 | #include "packfile.h" | |
7 | #include "strbuf.h" | |
8 | #include "trace2.h" | |
9 | #include "parse.h" | |
10 | #include "midx.h" | |
11 | #include "csum-file.h" | |
12 | ||
13 | struct revindex_entry { | |
14 | off_t offset; | |
15 | unsigned int nr; | |
16 | }; | |
17 | ||
18 | /* | |
19 | * Pack index for existing packs give us easy access to the offsets into | |
20 | * corresponding pack file where each object's data starts, but the entries | |
21 | * do not store the size of the compressed representation (uncompressed | |
22 | * size is easily available by examining the pack entry header). It is | |
23 | * also rather expensive to find the sha1 for an object given its offset. | |
24 | * | |
25 | * The pack index file is sorted by object name mapping to offset; | |
26 | * this revindex array is a list of offset/index_nr pairs | |
27 | * ordered by offset, so if you know the offset of an object, next offset | |
28 | * is where its packed representation ends and the index_nr can be used to | |
29 | * get the object sha1 from the main index. | |
30 | */ | |
31 | ||
32 | /* | |
33 | * This is a least-significant-digit radix sort. | |
34 | * | |
35 | * It sorts each of the "n" items in "entries" by its offset field. The "max" | |
36 | * parameter must be at least as large as the largest offset in the array, | |
37 | * and lets us quit the sort early. | |
38 | */ | |
39 | static void sort_revindex(struct revindex_entry *entries, unsigned n, off_t max) | |
40 | { | |
41 | /* | |
42 | * We use a "digit" size of 16 bits. That keeps our memory | |
43 | * usage reasonable, and we can generally (for a 4G or smaller | |
44 | * packfile) quit after two rounds of radix-sorting. | |
45 | */ | |
46 | #define DIGIT_SIZE (16) | |
47 | #define BUCKETS (1 << DIGIT_SIZE) | |
48 | /* | |
49 | * We want to know the bucket that a[i] will go into when we are using | |
50 | * the digit that is N bits from the (least significant) end. | |
51 | */ | |
52 | #define BUCKET_FOR(a, i, bits) (((a)[(i)].offset >> (bits)) & (BUCKETS-1)) | |
53 | ||
54 | /* | |
55 | * We need O(n) temporary storage. Rather than do an extra copy of the | |
56 | * partial results into "entries", we sort back and forth between the | |
57 | * real array and temporary storage. In each iteration of the loop, we | |
58 | * keep track of them with alias pointers, always sorting from "from" | |
59 | * to "to". | |
60 | */ | |
61 | struct revindex_entry *tmp, *from, *to; | |
62 | int bits; | |
63 | unsigned *pos; | |
64 | ||
65 | ALLOC_ARRAY(pos, BUCKETS); | |
66 | ALLOC_ARRAY(tmp, n); | |
67 | from = entries; | |
68 | to = tmp; | |
69 | ||
70 | /* | |
71 | * If (max >> bits) is zero, then we know that the radix digit we are | |
72 | * on (and any higher) will be zero for all entries, and our loop will | |
73 | * be a no-op, as everybody lands in the same zero-th bucket. | |
74 | */ | |
75 | for (bits = 0; max >> bits; bits += DIGIT_SIZE) { | |
76 | unsigned i; | |
77 | ||
78 | memset(pos, 0, BUCKETS * sizeof(*pos)); | |
79 | ||
80 | /* | |
81 | * We want pos[i] to store the index of the last element that | |
82 | * will go in bucket "i" (actually one past the last element). | |
