summaryrefslogtreecommitdiff
path: root/commit-graph.c
blob: ae6cabb4cda46a74d5f4f59bbf54a550361fd10f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
#include "cache.h"
#include "config.h"
#include "dir.h"
#include "git-compat-util.h"
#include "lockfile.h"
#include "pack.h"
#include "packfile.h"
#include "commit.h"
#include "object.h"
#include "refs.h"
#include "revision.h"
#include "sha1-lookup.h"
#include "commit-graph.h"
#include "object-store.h"
#include "alloc.h"
 
#define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
#define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
#define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
#define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
#define GRAPH_CHUNKID_LARGEEDGES 0x45444745 /* "EDGE" */
 
#define GRAPH_DATA_WIDTH 36
 
#define GRAPH_VERSION_1 0x1
#define GRAPH_VERSION GRAPH_VERSION_1
 
#define GRAPH_OID_VERSION_SHA1 1
#define GRAPH_OID_LEN_SHA1 GIT_SHA1_RAWSZ
#define GRAPH_OID_VERSION GRAPH_OID_VERSION_SHA1
#define GRAPH_OID_LEN GRAPH_OID_LEN_SHA1
 
#define GRAPH_OCTOPUS_EDGES_NEEDED 0x80000000
#define GRAPH_PARENT_MISSING 0x7fffffff
#define GRAPH_EDGE_LAST_MASK 0x7fffffff
#define GRAPH_PARENT_NONE 0x70000000
 
#define GRAPH_LAST_EDGE 0x80000000
 
#define GRAPH_HEADER_SIZE 8
#define GRAPH_FANOUT_SIZE (4 * 256)
#define GRAPH_CHUNKLOOKUP_WIDTH 12
#define GRAPH_MIN_SIZE (GRAPH_HEADER_SIZE + 4 * GRAPH_CHUNKLOOKUP_WIDTH \
			+ GRAPH_FANOUT_SIZE + GRAPH_OID_LEN)
 
char *get_commit_graph_filename(const char *obj_dir)
{
	return xstrfmt("%s/info/commit-graph", obj_dir);
}
 
static struct commit_graph *alloc_commit_graph(void)
{
	struct commit_graph *g = xcalloc(1, sizeof(*g));
	g->graph_fd = -1;
 
	return g;
}
 
struct commit_graph *load_commit_graph_one(const char *graph_file)
{
	void *graph_map;
	const unsigned char *data, *chunk_lookup;
	size_t graph_size;
	struct stat st;
	uint32_t i;
	struct commit_graph *graph;
	int fd = git_open(graph_file);
	uint64_t last_chunk_offset;
	uint32_t last_chunk_id;
	uint32_t graph_signature;
	unsigned char graph_version, hash_version;
 
	if (fd < 0)
		return NULL;
	if (fstat(fd, &st)) {
		close(fd);
		return NULL;
	}
	graph_size = xsize_t(st.st_size);
 
	if (graph_size < GRAPH_MIN_SIZE) {
		close(fd);
		die(_("graph file %s is too small"), graph_file);
	}
	graph_map = xmmap(NULL, graph_size, PROT_READ, MAP_PRIVATE, fd, 0);
	data = (const unsigned char *)graph_map;
 
	graph_signature = get_be32(data);
	if (graph_signature != GRAPH_SIGNATURE) {
		error(_("graph signature %X does not match signature %X"),
		      graph_signature, GRAPH_SIGNATURE);
		goto cleanup_fail;
	}
 
	graph_version = *(unsigned char*)(data + 4);
	if (graph_version != GRAPH_VERSION) {
		error(_("graph version %X does not match version %X"),
		      graph_version, GRAPH_VERSION);
		goto cleanup_fail;
	}
 
	hash_version = *(unsigned char*)(data + 5);
	if (hash_version != GRAPH_OID_VERSION) {
		error(_("hash version %X does not match version %X"),
		      hash_version, GRAPH_OID_VERSION);
		goto cleanup_fail;
	}
 
	graph = alloc_commit_graph();
 
	graph->hash_len = GRAPH_OID_LEN;
	graph->num_chunks = *(unsigned char*)(data + 6);
	graph->graph_fd = fd;
	graph->data = graph_map;
	graph->data_len = graph_size;
 
	last_chunk_id = 0;
	last_chunk_offset = 8;
	chunk_lookup = data + 8;
	for (i = 0; i < graph->num_chunks; i++) {
		uint32_t chunk_id = get_be32(chunk_lookup + 0);
		uint64_t chunk_offset = get_be64(chunk_lookup + 4);
		int chunk_repeated = 0;
 
