summaryrefslogtreecommitdiff
path: root/index-pack.c
blob: 43e007f8238006313e95b7d386a590ce51144dfa (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
#include "cache.h"
#include "delta.h"
#include "pack.h"
#include "csum-file.h"
#include "blob.h"
#include "commit.h"
#include "tag.h"
#include "tree.h"
 
static const char index_pack_usage[] =
"git-index-pack [-v] [-o <index-file>] [{ ---keep | --keep=<msg> }] { <pack-file> | --stdin [--fix-thin] [<pack-file>] }";
 
struct object_entry
{
	unsigned long offset;
	unsigned long size;
	unsigned int hdr_size;
	enum object_type type;
	enum object_type real_type;
	unsigned char sha1[20];
};
 
union delta_base {
	unsigned char sha1[20];
	unsigned long offset;
};
 
/*
 * Even if sizeof(union delta_base) == 24 on 64-bit archs, we really want
 * to memcmp() only the first 20 bytes.
 */
#define UNION_BASE_SZ	20
 
struct delta_entry
{
	union delta_base base;
	int obj_no;
};
 
static struct object_entry *objects;
static struct delta_entry *deltas;
static int nr_objects;
static int nr_deltas;
static int nr_resolved_deltas;
 
static int from_stdin;
static int verbose;
 
static volatile sig_atomic_t progress_update;
 
static void progress_interval(int signum)
{
	progress_update = 1;
}
 
static void setup_progress_signal(void)
{
	struct sigaction sa;
	struct itimerval v;
 
	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = progress_interval;
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_RESTART;
	sigaction(SIGALRM, &sa, NULL);
 
	v.it_interval.tv_sec = 1;
	v.it_interval.tv_usec = 0;
	v.it_value = v.it_interval;
	setitimer(ITIMER_REAL, &v, NULL);
 
}
 
static unsigned display_progress(unsigned n, unsigned total, unsigned last_pc)
{
	unsigned percent = n * 100 / total;
	if (percent != last_pc || progress_update) {
		fprintf(stderr, "%4u%% (%u/%u) done\r", percent, n, total);
		progress_update = 0;
	}
	return percent;
}
 
/* We always read in 4kB chunks. */
static unsigned char input_buffer[4096];
static unsigned long input_offset, input_len, consumed_bytes;
static SHA_CTX input_ctx;
static int input_fd, output_fd, pack_fd;
 
/* Discard current buffer used content. */
static void flush(void)
{
	if (input_offset) {
		if (output_fd >= 0)
			write_or_die(output_fd, input_buffer, input_offset);
		SHA1_Update(&input_ctx, input_buffer, input_offset);
		memmove(input_buffer, input_buffer + input_offset, input_len);
		input_offset = 0;
	}
}
 
/*
 * Make sure at least "min" bytes are available in the buffer, and
 * return the pointer to the buffer.
 */
static void *fill(int min)
{
	if (min <= input_len)
		return input_buffer + input_offset;
	if (min > sizeof(input_buffer))
		die("cannot fill %d bytes", min);
	flush();
	do {
		int ret = xread(input_fd, input_buffer + input_len,
				sizeof(input_buffer) - input_len);
		if (ret <= 0) {
			if (!ret)
				die("early EOF");
			die("read error on input: %s", strerror(errno));
		}
		input_len += ret;
	} while (input_len < min);
	return input_buffer;
}
 
static void use(int bytes)
{
	if (bytes > input_len)
		die("used more bytes than were available");
	input_len -= bytes;
	input_offset += bytes;
	consumed_bytes += bytes;
}
 
static const char *open_pack_file(const char *pack_name)
{
	if (from_stdin) {
		input_fd = 0;
		if (!pack_name) {
			static char tmpfile[PATH_MAX];
			snprintf(tmpfile, sizeof(tmpfile),
				 "%s/pack_XXXXXX", get_object_directory());
			output_fd = mkstemp(tmpfile);
			pack_name = xstrdup(tmpfile);
		} else
			output_fd = open(pack_name, O_CREAT|O_EXCL|O_RDWR, 0600);
		if (output_fd < 0)
			die("unable to create %s: %s\n", pack_name, strerror(errno));
		pack_fd = output_fd;
	} else {
		input_fd = open(pack_name, O_RDONLY);
		if (input_fd < 0)
			die("cannot open packfile '%s': %s",
			    pack_name, strerror(errno));
		output_fd = -1;
		pack_fd = input_fd;
	}
	SHA1_Init(&input_ctx);
	return pack_name;
}
 
static void parse_pack_header(void)
{
	struct pack_header *hdr = fill(sizeof(struct pack_header));
 
