Merge branch 'bw/config-refer-to-gitsubmodules-doc'
[git] / commit-graph.c
1 #include "cache.h"
2 #include "config.h"
3 #include "dir.h"
4 #include "git-compat-util.h"
5 #include "lockfile.h"
6 #include "pack.h"
7 #include "packfile.h"
8 #include "commit.h"
9 #include "object.h"
10 #include "revision.h"
11 #include "sha1-lookup.h"
12 #include "commit-graph.h"
13 #include "object-store.h"
14
15 #define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
16 #define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
17 #define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
18 #define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
19 #define GRAPH_CHUNKID_LARGEEDGES 0x45444745 /* "EDGE" */
20
21 #define GRAPH_DATA_WIDTH 36
22
23 #define GRAPH_VERSION_1 0x1
24 #define GRAPH_VERSION GRAPH_VERSION_1
25
26 #define GRAPH_OID_VERSION_SHA1 1
27 #define GRAPH_OID_LEN_SHA1 GIT_SHA1_RAWSZ
28 #define GRAPH_OID_VERSION GRAPH_OID_VERSION_SHA1
29 #define GRAPH_OID_LEN GRAPH_OID_LEN_SHA1
30
31 #define GRAPH_OCTOPUS_EDGES_NEEDED 0x80000000
32 #define GRAPH_PARENT_MISSING 0x7fffffff
33 #define GRAPH_EDGE_LAST_MASK 0x7fffffff
34 #define GRAPH_PARENT_NONE 0x70000000
35
36 #define GRAPH_LAST_EDGE 0x80000000
37
38 #define GRAPH_FANOUT_SIZE (4 * 256)
39 #define GRAPH_CHUNKLOOKUP_WIDTH 12
40 #define GRAPH_MIN_SIZE (5 * GRAPH_CHUNKLOOKUP_WIDTH + GRAPH_FANOUT_SIZE + \
41                         GRAPH_OID_LEN + 8)
42
43 char *get_commit_graph_filename(const char *obj_dir)
44 {
45         return xstrfmt("%s/info/commit-graph", obj_dir);
46 }
47
48 static struct commit_graph *alloc_commit_graph(void)
49 {
50         struct commit_graph *g = xcalloc(1, sizeof(*g));
51         g->graph_fd = -1;
52
53         return g;
54 }
55
56 struct commit_graph *load_commit_graph_one(const char *graph_file)
57 {
58         void *graph_map;
59         const unsigned char *data, *chunk_lookup;
60         size_t graph_size;
61         struct stat st;
62         uint32_t i;
63         struct commit_graph *graph;
64         int fd = git_open(graph_file);
65         uint64_t last_chunk_offset;
66         uint32_t last_chunk_id;
67         uint32_t graph_signature;
68         unsigned char graph_version, hash_version;
69
70         if (fd < 0)
71                 return NULL;
72         if (fstat(fd, &st)) {
73                 close(fd);
74                 return NULL;
75         }
76         graph_size = xsize_t(st.st_size);
77
78         if (graph_size < GRAPH_MIN_SIZE) {
79                 close(fd);
80                 die("graph file %s is too small", graph_file);
81         }
82         graph_map = xmmap(NULL, graph_size, PROT_READ, MAP_PRIVATE, fd, 0);
83         data = (const unsigned char *)graph_map;
84
85         graph_signature = get_be32(data);
86         if (graph_signature != GRAPH_SIGNATURE) {
87                 error("graph signature %X does not match signature %X",
88                       graph_signature, GRAPH_SIGNATURE);
89                 goto cleanup_fail;
90         }
91
92         graph_version = *(unsigned char*)(data + 4);
93         if (graph_version != GRAPH_VERSION) {
94                 error("graph version %X does not match version %X",
95                       graph_version, GRAPH_VERSION);
96                 goto cleanup_fail;
97         }
98
99         hash_version = *(unsigned char*)(data + 5);
100         if (hash_version != GRAPH_OID_VERSION) {
101                 error("hash version %X does not match version %X",
102                       hash_version, GRAPH_OID_VERSION);
103                 goto cleanup_fail;
104         }
105
106         graph = alloc_commit_graph();
107
108         graph->hash_len = GRAPH_OID_LEN;
109         graph->num_chunks = *(unsigned char*)(data + 6);
110         graph->graph_fd = fd;
111         graph->data = graph_map;
112         graph->data_len = graph_size;
113
114         last_chunk_id = 0;
115         last_chunk_offset = 8;
116         chunk_lookup = data + 8;
117         for (i = 0; i < graph->num_chunks; i++) {
118                 uint32_t chunk_id = get_be32(chunk_lookup + 0);
119                 uint64_t chunk_offset = get_be64(chunk_lookup + 4);
120                 int chunk_repeated = 0;
121
122                 chunk_lookup += GRAPH_CHUNKLOOKUP_WIDTH;
123
124                 if (chunk_offset > graph_size - GIT_MAX_RAWSZ) {
125                         error("improper chunk offset %08x%08x", (uint32_t)(chunk_offset >> 32),
126                               (uint32_t)chunk_offset);
