pack.c 28.2 KB
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/*
Edward Thomson committed
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 * Copyright (C) the libgit2 contributors. All rights reserved.
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 *
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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;
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	if (git_mutex_init(&cache->lock)) {
		giterr_set(GITERR_OS, "Failed to initialize pack cache mutex");

		git__free(cache->entries);
		cache->entries = NULL;

		return -1;
	}
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	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) {
		git__free(idx_name);
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		return error;
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	}
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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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/*
 * The per-object header is a pretty dense thing, which is
 *  - first byte: low four bits are "size",
 *    then three bits of "type",
 *    with the high bit being "size continues".
 *  - each byte afterwards: low seven bits are size continuation,
 *    with the high bit being "size continues"
 */
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size_t git_packfile__object_header(unsigned char *hdr, size_t size, git_otype type)
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{
	unsigned char *hdr_base;
	unsigned char c;

	assert(type >= GIT_OBJ_COMMIT && type <= GIT_OBJ_REF_DELTA);

	/* TODO: add support for chunked objects; see git.git 6c0d19b1 */

	c = (unsigned char)((type << 4) | (size & 15));
	size >>= 4;
	hdr_base = hdr;

	while (size) {
		*hdr++ = c | 0x80;
		c = size & 0x7f;
		size >>= 7;
	}
	*hdr++ = c;

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	return (hdr - hdr_base);
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}


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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;
685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714
	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);
}

715
int packfile_unpack_compressed(
716 717 718 719 720 721
	git_rawobj *obj,
	struct git_pack_file *p,
	git_mwindow **w_curs,
	git_off_t *curpos,
	size_t size,
	git_otype type)
722 723 724 725 726
{
	int st;
	z_stream stream;
	unsigned char *buffer, *in;

727 728
	buffer = git__calloc(1, size + 1);
	GITERR_CHECK_ALLOC(buffer);
729 730 731

	memset(&stream, 0, sizeof(stream));
	stream.next_out = buffer;
732
	stream.avail_out = (uInt)size + 1;
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733 734
	stream.zalloc = use_git_alloc;
	stream.zfree = use_git_free;
735 736 737

	st = inflateInit(&stream);
	if (st != Z_OK) {
738
		git__free(buffer);
739
		giterr_set(GITERR_ZLIB, "Failed to inflate packfile");
740

741
		return -1;
742 743 744
	}

	do {
745
		in = pack_window_open(p, w_curs, *curpos, &stream.avail_in);
746 747
		stream.next_in = in;
		st = inflate(&stream, Z_FINISH);
748
		git_mwindow_close(w_curs);
749 750 751 752

		if (!stream.avail_out)
			break; /* the payload is larger than it should be */

753 754 755
		if (st == Z_BUF_ERROR && in == NULL) {
			inflateEnd(&stream);
			git__free(buffer);
756
			return GIT_EBUFS;
757 758
		}

759
		*curpos += stream.next_in - in;
760 761 762 763 764
	} while (st == Z_OK || st == Z_BUF_ERROR);

	inflateEnd(&stream);

	if ((st != Z_STREAM_END) || stream.total_out != size) {
765
		git__free(buffer);
766 767
		giterr_set(GITERR_ZLIB, "Failed to inflate packfile");
		return -1;
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	}

	obj->type = type;
	obj->len = size;
	obj->data = buffer;
773
	return 0;
774 775
}

776 777 778 779
/*
 * curpos is where the data starts, delta_obj_offset is the where the
 * header starts
 */
780 781 782 783 784 785
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)
786
{
787 788
	unsigned int left = 0;
	unsigned char *base_info;
789
	git_off_t base_offset;
790 791
	git_oid unused;

792 793 794
	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)
795
		return GIT_EBUFS;
796 797
	/* 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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798 799
	 * end of the mapped window. Its actually the hash size
	 * that is assured. An OFS_DELTA longer than the hash size
800 801 802 803 804 805 806
	 * 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) {
807
			if (left <= used)
808
				return GIT_EBUFS;
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			base_offset += 1;
			if (!base_offset || MSB(base_offset, 7))
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811
				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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817
			return 0; /* out of bound */
818 819
		*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) {
822 823
			khiter_t k;
			git_oid oid;
824

825 826 827
			git_oid_fromraw(&oid, base_info);
			k = kh_get(oid, p->idx_cache, &oid);
			if (k != kh_end(p->idx_cache)) {
828
				*curpos += 20;
829
				return ((struct git_pack_entry *)kh_value(p->idx_cache, k))->offset;
830 831
			}
		}
832
		/* The base entry _must_ be in the same pack */
833 834
		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;
}
841 842 843 844 845 846 847

/***********************************************************
 *
 * PACKFILE METHODS
 *
 ***********************************************************/

848
void git_packfile_free(struct git_pack_file *p)
849
{
850 851 852
	if (!p)
		return;

853
	cache_free(&p->bases);
854

855 856
	git_mwindow_free_all(&p->mwf);

857
	if (p->mwf.fd >= 0)
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		p_close(p->mwf.fd);

	pack_index_free(p);

862
	git__free(p->bad_object_sha1);
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	git_mutex_free(&p->lock);
865
	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;

875
	if (p->index_version == -1 && pack_index_open(p) < 0)
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		return git_odb__error_notfound("failed to open packfile", NULL);
877

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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;
	}

887
	/* TODO: open with noatime */
888
	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:
938
	giterr_set(GITERR_OS, "Invalid packfile '%s'", p->pack_name);
939

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	if (p->mwf.fd >= 0)
		p_close(p->mwf.fd);
942
	p->mwf.fd = -1;
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	git_mutex_unlock(&p->lock);

