aboutsummaryrefslogtreecommitdiff
path: root/builtin-unpack-objects.c
blob: 7e3ea73006ecdc74c03580ac7297be4ebee174b3 (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
#include "builtin.h"
#include "cache.h"
#include "object.h"
#include "delta.h"
#include "pack.h"
#include "blob.h"
#include "commit.h"
#include "tag.h"
#include "tree.h"
#include "tree-walk.h"
#include "progress.h"
#include "decorate.h"
#include "fsck.h"

static int dry_run, quiet, recover, has_errors, strict;
static const char unpack_usage[] = "git unpack-objects [-n] [-q] [-r] [--strict] < pack-file";

/* We always read in 4kB chunks. */
static unsigned char buffer[4096];
static unsigned int offset, len;
static off_t consumed_bytes;
static git_SHA_CTX ctx;

/*
 * When running under --strict mode, objects whose reachability are
 * suspect are kept in core without getting written in the object
 * store.
 */
struct obj_buffer {
	char *buffer;
	unsigned long size;
};

static struct decoration obj_decorate;

static struct obj_buffer *lookup_object_buffer(struct object *base)
{
	return lookup_decoration(&obj_decorate, base);
}

static void add_object_buffer(struct object *object, char *buffer, unsigned long size)
{
	struct obj_buffer *obj;
	obj = xcalloc(1, sizeof(struct obj_buffer));
	obj->buffer = buffer;
	obj->size = size;
	if (add_decoration(&obj_decorate, object, obj))
		die("object %s tried to add buffer twice!", sha1_to_hex(object->sha1));
}

/*
 * 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 <= len)
		return buffer + offset;
	if (min > sizeof(buffer))
		die("cannot fill %d bytes", min);
	if (offset) {
		git_SHA1_Update(&ctx, buffer, offset);
		memmove(buffer, buffer + offset, len);
		offset = 0;
	}
	do {
		ssize_t ret = xread(0, buffer + len, sizeof(buffer) - len);
		if (ret <= 0) {
			if (!ret)
				die("early EOF");
			die("read error on input: %s", strerror(errno));
		}
		len += ret;
	} while (len < min);
	return buffer;
}

static void use(int bytes)
{
	if (bytes > len)
		die("used more bytes than were available");
	len -= bytes;
	offset += bytes;

	/* make sure off_t is sufficiently large not to wrap */
	if (consumed_bytes > consumed_bytes + bytes)
		die("pack too large for current definition of off_t");
	consumed_bytes += bytes;
}

static void *get_data(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 = len;
	git_inflate_init(&stream);

	for (;;) {
		int ret = git_inflate(&stream, 0);
		use(len - stream.avail_in);
		if (stream.total_out == size && ret == Z_STREAM_END)
			break;
		if (ret != Z_OK) {
			error("inflate returned %d\n", ret);
			free(buf);
			buf = NULL;
			if (!recover)
				exit(1);
			has_errors = 1;
			break;
		}
		stream.next_in = fill(1);
		stream.avail_in = len;
	}
	git_inflate_end(&stream);
	return buf;
}

struct delta_info {
	unsigned char base_sha1[20];
	unsigned nr;
	off_t base_offset;
	unsigned long size;
	void *delta;
	struct delta_info *next;
};

static struct delta_info *delta_list;

static void add_delta_to_list(unsigned nr, unsigned const char *base_sha1,
			      off_t base_offset,
			      void *delta, unsigned long size)
{
	struct delta_info *info = xmalloc(sizeof(*info));

	hashcpy(info->base_sha1, base_sha1);
	info->base_offset = base_offset;
	info->size = size;
	info->delta = delta;
	info->nr = nr;
	info->next = delta_list;
	delta_list = info;
}

struct obj_info {
	off_t offset;
	unsigned char sha1[20];
	struct object *obj;
};

#define FLAG_OPEN (1u<<20)
#define FLAG_WRITTEN (1u<<21)

static struct obj_info *obj_list;
static unsigned nr_objects;

/*
 * Called only from check_object() after it verified this object
 * is Ok.
 */
static void write_cached_object(struct object *obj)
{
	unsigned char sha1[20];
	struct obj_buffer *obj_buf = lookup_object_buffer(obj);
	if (write_sha1_file(obj_buf->buffer, obj_buf->size, typename(obj->type), sha1) < 0)
		die("failed to write object %s", sha1_to_hex(obj->sha1));
	obj->flags |= FLAG_WRITTEN;
}

