thodg/got/lib/pack.c

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• Show log

  Commit

• Author : Stefan Sperling
  Date : 2018-02-12 00:01:26
  Hash : bdd2fbb3
  Message : read delta data from the right offset

• lib/pack.c

• /*
   * Copyright (c) 2018 Stefan Sperling <stsp@openbsd.org>
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <sys/queue.h>
  
  #include <dirent.h>
  #include <errno.h>
  #include <stdio.h>
  #include <stdint.h>
  #include <stdlib.h>
  #include <string.h>
  #include <limits.h>
  #include <sha1.h>
  #include <endian.h>
  #include <zlib.h>
  
  #include "got_error.h"
  #include "got_object.h"
  #include "got_repository.h"
  #include "got_sha1.h"
  #include "pack.h"
  #include "path.h"
  #include "delta.h"
  #include "object.h"
  #include "zb.h"
  
  #define GOT_PACK_PREFIX		"pack-"
  #define GOT_PACKFILE_SUFFIX	".pack"
  #define GOT_PACKIDX_SUFFIX		".idx"
  #define GOT_PACKFILE_NAMELEN	(strlen(GOT_PACK_PREFIX) + \
  				SHA1_DIGEST_STRING_LENGTH - 1 + \
  				strlen(GOT_PACKFILE_SUFFIX))
  #define GOT_PACKIDX_NAMELEN	(strlen(GOT_PACK_PREFIX) + \
  				SHA1_DIGEST_STRING_LENGTH - 1 + \
  				strlen(GOT_PACKIDX_SUFFIX))
  
  #ifndef MIN
  #define	MIN(_a,_b) ((_a) < (_b) ? (_a) : (_b))
  #endif
  
  static const struct got_error *
  verify_fanout_table(uint32_t *fanout_table)
  {
  	int i;
  
  	for (i = 0; i < 0xff - 1; i++) {
  		if (be32toh(fanout_table[i]) > be32toh(fanout_table[i + 1]))
  			return got_error(GOT_ERR_BAD_PACKIDX);
  	}
  
  	return NULL;
  }
  
  static const struct got_error *
  get_packfile_size(size_t *size, const char *path_idx)
  {
  	struct stat sb;
  	char *path_pack;
  	char base_path[PATH_MAX];
  	char *dot;
  
  	if (strlcpy(base_path, path_idx, PATH_MAX) > PATH_MAX)
  		return got_error(GOT_ERR_NO_SPACE);
  
  	dot = strrchr(base_path, '.');
  	if (dot == NULL)
  		return got_error(GOT_ERR_BAD_PATH);
  	*dot = '\0';
  	if (asprintf(&path_pack, "%s.pack", base_path) == -1)
  		return got_error(GOT_ERR_NO_MEM);
  
  	if (stat(path_pack, &sb) != 0) {
  		free(path_pack);
  		return got_error_from_errno();
  	}
  
  	free(path_pack);
  	*size = sb.st_size;
  	return 0;
  }
  
  const struct got_error *
  got_packidx_open(struct got_packidx_v2_hdr **packidx, const char *path)
  {
  	struct got_packidx_v2_hdr *p;
  	FILE *f;
  	const struct got_error *err = NULL;
  	size_t n, nobj, packfile_size;
  	SHA1_CTX ctx;
  	uint8_t sha1[SHA1_DIGEST_LENGTH];
  
  	SHA1Init(&ctx);
  
  	f = fopen(path, "rb");
  	if (f == NULL)
  		return got_error(GOT_ERR_BAD_PATH);
  
  	err = get_packfile_size(&packfile_size, path);
  	if (err)
  		return err;
  
  	p = calloc(1, sizeof(*p));
  	if (p == NULL) {
  		err = got_error(GOT_ERR_NO_MEM);
  		goto done;
  	}
  
  	n = fread(&p->magic, sizeof(p->magic), 1, f);
  	if (n != 1) {
  		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  
  	if (betoh32(p->magic) != GOT_PACKIDX_V2_MAGIC) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  
  	SHA1Update(&ctx, (uint8_t *)&p->magic, sizeof(p->magic));
  
  	n = fread(&p->version, sizeof(p->version), 1, f);
  	if (n != 1) {
  		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  
  	if (betoh32(p->version) != GOT_PACKIDX_VERSION) {
  		err = got_error(GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  
  	SHA1Update(&ctx, (uint8_t *)&p->version, sizeof(p->version));
  
  	n = fread(&p->fanout_table, sizeof(p->fanout_table), 1, f);
  	if (n != 1) {
  		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  
  	err = verify_fanout_table(p->fanout_table);
  	if (err)
  		goto done;
  