	/* Header consistency check */
	if (hdr->hdr_signature != htonl(PACK_SIGNATURE))
		die("pack signature mismatch");
	if (!pack_version_ok(hdr->hdr_version))
		die("pack version %d unsupported", ntohl(hdr->hdr_version));
 
	nr_objects = ntohl(hdr->hdr_entries);
	use(sizeof(struct pack_header));
}
 
static void bad_object(unsigned long offset, const char *format,
		       ...) NORETURN __attribute__((format (printf, 2, 3)));
 
static void bad_object(unsigned long offset, const char *format, ...)
{
	va_list params;
	char buf[1024];
 
	va_start(params, format);
	vsnprintf(buf, sizeof(buf), format, params);
	va_end(params);
	die("pack has bad object at offset %lu: %s", offset, buf);
}
 
static void *unpack_entry_data(unsigned long offset, unsigned long size)
{
	z_stream stream;
	void *buf = xmalloc(size);
 
	memset(&stream, 0, sizeof(stream));
	stream.next_out = buf;
	stream.avail_out = size;
	stream.next_in = fill(1);
	stream.avail_in = input_len;
	inflateInit(&stream);
 
	for (;;) {
		int ret = inflate(&stream, 0);
		use(input_len - stream.avail_in);
		if (stream.total_out == size && ret == Z_STREAM_END)
			break;
		if (ret != Z_OK)
			bad_object(offset, "inflate returned %d", ret);
		stream.next_in = fill(1);
		stream.avail_in = input_len;
	}
	inflateEnd(&stream);
	return buf;
}
 
static void *unpack_raw_entry(struct object_entry *obj, union delta_base *delta_base)
{
	unsigned char *p, c;
	unsigned long size, base_offset;
	unsigned shift;
 
	obj->offset = consumed_bytes;
 
	p = fill(1);
	c = *p;
	use(1);
	obj->type = (c >> 4) & 7;
	size = (c & 15);
	shift = 4;
	while (c & 0x80) {
		p = fill(1);
		c = *p;
		use(1);
		size += (c & 0x7fUL) << shift;
		shift += 7;
	}
	obj->size = size;
 
	switch (obj->type) {
	case OBJ_REF_DELTA:
		hashcpy(delta_base->sha1, fill(20));
		use(20);
		break;
	case OBJ_OFS_DELTA:
		memset(delta_base, 0, sizeof(*delta_base));
		p = fill(1);
		c = *p;
		use(1);
		base_offset = c & 127;
		while (c & 128) {
			base_offset += 1;
			if (!base_offset || base_offset & ~(~0UL >> 7))
				bad_object(obj->offset, "offset value overflow for delta base object");
			p = fill(1);
			c = *p;
			use(1);
			base_offset = (base_offset << 7) + (c & 127);
		}
		delta_base->offset = obj->offset - base_offset;
		if (delta_base->offset >= obj->offset)
			bad_object(obj->offset, "delta base offset is out of bound");
		break;
	case OBJ_COMMIT:
	case OBJ_TREE:
	case OBJ_BLOB:
	case OBJ_TAG:
		break;
	default:
		bad_object(obj->offset, "bad object type %d", obj->type);
	}
	obj->hdr_size = consumed_bytes - obj->offset;
 
	return unpack_entry_data(obj->offset, obj->size);
}
 
static void *get_data_from_pack(struct object_entry *obj)
{
	unsigned long from = obj[0].offset + obj[0].hdr_size;
	unsigned long len = obj[1].offset - from;
	unsigned char *src, *data;
	z_stream stream;
	int st;
 
	src = xmalloc(len);
	if (pread(pack_fd, src, len, from) != len)
		die("cannot pread pack file: %s", strerror(errno));
	data = xmalloc(obj->size);
	memset(&stream, 0, sizeof(stream));
	stream.next_out = data;
	stream.avail_out = obj->size;
	stream.next_in = src;
	stream.avail_in = len;
	inflateInit(&stream);
	while ((st = inflate(&stream, Z_FINISH)) == Z_OK);
	inflateEnd(&stream);
	if (st != Z_STREAM_END || stream.total_out != obj->size)
		die("serious inflate inconsistency");
	free(src);
	return data;
}
 
