pack.c 27 KB
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/*
Edward Thomson committed
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 * Copyright (C) the libgit2 contributors. All rights reserved.
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 *
Vicent Marti committed
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 * This file is part of libgit2, distributed under the GNU GPL v2 with
 * a Linking Exception. For full terms see the included COPYING file.
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 */

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#include "common.h"
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#include "odb.h"
#include "pack.h"
#include "delta-apply.h"
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#include "sha1_lookup.h"
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#include "mwindow.h"
#include "fileops.h"
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#include "oid.h"
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#include <zlib.h>
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static int packfile_open(struct git_pack_file *p);
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static git_off_t nth_packed_object_offset(const struct git_pack_file *p, uint32_t n);
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int packfile_unpack_compressed(
		git_rawobj *obj,
		struct git_pack_file *p,
		git_mwindow **w_curs,
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		git_off_t *curpos,
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		size_t size,
		git_otype type);

/* Can find the offset of an object given
 * a prefix of an identifier.
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 * Throws GIT_EAMBIGUOUSOIDPREFIX if short oid
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 * is ambiguous within the pack.
 * This method assumes that len is between
 * GIT_OID_MINPREFIXLEN and GIT_OID_HEXSZ.
 */
static int pack_entry_find_offset(
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		git_off_t *offset_out,
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		git_oid *found_oid,
		struct git_pack_file *p,
		const git_oid *short_oid,
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		size_t len);
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static int packfile_error(const char *message)
{
	giterr_set(GITERR_ODB, "Invalid pack file - %s", message);
	return -1;
}

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/********************
 * Delta base cache
 ********************/
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static git_pack_cache_entry *new_cache_object(git_rawobj *source)
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{
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	git_pack_cache_entry *e = git__calloc(1, sizeof(git_pack_cache_entry));
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	if (!e)
		return NULL;

	memcpy(&e->raw, source, sizeof(git_rawobj));

	return e;
}

static void free_cache_object(void *o)
{
	git_pack_cache_entry *e = (git_pack_cache_entry *)o;

	if (e != NULL) {
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		assert(e->refcount.val == 0);
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		git__free(e->raw.data);
		git__free(e);
	}
}

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static void cache_free(git_pack_cache *cache)
{
	khiter_t k;

	if (cache->entries) {
		for (k = kh_begin(cache->entries); k != kh_end(cache->entries); k++) {
			if (kh_exist(cache->entries, k))
				free_cache_object(kh_value(cache->entries, k));
		}

		git_offmap_free(cache->entries);
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		git_mutex_free(&cache->lock);
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	}
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	memset(cache, 0, sizeof(*cache));
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}

static int cache_init(git_pack_cache *cache)
{
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	memset(cache, 0, sizeof(*cache));

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	cache->entries = git_offmap_alloc();
	GITERR_CHECK_ALLOC(cache->entries);
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	cache->memory_limit = GIT_PACK_CACHE_MEMORY_LIMIT;
	git_mutex_init(&cache->lock);

	return 0;
}

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static git_pack_cache_entry *cache_get(git_pack_cache *cache, git_off_t offset)
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{
	khiter_t k;
	git_pack_cache_entry *entry = NULL;

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	if (git_mutex_lock(&cache->lock) < 0)
		return NULL;

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	k = kh_get(off, cache->entries, offset);
	if (k != kh_end(cache->entries)) { /* found it */
		entry = kh_value(cache->entries, k);
		git_atomic_inc(&entry->refcount);
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		entry->last_usage = cache->use_ctr++;
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	}
	git_mutex_unlock(&cache->lock);

	return entry;
}

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/* Run with the cache lock held */
static void free_lowest_entry(git_pack_cache *cache)
{
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	git_pack_cache_entry *entry;
	khiter_t k;

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	for (k = kh_begin(cache->entries); k != kh_end(cache->entries); k++) {
		if (!kh_exist(cache->entries, k))
			continue;

		entry = kh_value(cache->entries, k);
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		if (entry && entry->refcount.val == 0) {
			cache->memory_used -= entry->raw.len;
			kh_del(off, cache->entries, k);
			free_cache_object(entry);
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		}
	}
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}

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static int cache_add(git_pack_cache *cache, git_rawobj *base, git_off_t offset)
{
	git_pack_cache_entry *entry;
	int error, exists = 0;
	khiter_t k;

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	if (base->len > GIT_PACK_CACHE_SIZE_LIMIT)
		return -1;