  	SHA1Update(&ctx, (uint8_t *)p->fanout_table, sizeof(p->fanout_table));
  
  	nobj = betoh32(p->fanout_table[0xff]);
  
  	p->sorted_ids = calloc(nobj, sizeof(*p->sorted_ids));
  	if (p->sorted_ids == NULL) {
  		err = got_error(GOT_ERR_NO_MEM);
  		goto done;
  	}
  
  	n = fread(p->sorted_ids, sizeof(*p->sorted_ids), nobj, f);
  	if (n != nobj) {
  		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  
  	SHA1Update(&ctx, (uint8_t *)p->sorted_ids,
  	    nobj * sizeof(*p->sorted_ids));
  
  	p->crc32 = calloc(nobj, sizeof(*p->crc32));
  	if (p->crc32 == NULL) {
  		err = got_error(GOT_ERR_NO_MEM);
  		goto done;
  	}
  
  	n = fread(p->crc32, sizeof(*p->crc32), nobj, f);
  	if (n != nobj) {
  		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  
  	SHA1Update(&ctx, (uint8_t *)p->crc32, nobj * sizeof(*p->crc32));
  
  	p->offsets = calloc(nobj, sizeof(*p->offsets));
  	if (p->offsets == NULL) {
  		err = got_error(GOT_ERR_NO_MEM);
  		goto done;
  	}
  
  	n = fread(p->offsets, sizeof(*p->offsets), nobj, f);
  	if (n != nobj) {
  		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  
  	SHA1Update(&ctx, (uint8_t *)p->offsets, nobj * sizeof(*p->offsets));
  
  	/* Large file offsets are contained only in files > 2GB. */
  	if (packfile_size <= 0x80000000)
  		goto checksum;
  
  	p->large_offsets = calloc(nobj, sizeof(*p->large_offsets));
  	if (p->large_offsets == NULL) {
  		err = got_error(GOT_ERR_NO_MEM);
  		goto done;
  	}
  
  	n = fread(p->large_offsets, sizeof(*p->large_offsets), nobj, f);
  	if (n != nobj) {
  		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  
  	SHA1Update(&ctx, (uint8_t*)p->large_offsets,
  	    nobj * sizeof(*p->large_offsets));
  
  checksum:
  	n = fread(&p->trailer, sizeof(p->trailer), 1, f);
  	if (n != 1) {
  		err = got_ferror(f, GOT_ERR_BAD_PACKIDX);
  		goto done;
  	}
  
  	SHA1Update(&ctx, p->trailer.packfile_sha1, SHA1_DIGEST_LENGTH);
  	SHA1Final(sha1, &ctx);
  	if (memcmp(p->trailer.packidx_sha1, sha1, SHA1_DIGEST_LENGTH) != 0)
  		err = got_error(GOT_ERR_PACKIDX_CSUM);
  done:
  	fclose(f);
  	if (err)
  		got_packidx_close(p);
  	else
  		*packidx = p;
  	return err;
  }
  
  void
  got_packidx_close(struct got_packidx_v2_hdr *packidx)
  {
  	free(packidx->sorted_ids);
  	free(packidx->offsets);
  	free(packidx->crc32);
  	free(packidx->large_offsets);
  	free(packidx);
  }
  
  static int
  is_packidx_filename(const char *name, size_t len)
  {
  	if (len != GOT_PACKIDX_NAMELEN)
  		return 0;
  
  	if (strncmp(name, GOT_PACK_PREFIX, strlen(GOT_PACK_PREFIX)) != 0)
  		return 0;
  