/*
 * At the very end of the processing, write_rest() scans the objects
 * that have reachability requirements and calls this function.
 * Verify its reachability and validity recursively and write it out.
 */
static int check_object(struct object *obj, int type, void *data)
{
	if (!obj)
		return 0;

	if (obj->flags & FLAG_WRITTEN)
		return 1;

	if (type != OBJ_ANY && obj->type != type)
		die("object type mismatch");

	if (!(obj->flags & FLAG_OPEN)) {
		unsigned long size;
		int type = sha1_object_info(obj->sha1, &size);
		if (type != obj->type || type <= 0)
			die("object of unexpected type");
		obj->flags |= FLAG_WRITTEN;
		return 1;
	}

	if (fsck_object(obj, 1, fsck_error_function))
		die("Error in object");
	if (!fsck_walk(obj, check_object, NULL))
		die("Error on reachable objects of %s", sha1_to_hex(obj->sha1));
	write_cached_object(obj);
	return 1;
}

static void write_rest(void)
{
	unsigned i;
	for (i = 0; i < nr_objects; i++)
		check_object(obj_list[i].obj, OBJ_ANY, NULL);
}

static void added_object(unsigned nr, enum object_type type,
			 void *data, unsigned long size);

/*
 * Write out nr-th object from the list, now we know the contents
 * of it.  Under --strict, this buffers structured objects in-core,
 * to be checked at the end.
 */
static void write_object(unsigned nr, enum object_type type,
			 void *buf, unsigned long size)
{
	if (!strict) {
		if (write_sha1_file(buf, size, typename(type), obj_list[nr].sha1) < 0)
			die("failed to write object");
		added_object(nr, type, buf, size);
		free(buf);
		obj_list[nr].obj = NULL;
	} else if (type == OBJ_BLOB) {
		struct blob *blob;
		if (write_sha1_file(buf, size, typename(type), obj_list[nr].sha1) < 0)
			die("failed to write object");
		added_object(nr, type, buf, size);
		free(buf);

		blob = lookup_blob(obj_list[nr].sha1);
		if (blob)
			blob->object.flags |= FLAG_WRITTEN;
		else
			die("invalid blob object");
		obj_list[nr].obj = NULL;
	} else {
		struct object *obj;
		int eaten;
		hash_sha1_file(buf, size, typename(type), obj_list[nr].sha1);
		added_object(nr, type, buf, size);
		obj = parse_object_buffer(obj_list[nr].sha1, type, size, buf, &eaten);
		if (!obj)
			die("invalid %s", typename(type));
		add_object_buffer(obj, buf, size);
		obj->flags |= FLAG_OPEN;
		obj_list[nr].obj = obj;
	}
}

static void resolve_delta(unsigned nr, enum object_type type,
			  void *base, unsigned long base_size,
			  void *delta, unsigned long delta_size)
{
	void *result;
	unsigned long result_size;

	result = patch_delta(base, base_size,
			     delta, delta_size,
			     &result_size);
	if (!result)
		die("failed to apply delta");
	free(delta);
	write_object(nr, type, result, result_size);
}

/*
 * We now know the contents of an object (which is nr-th in the pack);
 * resolve all the deltified objects that are based on it.
 */
static void added_object(unsigned nr, enum object_type type,
			 void *data, unsigned long size)
{
	struct delta_info **p = &delta_list;
	struct delta_info *info;

	while ((info = *p) != NULL) {
		if (!hashcmp(info->base_sha1, obj_list[nr].sha1) ||
		    info->base_offset == obj_list[nr].offset) {
			*p = info->next;
			p = &delta_list;
			resolve_delta(info->nr, type, data, size,
				      info->delta, info->size);
			free(info);
			continue;
		}
		p = &info->next;
	}
}

static void unpack_non_delta_entry(enum object_type type, unsigned long size,
				   unsigned nr)
{
	void *buf = get_data(size);

	if (!dry_run && buf)
		write_object(nr, type, buf, size);
	else
		free(buf);
}

static int resolve_against_held(unsigned nr, const unsigned char *base,
				void *delta_data, unsigned long delta_size)
{
	struct object *obj;
	struct obj_buffer *obj_buffer;
	obj = lookup_object(base);
	if (!obj)
		return 0;
	obj_buffer = lookup_object_buffer(obj);
	if (!obj_buffer)
		return 0;
	resolve_delta(nr, obj->type, obj_buffer->buffer,
		      obj_buffer->size, delta_data, delta_size);
	return 1;
}

static void unpack_delta_entry(enum object_type type, unsigned long delta_size,
			       unsigned nr)
{
	void *delta_data, *base;
	unsigned long base_size;
	unsigned char base_sha1[20];

	if (type == OBJ_REF_DELTA) {
		hashcpy(base_sha1, fill(20));
		use(20);
		delta_data = get_data(delta_size);
		if (dry_run || !delta_data) {
			free(delta_data);
			return;
		}
		if (has_sha1_file(base_sha1))
			; /* Ok we have this one */
		else if (resolve_against_held(nr, base_sha1,
					      delta_data, delta_size))
			return; /* we are done */
		else {
			/* cannot resolve yet --- queue it */
			hashcpy(obj_list[nr].sha1, null_sha1);
			add_delta_to_list(nr, base_sha1, 0, delta_data, delta_size);
			return;
		}
	} else {
		unsigned base_found = 0;
		unsigned char *pack, c;
		off_t base_offset;
		unsigned lo, mid, hi;