		chunk_lookup += GRAPH_CHUNKLOOKUP_WIDTH;
 
		if (chunk_offset > graph_size - GIT_MAX_RAWSZ) {
			error(_("improper chunk offset %08x%08x"), (uint32_t)(chunk_offset >> 32),
			      (uint32_t)chunk_offset);
			goto cleanup_fail;
		}
 
		switch (chunk_id) {
		case GRAPH_CHUNKID_OIDFANOUT:
			if (graph->chunk_oid_fanout)
				chunk_repeated = 1;
			else
				graph->chunk_oid_fanout = (uint32_t*)(data + chunk_offset);
			break;
 
		case GRAPH_CHUNKID_OIDLOOKUP:
			if (graph->chunk_oid_lookup)
				chunk_repeated = 1;
			else
				graph->chunk_oid_lookup = data + chunk_offset;
			break;
 
		case GRAPH_CHUNKID_DATA:
			if (graph->chunk_commit_data)
				chunk_repeated = 1;
			else
				graph->chunk_commit_data = data + chunk_offset;
			break;
 
		case GRAPH_CHUNKID_LARGEEDGES:
			if (graph->chunk_large_edges)
				chunk_repeated = 1;
			else
				graph->chunk_large_edges = data + chunk_offset;
			break;
		}
 
		if (chunk_repeated) {
			error(_("chunk id %08x appears multiple times"), chunk_id);
			goto cleanup_fail;
		}
 
		if (last_chunk_id == GRAPH_CHUNKID_OIDLOOKUP)
		{
			graph->num_commits = (chunk_offset - last_chunk_offset)
					     / graph->hash_len;
		}
 
		last_chunk_id = chunk_id;
		last_chunk_offset = chunk_offset;
	}
 
	return graph;
 
cleanup_fail:
	munmap(graph_map, graph_size);
	close(fd);
	exit(1);
}
 
static void prepare_commit_graph_one(struct repository *r, const char *obj_dir)
{
	char *graph_name;
 
	if (r->objects->commit_graph)
		return;
 
	graph_name = get_commit_graph_filename(obj_dir);
	r->objects->commit_graph =
		load_commit_graph_one(graph_name);
 
	FREE_AND_NULL(graph_name);
}
 
/*
 * Return 1 if commit_graph is non-NULL, and 0 otherwise.
 *
 * On the first invocation, this function attemps to load the commit
 * graph if the_repository is configured to have one.
 */
static int prepare_commit_graph(struct repository *r)
{
	struct alternate_object_database *alt;
	char *obj_dir;
	int config_value;
 
	if (r->objects->commit_graph_attempted)
		return !!r->objects->commit_graph;
	r->objects->commit_graph_attempted = 1;
 
	if (repo_config_get_bool(r, "core.commitgraph", &config_value) ||
	    !config_value)
		/*
		 * This repository is not configured to use commit graphs, so
		 * do not load one. (But report commit_graph_attempted anyway
		 * so that commit graph loading is not attempted again for this
		 * repository.)
		 */
		return 0;
 
	obj_dir = r->objects->objectdir;
	prepare_commit_graph_one(r, obj_dir);
	prepare_alt_odb(r);
	for (alt = r->objects->alt_odb_list;
	     !r->objects->commit_graph && alt;
	     alt = alt->next)
		prepare_commit_graph_one(r, alt->path);
	return !!r->objects->commit_graph;
}
 
int generation_numbers_enabled(struct repository *r)
{
	uint32_t first_generation;
	struct commit_graph *g;
	if (!prepare_commit_graph(r))
	       return 0;
 
	g = r->objects->commit_graph;
 
	if (!g->num_commits)
		return 0;
 
	first_generation = get_be32(g->chunk_commit_data +
				    g->hash_len + 8) >> 2;
 
	return !!first_generation;
}
 
static void close_commit_graph(void)
{
	free_commit_graph(the_repository->objects->commit_graph);
	the_repository->objects->commit_graph = NULL;
}
 
static int bsearch_graph(struct commit_graph *g, struct object_id *oid, uint32_t *pos)
{
	return bsearch_hash(oid->hash, g->chunk_oid_fanout,
			    g->chunk_oid_lookup, g->hash_len, pos);
}
 