946
	return -1;
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}

949
int git_packfile_alloc(struct git_pack_file **pack_out, const char *path)
950 951 952
{
	struct stat st;
	struct git_pack_file *p;
953
	size_t path_len = path ? strlen(path) : 0;
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	*pack_out = NULL;
956

957
	if (path_len < strlen(".idx"))
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		return git_odb__error_notfound("invalid packfile path", NULL);

960
	p = git__calloc(1, sizeof(*p) + path_len + 2);
961
	GITERR_CHECK_ALLOC(p);
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	memcpy(p->pack_name, path, path_len + 1);

965 966 967 968
	/*
	 * 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");
	}
979

980
	if (p_stat(p->pack_name, &st) < 0 || !S_ISREG(st.st_mode)) {
981
		git__free(p);
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982
		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.
	 */
988
	p->mwf.fd = -1;
989
	p->mwf.size = st.st_size;
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	p->pack_local = 1;
	p->mtime = (git_time_t)st.st_mtime;
992
	p->index_version = -1;
993

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	if (git_mutex_init(&p->lock)) {
		giterr_set(GITERR_OS, "Failed to initialize packfile mutex");
		git__free(p);
		return -1;
	}
999

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	/* see if we can parse the sha1 oid in the packfile name */
	if (path_len < 40 ||
1002
		git_oid_fromstr(&p->sha1, path + path_len - GIT_OID_HEXSZ) < 0)
1003 1004 1005
		memset(&p->sha1, 0x0, GIT_OID_RAWSZ);

	*pack_out = p;
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	return 0;
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}

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

1016
static git_off_t nth_packed_object_offset(const struct git_pack_file *p, uint32_t n)
1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029
{
	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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1030
					ntohl(*((uint32_t *)(index + 4)));
1031 1032 1033
	}
}

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

1038
int git_pack_foreach_entry(
1039
	struct git_pack_file *p,
1040
	git_odb_foreach_cb cb,
1041
	void *data)
1042 1043 1044
{
	const unsigned char *index = p->index_map.data, *current;
	uint32_t i;
1045
	int error = 0;
1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061

	if (index == NULL) {
		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;

1062 1063
	if (p->oids == NULL) {
		git_vector offsets, oids;
1064

1065 1066 1067 1068 1069
		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;
1070

1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084
		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]);
		}
1085

1086
		git_vector_free(&offsets);
1087
		p->oids = (git_oid **)git_vector_detach(NULL, NULL, &oids);
1088 1089
	}

1090
	for (i = 0; i < p->num_objects; i++)
1091 1092
		if ((error = cb(p->oids[i], data)) != 0)
			return giterr_set_after_callback(error);
1093

1094
	return error;
1095 1096
}

1097
static int pack_entry_find_offset(
1098 1099 1100 1101
	git_off_t *offset_out,
	git_oid *found_oid,
	struct git_pack_file *p,
	const git_oid *short_oid,
1102
	size_t len)
1103
{
1104 1105
	const uint32_t *level1_ofs = p->index_map.data;
	const unsigned char *index = p->index_map.data;
1106 1107 1108 1109 1110 1111
	unsigned hi, lo, stride;
	int pos, found = 0;
	const unsigned char *current = 0;

	*offset_out = 0;

1112
	if (p->index_version == -1) {
1113
		int error;
1114

1115 1116 1117
		if ((error = pack_index_open(p)) < 0)
			return error;
		assert(p->index_map.data);
1118

1119 1120 1121
		index = p->index_map.data;
		level1_ofs = p->index_map.data;
	}
1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143

	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

1144
#ifdef GIT_USE_LOOKUP
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1145
	pos = sha1_entry_pos(index, stride, 0, lo, hi, p->num_objects, short_oid->id);
1146 1147 1148
#else
	pos = sha1_position(index, stride, lo, hi, short_oid->id);
#endif
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	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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			if (!git_oid_ncmp(short_oid, (const git_oid *)current, len))
1162 1163 1164 1165
				found = 1;
		}
	}

1166
	if (found && len != GIT_OID_HEXSZ && pos + 1 < (int)p->num_objects) {
1167 1168 1169 1170 1171 1172 1173 1174
		/* Check for ambiguousity */
		const unsigned char *next = current + stride;

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

1175
	if (!found)
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		return git_odb__error_notfound("failed to find offset for pack entry", short_oid);
1177 1178
	if (found > 1)
		return git_odb__error_ambiguous("found multiple offsets for pack entry");
1179

1180 1181
	*offset_out = nth_packed_object_offset(p, pos);
	git_oid_fromraw(found_oid, current);
1182 1183

#ifdef INDEX_DEBUG_LOOKUP
1184
	{
1185 1186 1187 1188 1189
		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);
	}
1190
#endif
1191

1192
	return 0;
1193 1194 1195 1196 1197 1198
}

int git_pack_entry_find(
		struct git_pack_entry *e,
		struct git_pack_file *p,
		const git_oid *short_oid,
1199
		size_t len)
1200
{
1201
	git_off_t offset;
1202 1203 1204 1205 1206 1207 1208 1209
	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++)
1210
			if (git_oid__cmp(short_oid, &p->bad_object_sha1[i]) == 0)
1211
				return packfile_error("bad object found in packfile");
1212 1213 1214
	}

	error = pack_entry_find_offset(&offset, &found_oid, p, short_oid, len);
1215 1216
	if (error < 0)
		return error;
1217 1218 1219 1220

	/* we found a unique entry in the index;
	 * make sure the packfile backing the index
	 * still exists on disk */
1221 1222
	if (p->mwf.fd == -1 && (error = packfile_open(p)) < 0)
		return error;
1223 1224 1225 1226 1227

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

	git_oid_cpy(&e->sha1, &found_oid);
1228
	return 0;
1229
}