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	entry = new_cache_object(base);
	if (entry) {
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		if (git_mutex_lock(&cache->lock) < 0) {
			giterr_set(GITERR_OS, "failed to lock cache");
			return -1;
		}
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		/* Add it to the cache if nobody else has */
		exists = kh_get(off, cache->entries, offset) != kh_end(cache->entries);
		if (!exists) {
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			while (cache->memory_used + base->len > cache->memory_limit)
				free_lowest_entry(cache);

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			k = kh_put(off, cache->entries, offset, &error);
			assert(error != 0);
			kh_value(cache->entries, k) = entry;
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			cache->memory_used += entry->raw.len;
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		}
		git_mutex_unlock(&cache->lock);
		/* Somebody beat us to adding it into the cache */
		if (exists) {
			git__free(entry);
			return -1;
		}
	}

	return 0;
}

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/***********************************************************
 *
 * PACK INDEX METHODS
 *
 ***********************************************************/

static void pack_index_free(struct git_pack_file *p)
{
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	if (p->oids) {
		git__free(p->oids);
		p->oids = NULL;
	}
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	if (p->index_map.data) {
		git_futils_mmap_free(&p->index_map);
		p->index_map.data = NULL;
	}
}

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static int pack_index_check(const char *path, struct git_pack_file *p)
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{
	struct git_pack_idx_header *hdr;
	uint32_t version, nr, i, *index;
	void *idx_map;
	size_t idx_size;
	struct stat st;
	int error;
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	/* TODO: properly open the file without access time using O_NOATIME */
	git_file fd = git_futils_open_ro(path);
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	if (fd < 0)
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		return fd;
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	if (p_fstat(fd, &st) < 0) {
		p_close(fd);
		giterr_set(GITERR_OS, "Unable to stat pack index '%s'", path);
		return -1;
	}

	if (!S_ISREG(st.st_mode) ||
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		!git__is_sizet(st.st_size) ||
		(idx_size = (size_t)st.st_size) < 4 * 256 + 20 + 20)
	{
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		p_close(fd);
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		giterr_set(GITERR_ODB, "Invalid pack index '%s'", path);
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		return -1;
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	}

	error = git_futils_mmap_ro(&p->index_map, fd, 0, idx_size);
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	p_close(fd);

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	if (error < 0)
		return error;
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	hdr = idx_map = p->index_map.data;

	if (hdr->idx_signature == htonl(PACK_IDX_SIGNATURE)) {
		version = ntohl(hdr->idx_version);

		if (version < 2 || version > 2) {
			git_futils_mmap_free(&p->index_map);
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			return packfile_error("unsupported index version");
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		}

	} else
		version = 1;

	nr = 0;
	index = idx_map;

	if (version > 1)
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		index += 2; /* skip index header */
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	for (i = 0; i < 256; i++) {
		uint32_t n = ntohl(index[i]);
		if (n < nr) {
			git_futils_mmap_free(&p->index_map);
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			return packfile_error("index is non-monotonic");
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		}
		nr = n;
	}

	if (version == 1) {
		/*
		 * Total size:
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		 * - 256 index entries 4 bytes each
		 * - 24-byte entries * nr (20-byte sha1 + 4-byte offset)
		 * - 20-byte SHA1 of the packfile
		 * - 20-byte SHA1 file checksum
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		 */
		if (idx_size != 4*256 + nr * 24 + 20 + 20) {
			git_futils_mmap_free(&p->index_map);
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			return packfile_error("index is corrupted");
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		}
	} else if (version == 2) {
		/*
		 * Minimum size:
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		 * - 8 bytes of header
		 * - 256 index entries 4 bytes each
		 * - 20-byte sha1 entry * nr
		 * - 4-byte crc entry * nr
		 * - 4-byte offset entry * nr
		 * - 20-byte SHA1 of the packfile
		 * - 20-byte SHA1 file checksum
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		 * And after the 4-byte offset table might be a
		 * variable sized table containing 8-byte entries
		 * for offsets larger than 2^31.
		 */
		unsigned long min_size = 8 + 4*256 + nr*(20 + 4 + 4) + 20 + 20;
		unsigned long max_size = min_size;

		if (nr)
			max_size += (nr - 1)*8;

		if (idx_size < min_size || idx_size > max_size) {
			git_futils_mmap_free(&p->index_map);
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			return packfile_error("wrong index size");
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		}
	}

	p->num_objects = nr;
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	p->index_version = version;
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	return 0;
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}

static int pack_index_open(struct git_pack_file *p)
{
	char *idx_name;
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	int error = 0;
	size_t name_len, base_len;