static struct commit_list **insert_parent_or_die(struct commit_graph *g,
						 uint64_t pos,
						 struct commit_list **pptr)
{
	struct commit *c;
	struct object_id oid;
 
	if (pos >= g->num_commits)
		die("invalid parent position %"PRIu64, pos);
 
	hashcpy(oid.hash, g->chunk_oid_lookup + g->hash_len * pos);
	c = lookup_commit(the_repository, &oid);
	if (!c)
		die(_("could not find commit %s"), oid_to_hex(&oid));
	c->graph_pos = pos;
	return &commit_list_insert(c, pptr)->next;
}
 
static void fill_commit_graph_info(struct commit *item, struct commit_graph *g, uint32_t pos)
{
	const unsigned char *commit_data = g->chunk_commit_data + GRAPH_DATA_WIDTH * pos;
	item->graph_pos = pos;
	item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
}
 
static int fill_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t pos)
{
	uint32_t edge_value;
	uint32_t *parent_data_ptr;
	uint64_t date_low, date_high;
	struct commit_list **pptr;
	const unsigned char *commit_data = g->chunk_commit_data + (g->hash_len + 16) * pos;
 
	item->object.parsed = 1;
	item->graph_pos = pos;
 
	item->maybe_tree = NULL;
 
	date_high = get_be32(commit_data + g->hash_len + 8) & 0x3;
	date_low = get_be32(commit_data + g->hash_len + 12);
	item->date = (timestamp_t)((date_high << 32) | date_low);
 
	item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
 
	pptr = &item->parents;
 
	edge_value = get_be32(commit_data + g->hash_len);
	if (edge_value == GRAPH_PARENT_NONE)
		return 1;
	pptr = insert_parent_or_die(g, edge_value, pptr);
 
	edge_value = get_be32(commit_data + g->hash_len + 4);
	if (edge_value == GRAPH_PARENT_NONE)
		return 1;
	if (!(edge_value & GRAPH_OCTOPUS_EDGES_NEEDED)) {
		pptr = insert_parent_or_die(g, edge_value, pptr);
		return 1;
	}
 
	parent_data_ptr = (uint32_t*)(g->chunk_large_edges +
			  4 * (uint64_t)(edge_value & GRAPH_EDGE_LAST_MASK));
	do {
		edge_value = get_be32(parent_data_ptr);
		pptr = insert_parent_or_die(g,
					    edge_value & GRAPH_EDGE_LAST_MASK,
					    pptr);
		parent_data_ptr++;
	} while (!(edge_value & GRAPH_LAST_EDGE));
 
	return 1;
}
 
static int find_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t *pos)
{
	if (item->graph_pos != COMMIT_NOT_FROM_GRAPH) {
		*pos = item->graph_pos;
		return 1;
	} else {
		return bsearch_graph(g, &(item->object.oid), pos);
	}
}
 
static int parse_commit_in_graph_one(struct commit_graph *g, struct commit *item)
{
	uint32_t pos;
 
	if (item->object.parsed)
		return 1;
 
	if (find_commit_in_graph(item, g, &pos))
		return fill_commit_in_graph(item, g, pos);
 
	return 0;
}
 
int parse_commit_in_graph(struct repository *r, struct commit *item)
{
	if (!prepare_commit_graph(r))
		return 0;
	return parse_commit_in_graph_one(r->objects->commit_graph, item);
}
 
void load_commit_graph_info(struct repository *r, struct commit *item)
{
	uint32_t pos;
	if (!prepare_commit_graph(r))
		return;
	if (find_commit_in_graph(item, r->objects->commit_graph, &pos))
		fill_commit_graph_info(item, r->objects->commit_graph, pos);
}
 
static struct tree *load_tree_for_commit(struct commit_graph *g, struct commit *c)
{
	struct object_id oid;
	const unsigned char *commit_data = g->chunk_commit_data +
					   GRAPH_DATA_WIDTH * (c->graph_pos);
 
	hashcpy(oid.hash, commit_data);
	c->maybe_tree = lookup_tree(the_repository, &oid);
 
	return c->maybe_tree;
}
 
static struct tree *get_commit_tree_in_graph_one(struct commit_graph *g,
						 const struct commit *c)
{
	if (c->maybe_tree)
		return c->maybe_tree;
	if (c->graph_pos == COMMIT_NOT_FROM_GRAPH)
		BUG("get_commit_tree_in_graph_one called from non-commit-graph commit");
 
	return load_tree_for_commit(g, (struct commit *)c);
}
 
struct tree *get_commit_tree_in_graph(struct repository *r, const struct commit *c)
{
	return get_commit_tree_in_graph_one(r->objects->commit_graph, c);
}
 
static void write_graph_chunk_fanout(struct hashfile *f,
				     struct commit **commits,
				     int nr_commits)
{
	int i, count = 0;
	struct commit **list = commits;
 