static int find_delta(const union delta_base *base)
{
	int first = 0, last = nr_deltas;
 
        while (first < last) {
                int next = (first + last) / 2;
                struct delta_entry *delta = &deltas[next];
                int cmp;
 
                cmp = memcmp(base, &delta->base, UNION_BASE_SZ);
                if (!cmp)
                        return next;
                if (cmp < 0) {
                        last = next;
                        continue;
                }
                first = next+1;
        }
        return -first-1;
}
 
static int find_delta_children(const union delta_base *base,
			       int *first_index, int *last_index)
{
	int first = find_delta(base);
	int last = first;
	int end = nr_deltas - 1;
 
	if (first < 0)
		return -1;
	while (first > 0 && !memcmp(&deltas[first - 1].base, base, UNION_BASE_SZ))
		--first;
	while (last < end && !memcmp(&deltas[last + 1].base, base, UNION_BASE_SZ))
		++last;
	*first_index = first;
	*last_index = last;
	return 0;
}
 
static void sha1_object(const void *data, unsigned long size,
			enum object_type type, unsigned char *sha1)
{
	SHA_CTX ctx;
	char header[50];
	int header_size;
	const char *type_str;
 
	switch (type) {
	case OBJ_COMMIT: type_str = commit_type; break;
	case OBJ_TREE:   type_str = tree_type; break;
	case OBJ_BLOB:   type_str = blob_type; break;
	case OBJ_TAG:    type_str = tag_type; break;
	default:
		die("bad type %d", type);
	}
 
	header_size = sprintf(header, "%s %lu", type_str, size) + 1;
 
	SHA1_Init(&ctx);
	SHA1_Update(&ctx, header, header_size);
	SHA1_Update(&ctx, data, size);
	SHA1_Final(sha1, &ctx);
}
 
static void resolve_delta(struct object_entry *delta_obj, void *base_data,
			  unsigned long base_size, enum object_type type)
{
	void *delta_data;
	unsigned long delta_size;
	void *result;
	unsigned long result_size;
	union delta_base delta_base;
	int j, first, last;
 
	delta_obj->real_type = type;
	delta_data = get_data_from_pack(delta_obj);
	delta_size = delta_obj->size;
	result = patch_delta(base_data, base_size, delta_data, delta_size,
			     &result_size);
	free(delta_data);
	if (!result)
		bad_object(delta_obj->offset, "failed to apply delta");
	sha1_object(result, result_size, type, delta_obj->sha1);
	nr_resolved_deltas++;
 
	hashcpy(delta_base.sha1, delta_obj->sha1);
	if (!find_delta_children(&delta_base, &first, &last)) {
		for (j = first; j <= last; j++) {
			struct object_entry *child = objects + deltas[j].obj_no;
			if (child->real_type == OBJ_REF_DELTA)
				resolve_delta(child, result, result_size, type);
		}
	}
 
	memset(&delta_base, 0, sizeof(delta_base));
	delta_base.offset = delta_obj->offset;
	if (!find_delta_children(&delta_base, &first, &last)) {
		for (j = first; j <= last; j++) {
			struct object_entry *child = objects + deltas[j].obj_no;
			if (child->real_type == OBJ_OFS_DELTA)
				resolve_delta(child, result, result_size, type);
		}
	}
 
	free(result);
}
 
static int compare_delta_entry(const void *a, const void *b)
{
	const struct delta_entry *delta_a = a;
	const struct delta_entry *delta_b = b;
	return memcmp(&delta_a->base, &delta_b->base, UNION_BASE_SZ);
}
 
/* Parse all objects and return the pack content SHA1 hash */
static void parse_pack_objects(unsigned char *sha1)
{
	int i, percent = -1;
	struct delta_entry *delta = deltas;
	void *data;
	struct stat st;
 
	/*
	 * First pass:
	 * - find locations of all objects;
	 * - calculate SHA1 of all non-delta objects;
	 * - remember base (SHA1 or offset) for all deltas.
	 */
	if (verbose)
		fprintf(stderr, "Indexing %d objects.\n", nr_objects);
	for (i = 0; i < nr_objects; i++) {
		struct object_entry *obj = &objects[i];
		data = unpack_raw_entry(obj, &delta->base);
		obj->real_type = obj->type;
		if (obj->type == OBJ_REF_DELTA || obj->type == OBJ_OFS_DELTA) {
			nr_deltas++;
			delta->obj_no = i;
			delta++;
		} else
			sha1_object(data, obj->size, obj->type, obj->sha1);
		free(data);
		if (verbose)
			percent = display_progress(i+1, nr_objects, percent);
	}
	objects[i].offset = consumed_bytes;
	if (verbose)
		fputc('\n', stderr);
 