  	if (strcmp(name + strlen(GOT_PACK_PREFIX) +
  	    SHA1_DIGEST_STRING_LENGTH - 1, GOT_PACKIDX_SUFFIX) != 0)
  		return 0;
  
  	return 1;
  }
  
  static off_t
  get_object_offset(struct got_packidx_v2_hdr *packidx, int idx)
  {
  	uint32_t totobj = betoh32(packidx->fanout_table[0xff]);
  	uint32_t offset = betoh32(packidx->offsets[idx]);
  	if (offset & GOT_PACKIDX_OFFSET_VAL_IS_LARGE_IDX) {
  		uint64_t loffset;
  		idx = offset & GOT_PACKIDX_OFFSET_VAL_MASK;
  		if (idx < 0 || idx > totobj || packidx->large_offsets == NULL)
  			return -1;
  		loffset = betoh64(packidx->large_offsets[idx]);
  		return (loffset > INT64_MAX ? -1 : (off_t)loffset);
  	}
  	return (off_t)(offset & GOT_PACKIDX_OFFSET_VAL_MASK);
  }
  
  static int
  get_object_idx(struct got_packidx_v2_hdr *packidx, struct got_object_id *id)
  {
  	u_int8_t id0 = id->sha1[0];
  	uint32_t totobj = betoh32(packidx->fanout_table[0xff]);
  	int i = 0;
  
  	if (id0 > 0)
  		i = betoh32(packidx->fanout_table[id0 - 1]);
  
  	while (i < totobj) {
  		struct got_object_id *oid = &packidx->sorted_ids[i];
  		uint32_t offset;
  		int cmp = got_object_id_cmp(id, oid);
  
  		if (cmp == 0)
  			return i;
  		i++;
  	}
  
  	return -1;
  }
  
  static const struct got_error *
  search_packidx(struct got_packidx_v2_hdr **packidx, int *idx,
      struct got_repository *repo, struct got_object_id *id)
  {
  	const struct got_error *err;
  	char *path_packdir;
  	DIR *packdir;
  	struct dirent *dent;
  	char *path_packidx;
  
  	path_packdir = got_repo_get_path_objects_pack(repo);
  	if (path_packdir == NULL)
  		return got_error(GOT_ERR_NO_MEM);
  
  	packdir = opendir(path_packdir);
  	if (packdir == NULL) {
  		err = got_error_from_errno();
  		goto done;
  	}
  
  	while ((dent = readdir(packdir)) != NULL) {
  		if (!is_packidx_filename(dent->d_name, dent->d_namlen))
  			continue;
  
  		if (asprintf(&path_packidx, "%s/%s", path_packdir,
  		    dent->d_name) == -1) {
  			err = got_error(GOT_ERR_NO_MEM);
  			goto done;
  		}
  
  		err = got_packidx_open(packidx, path_packidx);
  		free(path_packidx);
  		if (err)
  			goto done;
  
  		*idx = get_object_idx(*packidx, id);
  		if (*idx != -1) {
  			err = NULL; /* found the object */
  			goto done;
  		}
  
  		got_packidx_close(*packidx);
  		*packidx = NULL;
  	}
  
  	err = got_error(GOT_ERR_NO_OBJ);
  done:
  	free(path_packdir);
  	if (packdir && closedir(packdir) != 0 && err == 0)
  		err = got_error_from_errno();
  	return err;
  }
  
  static const struct got_error *
  get_packfile_path(char **path_packfile, struct got_repository *repo,
      struct got_packidx_v2_hdr *packidx)
  {
  	char *path_packdir;
  	char hex[SHA1_DIGEST_STRING_LENGTH];
  	char *sha1str;
  	char *path_packidx;
  