	/*
	 * Write the first-level table (the list is sorted,
	 * but we use a 256-entry lookup to be able to avoid
	 * having to do eight extra binary search iterations).
	 */
	for (i = 0; i < 256; i++) {
		while (count < nr_commits) {
			if ((*list)->object.oid.hash[0] != i)
				break;
			count++;
			list++;
		}
 
		hashwrite_be32(f, count);
	}
}
 
static void write_graph_chunk_oids(struct hashfile *f, int hash_len,
				   struct commit **commits, int nr_commits)
{
	struct commit **list = commits;
	int count;
	for (count = 0; count < nr_commits; count++, list++)
		hashwrite(f, (*list)->object.oid.hash, (int)hash_len);
}
 
static const unsigned char *commit_to_sha1(size_t index, void *table)
{
	struct commit **commits = table;
	return commits[index]->object.oid.hash;
}
 
static void write_graph_chunk_data(struct hashfile *f, int hash_len,
				   struct commit **commits, int nr_commits)
{
	struct commit **list = commits;
	struct commit **last = commits + nr_commits;
	uint32_t num_extra_edges = 0;
 
	while (list < last) {
		struct commit_list *parent;
		int edge_value;
		uint32_t packedDate[2];
 
		parse_commit(*list);
		hashwrite(f, get_commit_tree_oid(*list)->hash, hash_len);
 
		parent = (*list)->parents;
 
		if (!parent)
			edge_value = GRAPH_PARENT_NONE;
		else {
			edge_value = sha1_pos(parent->item->object.oid.hash,
					      commits,
					      nr_commits,
					      commit_to_sha1);
 
			if (edge_value < 0)
				edge_value = GRAPH_PARENT_MISSING;
		}
 
		hashwrite_be32(f, edge_value);
 
		if (parent)
			parent = parent->next;
 
		if (!parent)
			edge_value = GRAPH_PARENT_NONE;
		else if (parent->next)
			edge_value = GRAPH_OCTOPUS_EDGES_NEEDED | num_extra_edges;
		else {
			edge_value = sha1_pos(parent->item->object.oid.hash,
					      commits,
					      nr_commits,
					      commit_to_sha1);
			if (edge_value < 0)
				edge_value = GRAPH_PARENT_MISSING;
		}
 
		hashwrite_be32(f, edge_value);
 
		if (edge_value & GRAPH_OCTOPUS_EDGES_NEEDED) {
			do {
				num_extra_edges++;
				parent = parent->next;
			} while (parent);
		}
 
		if (sizeof((*list)->date) > 4)
			packedDate[0] = htonl(((*list)->date >> 32) & 0x3);
		else
			packedDate[0] = 0;
 
		packedDate[0] |= htonl((*list)->generation << 2);
 
		packedDate[1] = htonl((*list)->date);
		hashwrite(f, packedDate, 8);
 
		list++;
	}
}
 
static void write_graph_chunk_large_edges(struct hashfile *f,
					  struct commit **commits,
					  int nr_commits)
{
	struct commit **list = commits;
	struct commit **last = commits + nr_commits;
	struct commit_list *parent;
 
	while (list < last) {
		int num_parents = 0;
		for (parent = (*list)->parents; num_parents < 3 && parent;
		     parent = parent->next)
			num_parents++;
 
		if (num_parents <= 2) {
			list++;
			continue;
		}
 
		/* Since num_parents > 2, this initializer is safe. */
		for (parent = (*list)->parents->next; parent; parent = parent->next) {
			int edge_value = sha1_pos(parent->item->object.oid.hash,
						  commits,
						  nr_commits,
						  commit_to_sha1);
 
			if (edge_value < 0)
				edge_value = GRAPH_PARENT_MISSING;
			else if (!parent->next)
				edge_value |= GRAPH_LAST_EDGE;
 
			hashwrite_be32(f, edge_value);
		}
 
		list++;
	}
}
 
static int commit_compare(const void *_a, const void *_b)
{
	const struct object_id *a = (const struct object_id *)_a;
	const struct object_id *b = (const struct object_id *)_b;
	return oidcmp(a, b);
}
 