127                         goto cleanup_fail;
128                 }
129
130                 switch (chunk_id) {
131                 case GRAPH_CHUNKID_OIDFANOUT:
132                         if (graph->chunk_oid_fanout)
133                                 chunk_repeated = 1;
134                         else
135                                 graph->chunk_oid_fanout = (uint32_t*)(data + chunk_offset);
136                         break;
137
138                 case GRAPH_CHUNKID_OIDLOOKUP:
139                         if (graph->chunk_oid_lookup)
140                                 chunk_repeated = 1;
141                         else
142                                 graph->chunk_oid_lookup = data + chunk_offset;
143                         break;
144
145                 case GRAPH_CHUNKID_DATA:
146                         if (graph->chunk_commit_data)
147                                 chunk_repeated = 1;
148                         else
149                                 graph->chunk_commit_data = data + chunk_offset;
150                         break;
151
152                 case GRAPH_CHUNKID_LARGEEDGES:
153                         if (graph->chunk_large_edges)
154                                 chunk_repeated = 1;
155                         else
156                                 graph->chunk_large_edges = data + chunk_offset;
157                         break;
158                 }
159
160                 if (chunk_repeated) {
161                         error("chunk id %08x appears multiple times", chunk_id);
162                         goto cleanup_fail;
163                 }
164
165                 if (last_chunk_id == GRAPH_CHUNKID_OIDLOOKUP)
166                 {
167                         graph->num_commits = (chunk_offset - last_chunk_offset)
168                                              / graph->hash_len;
169                 }
170
171                 last_chunk_id = chunk_id;
172                 last_chunk_offset = chunk_offset;
173         }
174
175         return graph;
176
177 cleanup_fail:
178         munmap(graph_map, graph_size);
179         close(fd);
180         exit(1);
181 }
182
183 /* global storage */
184 static struct commit_graph *commit_graph = NULL;
185
186 static void prepare_commit_graph_one(const char *obj_dir)
187 {
188         char *graph_name;
189
190         if (commit_graph)
191                 return;
192
193         graph_name = get_commit_graph_filename(obj_dir);
194         commit_graph = load_commit_graph_one(graph_name);
195
196         FREE_AND_NULL(graph_name);
197 }
198
199 static int prepare_commit_graph_run_once = 0;
200 static void prepare_commit_graph(void)
201 {
202         struct alternate_object_database *alt;
203         char *obj_dir;
204
205         if (prepare_commit_graph_run_once)
206                 return;
207         prepare_commit_graph_run_once = 1;
208
209         obj_dir = get_object_directory();
210         prepare_commit_graph_one(obj_dir);
211         prepare_alt_odb(the_repository);
212         for (alt = the_repository->objects->alt_odb_list;
213              !commit_graph && alt;
214              alt = alt->next)
215                 prepare_commit_graph_one(alt->path);
216 }
217
218 static void close_commit_graph(void)
219 {
220         if (!commit_graph)
221                 return;
222
223         if (commit_graph->graph_fd >= 0) {
224                 munmap((void *)commit_graph->data, commit_graph->data_len);
225                 commit_graph->data = NULL;
226                 close(commit_graph->graph_fd);
227         }
228
229         FREE_AND_NULL(commit_graph);
230 }
231
232 static int bsearch_graph(struct commit_graph *g, struct object_id *oid, uint32_t *pos)
233 {
234         return bsearch_hash(oid->hash, g->chunk_oid_fanout,
235                             g->chunk_oid_lookup, g->hash_len, pos);
236 }
237
238 static struct commit_list **insert_parent_or_die(struct commit_graph *g,
239                                                  uint64_t pos,
240                                                  struct commit_list **pptr)
241 {
242         struct commit *c;
243         struct object_id oid;
244         hashcpy(oid.hash, g->chunk_oid_lookup + g->hash_len * pos);
245         c = lookup_commit(&oid);
246         if (!c)
247                 die("could not find commit %s", oid_to_hex(&oid));
248         c->graph_pos = pos;
249         return &commit_list_insert(c, pptr)->next;
250 }
251
252 static void fill_commit_graph_info(struct commit *item, struct commit_graph *g, uint32_t pos)