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	if (p->index_version > -1)
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		return 0;
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	name_len = strlen(p->pack_name);
	assert(name_len > strlen(".pack")); /* checked by git_pack_file alloc */
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	if ((idx_name = git__malloc(name_len)) == NULL)
		return -1;
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	base_len = name_len - strlen(".pack");
	memcpy(idx_name, p->pack_name, base_len);
	memcpy(idx_name + base_len, ".idx", sizeof(".idx"));
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	if ((error = git_mutex_lock(&p->lock)) < 0)
		return error;

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	if (p->index_version == -1)
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		error = pack_index_check(idx_name, p);
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	git__free(idx_name);
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	git_mutex_unlock(&p->lock);

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	return error;
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}

static unsigned char *pack_window_open(
		struct git_pack_file *p,
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		git_mwindow **w_cursor,
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		git_off_t offset,
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		unsigned int *left)
{
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	if (p->mwf.fd == -1 && packfile_open(p) < 0)
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		return NULL;

	/* Since packfiles end in a hash of their content and it's
	 * pointless to ask for an offset into the middle of that
	 * hash, and the pack_window_contains function above wouldn't match
	 * don't allow an offset too close to the end of the file.
	 */
	if (offset > (p->mwf.size - 20))
		return NULL;

	return git_mwindow_open(&p->mwf, w_cursor, offset, 20, left);
 }

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static int packfile_unpack_header1(
		unsigned long *usedp,
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		size_t *sizep,
		git_otype *type,
		const unsigned char *buf,
		unsigned long len)
{
	unsigned shift;
	unsigned long size, c;
	unsigned long used = 0;
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	c = buf[used++];
	*type = (c >> 4) & 7;
	size = c & 15;
	shift = 4;
	while (c & 0x80) {
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		if (len <= used)
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			return GIT_EBUFS;
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		if (bitsizeof(long) <= shift) {
			*usedp = 0;
			return -1;
		}
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		c = buf[used++];
		size += (c & 0x7f) << shift;
		shift += 7;
	}

	*sizep = (size_t)size;
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	*usedp = used;
	return 0;
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}

int git_packfile_unpack_header(
		size_t *size_p,
		git_otype *type_p,
		git_mwindow_file *mwf,
		git_mwindow **w_curs,
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		git_off_t *curpos)
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{
	unsigned char *base;
	unsigned int left;
	unsigned long used;
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	int ret;
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	/* pack_window_open() assures us we have [base, base + 20) available
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	 * as a range that we can look at at. (Its actually the hash
	 * size that is assured.) With our object header encoding
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	 * the maximum deflated object size is 2^137, which is just
	 * insane, so we know won't exceed what we have been given.
	 */
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/*	base = pack_window_open(p, w_curs, *curpos, &left); */
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	base = git_mwindow_open(mwf, w_curs, *curpos, 20, &left);
	if (base == NULL)
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		return GIT_EBUFS;
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	ret = packfile_unpack_header1(&used, size_p, type_p, base, left);
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	git_mwindow_close(w_curs);
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	if (ret == GIT_EBUFS)
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		return ret;
	else if (ret < 0)
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		return packfile_error("header length is zero");
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	*curpos += used;
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	return 0;
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}

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int git_packfile_resolve_header(
		size_t *size_p,
		git_otype *type_p,
		struct git_pack_file *p,
		git_off_t offset)
{
	git_mwindow *w_curs = NULL;
	git_off_t curpos = offset;
	size_t size;
	git_otype type;
	git_off_t base_offset;
	int error;

	error = git_packfile_unpack_header(&size, &type, &p->mwf, &w_curs, &curpos);
	git_mwindow_close(&w_curs);
	if (error < 0)
		return error;

	if (type == GIT_OBJ_OFS_DELTA || type == GIT_OBJ_REF_DELTA) {
		size_t base_size;
		git_rawobj delta;
		base_offset = get_delta_base(p, &w_curs, &curpos, type, offset);
		git_mwindow_close(&w_curs);
		error = packfile_unpack_compressed(&delta, p, &w_curs, &curpos, size, type);
		git_mwindow_close(&w_curs);
		if (error < 0)
			return error;
		error = git__delta_read_header(delta.data, delta.len, &base_size, size_p);
		git__free(delta.data);
		if (error < 0)
			return error;
	} else
		*size_p = size;

	while (type == GIT_OBJ_OFS_DELTA || type == GIT_OBJ_REF_DELTA) {
		curpos = base_offset;
		error = git_packfile_unpack_header(&size, &type, &p->mwf, &w_curs, &curpos);
		git_mwindow_close(&w_curs);
		if (error < 0)
			return error;
		if (type != GIT_OBJ_OFS_DELTA && type != GIT_OBJ_REF_DELTA)
			break;
		base_offset = get_delta_base(p, &w_curs, &curpos, type, base_offset);
		git_mwindow_close(&w_curs);
	}
	*type_p = type;

