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Date:: Tue Jan 23 10:27:29 2018 UTC
Message:: compute off_delta offset correctly
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1 /*
2  * Copyright (c) 2018 Stefan Sperling <stsp@openbsd.org>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <sys/types.h>
18 #include <sys/stat.h>
19 #include <sys/queue.h>
20 
21 #include <dirent.h>
22 #include <errno.h>
23 #include <stdio.h>
24 #include <stdint.h>
25 #include <stdlib.h>
26 #include <string.h>
27 #include <limits.h>
28 #include <sha1.h>
29 #include <endian.h>
30 #include <zlib.h>
31 
32 #include "got_error.h"
33 #include "got_object.h"
34 #include "got_repository.h"
35 #include "got_sha1.h"
36 #include "pack.h"
37 #include "path.h"
38 #include "delta.h"
39 #include "object.h"
40 
41 #define GOT_PACK_PREFIX		"pack-"
42 #define GOT_PACKFILE_SUFFIX	".pack"
43 #define GOT_PACKIDX_SUFFIX		".idx"
44 #define GOT_PACKFILE_NAMELEN	(strlen(GOT_PACK_PREFIX) + \
45 				SHA1_DIGEST_STRING_LENGTH - 1 + \
46 				strlen(GOT_PACKFILE_SUFFIX))
47 #define GOT_PACKIDX_NAMELEN	(strlen(GOT_PACK_PREFIX) + \
48 				SHA1_DIGEST_STRING_LENGTH - 1 + \
49 				strlen(GOT_PACKIDX_SUFFIX))
50 
51 #ifndef MIN
52 #define	MIN(_a,_b) ((_a) < (_b) ? (_a) : (_b))
53 #endif
54 
55 static const struct got_error *
56 verify_fanout_table(uint32_t *fanout_table)
57 {
58 	int i;
59 
60 	for (i = 0; i < 0xff - 1; i++) {
61 		if (be32toh(fanout_table[i]) > be32toh(fanout_table[i + 1]))
62 			return got_error(GOT_ERR_BAD_PACKIDX);
63 	}
64 
65 	return NULL;
66 }
67 
68 static const struct got_error *
69 get_packfile_size(size_t *size, const char *path_idx)
70 {
71 	struct stat sb;
72 	char *path_pack;
73 	char base_path[PATH_MAX];
74 	char *dot;
75 
76 	if (strlcpy(base_path, path_idx, PATH_MAX) > PATH_MAX)
77 		return got_error(GOT_ERR_NO_SPACE);
78 
79 	dot = strrchr(base_path, '.');
80 	if (dot == NULL)
81 		return got_error(GOT_ERR_BAD_PATH);
82 	*dot = '\0';
83 	if (asprintf(&path_pack, "%s.pack", base_path) == -1)
84 		return got_error(GOT_ERR_NO_MEM);
85 
86 	if (stat(path_pack, &sb) != 0) {
87 		free(path_pack);
88 		return got_error_from_errno();
89 	}
90 
91 	free(path_pack);
92 	*size = sb.st_size;
93 	return 0;
94 }
95 
96 const struct got_error *
97 got_packidx_open(struct got_packidx_v2_hdr **packidx, const char *path)
98 {
99 	struct got_packidx_v2_hdr *p;
100 	FILE *f;
101 	const struct got_error *err = NULL;
102 	size_t n, nobj, packfile_size;
103 	SHA1_CTX ctx;
104 	uint8_t sha1[SHA1_DIGEST_LENGTH];
105 
106 	SHA1Init(&ctx);
107 
108 	f = fopen(path, "rb");
109 	if (f == NULL)
110 		return got_error(GOT_ERR_BAD_PATH);
111 
112 	err = get_packfile_size(&packfile_size, path);
113 	if (err)
114 		return err;
115 
116 	p = calloc(1, sizeof(*p));
117 	if (p == NULL) {
118 		err = got_error(GOT_ERR_NO_MEM);
119 		goto done;
120 	}
121 
122 	n = fread(&p->magic, sizeof(p->magic), 1, f);
123 	if (n != 1) {
124 		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
125 		goto done;
126 	}
127 
128 	if (betoh32(p->magic) != GOT_PACKIDX_V2_MAGIC) {
129 		err = got_error(GOT_ERR_BAD_PACKIDX);