253 {
254         const unsigned char *commit_data = g->chunk_commit_data + GRAPH_DATA_WIDTH * pos;
255         item->graph_pos = pos;
256         item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
257 }
258
259 static int fill_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t pos)
260 {
261         uint32_t edge_value;
262         uint32_t *parent_data_ptr;
263         uint64_t date_low, date_high;
264         struct commit_list **pptr;
265         const unsigned char *commit_data = g->chunk_commit_data + (g->hash_len + 16) * pos;
266
267         item->object.parsed = 1;
268         item->graph_pos = pos;
269
270         item->maybe_tree = NULL;
271
272         date_high = get_be32(commit_data + g->hash_len + 8) & 0x3;
273         date_low = get_be32(commit_data + g->hash_len + 12);
274         item->date = (timestamp_t)((date_high << 32) | date_low);
275
276         item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
277
278         pptr = &item->parents;
279
280         edge_value = get_be32(commit_data + g->hash_len);
281         if (edge_value == GRAPH_PARENT_NONE)
282                 return 1;
283         pptr = insert_parent_or_die(g, edge_value, pptr);
284
285         edge_value = get_be32(commit_data + g->hash_len + 4);
286         if (edge_value == GRAPH_PARENT_NONE)
287                 return 1;
288         if (!(edge_value & GRAPH_OCTOPUS_EDGES_NEEDED)) {
289                 pptr = insert_parent_or_die(g, edge_value, pptr);
290                 return 1;
291         }
292
293         parent_data_ptr = (uint32_t*)(g->chunk_large_edges +
294                           4 * (uint64_t)(edge_value & GRAPH_EDGE_LAST_MASK));
295         do {
296                 edge_value = get_be32(parent_data_ptr);
297                 pptr = insert_parent_or_die(g,
298                                             edge_value & GRAPH_EDGE_LAST_MASK,
299                                             pptr);
300                 parent_data_ptr++;
301         } while (!(edge_value & GRAPH_LAST_EDGE));
302
303         return 1;
304 }
305
306 static int find_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t *pos)
307 {
308         if (item->graph_pos != COMMIT_NOT_FROM_GRAPH) {
309                 *pos = item->graph_pos;
310                 return 1;
311         } else {
312                 return bsearch_graph(g, &(item->object.oid), pos);
313         }
314 }
315
316 int parse_commit_in_graph(struct commit *item)
317 {
318         uint32_t pos;
319
320         if (!core_commit_graph)
321                 return 0;
322         if (item->object.parsed)
323                 return 1;
324         prepare_commit_graph();
325         if (commit_graph && find_commit_in_graph(item, commit_graph, &pos))
326                 return fill_commit_in_graph(item, commit_graph, pos);
327         return 0;
328 }
329
330 void load_commit_graph_info(struct commit *item)
331 {
332         uint32_t pos;
333         if (!core_commit_graph)
334                 return;
335         prepare_commit_graph();
336         if (commit_graph && find_commit_in_graph(item, commit_graph, &pos))
337                 fill_commit_graph_info(item, commit_graph, pos);
338 }
339
340 static struct tree *load_tree_for_commit(struct commit_graph *g, struct commit *c)
341 {
342         struct object_id oid;
343         const unsigned char *commit_data = g->chunk_commit_data +
344                                            GRAPH_DATA_WIDTH * (c->graph_pos);
345
346         hashcpy(oid.hash, commit_data);
347         c->maybe_tree = lookup_tree(&oid);
348
349         return c->maybe_tree;
350 }
351
352 struct tree *get_commit_tree_in_graph(const struct commit *c)
353 {
354         if (c->maybe_tree)
355                 return c->maybe_tree;
356         if (c->graph_pos == COMMIT_NOT_FROM_GRAPH)
357                 BUG("get_commit_tree_in_graph called from non-commit-graph commit");
358
359         return load_tree_for_commit(commit_graph, (struct commit *)c);
360 }
361
362 static void write_graph_chunk_fanout(struct hashfile *f,
363                                      struct commit **commits,
364                                      int nr_commits)
365 {
366         int i, count = 0;
367         struct commit **list = commits;
368
369         /*
370          * Write the first-level table (the list is sorted,
371          * but we use a 256-entry lookup to be able to avoid
372          * having to do eight extra binary search iterations).