	/* Check pack integrity */
	flush();
	SHA1_Final(sha1, &input_ctx);
	if (hashcmp(fill(20), sha1))
		die("pack is corrupted (SHA1 mismatch)");
	use(20);
 
	/* If input_fd is a file, we should have reached its end now. */
	if (fstat(input_fd, &st))
		die("cannot fstat packfile: %s", strerror(errno));
	if (S_ISREG(st.st_mode) && st.st_size != consumed_bytes)
		die("pack has junk at the end");
 
	if (!nr_deltas)
		return;
 
	/* Sort deltas by base SHA1/offset for fast searching */
	qsort(deltas, nr_deltas, sizeof(struct delta_entry),
	      compare_delta_entry);
 
	/*
	 * Second pass:
	 * - for all non-delta objects, look if it is used as a base for
	 *   deltas;
	 * - if used as a base, uncompress the object and apply all deltas,
	 *   recursively checking if the resulting object is used as a base
	 *   for some more deltas.
	 */
	if (verbose)
		fprintf(stderr, "Resolving %d deltas.\n", nr_deltas);
	for (i = 0; i < nr_objects; i++) {
		struct object_entry *obj = &objects[i];
		union delta_base base;
		int j, ref, ref_first, ref_last, ofs, ofs_first, ofs_last;
 
		if (obj->type == OBJ_REF_DELTA || obj->type == OBJ_OFS_DELTA)
			continue;
		hashcpy(base.sha1, obj->sha1);
		ref = !find_delta_children(&base, &ref_first, &ref_last);
		memset(&base, 0, sizeof(base));
		base.offset = obj->offset;
		ofs = !find_delta_children(&base, &ofs_first, &ofs_last);
		if (!ref && !ofs)
			continue;
		data = get_data_from_pack(obj);
		if (ref)
			for (j = ref_first; j <= ref_last; j++) {
				struct object_entry *child = objects + deltas[j].obj_no;
				if (child->real_type == OBJ_REF_DELTA)
					resolve_delta(child, data,
						      obj->size, obj->type);
			}
		if (ofs)
			for (j = ofs_first; j <= ofs_last; j++) {
				struct object_entry *child = objects + deltas[j].obj_no;
				if (child->real_type == OBJ_OFS_DELTA)
					resolve_delta(child, data,
						      obj->size, obj->type);
			}
		free(data);
		if (verbose)
			percent = display_progress(nr_resolved_deltas,
						   nr_deltas, percent);
	}
	if (verbose && nr_resolved_deltas == nr_deltas)
		fputc('\n', stderr);
}
 
static int write_compressed(int fd, void *in, unsigned int size)
{
	z_stream stream;
	unsigned long maxsize;
	void *out;
 
	memset(&stream, 0, sizeof(stream));
	deflateInit(&stream, zlib_compression_level);
	maxsize = deflateBound(&stream, size);
	out = xmalloc(maxsize);
 
	/* Compress it */
	stream.next_in = in;
	stream.avail_in = size;
	stream.next_out = out;
	stream.avail_out = maxsize;
	while (deflate(&stream, Z_FINISH) == Z_OK);
	deflateEnd(&stream);
 
	size = stream.total_out;
	write_or_die(fd, out, size);
	free(out);
	return size;
}
 
static void append_obj_to_pack(void *buf,
			       unsigned long size, enum object_type type)
{
	struct object_entry *obj = &objects[nr_objects++];
	unsigned char header[10];
	unsigned long s = size;
	int n = 0;
	unsigned char c = (type << 4) | (s & 15);
	s >>= 4;
	while (s) {
		header[n++] = c | 0x80;
		c = s & 0x7f;
		s >>= 7;
	}
	header[n++] = c;
	write_or_die(output_fd, header, n);
	obj[1].offset = obj[0].offset + n;
	obj[1].offset += write_compressed(output_fd, buf, size);
	sha1_object(buf, size, type, obj->sha1);
}
 
static int delta_pos_compare(const void *_a, const void *_b)
{
	struct delta_entry *a = *(struct delta_entry **)_a;
	struct delta_entry *b = *(struct delta_entry **)_b;
	return a->obj_no - b->obj_no;
}
 
static void fix_unresolved_deltas(int nr_unresolved)
{
	struct delta_entry **sorted_by_pos;
	int i, n = 0, percent = -1;
 