83 | * To do this, we first count the items that will go in each | |
84 | * bucket, which gives us a relative offset from the last | |
85 | * bucket. We can then cumulatively add the index from the | |
86 | * previous bucket to get the true index. | |
87 | */ | |
88 | for (i = 0; i < n; i++) | |
89 | pos[BUCKET_FOR(from, i, bits)]++; | |
90 | for (i = 1; i < BUCKETS; i++) | |
91 | pos[i] += pos[i-1]; | |
92 | ||
93 | /* | |
94 | * Now we can drop the elements into their correct buckets (in | |
95 | * our temporary array). We iterate the pos counter backwards | |
96 | * to avoid using an extra index to count up. And since we are | |
97 | * going backwards there, we must also go backwards through the | |
98 | * array itself, to keep the sort stable. | |
99 | * | |
100 | * Note that we use an unsigned iterator to make sure we can | |
101 | * handle 2^32-1 objects, even on a 32-bit system. But this | |
102 | * means we cannot use the more obvious "i >= 0" loop condition | |
103 | * for counting backwards, and must instead check for | |
104 | * wrap-around with UINT_MAX. | |
105 | */ | |
106 | for (i = n - 1; i != UINT_MAX; i--) | |
107 | to[--pos[BUCKET_FOR(from, i, bits)]] = from[i]; | |
108 | ||
109 | /* | |
110 | * Now "to" contains the most sorted list, so we swap "from" and | |
111 | * "to" for the next iteration. | |
112 | */ | |
113 | SWAP(from, to); | |
114 | } | |
115 | ||
116 | /* | |
117 | * If we ended with our data in the original array, great. If not, | |
118 | * we have to move it back from the temporary storage. | |
119 | */ | |
120 | if (from != entries) | |
121 | COPY_ARRAY(entries, tmp, n); | |
122 | free(tmp); | |
123 | free(pos); | |
124 | ||
125 | #undef BUCKET_FOR | |
126 | #undef BUCKETS | |
127 | #undef DIGIT_SIZE | |
128 | } | |
129 | ||
130 | /* | |
131 | * Ordered list of offsets of objects in the pack. | |
132 | */ | |
133 | static void create_pack_revindex(struct packed_git *p) | |
134 | { | |
135 | const unsigned num_ent = p->num_objects; | |
136 | unsigned i; | |
137 | const char *index = p->index_data; | |
138 | const unsigned hashsz = the_hash_algo->rawsz; | |
139 | ||
140 | ALLOC_ARRAY(p->revindex, num_ent + 1); | |
141 | index += 4 * 256; | |
142 | ||
143 | if (p->index_version > 1) { | |
144 | const uint32_t *off_32 = | |
145 | (uint32_t *)(index + 8 + (size_t)p->num_objects * (hashsz + 4)); | |
146 | const uint32_t *off_64 = off_32 + p->num_objects; | |
147 | for (i = 0; i < num_ent; i++) { | |
148 | const uint32_t off = ntohl(*off_32++); | |
149 | if (!(off & 0x80000000)) { | |
150 | p->revindex[i].offset = off; | |
151 | } else { | |
152 | p->revindex[i].offset = get_be64(off_64); | |
153 | off_64 += 2; | |
154 | } | |
155 | p->revindex[i].nr = i; | |
156 | } | |
157 | } else { | |
158 | for (i = 0; i < num_ent; i++) { | |
159 | const uint32_t hl = *((uint32_t *)(index + (hashsz + 4) * i)); | |
160 | p->revindex[i].offset = ntohl(hl); | |
161 | p->revindex[i].nr = i; | |
162 | } | |
163 | } | |
164 | ||
165 | /* | |
166 | * This knows the pack format -- the hash trailer | |
167 | * follows immediately after the last object data. | |
168 | */ | |
169 | p->revindex[num_ent].offset = p->pack_size - hashsz; | |
170 | p->revindex[num_ent].nr = -1; | |