373          */
374         for (i = 0; i < 256; i++) {
375                 while (count < nr_commits) {
376                         if ((*list)->object.oid.hash[0] != i)
377                                 break;
378                         count++;
379                         list++;
380                 }
381
382                 hashwrite_be32(f, count);
383         }
384 }
385
386 static void write_graph_chunk_oids(struct hashfile *f, int hash_len,
387                                    struct commit **commits, int nr_commits)
388 {
389         struct commit **list = commits;
390         int count;
391         for (count = 0; count < nr_commits; count++, list++)
392                 hashwrite(f, (*list)->object.oid.hash, (int)hash_len);
393 }
394
395 static const unsigned char *commit_to_sha1(size_t index, void *table)
396 {
397         struct commit **commits = table;
398         return commits[index]->object.oid.hash;
399 }
400
401 static void write_graph_chunk_data(struct hashfile *f, int hash_len,
402                                    struct commit **commits, int nr_commits)
403 {
404         struct commit **list = commits;
405         struct commit **last = commits + nr_commits;
406         uint32_t num_extra_edges = 0;
407
408         while (list < last) {
409                 struct commit_list *parent;
410                 int edge_value;
411                 uint32_t packedDate[2];
412
413                 parse_commit(*list);
414                 hashwrite(f, get_commit_tree_oid(*list)->hash, hash_len);
415
416                 parent = (*list)->parents;
417
418                 if (!parent)
419                         edge_value = GRAPH_PARENT_NONE;
420                 else {
421                         edge_value = sha1_pos(parent->item->object.oid.hash,
422                                               commits,
423                                               nr_commits,
424                                               commit_to_sha1);
425
426                         if (edge_value < 0)
427                                 edge_value = GRAPH_PARENT_MISSING;
428                 }
429
430                 hashwrite_be32(f, edge_value);
431
432                 if (parent)
433                         parent = parent->next;
434
435                 if (!parent)
436                         edge_value = GRAPH_PARENT_NONE;
437                 else if (parent->next)
438                         edge_value = GRAPH_OCTOPUS_EDGES_NEEDED | num_extra_edges;
439                 else {
440                         edge_value = sha1_pos(parent->item->object.oid.hash,
441                                               commits,
442                                               nr_commits,
443                                               commit_to_sha1);
444                         if (edge_value < 0)
445                                 edge_value = GRAPH_PARENT_MISSING;
446                 }
447
448                 hashwrite_be32(f, edge_value);
449
450                 if (edge_value & GRAPH_OCTOPUS_EDGES_NEEDED) {
451                         do {
452                                 num_extra_edges++;
453                                 parent = parent->next;
454                         } while (parent);
455                 }
456
457                 if (sizeof((*list)->date) > 4)
458                         packedDate[0] = htonl(((*list)->date >> 32) & 0x3);
459                 else
460                         packedDate[0] = 0;
461
462                 packedDate[0] |= htonl((*list)->generation << 2);
463
464                 packedDate[1] = htonl((*list)->date);
465                 hashwrite(f, packedDate, 8);
466
467                 list++;
468         }
469 }
470
471 static void write_graph_chunk_large_edges(struct hashfile *f,
472                                           struct commit **commits,
473                                           int nr_commits)