	return error;
}

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static int packfile_unpack_delta(
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		git_rawobj *obj,
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		struct git_pack_file *p,
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		git_mwindow **w_curs,
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		git_off_t *curpos,
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		size_t delta_size,
		git_otype delta_type,
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		git_off_t obj_offset)
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{
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	git_off_t base_offset, base_key;
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	git_rawobj base, delta;
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	git_pack_cache_entry *cached = NULL;
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	int error, found_base = 0;
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	base_offset = get_delta_base(p, w_curs, curpos, delta_type, obj_offset);
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	git_mwindow_close(w_curs);
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	if (base_offset == 0)
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		return packfile_error("delta offset is zero");
	if (base_offset < 0) /* must actually be an error code */
		return (int)base_offset;
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	if (!p->bases.entries && (cache_init(&p->bases) < 0))
		return -1;
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	base_key = base_offset; /* git_packfile_unpack modifies base_offset */
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	if ((cached = cache_get(&p->bases, base_offset)) != NULL) {
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		memcpy(&base, &cached->raw, sizeof(git_rawobj));
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		found_base = 1;
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	}

	if (!cached) { /* have to inflate it */
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		error = git_packfile_unpack(&base, p, &base_offset);

		/*
		 * TODO: git.git tries to load the base from other packfiles
		 * or loose objects.
		 *
		 * We'll need to do this in order to support thin packs.
		 */
		if (error < 0)
			return error;
	}
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	error = packfile_unpack_compressed(&delta, p, w_curs, curpos, delta_size, delta_type);
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	git_mwindow_close(w_curs);
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	if (error < 0) {
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		if (!found_base)
			git__free(base.data);
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		return error;
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	}

	obj->type = base.type;
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	error = git__delta_apply(obj, base.data, base.len, delta.data, delta.len);
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	if (error < 0)
		goto on_error;

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	if (found_base)
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		git_atomic_dec(&cached->refcount);
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	else if (cache_add(&p->bases, &base, base_key) < 0)
		git__free(base.data);
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on_error:
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	git__free(delta.data);
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	return error; /* error set by git__delta_apply */
}

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int git_packfile_unpack(
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	git_rawobj *obj,
	struct git_pack_file *p,
	git_off_t *obj_offset)
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{
	git_mwindow *w_curs = NULL;
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	git_off_t curpos = *obj_offset;
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	int error;

	size_t size = 0;
	git_otype type;

	/*
	 * TODO: optionally check the CRC on the packfile
	 */

	obj->data = NULL;
	obj->len = 0;
	obj->type = GIT_OBJ_BAD;

	error = git_packfile_unpack_header(&size, &type, &p->mwf, &w_curs, &curpos);
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	git_mwindow_close(&w_curs);

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	if (error < 0)
		return error;
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	switch (type) {
	case GIT_OBJ_OFS_DELTA:
	case GIT_OBJ_REF_DELTA:
		error = packfile_unpack_delta(
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				obj, p, &w_curs, &curpos,
				size, type, *obj_offset);
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		break;

	case GIT_OBJ_COMMIT:
	case GIT_OBJ_TREE:
	case GIT_OBJ_BLOB:
	case GIT_OBJ_TAG:
		error = packfile_unpack_compressed(
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				obj, p, &w_curs, &curpos,
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				size, type);
		break;

	default:
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		error = packfile_error("invalid packfile type in header");;
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		break;
	}

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	*obj_offset = curpos;
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	return error;
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}

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static void *use_git_alloc(void *opaq, unsigned int count, unsigned int size)
{
	GIT_UNUSED(opaq);
	return git__calloc(count, size);
}

static void use_git_free(void *opaq, void *ptr)
{
	GIT_UNUSED(opaq);
	git__free(ptr);
}