130 		goto done;
131 	}
132 
133 	SHA1Update(&ctx, (uint8_t *)&p->magic, sizeof(p->magic));
134 
135 	n = fread(&p->version, sizeof(p->version), 1, f);
136 	if (n != 1) {
137 		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
138 		goto done;
139 	}
140 
141 	if (betoh32(p->version) != GOT_PACKIDX_VERSION) {
142 		err = got_error(GOT_ERR_BAD_PACKIDX);
143 		goto done;
144 	}
145 
146 	SHA1Update(&ctx, (uint8_t *)&p->version, sizeof(p->version));
147 
148 	n = fread(&p->fanout_table, sizeof(p->fanout_table), 1, f);
149 	if (n != 1) {
150 		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
151 		goto done;
152 	}
153 
154 	err = verify_fanout_table(p->fanout_table);
155 	if (err)
156 		goto done;
157 
158 	SHA1Update(&ctx, (uint8_t *)p->fanout_table, sizeof(p->fanout_table));
159 
160 	nobj = betoh32(p->fanout_table[0xff]);
161 
162 	p->sorted_ids = calloc(nobj, sizeof(*p->sorted_ids));
163 	if (p->sorted_ids == NULL) {
164 		err = got_error(GOT_ERR_NO_MEM);
165 		goto done;
166 	}
167 
168 	n = fread(p->sorted_ids, sizeof(*p->sorted_ids), nobj, f);
169 	if (n != nobj) {
170 		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
171 		goto done;
172 	}
173 
174 	SHA1Update(&ctx, (uint8_t *)p->sorted_ids,
175 	    nobj * sizeof(*p->sorted_ids));
176 
177 	p->crc32 = calloc(nobj, sizeof(*p->crc32));
178 	if (p->crc32 == NULL) {
179 		err = got_error(GOT_ERR_NO_MEM);
180 		goto done;
181 	}
182 
183 	n = fread(p->crc32, sizeof(*p->crc32), nobj, f);
184 	if (n != nobj) {
185 		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
186 		goto done;
187 	}
188 
189 	SHA1Update(&ctx, (uint8_t *)p->crc32, nobj * sizeof(*p->crc32));
190 
191 	p->offsets = calloc(nobj, sizeof(*p->offsets));
192 	if (p->offsets == NULL) {
193 		err = got_error(GOT_ERR_NO_MEM);
194 		goto done;
195 	}
196 
197 	n = fread(p->offsets, sizeof(*p->offsets), nobj, f);
198 	if (n != nobj) {
199 		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
200 		goto done;
201 	}
202 
203 	SHA1Update(&ctx, (uint8_t *)p->offsets, nobj * sizeof(*p->offsets));
204 
205 	/* Large file offsets are contained only in files > 2GB. */
206 	if (packfile_size <= 0x80000000)
207 		goto checksum;
208 
209 	p->large_offsets = calloc(nobj, sizeof(*p->large_offsets));
210 	if (p->large_offsets == NULL) {
211 		err = got_error(GOT_ERR_NO_MEM);
212 		goto done;
213 	}
214 
215 	n = fread(p->large_offsets, sizeof(*p->large_offsets), nobj, f);
216 	if (n != nobj) {
217 		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
218 		goto done;
219 	}
220 
221 	SHA1Update(&ctx, (uint8_t*)p->large_offsets,
222 	    nobj * sizeof(*p->large_offsets));
223 
224 checksum:
225 	n = fread(&p->trailer, sizeof(p->trailer), 1, f);
226 	if (n != 1) {
227 		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
228 		goto done;
229 	}
230 
231 	SHA1Update(&ctx, p->trailer.packfile_sha1, SHA1_DIGEST_LENGTH);
232 	SHA1Final(sha1, &ctx);
233 	if (memcmp(p->trailer.packidx_sha1, sha1, SHA1_DIGEST_LENGTH) != 0)
234 		err = got_error(GOT_ERR_PACKIDX_CSUM);
235 done:
236 	fclose(f);
237 	if (err)