struct packed_commit_list {
	struct commit **list;
	int nr;
	int alloc;
};
 
struct packed_oid_list {
	struct object_id *list;
	int nr;
	int alloc;
};
 
static int add_packed_commits(const struct object_id *oid,
			      struct packed_git *pack,
			      uint32_t pos,
			      void *data)
{
	struct packed_oid_list *list = (struct packed_oid_list*)data;
	enum object_type type;
	off_t offset = nth_packed_object_offset(pack, pos);
	struct object_info oi = OBJECT_INFO_INIT;
 
	oi.typep = &type;
	if (packed_object_info(the_repository, pack, offset, &oi) < 0)
		die(_("unable to get type of object %s"), oid_to_hex(oid));
 
	if (type != OBJ_COMMIT)
		return 0;
 
	ALLOC_GROW(list->list, list->nr + 1, list->alloc);
	oidcpy(&(list->list[list->nr]), oid);
	list->nr++;
 
	return 0;
}
 
static void add_missing_parents(struct packed_oid_list *oids, struct commit *commit)
{
	struct commit_list *parent;
	for (parent = commit->parents; parent; parent = parent->next) {
		if (!(parent->item->object.flags & UNINTERESTING)) {
			ALLOC_GROW(oids->list, oids->nr + 1, oids->alloc);
			oidcpy(&oids->list[oids->nr], &(parent->item->object.oid));
			oids->nr++;
			parent->item->object.flags |= UNINTERESTING;
		}
	}
}
 
static void close_reachable(struct packed_oid_list *oids)
{
	int i;
	struct commit *commit;
 
	for (i = 0; i < oids->nr; i++) {
		commit = lookup_commit(the_repository, &oids->list[i]);
		if (commit)
			commit->object.flags |= UNINTERESTING;
	}
 
	/*
	 * As this loop runs, oids->nr may grow, but not more
	 * than the number of missing commits in the reachable
	 * closure.
	 */
	for (i = 0; i < oids->nr; i++) {
		commit = lookup_commit(the_repository, &oids->list[i]);
 
		if (commit && !parse_commit(commit))
			add_missing_parents(oids, commit);
	}
 
	for (i = 0; i < oids->nr; i++) {
		commit = lookup_commit(the_repository, &oids->list[i]);
 
		if (commit)
			commit->object.flags &= ~UNINTERESTING;
	}
}
 
static void compute_generation_numbers(struct packed_commit_list* commits)
{
	int i;
	struct commit_list *list = NULL;
 
	for (i = 0; i < commits->nr; i++) {
		if (commits->list[i]->generation != GENERATION_NUMBER_INFINITY &&
		    commits->list[i]->generation != GENERATION_NUMBER_ZERO)
			continue;
 
		commit_list_insert(commits->list[i], &list);
		while (list) {
			struct commit *current = list->item;
			struct commit_list *parent;
			int all_parents_computed = 1;
			uint32_t max_generation = 0;
 
			for (parent = current->parents; parent; parent = parent->next) {
				if (parent->item->generation == GENERATION_NUMBER_INFINITY ||
				    parent->item->generation == GENERATION_NUMBER_ZERO) {
					all_parents_computed = 0;
					commit_list_insert(parent->item, &list);
					break;
				} else if (parent->item->generation > max_generation) {
					max_generation = parent->item->generation;
				}
			}
 
			if (all_parents_computed) {
				current->generation = max_generation + 1;
				pop_commit(&list);
 
				if (current->generation > GENERATION_NUMBER_MAX)
					current->generation = GENERATION_NUMBER_MAX;
			}
		}
	}
}
 
static int add_ref_to_list(const char *refname,
			   const struct object_id *oid,
			   int flags, void *cb_data)
{
	struct string_list *list = (struct string_list *)cb_data;
 
	string_list_append(list, oid_to_hex(oid));
	return 0;
}
 
void write_commit_graph_reachable(const char *obj_dir, int append)
{
	struct string_list list;
 
	string_list_init(&list, 1);
	for_each_ref(add_ref_to_list, &list);
	write_commit_graph(obj_dir, NULL, &list, append);
}
 
void write_commit_graph(const char *obj_dir,
			struct string_list *pack_indexes,
			struct string_list *commit_hex,
			int append)
{
	struct packed_oid_list oids;
	struct packed_commit_list commits;
	struct hashfile *f;
	uint32_t i, count_distinct = 0;
	char *graph_name;
	struct lock_file lk = LOCK_INIT;
	uint32_t chunk_ids[5];
	uint64_t chunk_offsets[5];
	int num_chunks;
	int num_extra_edges;
	struct commit_list *parent;
 