  	*path_packfile = NULL;
  
  	path_packdir = got_repo_get_path_objects_pack(repo);
  	if (path_packdir == NULL)
  		return got_error(GOT_ERR_NO_MEM);
  
  	sha1str = got_sha1_digest_to_str(packidx->trailer.packfile_sha1,
  	    hex, sizeof(hex));
  	if (sha1str == NULL)
  		return got_error(GOT_ERR_PACKIDX_CSUM);
  
  	if (asprintf(path_packfile, "%s/%s%s%s", path_packdir,
  	    GOT_PACK_PREFIX, sha1str, GOT_PACKFILE_SUFFIX) == -1) {
  		*path_packfile = NULL;
  		return got_error(GOT_ERR_NO_MEM);
  	}
  
  	return NULL;
  }
  
  const struct got_error *
  read_packfile_hdr(FILE *f, struct got_packidx_v2_hdr *packidx)
  {
  	const struct got_error *err = NULL;
  	uint32_t totobj = betoh32(packidx->fanout_table[0xff]);
  	struct got_packfile_hdr hdr;
  	size_t n;
  
  	n = fread(&hdr, sizeof(hdr), 1, f);
  	if (n != 1)
  		return got_ferror(f, GOT_ERR_BAD_PACKIDX);
  
  	if (betoh32(hdr.signature) != GOT_PACKFILE_SIGNATURE ||
  	    betoh32(hdr.version) != GOT_PACKFILE_VERSION ||
  	    betoh32(hdr.nobjects) != totobj)
  		err = got_error(GOT_ERR_BAD_PACKFILE);
  
  	return err;
  }
  
  static const struct got_error *
  open_packfile(FILE **packfile, char **path_packfile,
      struct got_repository *repo, struct got_packidx_v2_hdr *packidx)
  {
  	const struct got_error *err;
  
  	*packfile = NULL;
  
  	err = get_packfile_path(path_packfile, repo, packidx);
  	if (err)
  		return err;
  
  	*packfile = fopen(*path_packfile, "rb");
  	if (*packfile == NULL) {
  		err = got_error_from_errno();
  		free(*path_packfile);
  		return err;
  	}
  
  	err = read_packfile_hdr(*packfile, packidx);
  	if (err) {
  		fclose(*packfile);
  		*packfile = NULL;
  	}
  	return err;
  }
  
  static const struct got_error *
  parse_object_type_and_size(uint8_t *type, uint64_t *size, size_t *len,
      FILE *packfile)
  {
  	uint8_t t = 0;
  	uint64_t s = 0;
  	uint8_t sizeN;
  	size_t n;
  	int i = 0;
  
  	do {
  		/* We do not support size values which don't fit in 64 bit. */
  		if (i > 9)
  			return got_error(GOT_ERR_NO_SPACE);
  
  		n = fread(&sizeN, sizeof(sizeN), 1, packfile);
  		if (n != 1)
  			return got_ferror(packfile, GOT_ERR_BAD_PACKIDX);
  
  		if (i == 0) {
  			t = (sizeN & GOT_PACK_OBJ_SIZE0_TYPE_MASK) >>
  			    GOT_PACK_OBJ_SIZE0_TYPE_MASK_SHIFT;
  			s = (sizeN & GOT_PACK_OBJ_SIZE0_VAL_MASK);
  		} else {
  			size_t shift = 4 + 7 * (i - 1);
  			s |= ((sizeN & GOT_PACK_OBJ_SIZE_VAL_MASK) << shift);
  		}
  		i++;
  	} while (sizeN & GOT_PACK_OBJ_SIZE_MORE);
  
  	*type = t;
  	*size = s;
  	*len = i * sizeof(sizeN);
  	return NULL;
  }
  
  static const struct got_error *
  open_plain_object(struct got_object **obj, const char *path_packfile,
      struct got_object_id *id, uint8_t type, off_t offset, size_t size)
  {
  	*obj = calloc(1, sizeof(**obj));
  	if (*obj == NULL)
  		return got_error(GOT_ERR_NO_MEM);
  
  	(*obj)->path_packfile = strdup(path_packfile);
  	if ((*obj)->path_packfile == NULL) {
  		free(*obj);
  		*obj = NULL;
  		return got_error(GOT_ERR_NO_MEM);
  	}
  