238 		got_packidx_close(p);
239 	else
240 		*packidx = p;
241 	return err;
242 }
243 
244 void
245 got_packidx_close(struct got_packidx_v2_hdr *packidx)
246 {
247 	free(packidx->sorted_ids);
248 	free(packidx->offsets);
249 	free(packidx->crc32);
250 	free(packidx->large_offsets);
251 	free(packidx);
252 }
253 
254 static int
255 is_packidx_filename(const char *name, size_t len)
256 {
257 	if (len != GOT_PACKIDX_NAMELEN)
258 		return 0;
259 
260 	if (strncmp(name, GOT_PACK_PREFIX, strlen(GOT_PACK_PREFIX)) != 0)
261 		return 0;
262 
263 	if (strcmp(name + strlen(GOT_PACK_PREFIX) +
264 	    SHA1_DIGEST_STRING_LENGTH - 1, GOT_PACKIDX_SUFFIX) != 0)
265 		return 0;
266 
267 	return 1;
268 }
269 
270 static off_t
271 get_object_offset(struct got_packidx_v2_hdr *packidx, int idx)
272 {
273 	uint32_t totobj = betoh32(packidx->fanout_table[0xff]);
274 	uint32_t offset = betoh32(packidx->offsets[idx]);
275 	if (offset & GOT_PACKIDX_OFFSET_VAL_IS_LARGE_IDX) {
276 		uint64_t loffset;
277 		idx = offset & GOT_PACKIDX_OFFSET_VAL_MASK;
278 		if (idx < 0 || idx > totobj || packidx->large_offsets == NULL)
279 			return -1;
280 		loffset = betoh64(packidx->large_offsets[idx]);
281 		return (loffset > INT64_MAX ? -1 : (off_t)loffset);
282 	}
283 	return (off_t)(offset & GOT_PACKIDX_OFFSET_VAL_MASK);
284 }
285 
286 static int
287 get_object_idx(struct got_packidx_v2_hdr *packidx, struct got_object_id *id)
288 {
289 	u_int8_t id0 = id->sha1[0];
290 	uint32_t totobj = betoh32(packidx->fanout_table[0xff]);
291 	int i = 0;
292 
293 	if (id0 > 0)
294 		i = betoh32(packidx->fanout_table[id0 - 1]);
295 
296 	while (i < totobj) {
297 		struct got_object_id *oid = &packidx->sorted_ids[i];
298 		uint32_t offset;
299 		int cmp = got_object_id_cmp(id, oid);
300 
301 		if (cmp == 0)
302 			return i;
303 		else if (cmp > 0)
304 			break;
305 		i++;
306 	}
307 
308 	return -1;
309 }
310 
311 const struct got_error *
312 read_packfile_hdr(FILE *f, struct got_packidx_v2_hdr *packidx)
313 {
314 	const struct got_error *err = NULL;
315 	uint32_t totobj = betoh32(packidx->fanout_table[0xff]);
316 	struct got_packfile_hdr hdr;
317 	size_t n;
318 
319 	n = fread(&hdr, sizeof(hdr), 1, f);
320 	if (n != 1)
321 		return got_ferror(f, GOT_ERR_BAD_PACKIDX);
322 
323 	if (betoh32(hdr.signature) != GOT_PACKFILE_SIGNATURE ||
324 	    betoh32(hdr.version) != GOT_PACKFILE_VERSION ||
325 	    betoh32(hdr.nobjects) != totobj)
326 		err = got_error(GOT_ERR_BAD_PACKFILE);
327 
328 	return err;
329 }
330 
331 static const struct got_error *
332 decode_type_and_size(uint8_t *type, uint64_t *size, size_t *len, FILE *packfile)
333 {
334 	uint8_t t = 0;
335 	uint64_t s = 0;
336 	uint8_t sizeN;
337 	size_t n;
338 	int i = 0;
339 
340 	do {
341 		/* We do not support size values which don't fit in 64 bit. */
342 		if (i > 9)
343 			return got_error(GOT_ERR_NO_SPACE);
344 
345 		n = fread(&sizeN, sizeof(sizeN), 1, packfile);
346 		if (n != 1)
347 			return got_ferror(packfile, GOT_ERR_BAD_PACKIDX);
348 
349 		if (i == 0) {
350 			t = (sizeN & GOT_PACK_OBJ_SIZE0_TYPE_MASK) >>
351 			    GOT_PACK_OBJ_SIZE0_TYPE_MASK_SHIFT;