	oids.nr = 0;
	oids.alloc = approximate_object_count() / 4;
 
	if (append) {
		prepare_commit_graph_one(the_repository, obj_dir);
		if (the_repository->objects->commit_graph)
			oids.alloc += the_repository->objects->commit_graph->num_commits;
	}
 
	if (oids.alloc < 1024)
		oids.alloc = 1024;
	ALLOC_ARRAY(oids.list, oids.alloc);
 
	if (append && the_repository->objects->commit_graph) {
		struct commit_graph *commit_graph =
			the_repository->objects->commit_graph;
		for (i = 0; i < commit_graph->num_commits; i++) {
			const unsigned char *hash = commit_graph->chunk_oid_lookup +
				commit_graph->hash_len * i;
			hashcpy(oids.list[oids.nr++].hash, hash);
		}
	}
 
	if (pack_indexes) {
		struct strbuf packname = STRBUF_INIT;
		int dirlen;
		strbuf_addf(&packname, "%s/pack/", obj_dir);
		dirlen = packname.len;
		for (i = 0; i < pack_indexes->nr; i++) {
			struct packed_git *p;
			strbuf_setlen(&packname, dirlen);
			strbuf_addstr(&packname, pack_indexes->items[i].string);
			p = add_packed_git(packname.buf, packname.len, 1);
			if (!p)
				die(_("error adding pack %s"), packname.buf);
			if (open_pack_index(p))
				die(_("error opening index for %s"), packname.buf);
			for_each_object_in_pack(p, add_packed_commits, &oids, 0);
			close_pack(p);
		}
		strbuf_release(&packname);
	}
 
	if (commit_hex) {
		for (i = 0; i < commit_hex->nr; i++) {
			const char *end;
			struct object_id oid;
			struct commit *result;
 
			if (commit_hex->items[i].string &&
			    parse_oid_hex(commit_hex->items[i].string, &oid, &end))
				continue;
 
			result = lookup_commit_reference_gently(the_repository, &oid, 1);
 
			if (result) {
				ALLOC_GROW(oids.list, oids.nr + 1, oids.alloc);
				oidcpy(&oids.list[oids.nr], &(result->object.oid));
				oids.nr++;
			}
		}
	}
 
	if (!pack_indexes && !commit_hex)
		for_each_packed_object(add_packed_commits, &oids, 0);
 
	close_reachable(&oids);
 
	QSORT(oids.list, oids.nr, commit_compare);
 
	count_distinct = 1;
	for (i = 1; i < oids.nr; i++) {
		if (!oideq(&oids.list[i - 1], &oids.list[i]))
			count_distinct++;
	}
 
	if (count_distinct >= GRAPH_PARENT_MISSING)
		die(_("the commit graph format cannot write %d commits"), count_distinct);
 
	commits.nr = 0;
	commits.alloc = count_distinct;
	ALLOC_ARRAY(commits.list, commits.alloc);
 
	num_extra_edges = 0;
	for (i = 0; i < oids.nr; i++) {
		int num_parents = 0;
		if (i > 0 && oideq(&oids.list[i - 1], &oids.list[i]))
			continue;
 
		commits.list[commits.nr] = lookup_commit(the_repository, &oids.list[i]);
		parse_commit(commits.list[commits.nr]);
 
		for (parent = commits.list[commits.nr]->parents;
		     parent; parent = parent->next)
			num_parents++;
 
		if (num_parents > 2)
			num_extra_edges += num_parents - 1;
 
		commits.nr++;
	}
	num_chunks = num_extra_edges ? 4 : 3;
 
	if (commits.nr >= GRAPH_PARENT_MISSING)
		die(_("too many commits to write graph"));
 
	compute_generation_numbers(&commits);
 
	graph_name = get_commit_graph_filename(obj_dir);
	if (safe_create_leading_directories(graph_name))
		die_errno(_("unable to create leading directories of %s"),
			  graph_name);
 
	hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
	f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
 
	hashwrite_be32(f, GRAPH_SIGNATURE);
 
	hashwrite_u8(f, GRAPH_VERSION);
	hashwrite_u8(f, GRAPH_OID_VERSION);
	hashwrite_u8(f, num_chunks);
	hashwrite_u8(f, 0); /* unused padding byte */
 