	/*
	 * Since many unresolved deltas may well be themselves base objects
	 * for more unresolved deltas, we really want to include the
	 * smallest number of base objects that would cover as much delta
	 * as possible by picking the
	 * trunc deltas first, allowing for other deltas to resolve without
	 * additional base objects.  Since most base objects are to be found
	 * before deltas depending on them, a good heuristic is to start
	 * resolving deltas in the same order as their position in the pack.
	 */
	sorted_by_pos = xmalloc(nr_unresolved * sizeof(*sorted_by_pos));
	for (i = 0; i < nr_deltas; i++) {
		if (objects[deltas[i].obj_no].real_type != OBJ_REF_DELTA)
			continue;
		sorted_by_pos[n++] = &deltas[i];
	}
	qsort(sorted_by_pos, n, sizeof(*sorted_by_pos), delta_pos_compare);
 
	for (i = 0; i < n; i++) {
		struct delta_entry *d = sorted_by_pos[i];
		void *data;
		unsigned long size;
		char type[10];
		enum object_type obj_type;
		int j, first, last;
 
		if (objects[d->obj_no].real_type != OBJ_REF_DELTA)
			continue;
		data = read_sha1_file(d->base.sha1, type, &size);
		if (!data)
			continue;
		if      (!strcmp(type, blob_type))   obj_type = OBJ_BLOB;
		else if (!strcmp(type, tree_type))   obj_type = OBJ_TREE;
		else if (!strcmp(type, commit_type)) obj_type = OBJ_COMMIT;
		else if (!strcmp(type, tag_type))    obj_type = OBJ_TAG;
		else die("base object %s is of type '%s'",
			 sha1_to_hex(d->base.sha1), type);
 
		find_delta_children(&d->base, &first, &last);
		for (j = first; j <= last; j++) {
			struct object_entry *child = objects + deltas[j].obj_no;
			if (child->real_type == OBJ_REF_DELTA)
				resolve_delta(child, data, size, obj_type);
		}
 
		append_obj_to_pack(data, size, obj_type);
		free(data);
		if (verbose)
			percent = display_progress(nr_resolved_deltas,
						   nr_deltas, percent);
	}
	free(sorted_by_pos);
	if (verbose)
		fputc('\n', stderr);
}
 
static void readjust_pack_header_and_sha1(unsigned char *sha1)
{
	struct pack_header hdr;
	SHA_CTX ctx;
	int size;
 
	/* Rewrite pack header with updated object number */
	if (lseek(output_fd, 0, SEEK_SET) != 0)
		die("cannot seek back: %s", strerror(errno));
	if (xread(output_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
		die("cannot read pack header back: %s", strerror(errno));
	hdr.hdr_entries = htonl(nr_objects);
	if (lseek(output_fd, 0, SEEK_SET) != 0)
		die("cannot seek back: %s", strerror(errno));
	write_or_die(output_fd, &hdr, sizeof(hdr));
	if (lseek(output_fd, 0, SEEK_SET) != 0)
		die("cannot seek back: %s", strerror(errno));
 
	/* Recompute and store the new pack's SHA1 */
	SHA1_Init(&ctx);
	do {
		unsigned char *buf[4096];
		size = xread(output_fd, buf, sizeof(buf));
		if (size < 0)
			die("cannot read pack data back: %s", strerror(errno));
		SHA1_Update(&ctx, buf, size);
	} while (size > 0);
	SHA1_Final(sha1, &ctx);
	write_or_die(output_fd, sha1, 20);
}
 
static int sha1_compare(const void *_a, const void *_b)
{
	struct object_entry *a = *(struct object_entry **)_a;
	struct object_entry *b = *(struct object_entry **)_b;
	return hashcmp(a->sha1, b->sha1);
}
 
/*
 * On entry *sha1 contains the pack content SHA1 hash, on exit it is
 * the SHA1 hash of sorted object names.
 */
static const char *write_index_file(const char *index_name, unsigned char *sha1)
{
	struct sha1file *f;
	struct object_entry **sorted_by_sha, **list, **last;
	unsigned int array[256];
	int i, fd;
	SHA_CTX ctx;
 
	if (nr_objects) {
		sorted_by_sha =
			xcalloc(nr_objects, sizeof(struct object_entry *));
		list = sorted_by_sha;
		last = sorted_by_sha + nr_objects;
		for (i = 0; i < nr_objects; ++i)
			sorted_by_sha[i] = &objects[i];
		qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
		      sha1_compare);
 