  	(*obj)->type = type;
  	(*obj)->flags = GOT_OBJ_FLAG_PACKED;
  	(*obj)->hdrlen = 0;
  	(*obj)->size = size;
  	memcpy(&(*obj)->id, id, sizeof((*obj)->id));
  	(*obj)->pack_offset = offset;
  
  	return NULL;
  }
  
  static const struct got_error *
  parse_negative_offset(int64_t *offset, size_t *len, FILE *packfile)
  {
  	int64_t o = 0;
  	uint8_t offN;
  	size_t n;
  	int i = 0;
  
  	do {
  		/* We do not support offset values which don't fit in 64 bit. */
  		if (i > 8)
  			return got_error(GOT_ERR_NO_SPACE);
  
  		n = fread(&offN, sizeof(offN), 1, packfile);
  		if (n != 1)
  			return got_ferror(packfile, GOT_ERR_BAD_PACKIDX);
  
  		if (i == 0)
  			o = (offN & GOT_PACK_OBJ_DELTA_OFF_VAL_MASK);
  		else {
  			o++;
  			o <<= 7;
  			o += (offN & GOT_PACK_OBJ_DELTA_OFF_VAL_MASK);
  		}
  		i++;
  	} while (offN & GOT_PACK_OBJ_DELTA_OFF_MORE);
  
  	*offset = o;
  	*len = i * sizeof(offN);
  	return NULL;
  }
  
  static const struct got_error *
  parse_offset_delta(off_t *base_offset, FILE *packfile, off_t offset)
  {
  	const struct got_error *err;
  	int64_t negoffset;
  	size_t negofflen;
  
  	err = parse_negative_offset(&negoffset, &negofflen, packfile);
  	if (err)
  		return err;
  
  	/* Compute the base object's offset (must be in the same pack file). */
  	*base_offset = (offset - negoffset);
  	if (*base_offset <= 0)
  		return got_error(GOT_ERR_BAD_PACKFILE);
  
  	return NULL;
  }
  
  static const struct got_error *
  resolve_delta_chain(struct got_delta_chain *, struct got_repository *,
      FILE *, const char *, off_t, size_t, int, size_t);
  
  static const struct got_error *
  add_delta(struct got_delta_chain *deltas, const char *path_packfile,
      off_t delta_offset, size_t tslen, int delta_type, size_t delta_size,
      size_t delta_data_offset)
  {
  	struct got_delta *delta;
  
  	delta = got_delta_open(path_packfile, delta_offset, tslen,
  	    delta_type, delta_size, delta_data_offset);
  	if (delta == NULL)
  		return got_error(GOT_ERR_NO_MEM);
  	/* delta is freed in got_object_close() */
  	deltas->nentries++;
  	SIMPLEQ_INSERT_HEAD(&deltas->entries, delta, entry);
  	return NULL;
  }
  
  static const struct got_error *
  resolve_offset_delta(struct got_delta_chain *deltas,
      struct got_repository *repo, FILE *packfile, const char *path_packfile,
      off_t delta_offset,size_t tslen, int delta_type, size_t delta_size)
  
  {
  	const struct got_error *err;
  	off_t base_offset;
  	uint8_t base_type;
  	uint64_t base_size;
  	size_t base_tslen;
  	off_t delta_data_offset;
  
  	err = parse_offset_delta(&base_offset, packfile, delta_offset);
  	if (err)
  		return err;
  
  	delta_data_offset = ftello(packfile);
  	if (delta_data_offset == -1)
  		return got_error_from_errno();
  
  	err = add_delta(deltas, path_packfile, delta_offset, tslen,
  	    delta_type, delta_size, delta_data_offset);
  	if (err)
  		return err;
  