	chunk_ids[0] = GRAPH_CHUNKID_OIDFANOUT;
	chunk_ids[1] = GRAPH_CHUNKID_OIDLOOKUP;
	chunk_ids[2] = GRAPH_CHUNKID_DATA;
	if (num_extra_edges)
		chunk_ids[3] = GRAPH_CHUNKID_LARGEEDGES;
	else
		chunk_ids[3] = 0;
	chunk_ids[4] = 0;
 
	chunk_offsets[0] = 8 + (num_chunks + 1) * GRAPH_CHUNKLOOKUP_WIDTH;
	chunk_offsets[1] = chunk_offsets[0] + GRAPH_FANOUT_SIZE;
	chunk_offsets[2] = chunk_offsets[1] + GRAPH_OID_LEN * commits.nr;
	chunk_offsets[3] = chunk_offsets[2] + (GRAPH_OID_LEN + 16) * commits.nr;
	chunk_offsets[4] = chunk_offsets[3] + 4 * num_extra_edges;
 
	for (i = 0; i <= num_chunks; i++) {
		uint32_t chunk_write[3];
 
		chunk_write[0] = htonl(chunk_ids[i]);
		chunk_write[1] = htonl(chunk_offsets[i] >> 32);
		chunk_write[2] = htonl(chunk_offsets[i] & 0xffffffff);
		hashwrite(f, chunk_write, 12);
	}
 
	write_graph_chunk_fanout(f, commits.list, commits.nr);
	write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
	write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
	write_graph_chunk_large_edges(f, commits.list, commits.nr);
 
	close_commit_graph();
	finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);
	commit_lock_file(&lk);
 
	free(oids.list);
	oids.alloc = 0;
	oids.nr = 0;
}
 
#define VERIFY_COMMIT_GRAPH_ERROR_HASH 2
static int verify_commit_graph_error;
 
static void graph_report(const char *fmt, ...)
{
	va_list ap;
 
	verify_commit_graph_error = 1;
	va_start(ap, fmt);
	vfprintf(stderr, fmt, ap);
	fprintf(stderr, "\n");
	va_end(ap);
}
 
#define GENERATION_ZERO_EXISTS 1
#define GENERATION_NUMBER_EXISTS 2
 
int verify_commit_graph(struct repository *r, struct commit_graph *g)
{
	uint32_t i, cur_fanout_pos = 0;
	struct object_id prev_oid, cur_oid, checksum;
	int generation_zero = 0;
	struct hashfile *f;
	int devnull;
 
	if (!g) {
		graph_report("no commit-graph file loaded");
		return 1;
	}
 
	verify_commit_graph_error = 0;
 
	if (!g->chunk_oid_fanout)
		graph_report("commit-graph is missing the OID Fanout chunk");
	if (!g->chunk_oid_lookup)
		graph_report("commit-graph is missing the OID Lookup chunk");
	if (!g->chunk_commit_data)
		graph_report("commit-graph is missing the Commit Data chunk");
 
	if (verify_commit_graph_error)
		return verify_commit_graph_error;
 
	devnull = open("/dev/null", O_WRONLY);
	f = hashfd(devnull, NULL);
	hashwrite(f, g->data, g->data_len - g->hash_len);
	finalize_hashfile(f, checksum.hash, CSUM_CLOSE);
	if (!hasheq(checksum.hash, g->data + g->data_len - g->hash_len)) {
		graph_report(_("the commit-graph file has incorrect checksum and is likely corrupt"));
		verify_commit_graph_error = VERIFY_COMMIT_GRAPH_ERROR_HASH;
	}
 
	for (i = 0; i < g->num_commits; i++) {
		struct commit *graph_commit;
 
		hashcpy(cur_oid.hash, g->chunk_oid_lookup + g->hash_len * i);
 
		if (i && oidcmp(&prev_oid, &cur_oid) >= 0)
			graph_report("commit-graph has incorrect OID order: %s then %s",
				     oid_to_hex(&prev_oid),
				     oid_to_hex(&cur_oid));
 
		oidcpy(&prev_oid, &cur_oid);
 
		while (cur_oid.hash[0] > cur_fanout_pos) {
			uint32_t fanout_value = get_be32(g->chunk_oid_fanout + cur_fanout_pos);
 
			if (i != fanout_value)
				graph_report("commit-graph has incorrect fanout value: fanout[%d] = %u != %u",
					     cur_fanout_pos, fanout_value, i);
			cur_fanout_pos++;
		}
 