	}
	else
		sorted_by_sha = list = last = NULL;
 
	if (!index_name) {
		static char tmpfile[PATH_MAX];
		snprintf(tmpfile, sizeof(tmpfile),
			 "%s/index_XXXXXX", get_object_directory());
		fd = mkstemp(tmpfile);
		index_name = xstrdup(tmpfile);
	} else {
		unlink(index_name);
		fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
	}
	if (fd < 0)
		die("unable to create %s: %s", index_name, strerror(errno));
	f = sha1fd(fd, index_name);
 
	/*
	 * 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++) {
		struct object_entry **next = list;
		while (next < last) {
			struct object_entry *obj = *next;
			if (obj->sha1[0] != i)
				break;
			next++;
		}
		array[i] = htonl(next - sorted_by_sha);
		list = next;
	}
	sha1write(f, array, 256 * sizeof(int));
 
	/* recompute the SHA1 hash of sorted object names.
	 * currently pack-objects does not do this, but that
	 * can be fixed.
	 */
	SHA1_Init(&ctx);
	/*
	 * Write the actual SHA1 entries..
	 */
	list = sorted_by_sha;
	for (i = 0; i < nr_objects; i++) {
		struct object_entry *obj = *list++;
		unsigned int offset = htonl(obj->offset);
		sha1write(f, &offset, 4);
		sha1write(f, obj->sha1, 20);
		SHA1_Update(&ctx, obj->sha1, 20);
	}
	sha1write(f, sha1, 20);
	sha1close(f, NULL, 1);
	free(sorted_by_sha);
	SHA1_Final(sha1, &ctx);
	return index_name;
}
 
static void final(const char *final_pack_name, const char *curr_pack_name,
		  const char *final_index_name, const char *curr_index_name,
		  const char *keep_name, const char *keep_msg,
		  unsigned char *sha1)
{
	char *report = "pack";
	char name[PATH_MAX];
	int err;
 
	if (!from_stdin) {
		close(input_fd);
	} else {
		err = close(output_fd);
		if (err)
			die("error while closing pack file: %s", strerror(errno));
		chmod(curr_pack_name, 0444);
	}
 
	if (keep_msg) {
		int keep_fd, keep_msg_len = strlen(keep_msg);
		if (!keep_name) {
			snprintf(name, sizeof(name), "%s/pack/pack-%s.keep",
				 get_object_directory(), sha1_to_hex(sha1));
			keep_name = name;
		}
		keep_fd = open(keep_name, O_RDWR|O_CREAT|O_EXCL, 0600);
		if (keep_fd < 0) {
			if (errno != EEXIST)
				die("cannot write keep file");
		} else {
			if (keep_msg_len > 0) {
				write_or_die(keep_fd, keep_msg, keep_msg_len);
				write_or_die(keep_fd, "\n", 1);
			}
			close(keep_fd);
			report = "keep";
		}
	}
 
	if (final_pack_name != curr_pack_name) {
		if (!final_pack_name) {
			snprintf(name, sizeof(name), "%s/pack/pack-%s.pack",
				 get_object_directory(), sha1_to_hex(sha1));
			final_pack_name = name;
		}
		if (move_temp_to_file(curr_pack_name, final_pack_name))
			die("cannot store pack file");
	}
 
	chmod(curr_index_name, 0444);
	if (final_index_name != curr_index_name) {
		if (!final_index_name) {
			snprintf(name, sizeof(name), "%s/pack/pack-%s.idx",
				 get_object_directory(), sha1_to_hex(sha1));
			final_index_name = name;
		}
		if (move_temp_to_file(curr_index_name, final_index_name))
			die("cannot store index file");
	}
 
	if (!from_stdin) {
		printf("%s\n", sha1_to_hex(sha1));
	} else {
		char buf[48];
		int len = snprintf(buf, sizeof(buf), "%s\t%s\n",
				   report, sha1_to_hex(sha1));
		xwrite(1, buf, len);
 