171 | sort_revindex(p->revindex, num_ent, p->pack_size); | |
172 | } | |
173 | ||
174 | static int create_pack_revindex_in_memory(struct packed_git *p) | |
175 | { | |
176 | if (git_env_bool(GIT_TEST_REV_INDEX_DIE_IN_MEMORY, 0)) | |
177 | die("dying as requested by '%s'", | |
178 | GIT_TEST_REV_INDEX_DIE_IN_MEMORY); | |
179 | if (open_pack_index(p)) | |
180 | return -1; | |
181 | create_pack_revindex(p); | |
182 | return 0; | |
183 | } | |
184 | ||
185 | static char *pack_revindex_filename(struct packed_git *p) | |
186 | { | |
187 | size_t len; | |
188 | if (!strip_suffix(p->pack_name, ".pack", &len)) | |
189 | BUG("pack_name does not end in .pack"); | |
190 | return xstrfmt("%.*s.rev", (int)len, p->pack_name); | |
191 | } | |
192 | ||
193 | #define RIDX_HEADER_SIZE (12) | |
194 | #define RIDX_MIN_SIZE (RIDX_HEADER_SIZE + (2 * the_hash_algo->rawsz)) | |
195 | ||
196 | struct revindex_header { | |
197 | uint32_t signature; | |
198 | uint32_t version; | |
199 | uint32_t hash_id; | |
200 | }; | |
201 | ||
202 | static int load_revindex_from_disk(char *revindex_name, | |
203 | uint32_t num_objects, | |
204 | const uint32_t **data_p, size_t *len_p) | |
205 | { | |
206 | int fd, ret = 0; | |
207 | struct stat st; | |
208 | void *data = NULL; | |
209 | size_t revindex_size; | |
210 | struct revindex_header *hdr; | |
211 | ||
212 | if (git_env_bool(GIT_TEST_REV_INDEX_DIE_ON_DISK, 0)) | |
213 | die("dying as requested by '%s'", GIT_TEST_REV_INDEX_DIE_ON_DISK); | |
214 | ||
215 | fd = git_open(revindex_name); | |
216 | ||
217 | if (fd < 0) { | |
218 | /* "No file" means return 1. */ | |
219 | ret = 1; | |
220 | goto cleanup; | |
221 | } | |
222 | if (fstat(fd, &st)) { | |
223 | ret = error_errno(_("failed to read %s"), revindex_name); | |
224 | goto cleanup; | |
225 | } | |
226 | ||
227 | revindex_size = xsize_t(st.st_size); | |
228 | ||
229 | if (revindex_size < RIDX_MIN_SIZE) { | |
230 | ret = error(_("reverse-index file %s is too small"), revindex_name); | |
231 | goto cleanup; | |
232 | } | |
233 | ||
234 | if (revindex_size - RIDX_MIN_SIZE != st_mult(sizeof(uint32_t), num_objects)) { | |
235 | ret = error(_("reverse-index file %s is corrupt"), revindex_name); | |
236 | goto cleanup; | |
237 | } | |
238 | ||
239 | data = xmmap(NULL, revindex_size, PROT_READ, MAP_PRIVATE, fd, 0); | |
240 | hdr = data; | |
241 | ||
242 | if (ntohl(hdr->signature) != RIDX_SIGNATURE) { | |
243 | ret = error(_("reverse-index file %s has unknown signature"), revindex_name); | |
244 | goto cleanup; | |
245 | } | |
246 | if (ntohl(hdr->version) != 1) { | |
247 | ret = error(_("reverse-index file %s has unsupported version %"PRIu32), | |
248 | revindex_name, ntohl(hdr->version)); | |
249 | goto cleanup; | |
250 | } | |
251 | if (!(ntohl(hdr->hash_id) == 1 || ntohl(hdr->hash_id) == 2)) { | |
252 | ret = error(_("reverse-index file %s has unsupported hash id %"PRIu32), | |
253 | revindex_name, ntohl(hdr->hash_id)); | |
254 | goto cleanup; | |
255 | } | |
256 | ||
257 | cleanup: | |
258 | if (ret) { | |
259 | if (data) | |
260 | munmap(data, revindex_size); | |
261 | } else { | |
262 | *len_p = revindex_size; | |
263 | *data_p = (const uint32_t *)data; | |
264 | } | |