352 			s = (sizeN & GOT_PACK_OBJ_SIZE0_VAL_MASK);
353 		} else {
354 			size_t shift = 4 + 7 * (i - 1);
355 			s |= ((sizeN & GOT_PACK_OBJ_SIZE_VAL_MASK) << shift);
356 		}
357 		i++;
358 	} while (sizeN & GOT_PACK_OBJ_SIZE_MORE);
359 
360 	*type = t;
361 	*size = s;
362 	*len = i * sizeof(sizeN);
363 	return NULL;
364 }
365 
366 static const struct got_error *
367 open_plain_object(struct got_object **obj, const char *path_packfile,
368     struct got_object_id *id, uint8_t type, off_t offset, size_t size)
369 {
370 	*obj = calloc(1, sizeof(**obj));
371 	if (*obj == NULL)
372 		return got_error(GOT_ERR_NO_MEM);
373 
374 	(*obj)->path_packfile = strdup(path_packfile);
375 	if ((*obj)->path_packfile == NULL) {
376 		free(*obj);
377 		*obj = NULL;
378 		return got_error(GOT_ERR_NO_MEM);
379 	}
380 
381 	(*obj)->type = type;
382 	(*obj)->flags = GOT_OBJ_FLAG_PACKED;
383 	(*obj)->hdrlen = 0;
384 	(*obj)->size = size;
385 	memcpy(&(*obj)->id, id, sizeof((*obj)->id));
386 	(*obj)->pack_offset = offset;
387 
388 	return NULL;
389 }
390 
391 static const struct got_error *
392 decode_negative_offset(int64_t *offset, size_t *len, FILE *packfile)
393 {
394 	int64_t o = 0;
395 	uint8_t offN;
396 	size_t n;
397 	int i = 0;
398 
399 	do {
400 		/* We do not support offset values which don't fit in 64 bit. */
401 		if (i > 8)
402 			return got_error(GOT_ERR_NO_SPACE);
403 
404 		n = fread(&offN, sizeof(offN), 1, packfile);
405 		if (n != 1)
406 			return got_ferror(packfile, GOT_ERR_BAD_PACKIDX);
407 
408 		if (i == 0)
409 			o = (offN & GOT_PACK_OBJ_DELTA_OFF_VAL_MASK);
410 		else {
411 			o++;
412 			o <<= 7;
413 			o += (offN & GOT_PACK_OBJ_DELTA_OFF_VAL_MASK);
414 		}
415 		i++;
416 	} while (offN & GOT_PACK_OBJ_DELTA_OFF_MORE);
417 
418 	*offset = o;
419 	*len = i * sizeof(offN);
420 	return NULL;
421 }
422 
423 static const struct got_error *
424 open_offset_delta_object(struct got_object **obj, struct got_repository *repo,
425     const char *path_packfile, FILE *packfile, struct got_object_id *id,
426     off_t offset, size_t tslen, size_t size)
427 {
428 	const struct got_error *err = NULL;
429 	int64_t negoffset;
430 	size_t negofflen;
431 	off_t base_obj_offset;
432 	struct got_object *base_obj;
433 	struct got_object_id base_id;
434 	uint8_t base_type;
435 	uint64_t base_size;
436 	size_t base_tslen;
437 
438 	err = decode_negative_offset(&negoffset, &negofflen, packfile);
439 	if (err)
440 		return err;
441 
442 	/* Compute the base object's offset (must be in the same pack file). */
443 	base_obj_offset = (offset - negoffset);
444 	if (base_obj_offset <= 0)
445 		return got_error(GOT_ERR_BAD_PACKFILE);
446 
447 	if (fseeko(packfile, base_obj_offset, SEEK_SET) != 0)
448 		return got_error_from_errno();
449 
450 	err = decode_type_and_size(&base_type, &base_size, &base_tslen,
451 	    packfile);
452 	if (err)
453 		return err;
454 
455 	/*
456 	 * XXX We currently only support plain objects as a delta base,
457 	 * i.e. deltas cannot be chained. Is this a problem?
458 	 * If so, we would have to resolve a plain object base type here.