  	/* An offset delta must be in the same packfile. */
  	if (fseeko(packfile, base_offset, SEEK_SET) != 0)
  		return got_error_from_errno();
  
  	err = parse_object_type_and_size(&base_type, &base_size, &base_tslen,
  	    packfile);
  	if (err)
  		return err;
  
  	return resolve_delta_chain(deltas, repo, packfile, path_packfile,
  	    base_offset, base_tslen, base_type, base_size);
  }
  
  static const struct got_error *
  resolve_ref_delta(struct got_delta_chain *deltas, struct got_repository *repo,
      FILE *packfile, const char *path_packfile, off_t delta_offset,
      size_t tslen, int delta_type, size_t delta_size)
  {
  	const struct got_error *err;
  	struct got_object_id id;
  	struct got_packidx_v2_hdr *packidx;
  	int idx;
  	off_t base_offset;
  	uint8_t base_type;
  	uint64_t base_size;
  	size_t base_tslen;
  	size_t n;
  	FILE *base_packfile;
  	char *path_base_packfile;
  	off_t delta_data_offset;
  
  	n = fread(&id, sizeof(id), 1, packfile);
  	if (n != 1)
  		return got_ferror(packfile, GOT_ERR_IO);
  
  	delta_data_offset = ftello(packfile);
  	if (delta_data_offset == -1)
  		return got_error_from_errno();
  
  	err = add_delta(deltas, path_packfile, delta_offset, tslen,
  	    delta_type, delta_size, delta_data_offset);
  	if (err)
  		return err;
  
  	err = search_packidx(&packidx, &idx, repo, &id);
  	if (err)
  		return err;
  
  	base_offset = get_object_offset(packidx, idx);
  	if (base_offset == (uint64_t)-1) {
  		got_packidx_close(packidx);
  		return got_error(GOT_ERR_BAD_PACKIDX);
  	}
  
  	err = open_packfile(&base_packfile, &path_base_packfile, repo, packidx);
  	got_packidx_close(packidx);
  	if (err)
  		return err;
  
  	if (fseeko(base_packfile, base_offset, SEEK_SET) != 0) {
  		err = got_error_from_errno();
  		goto done;
  	}
  
  	err = parse_object_type_and_size(&base_type, &base_size, &base_tslen,
  	    base_packfile);
  	if (err)
  		goto done;
  
  	err = resolve_delta_chain(deltas, repo, base_packfile,
  	    path_base_packfile, base_offset, base_tslen, base_type,
  	    base_size);
  done:
  	free(path_base_packfile);
  	if (base_packfile && fclose(base_packfile) == -1 && err == 0)
  		err = got_error_from_errno();
  	return err;
  }
  
  static const struct got_error *
  resolve_delta_chain(struct got_delta_chain *deltas, struct got_repository *repo,
      FILE *packfile, const char *path_packfile, off_t delta_offset, size_t tslen,
      int delta_type, size_t delta_size)
  {
  	const struct got_error *err = NULL;
  
  	switch (delta_type) {
  	case GOT_OBJ_TYPE_COMMIT:
  	case GOT_OBJ_TYPE_TREE:
  	case GOT_OBJ_TYPE_BLOB:
  	case GOT_OBJ_TYPE_TAG:
  		/* Plain types are the final delta base. Recursion ends. */
  		err = add_delta(deltas, path_packfile, delta_offset, tslen,
  		    delta_type, delta_size, 0);
  		break;
  	case GOT_OBJ_TYPE_OFFSET_DELTA:
  		err = resolve_offset_delta(deltas, repo, packfile,
  		    path_packfile, delta_offset, tslen, delta_type,
  		    delta_size);
  		break;
  	case GOT_OBJ_TYPE_REF_DELTA:
  		err = resolve_ref_delta(deltas, repo, packfile,
  		    path_packfile, delta_offset, tslen, delta_type,
  		    delta_size);
  		break;
  	default:
  		return got_error(GOT_ERR_NOT_IMPL);
  	}
  
  	return err;
  }
  
  static const struct got_error *
  open_delta_object(struct got_object **obj, struct got_repository *repo,
      struct got_packidx_v2_hdr *packidx, const char *path_packfile,
      FILE *packfile, struct got_object_id *id, off_t offset, size_t tslen,
      int delta_type, size_t delta_size)
  {
  	const struct got_error *err = NULL;
  	struct got_object_id base_id;
  	uint8_t base_type;
  	int resolved_type;
  	uint64_t base_size;
  	size_t base_tslen;
  