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int git_packfile_stream_open(git_packfile_stream *obj, struct git_pack_file *p, git_off_t curpos)
{
	int st;

	memset(obj, 0, sizeof(git_packfile_stream));
	obj->curpos = curpos;
	obj->p = p;
	obj->zstream.zalloc = use_git_alloc;
	obj->zstream.zfree = use_git_free;
	obj->zstream.next_in = Z_NULL;
	obj->zstream.next_out = Z_NULL;
	st = inflateInit(&obj->zstream);
	if (st != Z_OK) {
		git__free(obj);
		giterr_set(GITERR_ZLIB, "Failed to inflate packfile");
		return -1;
	}

	return 0;
}

ssize_t git_packfile_stream_read(git_packfile_stream *obj, void *buffer, size_t len)
{
	unsigned char *in;
	size_t written;
	int st;

	if (obj->done)
		return 0;

	in = pack_window_open(obj->p, &obj->mw, obj->curpos, &obj->zstream.avail_in);
	if (in == NULL)
		return GIT_EBUFS;

	obj->zstream.next_out = buffer;
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	obj->zstream.avail_out = (unsigned int)len;
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	obj->zstream.next_in = in;

	st = inflate(&obj->zstream, Z_SYNC_FLUSH);
	git_mwindow_close(&obj->mw);

	obj->curpos += obj->zstream.next_in - in;
	written = len - obj->zstream.avail_out;

	if (st != Z_OK && st != Z_STREAM_END) {
		giterr_set(GITERR_ZLIB, "Failed to inflate packfile");
		return -1;
	}

	if (st == Z_STREAM_END)
		obj->done = 1;


	/* If we didn't write anything out but we're not done, we need more data */
	if (!written && st != Z_STREAM_END)
		return GIT_EBUFS;

	return written;

}

void git_packfile_stream_free(git_packfile_stream *obj)
{
	inflateEnd(&obj->zstream);
}

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int packfile_unpack_compressed(
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	git_rawobj *obj,
	struct git_pack_file *p,
	git_mwindow **w_curs,
	git_off_t *curpos,
	size_t size,
	git_otype type)
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{
	int st;
	z_stream stream;
	unsigned char *buffer, *in;

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	buffer = git__calloc(1, size + 1);
	GITERR_CHECK_ALLOC(buffer);
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	memset(&stream, 0, sizeof(stream));
	stream.next_out = buffer;
690
	stream.avail_out = (uInt)size + 1;
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	stream.zalloc = use_git_alloc;
	stream.zfree = use_git_free;
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	st = inflateInit(&stream);
	if (st != Z_OK) {
696
		git__free(buffer);
697
		giterr_set(GITERR_ZLIB, "Failed to inflate packfile");
698

699
		return -1;
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	}

	do {
703
		in = pack_window_open(p, w_curs, *curpos, &stream.avail_in);
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		stream.next_in = in;
		st = inflate(&stream, Z_FINISH);
706
		git_mwindow_close(w_curs);
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		if (!stream.avail_out)
			break; /* the payload is larger than it should be */

711 712 713
		if (st == Z_BUF_ERROR && in == NULL) {
			inflateEnd(&stream);
			git__free(buffer);
714
			return GIT_EBUFS;
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		}

717
		*curpos += stream.next_in - in;
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	} while (st == Z_OK || st == Z_BUF_ERROR);

	inflateEnd(&stream);

	if ((st != Z_STREAM_END) || stream.total_out != size) {
723
		git__free(buffer);
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		giterr_set(GITERR_ZLIB, "Failed to inflate packfile");
		return -1;
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	}

	obj->type = type;
	obj->len = size;
	obj->data = buffer;
731
	return 0;
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}

734 735 736 737
/*
 * curpos is where the data starts, delta_obj_offset is the where the
 * header starts
 */
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git_off_t get_delta_base(
	struct git_pack_file *p,
	git_mwindow **w_curs,
	git_off_t *curpos,
	git_otype type,
	git_off_t delta_obj_offset)
744
{
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	unsigned int left = 0;
	unsigned char *base_info;
747
	git_off_t base_offset;
748 749
	git_oid unused;

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	base_info = pack_window_open(p, w_curs, *curpos, &left);
	/* Assumption: the only reason this would fail is because the file is too small */
	if (base_info == NULL)
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		return GIT_EBUFS;
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	/* pack_window_open() assured us we have [base_info, base_info + 20)
	 * as a range that we can look at without walking off the
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	 * end of the mapped window. Its actually the hash size
	 * that is assured. An OFS_DELTA longer than the hash size
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	 * is stupid, as then a REF_DELTA would be smaller to store.
	 */
	if (type == GIT_OBJ_OFS_DELTA) {
		unsigned used = 0;
		unsigned char c = base_info[used++];
		base_offset = c & 127;
		while (c & 128) {
765
			if (left <= used)
766
				return GIT_EBUFS;
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			base_offset += 1;
			if (!base_offset || MSB(base_offset, 7))
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769
				return 0; /* overflow */
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			c = base_info[used++];
			base_offset = (base_offset << 7) + (c & 127);
		}
		base_offset = delta_obj_offset - base_offset;
		if (base_offset <= 0 || base_offset >= delta_obj_offset)
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			return 0; /* out of bound */
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		*curpos += used;
	} else if (type == GIT_OBJ_REF_DELTA) {
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		/* If we have the cooperative cache, search in it first */
		if (p->has_cache) {
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			khiter_t k;
			git_oid oid;
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			git_oid_fromraw(&oid, base_info);
			k = kh_get(oid, p->idx_cache, &oid);
			if (k != kh_end(p->idx_cache)) {
786
				*curpos += 20;
787
				return ((struct git_pack_entry *)kh_value(p->idx_cache, k))->offset;
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			}
		}
790
		/* The base entry _must_ be in the same pack */
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		if (pack_entry_find_offset(&base_offset, &unused, p, (git_oid *)base_info, GIT_OID_HEXSZ) < 0)
			return packfile_error("base entry delta is not in the same pack");
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		*curpos += 20;
	} else
		return 0;