459 	 */
460 	switch (base_type) {
461 	case GOT_OBJ_TYPE_COMMIT:
462 	case GOT_OBJ_TYPE_TREE:
463 	case GOT_OBJ_TYPE_BLOB:
464 	case GOT_OBJ_TYPE_TAG:
465 		break;
466 	case GOT_OBJ_TYPE_OFFSET_DELTA:
467 	case GOT_OBJ_TYPE_REF_DELTA:
468 	default:
469 		return got_error(GOT_ERR_NOT_IMPL);
470 	}
471 
472 	*obj = calloc(1, sizeof(**obj));
473 	if (*obj == NULL)
474 		return got_error(GOT_ERR_NO_MEM);
475 
476 	(*obj)->path_packfile = strdup(path_packfile);
477 	if ((*obj)->path_packfile == NULL) {
478 		free(*obj);
479 		return got_error(GOT_ERR_NO_MEM);
480 	}
481 	(*obj)->type = GOT_OBJ_TYPE_OFFSET_DELTA;
482 	(*obj)->flags = GOT_OBJ_FLAG_PACKED;
483 	(*obj)->hdrlen = 0;
484 	(*obj)->size = size;
485 	memcpy(&(*obj)->id, id, sizeof((*obj)->id));
486 	(*obj)->pack_offset = offset + tslen;
487 	(*obj)->base_type = base_type;
488 	(*obj)->base_size = base_size;
489 	(*obj)->base_obj_offset = base_obj_offset;
490 
491 	return NULL;
492 }
493 
494 static const struct got_error *
495 open_packed_object(struct got_object **obj, struct got_repository *repo,
496     const char *path_packdir, struct got_packidx_v2_hdr *packidx,
497     struct got_object_id *id)
498 {
499 	const struct got_error *err = NULL;
500 	int idx = get_object_idx(packidx, id);
501 	off_t offset;
502 	char hex[SHA1_DIGEST_STRING_LENGTH];
503 	char *sha1str;
504 	char *path_packfile;
505 	FILE *packfile;
506 	uint8_t type;
507 	uint64_t size;
508 	size_t tslen;
509 
510 	*obj = NULL;
511 	if (idx == -1) /* object not found in pack index */
512 		return NULL;
513 
514 	offset = get_object_offset(packidx, idx);
515 	if (offset == (uint64_t)-1)
516 		return got_error(GOT_ERR_BAD_PACKIDX);
517 
518 	sha1str = got_sha1_digest_to_str(packidx->trailer.packfile_sha1,
519 	    hex, sizeof(hex));
520 	if (sha1str == NULL)
521 		return got_error(GOT_ERR_PACKIDX_CSUM);
522 
523 	if (asprintf(&path_packfile, "%s/%s%s%s", path_packdir,
524 	    GOT_PACK_PREFIX, sha1str, GOT_PACKFILE_SUFFIX) == -1)
525 		return got_error(GOT_ERR_NO_MEM);
526 
527 	packfile = fopen(path_packfile, "rb");
528 	if (packfile == NULL) {
529 		err = got_error_from_errno();
530 		goto done;
531 	}
532 
533 	err = read_packfile_hdr(packfile, packidx);
534 	if (err)
535 		goto done;
536 
537 	if (fseeko(packfile, offset, SEEK_SET) != 0) {
538 		err = got_error_from_errno();
539 		goto done;
540 	}
541 
542 	err = decode_type_and_size(&type, &size, &tslen, packfile);
543 	if (err)
544 		goto done;
545 
546 	switch (type) {
547 	case GOT_OBJ_TYPE_COMMIT:
548 	case GOT_OBJ_TYPE_TREE:
549 	case GOT_OBJ_TYPE_BLOB:
550 		err = open_plain_object(obj, path_packfile, id, type,
551 		    offset + tslen, size);
552 		break;
553 
554 	case GOT_OBJ_TYPE_OFFSET_DELTA:
555 		err = open_offset_delta_object(obj, repo, path_packfile,
556 		    packfile, id, offset, tslen, size);
557 		break;
558 
559 	case GOT_OBJ_TYPE_REF_DELTA:
560 	case GOT_OBJ_TYPE_TAG:
561 		break;
562 	default:
563 		err = got_error(GOT_ERR_NOT_IMPL);
564 		goto done;
565 	}
566 done:
567 	free(path_packfile);
568 	if (err)
569 		free(*obj);
570 	if (packfile && fclose(packfile) == -1 && err == 0)
571 		err = got_error_from_errno();
572 	return err;
573 }
574 
575 const struct got_error *
576 got_packfile_open_object(struct got_object **obj, struct got_object_id *id,
577     struct got_repository *repo)
578 {
579 	const struct got_error *err = NULL;
580 	DIR *packdir = NULL;
581 	struct dirent *dent;
582 	char *path_packdir = got_repo_get_path_objects_pack(repo);
583 
584 	if (path_packdir == NULL) {
585 		err = got_error(GOT_ERR_NO_MEM);
586 		goto done;
587 	}
588 
589 	packdir = opendir(path_packdir);