		graph_commit = lookup_commit(r, &cur_oid);
		if (!parse_commit_in_graph_one(g, graph_commit))
			graph_report("failed to parse %s from commit-graph",
				     oid_to_hex(&cur_oid));
	}
 
	while (cur_fanout_pos < 256) {
		uint32_t fanout_value = get_be32(g->chunk_oid_fanout + cur_fanout_pos);
 
		if (g->num_commits != fanout_value)
			graph_report("commit-graph has incorrect fanout value: fanout[%d] = %u != %u",
				     cur_fanout_pos, fanout_value, i);
 
		cur_fanout_pos++;
	}
 
	if (verify_commit_graph_error & ~VERIFY_COMMIT_GRAPH_ERROR_HASH)
		return verify_commit_graph_error;
 
	for (i = 0; i < g->num_commits; i++) {
		struct commit *graph_commit, *odb_commit;
		struct commit_list *graph_parents, *odb_parents;
		uint32_t max_generation = 0;
 
		hashcpy(cur_oid.hash, g->chunk_oid_lookup + g->hash_len * i);
 
		graph_commit = lookup_commit(r, &cur_oid);
		odb_commit = (struct commit *)create_object(r, cur_oid.hash, alloc_commit_node(r));
		if (parse_commit_internal(odb_commit, 0, 0)) {
			graph_report("failed to parse %s from object database",
				     oid_to_hex(&cur_oid));
			continue;
		}
 
		if (!oideq(&get_commit_tree_in_graph_one(g, graph_commit)->object.oid,
			   get_commit_tree_oid(odb_commit)))
			graph_report("root tree OID for commit %s in commit-graph is %s != %s",
				     oid_to_hex(&cur_oid),
				     oid_to_hex(get_commit_tree_oid(graph_commit)),
				     oid_to_hex(get_commit_tree_oid(odb_commit)));
 
		graph_parents = graph_commit->parents;
		odb_parents = odb_commit->parents;
 
		while (graph_parents) {
			if (odb_parents == NULL) {
				graph_report("commit-graph parent list for commit %s is too long",
					     oid_to_hex(&cur_oid));
				break;
			}
 
			if (!oideq(&graph_parents->item->object.oid, &odb_parents->item->object.oid))
				graph_report("commit-graph parent for %s is %s != %s",
					     oid_to_hex(&cur_oid),
					     oid_to_hex(&graph_parents->item->object.oid),
					     oid_to_hex(&odb_parents->item->object.oid));
 
			if (graph_parents->item->generation > max_generation)
				max_generation = graph_parents->item->generation;
 
			graph_parents = graph_parents->next;
			odb_parents = odb_parents->next;
		}
 
		if (odb_parents != NULL)
			graph_report("commit-graph parent list for commit %s terminates early",
				     oid_to_hex(&cur_oid));
 
		if (!graph_commit->generation) {
			if (generation_zero == GENERATION_NUMBER_EXISTS)
				graph_report("commit-graph has generation number zero for commit %s, but non-zero elsewhere",
					     oid_to_hex(&cur_oid));
			generation_zero = GENERATION_ZERO_EXISTS;
		} else if (generation_zero == GENERATION_ZERO_EXISTS)
			graph_report("commit-graph has non-zero generation number for commit %s, but zero elsewhere",
				     oid_to_hex(&cur_oid));
 
		if (generation_zero == GENERATION_ZERO_EXISTS)
			continue;
 
		/*
		 * If one of our parents has generation GENERATION_NUMBER_MAX, then
		 * our generation is also GENERATION_NUMBER_MAX. Decrement to avoid
		 * extra logic in the following condition.
		 */
		if (max_generation == GENERATION_NUMBER_MAX)
			max_generation--;
 
		if (graph_commit->generation != max_generation + 1)
			graph_report("commit-graph generation for commit %s is %u != %u",
				     oid_to_hex(&cur_oid),
				     graph_commit->generation,
				     max_generation + 1);
 
		if (graph_commit->date != odb_commit->date)
			graph_report("commit date for commit %s in commit-graph is %"PRItime" != %"PRItime,
				     oid_to_hex(&cur_oid),
				     graph_commit->date,
				     odb_commit->date);
	}
 
	return verify_commit_graph_error;
}
 
void free_commit_graph(struct commit_graph *g)
{
	if (!g)
		return;
	if (g->graph_fd >= 0) {
		munmap((void *)g->data, g->data_len);
		g->data = NULL;
		close(g->graph_fd);
	}
	free(g);
}