265 | ||
266 | if (fd >= 0) | |
267 | close(fd); | |
268 | return ret; | |
269 | } | |
270 | ||
271 | int load_pack_revindex_from_disk(struct packed_git *p) | |
272 | { | |
273 | char *revindex_name; | |
274 | int ret; | |
275 | if (open_pack_index(p)) | |
276 | return -1; | |
277 | ||
278 | revindex_name = pack_revindex_filename(p); | |
279 | ||
280 | ret = load_revindex_from_disk(revindex_name, | |
281 | p->num_objects, | |
282 | &p->revindex_map, | |
283 | &p->revindex_size); | |
284 | if (ret) | |
285 | goto cleanup; | |
286 | ||
287 | p->revindex_data = (const uint32_t *)((const char *)p->revindex_map + RIDX_HEADER_SIZE); | |
288 | ||
289 | cleanup: | |
290 | free(revindex_name); | |
291 | return ret; | |
292 | } | |
293 | ||
294 | int load_pack_revindex(struct repository *r, struct packed_git *p) | |
295 | { | |
296 | if (p->revindex || p->revindex_data) | |
297 | return 0; | |
298 | ||
299 | prepare_repo_settings(r); | |
300 | ||
301 | if (r->settings.pack_read_reverse_index && | |
302 | !load_pack_revindex_from_disk(p)) | |
303 | return 0; | |
304 | else if (!create_pack_revindex_in_memory(p)) | |
305 | return 0; | |
306 | return -1; | |
307 | } | |
308 | ||
309 | /* | |
310 | * verify_pack_revindex verifies that the on-disk rev-index for the given | |
311 | * pack-file is the same that would be created if written from scratch. | |
312 | * | |
313 | * A negative number is returned on error. | |
314 | */ | |
315 | int verify_pack_revindex(struct packed_git *p) | |
316 | { | |
317 | int res = 0; | |
318 | ||
319 | /* Do not bother checking if not initialized. */ | |
320 | if (!p->revindex_map || !p->revindex_data) | |
321 | return res; | |
322 | ||
323 | if (!hashfile_checksum_valid((const unsigned char *)p->revindex_map, p->revindex_size)) { | |
324 | error(_("invalid checksum")); | |
325 | res = -1; | |
326 | } | |
327 | ||
328 | /* This may fail due to a broken .idx. */ | |
329 | if (create_pack_revindex_in_memory(p)) | |
330 | return res; | |
331 | ||
332 | for (size_t i = 0; i < p->num_objects; i++) { | |
333 | uint32_t nr = p->revindex[i].nr; | |
334 | uint32_t rev_val = get_be32(p->revindex_data + i); | |
335 | ||
336 | if (nr != rev_val) { | |
337 | error(_("invalid rev-index position at %"PRIu64": %"PRIu32" != %"PRIu32""), | |
338 | (uint64_t)i, nr, rev_val); | |
339 | res = -1; | |
340 | } | |
341 | } | |
342 | ||
343 | return res; | |
344 | } | |
345 | ||
346 | static int can_use_midx_ridx_chunk(struct multi_pack_index *m) | |
347 | { | |
348 | if (!m->chunk_revindex) | |
349 | return 0; | |
350 | if (m->chunk_revindex_len != st_mult(sizeof(uint32_t), m->num_objects)) { | |
351 | error(_("multi-pack-index reverse-index chunk is the wrong size")); | |
352 | return 0; | |
353 | } | |
354 | return 1; | |
355 | } | |
356 | ||
357 | int load_midx_revindex(struct multi_pack_index *m) | |
358 | { | |
359 | struct strbuf revindex_name = STRBUF_INIT; | |
360 | int ret; | |
361 | ||
362 | if (m->revindex_data) | |
363 | return 0; | |
364 | ||
365 | if (can_use_midx_ridx_chunk(m)) { | |
366 | /* | |
367 | * If the MIDX `m` has a `RIDX` chunk, then use its contents for | |
368 | * the reverse index instead of trying to load a separate `.rev` | |