	return base_offset;
}
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/***********************************************************
 *
 * PACKFILE METHODS
 *
 ***********************************************************/

806
void git_packfile_free(struct git_pack_file *p)
807
{
808 809 810
	if (!p)
		return;

811
	cache_free(&p->bases);
812

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	git_mwindow_free_all(&p->mwf);

	if (p->mwf.fd != -1)
		p_close(p->mwf.fd);

	pack_index_free(p);

820
	git__free(p->bad_object_sha1);
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	git_mutex_free(&p->lock);
823
	git__free(p);
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}

static int packfile_open(struct git_pack_file *p)
{
	struct stat st;
	struct git_pack_header hdr;
	git_oid sha1;
	unsigned char *idx_sha1;

833
	if (p->index_version == -1 && pack_index_open(p) < 0)
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		return git_odb__error_notfound("failed to open packfile", NULL);
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	/* if mwf opened by another thread, return now */
	if (git_mutex_lock(&p->lock) < 0)
		return packfile_error("failed to get lock for open");

	if (p->mwf.fd >= 0) {
		git_mutex_unlock(&p->lock);
		return 0;
	}

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	/* TODO: open with noatime */
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	p->mwf.fd = git_futils_open_ro(p->pack_name);
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	if (p->mwf.fd < 0)
		goto cleanup;
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	if (p_fstat(p->mwf.fd, &st) < 0 ||
		git_mwindow_file_register(&p->mwf) < 0)
		goto cleanup;
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	/* If we created the struct before we had the pack we lack size. */
	if (!p->mwf.size) {
		if (!S_ISREG(st.st_mode))
			goto cleanup;
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		p->mwf.size = (git_off_t)st.st_size;
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	} else if (p->mwf.size != st.st_size)
		goto cleanup;

#if 0
	/* We leave these file descriptors open with sliding mmap;
	 * there is no point keeping them open across exec(), though.
	 */
	fd_flag = fcntl(p->mwf.fd, F_GETFD, 0);
	if (fd_flag < 0)
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		goto cleanup;
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	fd_flag |= FD_CLOEXEC;
	if (fcntl(p->pack_fd, F_SETFD, fd_flag) == -1)
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		goto cleanup;
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#endif

	/* Verify we recognize this pack file format. */
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	if (p_read(p->mwf.fd, &hdr, sizeof(hdr)) < 0 ||
		hdr.hdr_signature != htonl(PACK_SIGNATURE) ||
		!pack_version_ok(hdr.hdr_version))
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		goto cleanup;

	/* Verify the pack matches its index. */
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	if (p->num_objects != ntohl(hdr.hdr_entries) ||
		p_lseek(p->mwf.fd, p->mwf.size - GIT_OID_RAWSZ, SEEK_SET) == -1 ||
		p_read(p->mwf.fd, sha1.id, GIT_OID_RAWSZ) < 0)
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		goto cleanup;

	idx_sha1 = ((unsigned char *)p->index_map.data) + p->index_map.len - 40;

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	if (git_oid__cmp(&sha1, (git_oid *)idx_sha1) != 0)
		goto cleanup;

	git_mutex_unlock(&p->lock);
	return 0;
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cleanup:
896
	giterr_set(GITERR_OS, "Invalid packfile '%s'", p->pack_name);
897

898 899
	p_close(p->mwf.fd);
	p->mwf.fd = -1;
900 901 902

	git_mutex_unlock(&p->lock);

903
	return -1;
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}

906
int git_packfile_alloc(struct git_pack_file **pack_out, const char *path)
907 908 909
{
	struct stat st;
	struct git_pack_file *p;
910
	size_t path_len = path ? strlen(path) : 0;
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	*pack_out = NULL;
913