  	*obj = calloc(1, sizeof(**obj));
  	if (*obj == NULL)
  		return got_error(GOT_ERR_NO_MEM);
  
  	(*obj)->flags = 0;
  	(*obj)->hdrlen = 0;
  	(*obj)->size = 0; /* Not yet known because deltas aren't combined. */
  	memcpy(&(*obj)->id, id, sizeof((*obj)->id));
  	(*obj)->pack_offset = offset + tslen;
  
  	(*obj)->path_packfile = strdup(path_packfile);
  	if ((*obj)->path_packfile == NULL) {
  		err = got_error(GOT_ERR_NO_MEM);
  		goto done;
  	}
  	(*obj)->flags |= GOT_OBJ_FLAG_PACKED;
  
  	SIMPLEQ_INIT(&(*obj)->deltas.entries);
  	(*obj)->flags |= GOT_OBJ_FLAG_DELTIFIED;
  
  	err = resolve_delta_chain(&(*obj)->deltas, repo, packfile,
  	    path_packfile, offset, tslen, delta_type, delta_size);
  	if (err)
  		goto done;
  
  	err = got_delta_chain_get_base_type(&resolved_type, &(*obj)->deltas);
  	if (err)
  		goto done;
  	(*obj)->type = resolved_type;
  
  done:
  	if (err) {
  		got_object_close(*obj);
  		*obj = NULL;
  	}
  	return err;
  }
  
  static const struct got_error *
  open_packed_object(struct got_object **obj, struct got_repository *repo,
      struct got_packidx_v2_hdr *packidx, int idx, struct got_object_id *id)
  {
  	const struct got_error *err = NULL;
  	off_t offset;
  	char *path_packfile;
  	FILE *packfile;
  	uint8_t type;
  	uint64_t size;
  	size_t tslen;
  
  	*obj = NULL;
  
  	offset = get_object_offset(packidx, idx);
  	if (offset == (uint64_t)-1)
  		return got_error(GOT_ERR_BAD_PACKIDX);
  
  	err = open_packfile(&packfile, &path_packfile, repo, packidx);
  	if (err)
  		return err;
  
  	if (fseeko(packfile, offset, SEEK_SET) != 0) {
  		err = got_error_from_errno();
  		goto done;
  	}
  
  	err = parse_object_type_and_size(&type, &size, &tslen, packfile);
  	if (err)
  		goto done;
  
  	switch (type) {
  	case GOT_OBJ_TYPE_COMMIT:
  	case GOT_OBJ_TYPE_TREE:
  	case GOT_OBJ_TYPE_BLOB:
  	case GOT_OBJ_TYPE_TAG:
  		err = open_plain_object(obj, path_packfile, id, type,
  		    offset + tslen, size);
  		break;
  
  	case GOT_OBJ_TYPE_OFFSET_DELTA:
  	case GOT_OBJ_TYPE_REF_DELTA:
  		err = open_delta_object(obj, repo, packidx, path_packfile,
  		    packfile, id, offset, tslen, type, size);
  		break;
  
  	default:
  		err = got_error(GOT_ERR_NOT_IMPL);
  		goto done;
  	}
  done:
  	free(path_packfile);
  	if (packfile && fclose(packfile) == -1 && err == 0)
  		err = got_error_from_errno();
  	return err;
  }
  
  const struct got_error *
  got_packfile_open_object(struct got_object **obj, struct got_object_id *id,
      struct got_repository *repo)
  {
  	const struct got_error *err = NULL;
  	struct got_packidx_v2_hdr *packidx = NULL;
  	int idx;
  
  	err = search_packidx(&packidx, &idx, repo, id);
  	if (err)
  		return err;
  
  	err = open_packed_object(obj, repo, packidx, idx, id);
  	got_packidx_close(packidx);
  	return err;
  }
  
  static const struct got_error *
  dump_delta_chain(struct got_delta_chain *deltas, FILE *outfile)
  {
  	const struct got_error *err = NULL;
  	struct got_delta *delta;
  	FILE *base_file, *accum_file;
  	int n = 0;
  
  	if (SIMPLEQ_EMPTY(&deltas->entries))
  		return got_error(GOT_ERR_BAD_DELTA_CHAIN);
  
  	base_file = got_opentemp();
  	if (base_file == NULL)
  		return got_error_from_errno();
  
  	accum_file = got_opentemp();
  	if (accum_file == NULL) {
  		err = got_error_from_errno();
  		fclose(base_file);
  		return err;
  	}
  