474 {
475         struct commit **list = commits;
476         struct commit **last = commits + nr_commits;
477         struct commit_list *parent;
478
479         while (list < last) {
480                 int num_parents = 0;
481                 for (parent = (*list)->parents; num_parents < 3 && parent;
482                      parent = parent->next)
483                         num_parents++;
484
485                 if (num_parents <= 2) {
486                         list++;
487                         continue;
488                 }
489
490                 /* Since num_parents > 2, this initializer is safe. */
491                 for (parent = (*list)->parents->next; parent; parent = parent->next) {
492                         int edge_value = sha1_pos(parent->item->object.oid.hash,
493                                                   commits,
494                                                   nr_commits,
495                                                   commit_to_sha1);
496
497                         if (edge_value < 0)
498                                 edge_value = GRAPH_PARENT_MISSING;
499                         else if (!parent->next)
500                                 edge_value |= GRAPH_LAST_EDGE;
501
502                         hashwrite_be32(f, edge_value);
503                 }
504
505                 list++;
506         }
507 }
508
509 static int commit_compare(const void *_a, const void *_b)
510 {
511         const struct object_id *a = (const struct object_id *)_a;
512         const struct object_id *b = (const struct object_id *)_b;
513         return oidcmp(a, b);
514 }
515
516 struct packed_commit_list {
517         struct commit **list;
518         int nr;
519         int alloc;
520 };
521
522 struct packed_oid_list {
523         struct object_id *list;
524         int nr;
525         int alloc;
526 };
527
528 static int add_packed_commits(const struct object_id *oid,
529                               struct packed_git *pack,
530                               uint32_t pos,
531                               void *data)
532 {
533         struct packed_oid_list *list = (struct packed_oid_list*)data;
534         enum object_type type;
535         off_t offset = nth_packed_object_offset(pack, pos);
536         struct object_info oi = OBJECT_INFO_INIT;
537
538         oi.typep = &type;
539         if (packed_object_info(the_repository, pack, offset, &oi) < 0)
540                 die("unable to get type of object %s", oid_to_hex(oid));
541
542         if (type != OBJ_COMMIT)
543                 return 0;
544
545         ALLOC_GROW(list->list, list->nr + 1, list->alloc);
546         oidcpy(&(list->list[list->nr]), oid);
547         list->nr++;
548
549         return 0;
550 }
551
552 static void add_missing_parents(struct packed_oid_list *oids, struct commit *commit)
553 {
554         struct commit_list *parent;
555         for (parent = commit->parents; parent; parent = parent->next) {
556                 if (!(parent->item->object.flags & UNINTERESTING)) {
557                         ALLOC_GROW(oids->list, oids->nr + 1, oids->alloc);
558                         oidcpy(&oids->list[oids->nr], &(parent->item->object.oid));
559                         oids->nr++;
560                         parent->item->object.flags |= UNINTERESTING;
561                 }
562         }
563 }
564
565 static void close_reachable(struct packed_oid_list *oids)
566 {
567         int i;
568         struct commit *commit;
569
570         for (i = 0; i < oids->nr; i++) {
571                 commit = lookup_commit(&oids->list[i]);
572                 if (commit)
573                         commit->object.flags |= UNINTERESTING;
574         }
575
576         /*
577          * As this loop runs, oids->nr may grow, but not more
578          * than the number of missing commits in the reachable
579          * closure.