		pack = fill(1);
		c = *pack;
		use(1);
		base_offset = c & 127;
		while (c & 128) {
			base_offset += 1;
			if (!base_offset || MSB(base_offset, 7))
				die("offset value overflow for delta base object");
			pack = fill(1);
			c = *pack;
			use(1);
			base_offset = (base_offset << 7) + (c & 127);
		}
		base_offset = obj_list[nr].offset - base_offset;
		if (base_offset <= 0 || base_offset >= obj_list[nr].offset)
			die("offset value out of bound for delta base object");

		delta_data = get_data(delta_size);
		if (dry_run || !delta_data) {
			free(delta_data);
			return;
		}
		lo = 0;
		hi = nr;
		while (lo < hi) {
			mid = (lo + hi)/2;
			if (base_offset < obj_list[mid].offset) {
				hi = mid;
			} else if (base_offset > obj_list[mid].offset) {
				lo = mid + 1;
			} else {
				hashcpy(base_sha1, obj_list[mid].sha1);
				base_found = !is_null_sha1(base_sha1);
				break;
			}
		}
		if (!base_found) {
			/*
			 * The delta base object is itself a delta that
			 * has not been resolved yet.
			 */
			hashcpy(obj_list[nr].sha1, null_sha1);
			add_delta_to_list(nr, null_sha1, base_offset, delta_data, delta_size);
			return;
		}
	}

	if (resolve_against_held(nr, base_sha1, delta_data, delta_size))
		return;

	base = read_sha1_file(base_sha1, &type, &base_size);
	if (!base) {
		error("failed to read delta-pack base object %s",
		      sha1_to_hex(base_sha1));
		if (!recover)
			exit(1);
		has_errors = 1;
		return;
	}
	resolve_delta(nr, type, base, base_size, delta_data, delta_size);
	free(base);
}

static void unpack_one(unsigned nr)
{
	unsigned shift;
	unsigned char *pack;
	unsigned long size, c;
	enum object_type type;

	obj_list[nr].offset = consumed_bytes;

	pack = fill(1);
	c = *pack;
	use(1);
	type = (c >> 4) & 7;
	size = (c & 15);
	shift = 4;
	while (c & 0x80) {
		pack = fill(1);
		c = *pack;
		use(1);
		size += (c & 0x7f) << shift;
		shift += 7;
	}

	switch (type) {
	case OBJ_COMMIT:
	case OBJ_TREE:
	case OBJ_BLOB:
	case OBJ_TAG:
		unpack_non_delta_entry(type, size, nr);
		return;
	case OBJ_REF_DELTA:
	case OBJ_OFS_DELTA:
		unpack_delta_entry(type, size, nr);
		return;
	default:
		error("bad object type %d", type);
		has_errors = 1;
		if (recover)
			return;
		exit(1);
	}
}

static void unpack_all(void)
{
	int i;
	struct progress *progress = NULL;
	struct pack_header *hdr = fill(sizeof(struct pack_header));

	nr_objects = ntohl(hdr->hdr_entries);

	if (ntohl(hdr->hdr_signature) != PACK_SIGNATURE)
		die("bad pack file");
	if (!pack_version_ok(hdr->hdr_version))
		die("unknown pack file version %"PRIu32,
			ntohl(hdr->hdr_version));
	use(sizeof(struct pack_header));

	if (!quiet)
		progress = start_progress("Unpacking objects", nr_objects);
	obj_list = xcalloc(nr_objects, sizeof(*obj_list));
	for (i = 0; i < nr_objects; i++) {
		unpack_one(i);
		display_progress(progress, i + 1);
	}
	stop_progress(&progress);

	if (delta_list)
		die("unresolved deltas left after unpacking");
}

int cmd_unpack_objects(int argc, const char **argv, const char *prefix)
{
	int i;
	unsigned char sha1[20];

	git_config(git_default_config, NULL);

	quiet = !isatty(2);

	for (i = 1 ; i < argc; i++) {
		const char *arg = argv[i];

		if (*arg == '-') {
			if (!strcmp(arg, "-n")) {
				dry_run = 1;
				continue;
			}
			if (!strcmp(arg, "-q")) {
				quiet = 1;
				continue;
			}
			if (!strcmp(arg, "-r")) {
				recover = 1;
				continue;
			}
			if (!strcmp(arg, "--strict")) {
				strict = 1;
				continue;
			}
			if (!prefixcmp(arg, "--pack_header=")) {
				struct pack_header *hdr;
				char *c;

				hdr = (struct pack_header *)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);
				len = sizeof(*hdr);
				continue;
			}
			usage(unpack_usage);
		}

		/* We don't take any non-flag arguments now.. Maybe some day */
		usage(unpack_usage);
	}
	git_SHA1_Init(&ctx);
	unpack_all();
	git_SHA1_Update(&ctx, buffer, offset);
	git_SHA1_Final(sha1, &ctx);
	if (strict)
		write_rest();
	if (hashcmp(fill(20), sha1))
		die("final sha1 did not match");
	use(20);

	/* Write the last part of the buffer to stdout */
	while (len) {
		int ret = xwrite(1, buffer + offset, len);
		if (ret <= 0)
			break;
		len -= ret;
		offset += ret;
	}

	/* All done */
	return has_errors;
}