  	/* Deltas are ordered in ascending order. */
  	SIMPLEQ_FOREACH(delta, &deltas->entries, entry) {
  		uint8_t *delta_buf = NULL;
  		size_t delta_len = 0;
  		FILE *delta_file;
  
  		delta_file = fopen(delta->path_packfile, "rb");
  		if (delta_file == NULL) {
  			err = got_error_from_errno();
  			goto done;
  		}
  
  
  		if (n == 0) {
  			/* Plain object types are the delta base. */
  			if (delta->type != GOT_OBJ_TYPE_COMMIT &&
  			    delta->type != GOT_OBJ_TYPE_TREE &&
  			    delta->type != GOT_OBJ_TYPE_BLOB &&
  			    delta->type != GOT_OBJ_TYPE_TAG) {
  				err = got_error(GOT_ERR_BAD_DELTA_CHAIN);
  				goto done;
  			}
  
  			if (fseeko(delta_file, delta->offset + delta->tslen,
  			    SEEK_SET) != 0) {
  				fclose(delta_file);
  				err = got_error_from_errno();
  				goto done;
  			}
  			err = got_inflate_to_file(&delta_len, delta_file,
  			    base_file);
  			fclose(delta_file);
  			if (err)
  				goto done;
  			n++;
  			rewind(base_file);
  			continue;
  		}
  
  		if (fseeko(delta_file, delta->data_offset, SEEK_CUR) != 0) {
  			fclose(delta_file);
  			err = got_error_from_errno();
  			goto done;
  		}
  
  		/* Delta streams should always fit in memory. */
  		err = got_inflate_to_mem(&delta_buf, &delta_len, delta_file);
  		fclose(delta_file);
  		if (err)
  			goto done;
  
  		err = got_delta_apply(base_file, delta_buf, delta_len,
  		    /* Final delta application writes to the output file. */
  		    ++n < deltas->nentries ? accum_file : outfile);
  		free(delta_buf);
  		if (err)
  			goto done;
  
  		if (n < deltas->nentries) {
  			/* Accumulated delta becomes the new base. */
  			FILE *tmp = accum_file;
  			accum_file = base_file;
  			base_file = tmp;
  			rewind(base_file);
  			rewind(accum_file);
  		}
  	}
  
  done:
  	fclose(base_file);
  	fclose(accum_file);
  	rewind(outfile);
  	return err;
  }
  
  const struct got_error *
  got_packfile_extract_object(FILE **f, struct got_object *obj,
      struct got_repository *repo)
  {
  	const struct got_error *err = NULL;
  	FILE *packfile = NULL;
  
  	if ((obj->flags & GOT_OBJ_FLAG_PACKED) == 0)
  		return got_error(GOT_ERR_OBJ_NOT_PACKED);
  
  	*f = got_opentemp();
  	if (*f == NULL) {
  		err = got_error(GOT_ERR_FILE_OPEN);
  		goto done;
  	}
  
  	if ((obj->flags & GOT_OBJ_FLAG_DELTIFIED) == 0) {
  		packfile = fopen(obj->path_packfile, "rb");
  		if (packfile == NULL) {
  			err = got_error_from_errno();
  			goto done;
  		}
  
  		if (fseeko(packfile, obj->pack_offset, SEEK_SET) != 0) {
  			err = got_error_from_errno();
  			goto done;
  		}
  
  		err = got_inflate_to_file(&obj->size, packfile, *f);
  	} else
  		err = dump_delta_chain(&obj->deltas, *f);
  done:
  	if (packfile)
  		fclose(packfile);
  	if (err && *f)
  		fclose(*f);
  	return err;
  }