369 | * file. | |
370 | * | |
371 | * Note that we do *not* set `m->revindex_map` here, since we do | |
372 | * not want to accidentally call munmap() in the middle of the | |
373 | * MIDX. | |
374 | */ | |
375 | trace2_data_string("load_midx_revindex", the_repository, | |
376 | "source", "midx"); | |
377 | m->revindex_data = (const uint32_t *)m->chunk_revindex; | |
378 | return 0; | |
379 | } | |
380 | ||
381 | trace2_data_string("load_midx_revindex", the_repository, | |
382 | "source", "rev"); | |
383 | ||
384 | get_midx_rev_filename(&revindex_name, m); | |
385 | ||
386 | ret = load_revindex_from_disk(revindex_name.buf, | |
387 | m->num_objects, | |
388 | &m->revindex_map, | |
389 | &m->revindex_len); | |
390 | if (ret) | |
391 | goto cleanup; | |
392 | ||
393 | m->revindex_data = (const uint32_t *)((const char *)m->revindex_map + RIDX_HEADER_SIZE); | |
394 | ||
395 | cleanup: | |
396 | strbuf_release(&revindex_name); | |
397 | return ret; | |
398 | } | |
399 | ||
400 | int close_midx_revindex(struct multi_pack_index *m) | |
401 | { | |
402 | if (!m || !m->revindex_map) | |
403 | return 0; | |
404 | ||
405 | munmap((void*)m->revindex_map, m->revindex_len); | |
406 | ||
407 | m->revindex_map = NULL; | |
408 | m->revindex_data = NULL; | |
409 | m->revindex_len = 0; | |
410 | ||
411 | return 0; | |
412 | } | |
413 | ||
414 | int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos) | |
415 | { | |
416 | unsigned lo, hi; | |
417 | ||
418 | if (load_pack_revindex(the_repository, p) < 0) | |
419 | return -1; | |
420 | ||
421 | lo = 0; | |
422 | hi = p->num_objects + 1; | |
423 | ||
424 | do { | |
425 | const unsigned mi = lo + (hi - lo) / 2; | |
426 | off_t got = pack_pos_to_offset(p, mi); | |
427 | ||
428 | if (got == ofs) { | |
429 | *pos = mi; | |
430 | return 0; | |
431 | } else if (ofs < got) | |
432 | hi = mi; | |
433 | else | |
434 | lo = mi + 1; | |
435 | } while (lo < hi); | |
436 | ||
437 | error("bad offset for revindex"); | |
438 | return -1; | |
439 | } | |
440 | ||
441 | uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos) | |
442 | { | |
443 | if (!(p->revindex || p->revindex_data)) | |
444 | BUG("pack_pos_to_index: reverse index not yet loaded"); | |
445 | if (p->num_objects <= pos) | |
446 | BUG("pack_pos_to_index: out-of-bounds object at %"PRIu32, pos); | |
447 | ||
448 | if (p->revindex) | |
449 | return p->revindex[pos].nr; | |
450 | else | |
451 | return get_be32(p->revindex_data + pos); | |
452 | } | |
453 | ||
454 | off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos) | |
455 | { | |
456 | if (!(p->revindex || p->revindex_data)) | |
457 | BUG("pack_pos_to_index: reverse index not yet loaded"); | |
458 | if (p->num_objects < pos) | |
459 | BUG("pack_pos_to_offset: out-of-bounds object at %"PRIu32, pos); | |
460 | ||
461 | if (p->revindex) | |
462 | return p->revindex[pos].offset; | |
463 | else if (pos == p->num_objects) | |
464 | return p->pack_size - the_hash_algo->rawsz; | |
465 | else | |
466 | return nth_packed_object_offset(p, pack_pos_to_index(p, pos)); | |
467 | } | |
468 | ||
469 | uint32_t pack_pos_to_midx(struct multi_pack_index *m, uint32_t pos) | |
470 | { | |
471 | if (!m->revindex_data) | |