		/*
		 * Let's just mimic git-unpack-objects here and write
		 * the last part of the input buffer to stdout.
		 */
		while (input_len) {
			err = xwrite(1, input_buffer + input_offset, input_len);
			if (err <= 0)
				break;
			input_len -= err;
			input_offset += err;
		}
	}
}
 
int main(int argc, char **argv)
{
	int i, fix_thin_pack = 0;
	const char *curr_pack, *pack_name = NULL;
	const char *curr_index, *index_name = NULL;
	const char *keep_name = NULL, *keep_msg = NULL;
	char *index_name_buf = NULL, *keep_name_buf = NULL;
	unsigned char sha1[20];
 
	for (i = 1; i < argc; i++) {
		const char *arg = argv[i];
 
		if (*arg == '-') {
			if (!strcmp(arg, "--stdin")) {
				from_stdin = 1;
			} else if (!strcmp(arg, "--fix-thin")) {
				fix_thin_pack = 1;
			} else if (!strcmp(arg, "--keep")) {
				keep_msg = "";
			} else if (!strncmp(arg, "--keep=", 7)) {
				keep_msg = arg + 7;
			} else if (!strncmp(arg, "--pack_header=", 14)) {
				struct pack_header *hdr;
				char *c;
 
				hdr = (struct pack_header *)input_buffer;
				hdr->hdr_signature = htonl(PACK_SIGNATURE);
				hdr->hdr_version = htonl(strtoul(arg + 14, &c, 10));
				if (*c != ',')
					die("bad %s", arg);
				hdr->hdr_entries = htonl(strtoul(c + 1, &c, 10));
				if (*c)
					die("bad %s", arg);
				input_len = sizeof(*hdr);
			} else if (!strcmp(arg, "-v")) {
				verbose = 1;
			} else if (!strcmp(arg, "-o")) {
				if (index_name || (i+1) >= argc)
					usage(index_pack_usage);
				index_name = argv[++i];
			} else
				usage(index_pack_usage);
			continue;
		}
 
		if (pack_name)
			usage(index_pack_usage);
		pack_name = arg;
	}
 
	if (!pack_name && !from_stdin)
		usage(index_pack_usage);
	if (fix_thin_pack && !from_stdin)
		die("--fix-thin cannot be used without --stdin");
	if (!index_name && pack_name) {
		int len = strlen(pack_name);
		if (!has_extension(pack_name, ".pack"))
			die("packfile name '%s' does not end with '.pack'",
			    pack_name);
		index_name_buf = xmalloc(len);
		memcpy(index_name_buf, pack_name, len - 5);
		strcpy(index_name_buf + len - 5, ".idx");
		index_name = index_name_buf;
	}
	if (keep_msg && !keep_name && pack_name) {
		int len = strlen(pack_name);
		if (!has_extension(pack_name, ".pack"))
			die("packfile name '%s' does not end with '.pack'",
			    pack_name);
		keep_name_buf = xmalloc(len);
		memcpy(keep_name_buf, pack_name, len - 5);
		strcpy(keep_name_buf + len - 5, ".keep");
		keep_name = keep_name_buf;
	}
 
	curr_pack = open_pack_file(pack_name);
	parse_pack_header();
	objects = xmalloc((nr_objects + 1) * sizeof(struct object_entry));
	deltas = xmalloc(nr_objects * sizeof(struct delta_entry));
	if (verbose)
		setup_progress_signal();
	parse_pack_objects(sha1);
	if (nr_deltas != nr_resolved_deltas) {
		if (fix_thin_pack) {
			int nr_unresolved = nr_deltas - nr_resolved_deltas;
			int nr_objects_initial = nr_objects;
			if (nr_unresolved <= 0)
				die("confusion beyond insanity");
			objects = xrealloc(objects,
					   (nr_objects + nr_unresolved + 1)
					   * sizeof(*objects));
			fix_unresolved_deltas(nr_unresolved);
			if (verbose)
				fprintf(stderr, "%d objects were added to complete this thin pack.\n",
					nr_objects - nr_objects_initial);
			readjust_pack_header_and_sha1(sha1);
		}
		if (nr_deltas != nr_resolved_deltas)
			die("pack has %d unresolved deltas",
			    nr_deltas - nr_resolved_deltas);
	} else {
		/* Flush remaining pack final 20-byte SHA1. */
		flush();
	}
	free(deltas);
	curr_index = write_index_file(index_name, sha1);
	final(pack_name, curr_pack,
		index_name, curr_index,
		keep_name, keep_msg,
		sha1);
	free(objects);
	free(index_name_buf);
	free(keep_name_buf);
 
	return 0;
}