590 	if (packdir == NULL) {
591 		err = got_error_from_errno();
592 		goto done;
593 	}
594 
595 	while ((dent = readdir(packdir)) != NULL) {
596 		struct got_packidx_v2_hdr *packidx;
597 		char *path_packidx, *path_object;
598 
599 		if (!is_packidx_filename(dent->d_name, dent->d_namlen))
600 			continue;
601 
602 		if (asprintf(&path_packidx, "%s/%s", path_packdir,
603 		    dent->d_name) == -1) {
604 			err = got_error(GOT_ERR_NO_MEM);
605 			goto done;
606 		}
607 
608 		err = got_packidx_open(&packidx, path_packidx);
609 		free(path_packidx);
610 		if (err)
611 			goto done;
612 
613 		err = open_packed_object(obj, repo, path_packdir, packidx, id);
614 		got_packidx_close(packidx);
615 		if (err)
616 			goto done;
617 		if (*obj != NULL)
618 			break;
619 	}
620 
621 done:
622 	free(path_packdir);
623 	if (packdir && closedir(packdir) != 0 && err == 0)
624 		err = got_error_from_errno();
625 	return err;
626 }
627 
628 static const struct got_error *
629 dump_plain_object(FILE *infile, uint8_t type, size_t size, FILE *outfile)
630 {
631 	size_t n;
632 
633 	while (size > 0) {
634 		uint8_t data[2048];
635 		size_t len = MIN(size, sizeof(data));
636 
637 		n = fread(data, len, 1, infile);
638 		if (n != 1)
639 			return got_ferror(infile, GOT_ERR_BAD_PACKFILE);
640 
641 		n = fwrite(data, len, 1, outfile);
642 		if (n != 1)
643 			return got_ferror(outfile, GOT_ERR_IO);
644 
645 		size -= len;
646 	}
647 
648 	rewind(outfile);
649 	return NULL;
650 }
651 
652 static const struct got_error *
653 dump_ref_delta_object(struct got_repository *repo, FILE *infile, uint8_t type,
654     size_t size, FILE *outfile)
655 {
656 	const struct got_error *err = NULL;
657 	struct got_object_id base_id;
658 	struct got_object *base_obj;
659 	size_t n;
660 
661 	if (size < sizeof(base_id))
662 		return got_ferror(infile, GOT_ERR_BAD_PACKFILE);
663 
664 	n = fread(&base_id, sizeof(base_id), 1, infile);
665 	if (n != 1)
666 		return got_ferror(infile, GOT_ERR_BAD_PACKFILE);
667 
668 	size -= sizeof(base_id);
669 	if (size <= 0)
670 		return got_ferror(infile, GOT_ERR_BAD_PACKFILE);
671 
672 	err = got_object_open(&base_obj, repo, &base_id);
673 	if (err)
674 		return err;
675 
676 	err = got_delta_apply(repo, infile, size, base_obj, outfile);
677 	got_object_close(base_obj);
678 	return err;
679 }
680 
681 const struct got_error *
682 got_packfile_extract_object(FILE **f, struct got_object *obj,
683     struct got_repository *repo)
684 {
685 	const struct got_error *err = NULL;
686 	FILE *packfile = NULL;
687 
688 	if ((obj->flags & GOT_OBJ_FLAG_PACKED) == 0)
689 		return got_error(GOT_ERR_OBJ_NOT_PACKED);
690 
691 	*f = got_opentemp();
692 	if (*f == NULL) {
693 		err = got_error(GOT_ERR_FILE_OPEN);
694 		goto done;
695 	}
696 
697 	packfile = fopen(obj->path_packfile, "rb");
698 	if (packfile == NULL) {
699 		err = got_error_from_errno();
700 		goto done;
701 	}
702 
703 	if (fseeko(packfile, obj->pack_offset, SEEK_SET) != 0) {
704 		err = got_error_from_errno();
705 		goto done;
706 	}
707 
708 	switch (obj->type) {
709 	case GOT_OBJ_TYPE_COMMIT:
710 	case GOT_OBJ_TYPE_TREE:
711 	case GOT_OBJ_TYPE_BLOB:
712 		err = dump_plain_object(packfile, obj->type, obj->size, *f);
713 		break;
714 	case GOT_OBJ_TYPE_REF_DELTA:
715 		err = dump_ref_delta_object(repo, packfile, obj->type,
716 		    obj->size, *f);
717 		break;
718 	case GOT_OBJ_TYPE_TAG:
719 	case GOT_OBJ_TYPE_OFFSET_DELTA:
720 	default:
721 		err = got_error(GOT_ERR_NOT_IMPL);
722 		goto done;
723 	}
724 done:
725 	if (packfile)
726 		fclose(packfile);
727 	if (err && *f)
728 		fclose(*f);
729 	return err;
730 }