580          */
581         for (i = 0; i < oids->nr; i++) {
582                 commit = lookup_commit(&oids->list[i]);
583
584                 if (commit && !parse_commit(commit))
585                         add_missing_parents(oids, commit);
586         }
587
588         for (i = 0; i < oids->nr; i++) {
589                 commit = lookup_commit(&oids->list[i]);
590
591                 if (commit)
592                         commit->object.flags &= ~UNINTERESTING;
593         }
594 }
595
596 static void compute_generation_numbers(struct packed_commit_list* commits)
597 {
598         int i;
599         struct commit_list *list = NULL;
600
601         for (i = 0; i < commits->nr; i++) {
602                 if (commits->list[i]->generation != GENERATION_NUMBER_INFINITY &&
603                     commits->list[i]->generation != GENERATION_NUMBER_ZERO)
604                         continue;
605
606                 commit_list_insert(commits->list[i], &list);
607                 while (list) {
608                         struct commit *current = list->item;
609                         struct commit_list *parent;
610                         int all_parents_computed = 1;
611                         uint32_t max_generation = 0;
612
613                         for (parent = current->parents; parent; parent = parent->next) {
614                                 if (parent->item->generation == GENERATION_NUMBER_INFINITY ||
615                                     parent->item->generation == GENERATION_NUMBER_ZERO) {
616                                         all_parents_computed = 0;
617                                         commit_list_insert(parent->item, &list);
618                                         break;
619                                 } else if (parent->item->generation > max_generation) {
620                                         max_generation = parent->item->generation;
621                                 }
622                         }
623
624                         if (all_parents_computed) {
625                                 current->generation = max_generation + 1;
626                                 pop_commit(&list);
627
628                                 if (current->generation > GENERATION_NUMBER_MAX)
629                                         current->generation = GENERATION_NUMBER_MAX;
630                         }
631                 }
632         }
633 }
634
635 void write_commit_graph(const char *obj_dir,
636                         const char **pack_indexes,
637                         int nr_packs,
638                         const char **commit_hex,
639                         int nr_commits,
640                         int append)
641 {
642         struct packed_oid_list oids;
643         struct packed_commit_list commits;
644         struct hashfile *f;
645         uint32_t i, count_distinct = 0;
646         char *graph_name;
647         struct lock_file lk = LOCK_INIT;
648         uint32_t chunk_ids[5];
649         uint64_t chunk_offsets[5];
650         int num_chunks;
651         int num_extra_edges;
652         struct commit_list *parent;
653
654         oids.nr = 0;
655         oids.alloc = approximate_object_count() / 4;
656
657         if (append) {
658                 prepare_commit_graph_one(obj_dir);
659                 if (commit_graph)
660                         oids.alloc += commit_graph->num_commits;
661         }
662
663         if (oids.alloc < 1024)
664                 oids.alloc = 1024;
665         ALLOC_ARRAY(oids.list, oids.alloc);
666
667         if (append && commit_graph) {
668                 for (i = 0; i < commit_graph->num_commits; i++) {
669                         const unsigned char *hash = commit_graph->chunk_oid_lookup +
670                                 commit_graph->hash_len * i;
671                         hashcpy(oids.list[oids.nr++].hash, hash);
672                 }
673         }
674
675         if (pack_indexes) {
676                 struct strbuf packname = STRBUF_INIT;
677                 int dirlen;
678                 strbuf_addf(&packname, "%s/pack/", obj_dir);
679                 dirlen = packname.len;
680                 for (i = 0; i < nr_packs; i++) {
681                         struct packed_git *p;
682                         strbuf_setlen(&packname, dirlen);
683                         strbuf_addstr(&packname, pack_indexes[i]);
684                         p = add_packed_git(packname.buf, packname.len, 1);
685                         if (!p)
686                                 die("error adding pack %s", packname.buf);
687                         if (open_pack_index(p))
688                                 die("error opening index for %s", packname.buf);
689                         for_each_object_in_pack(p, add_packed_commits, &oids);