472 | BUG("pack_pos_to_midx: reverse index not yet loaded"); | |
473 | if (m->num_objects <= pos) | |
474 | BUG("pack_pos_to_midx: out-of-bounds object at %"PRIu32, pos); | |
475 | return get_be32(m->revindex_data + pos); | |
476 | } | |
477 | ||
478 | struct midx_pack_key { | |
479 | uint32_t pack; | |
480 | off_t offset; | |
481 | ||
482 | uint32_t preferred_pack; | |
483 | struct multi_pack_index *midx; | |
484 | }; | |
485 | ||
486 | static int midx_pack_order_cmp(const void *va, const void *vb) | |
487 | { | |
488 | const struct midx_pack_key *key = va; | |
489 | struct multi_pack_index *midx = key->midx; | |
490 | ||
491 | uint32_t versus = pack_pos_to_midx(midx, (uint32_t*)vb - (const uint32_t *)midx->revindex_data); | |
492 | uint32_t versus_pack = nth_midxed_pack_int_id(midx, versus); | |
493 | off_t versus_offset; | |
494 | ||
495 | uint32_t key_preferred = key->pack == key->preferred_pack; | |
496 | uint32_t versus_preferred = versus_pack == key->preferred_pack; | |
497 | ||
498 | /* | |
499 | * First, compare the preferred-ness, noting that the preferred pack | |
500 | * comes first. | |
501 | */ | |
502 | if (key_preferred && !versus_preferred) | |
503 | return -1; | |
504 | else if (!key_preferred && versus_preferred) | |
505 | return 1; | |
506 | ||
507 | /* Then, break ties first by comparing the pack IDs. */ | |
508 | if (key->pack < versus_pack) | |
509 | return -1; | |
510 | else if (key->pack > versus_pack) | |
511 | return 1; | |
512 | ||
513 | /* Finally, break ties by comparing offsets within a pack. */ | |
514 | versus_offset = nth_midxed_offset(midx, versus); | |
515 | if (key->offset < versus_offset) | |
516 | return -1; | |
517 | else if (key->offset > versus_offset) | |
518 | return 1; | |
519 | ||
520 | return 0; | |
521 | } | |
522 | ||
523 | int midx_to_pack_pos(struct multi_pack_index *m, uint32_t at, uint32_t *pos) | |
524 | { | |
525 | struct midx_pack_key key; | |
526 | uint32_t *found; | |
527 | ||
528 | if (!m->revindex_data) | |
529 | BUG("midx_to_pack_pos: reverse index not yet loaded"); | |
530 | if (m->num_objects <= at) | |
531 | BUG("midx_to_pack_pos: out-of-bounds object at %"PRIu32, at); | |
532 | ||
533 | key.pack = nth_midxed_pack_int_id(m, at); | |
534 | key.offset = nth_midxed_offset(m, at); | |
535 | key.midx = m; | |
536 | /* | |
537 | * The preferred pack sorts first, so determine its identifier by | |
538 | * looking at the first object in pseudo-pack order. | |
539 | * | |
540 | * Note that if no --preferred-pack is explicitly given when writing a | |
541 | * multi-pack index, then whichever pack has the lowest identifier | |
542 | * implicitly is preferred (and includes all its objects, since ties are | |
543 | * broken first by pack identifier). | |
544 | */ | |
545 | if (midx_preferred_pack(key.midx, &key.preferred_pack) < 0) | |
546 | return error(_("could not determine preferred pack")); | |
547 | ||
548 | ||
549 | found = bsearch(&key, m->revindex_data, m->num_objects, | |
550 | sizeof(*m->revindex_data), midx_pack_order_cmp); | |
551 | ||
552 | if (!found) | |
553 | return error("bad offset for revindex"); | |
554 | ||
555 | *pos = found - m->revindex_data; | |
556 | return 0; | |
557 | } |