914
	if (path_len < strlen(".idx"))
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		return git_odb__error_notfound("invalid packfile path", NULL);

917
	p = git__calloc(1, sizeof(*p) + path_len + 2);
918
	GITERR_CHECK_ALLOC(p);
919

920 921
	memcpy(p->pack_name, path, path_len + 1);

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	/*
	 * Make sure a corresponding .pack file exists and that
	 * the index looks sane.
	 */
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	if (git__suffixcmp(path, ".idx") == 0) {
		size_t root_len = path_len - strlen(".idx");

		memcpy(p->pack_name + root_len, ".keep", sizeof(".keep"));
		if (git_path_exists(p->pack_name) == true)
			p->pack_keep = 1;
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		memcpy(p->pack_name + root_len, ".pack", sizeof(".pack"));
		path_len = path_len - strlen(".idx") + strlen(".pack");
	}
936

937
	if (p_stat(p->pack_name, &st) < 0 || !S_ISREG(st.st_mode)) {
938
		git__free(p);
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939
		return git_odb__error_notfound("packfile not found", NULL);
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	}

	/* ok, it looks sane as far as we can check without
	 * actually mapping the pack file.
	 */
945
	p->mwf.fd = -1;
946
	p->mwf.size = st.st_size;
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	p->pack_local = 1;
	p->mtime = (git_time_t)st.st_mtime;
949
	p->index_version = -1;
950

951 952
	git_mutex_init(&p->lock);

953 954
	/* see if we can parse the sha1 oid in the packfile name */
	if (path_len < 40 ||
955
		git_oid_fromstr(&p->sha1, path + path_len - GIT_OID_HEXSZ) < 0)
956 957 958
		memset(&p->sha1, 0x0, GIT_OID_RAWSZ);

	*pack_out = p;
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	return 0;
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}

/***********************************************************
 *
 * PACKFILE ENTRY SEARCH INTERNALS
 *
 ***********************************************************/

969
static git_off_t nth_packed_object_offset(const struct git_pack_file *p, uint32_t n)
970 971 972 973 974 975 976 977 978 979 980 981 982
{
	const unsigned char *index = p->index_map.data;
	index += 4 * 256;
	if (p->index_version == 1) {
		return ntohl(*((uint32_t *)(index + 24 * n)));
	} else {
		uint32_t off;
		index += 8 + p->num_objects * (20 + 4);
		off = ntohl(*((uint32_t *)(index + 4 * n)));
		if (!(off & 0x80000000))
			return off;
		index += p->num_objects * 4 + (off & 0x7fffffff) * 8;
		return (((uint64_t)ntohl(*((uint32_t *)(index + 0)))) << 32) |
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983
					ntohl(*((uint32_t *)(index + 4)));
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	}
}

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static int git__memcmp4(const void *a, const void *b) {
	return memcmp(a, b, 4);
}

991
int git_pack_foreach_entry(
992
	struct git_pack_file *p,
993
	git_odb_foreach_cb cb,
994
	void *data)
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{
	const unsigned char *index = p->index_map.data, *current;
	uint32_t i;

	if (index == NULL) {
		int error;

		if ((error = pack_index_open(p)) < 0)
			return error;

		assert(p->index_map.data);

		index = p->index_map.data;
	}

	if (p->index_version > 1) {
		index += 8;
	}

	index += 4 * 256;

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	if (p->oids == NULL) {
		git_vector offsets, oids;
		int error;
1019

1020 1021 1022 1023 1024
		if ((error = git_vector_init(&oids, p->num_objects, NULL)))
			return error;

		if ((error = git_vector_init(&offsets, p->num_objects, git__memcmp4)))
			return error;
1025

1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041
		if (p->index_version > 1) {
			const unsigned char *off = index + 24 * p->num_objects;
			for (i = 0; i < p->num_objects; i++)
				git_vector_insert(&offsets, (void*)&off[4 * i]);
			git_vector_sort(&offsets);
			git_vector_foreach(&offsets, i, current)
				git_vector_insert(&oids, (void*)&index[5 * (current - off)]);
		} else {
			for (i = 0; i < p->num_objects; i++)
				git_vector_insert(&offsets, (void*)&index[24 * i]);
			git_vector_sort(&offsets);
			git_vector_foreach(&offsets, i, current)
				git_vector_insert(&oids, (void*)&current[4]);
		}
		git_vector_free(&offsets);
		p->oids = (git_oid **)oids.contents;
1042 1043
	}

1044 1045 1046 1047
	for (i = 0; i < p->num_objects; i++)
		if (cb(p->oids[i], data))
			return GIT_EUSER;