690                         close_pack(p);
691                 }
692                 strbuf_release(&packname);
693         }
694
695         if (commit_hex) {
696                 for (i = 0; i < nr_commits; i++) {
697                         const char *end;
698                         struct object_id oid;
699                         struct commit *result;
700
701                         if (commit_hex[i] && parse_oid_hex(commit_hex[i], &oid, &end))
702                                 continue;
703
704                         result = lookup_commit_reference_gently(&oid, 1);
705
706                         if (result) {
707                                 ALLOC_GROW(oids.list, oids.nr + 1, oids.alloc);
708                                 oidcpy(&oids.list[oids.nr], &(result->object.oid));
709                                 oids.nr++;
710                         }
711                 }
712         }
713
714         if (!pack_indexes && !commit_hex)
715                 for_each_packed_object(add_packed_commits, &oids, 0);
716
717         close_reachable(&oids);
718
719         QSORT(oids.list, oids.nr, commit_compare);
720
721         count_distinct = 1;
722         for (i = 1; i < oids.nr; i++) {
723                 if (oidcmp(&oids.list[i-1], &oids.list[i]))
724                         count_distinct++;
725         }
726
727         if (count_distinct >= GRAPH_PARENT_MISSING)
728                 die(_("the commit graph format cannot write %d commits"), count_distinct);
729
730         commits.nr = 0;
731         commits.alloc = count_distinct;
732         ALLOC_ARRAY(commits.list, commits.alloc);
733
734         num_extra_edges = 0;
735         for (i = 0; i < oids.nr; i++) {
736                 int num_parents = 0;
737                 if (i > 0 && !oidcmp(&oids.list[i-1], &oids.list[i]))
738                         continue;
739
740                 commits.list[commits.nr] = lookup_commit(&oids.list[i]);
741                 parse_commit(commits.list[commits.nr]);
742
743                 for (parent = commits.list[commits.nr]->parents;
744                      parent; parent = parent->next)
745                         num_parents++;
746
747                 if (num_parents > 2)
748                         num_extra_edges += num_parents - 1;
749
750                 commits.nr++;
751         }
752         num_chunks = num_extra_edges ? 4 : 3;
753
754         if (commits.nr >= GRAPH_PARENT_MISSING)
755                 die(_("too many commits to write graph"));
756
757         compute_generation_numbers(&commits);
758
759         graph_name = get_commit_graph_filename(obj_dir);
760         if (safe_create_leading_directories(graph_name))
761                 die_errno(_("unable to create leading directories of %s"),
762                           graph_name);
763
764         hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
765         f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
766
767         hashwrite_be32(f, GRAPH_SIGNATURE);
768
769         hashwrite_u8(f, GRAPH_VERSION);
770         hashwrite_u8(f, GRAPH_OID_VERSION);
771         hashwrite_u8(f, num_chunks);
772         hashwrite_u8(f, 0); /* unused padding byte */
773
774         chunk_ids[0] = GRAPH_CHUNKID_OIDFANOUT;
775         chunk_ids[1] = GRAPH_CHUNKID_OIDLOOKUP;
776         chunk_ids[2] = GRAPH_CHUNKID_DATA;
777         if (num_extra_edges)
778                 chunk_ids[3] = GRAPH_CHUNKID_LARGEEDGES;
779         else
780                 chunk_ids[3] = 0;
781         chunk_ids[4] = 0;
782
783         chunk_offsets[0] = 8 + (num_chunks + 1) * GRAPH_CHUNKLOOKUP_WIDTH;
784         chunk_offsets[1] = chunk_offsets[0] + GRAPH_FANOUT_SIZE;
785         chunk_offsets[2] = chunk_offsets[1] + GRAPH_OID_LEN * commits.nr;
786         chunk_offsets[3] = chunk_offsets[2] + (GRAPH_OID_LEN + 16) * commits.nr;
787         chunk_offsets[4] = chunk_offsets[3] + 4 * num_extra_edges;
788
789         for (i = 0; i <= num_chunks; i++) {
790                 uint32_t chunk_write[3];
791
792                 chunk_write[0] = htonl(chunk_ids[i]);
793                 chunk_write[1] = htonl(chunk_offsets[i] >> 32);
794                 chunk_write[2] = htonl(chunk_offsets[i] & 0xffffffff);
795                 hashwrite(f, chunk_write, 12);
796         }
797
798         write_graph_chunk_fanout(f, commits.list, commits.nr);
799         write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
800         write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
801         write_graph_chunk_large_edges(f, commits.list, commits.nr);
802
803         close_commit_graph();
804         finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);
805         commit_lock_file(&lk);
806
807         free(oids.list);
808         oids.alloc = 0;
809         oids.nr = 0;
810 }