1048 1049 1050
	return 0;
}

1051
static int pack_entry_find_offset(
1052 1053 1054 1055
	git_off_t *offset_out,
	git_oid *found_oid,
	struct git_pack_file *p,
	const git_oid *short_oid,
1056
	size_t len)
1057
{
1058 1059
	const uint32_t *level1_ofs = p->index_map.data;
	const unsigned char *index = p->index_map.data;
1060 1061 1062 1063 1064 1065
	unsigned hi, lo, stride;
	int pos, found = 0;
	const unsigned char *current = 0;

	*offset_out = 0;

1066
	if (p->index_version == -1) {
1067
		int error;
1068

1069 1070 1071
		if ((error = pack_index_open(p)) < 0)
			return error;
		assert(p->index_map.data);
1072

1073 1074 1075
		index = p->index_map.data;
		level1_ofs = p->index_map.data;
	}
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	if (p->index_version > 1) {
		level1_ofs += 2;
		index += 8;
	}

	index += 4 * 256;
	hi = ntohl(level1_ofs[(int)short_oid->id[0]]);
	lo = ((short_oid->id[0] == 0x0) ? 0 : ntohl(level1_ofs[(int)short_oid->id[0] - 1]));

	if (p->index_version > 1) {
		stride = 20;
	} else {
		stride = 24;
		index += 4;
	}

#ifdef INDEX_DEBUG_LOOKUP
	printf("%02x%02x%02x... lo %u hi %u nr %d\n",
		short_oid->id[0], short_oid->id[1], short_oid->id[2], lo, hi, p->num_objects);
#endif

	/* Use git.git lookup code */
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	pos = sha1_entry_pos(index, stride, 0, lo, hi, p->num_objects, short_oid->id);
1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111

	if (pos >= 0) {
		/* An object matching exactly the oid was found */
		found = 1;
		current = index + pos * stride;
	} else {
		/* No object was found */
		/* pos refers to the object with the "closest" oid to short_oid */
		pos = - 1 - pos;
		if (pos < (int)p->num_objects) {
			current = index + pos * stride;

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1112
			if (!git_oid_ncmp(short_oid, (const git_oid *)current, len))
1113 1114 1115 1116
				found = 1;
		}
	}

1117
	if (found && len != GIT_OID_HEXSZ && pos + 1 < (int)p->num_objects) {
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		/* Check for ambiguousity */
		const unsigned char *next = current + stride;

		if (!git_oid_ncmp(short_oid, (const git_oid *)next, len)) {
			found = 2;
		}
	}

1126
	if (!found)
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1127
		return git_odb__error_notfound("failed to find offset for pack entry", short_oid);
1128 1129
	if (found > 1)
		return git_odb__error_ambiguous("found multiple offsets for pack entry");
1130

1131 1132
	*offset_out = nth_packed_object_offset(p, pos);
	git_oid_fromraw(found_oid, current);
1133 1134

#ifdef INDEX_DEBUG_LOOKUP
1135
	{
1136 1137 1138 1139 1140
		unsigned char hex_sha1[GIT_OID_HEXSZ + 1];
		git_oid_fmt(hex_sha1, found_oid);
		hex_sha1[GIT_OID_HEXSZ] = '\0';
		printf("found lo=%d %s\n", lo, hex_sha1);
	}
1141
#endif
1142

1143
	return 0;
1144 1145 1146 1147 1148 1149
}

int git_pack_entry_find(
		struct git_pack_entry *e,
		struct git_pack_file *p,
		const git_oid *short_oid,
1150
		size_t len)
1151
{
1152
	git_off_t offset;
1153 1154 1155 1156 1157 1158 1159 1160
	git_oid found_oid;
	int error;

	assert(p);

	if (len == GIT_OID_HEXSZ && p->num_bad_objects) {
		unsigned i;
		for (i = 0; i < p->num_bad_objects; i++)
1161
			if (git_oid__cmp(short_oid, &p->bad_object_sha1[i]) == 0)
1162
				return packfile_error("bad object found in packfile");
1163 1164 1165
	}

	error = pack_entry_find_offset(&offset, &found_oid, p, short_oid, len);
1166 1167
	if (error < 0)
		return error;
1168 1169 1170 1171

	/* we found a unique entry in the index;
	 * make sure the packfile backing the index
	 * still exists on disk */
1172 1173
	if (p->mwf.fd == -1 && (error = packfile_open(p)) < 0)
		return error;
1174 1175 1176 1177 1178

	e->offset = offset;
	e->p = p;

	git_oid_cpy(&e->sha1, &found_oid);
1179
	return 0;
1180
}