[thirdparty/git.git] / pack-revindex.c

#include "cache.h"
#include "pack-revindex.h"
#include "object-store.h"
#include "packfile.h"
#include "config.h"
#include "midx.h"

struct revindex_entry {
	off_t offset;
	unsigned int nr;
};

/*
 * Pack index for existing packs give us easy access to the offsets into
 * corresponding pack file where each object's data starts, but the entries
 * do not store the size of the compressed representation (uncompressed
 * size is easily available by examining the pack entry header).  It is
 * also rather expensive to find the sha1 for an object given its offset.
 *
 * The pack index file is sorted by object name mapping to offset;
 * this revindex array is a list of offset/index_nr pairs
 * ordered by offset, so if you know the offset of an object, next offset
 * is where its packed representation ends and the index_nr can be used to
 * get the object sha1 from the main index.
 */

/*
 * This is a least-significant-digit radix sort.
 *
 * It sorts each of the "n" items in "entries" by its offset field. The "max"
 * parameter must be at least as large as the largest offset in the array,
 * and lets us quit the sort early.
 */
static void sort_revindex(struct revindex_entry *entries, unsigned n, off_t max)
{
	/*
	 * We use a "digit" size of 16 bits. That keeps our memory
	 * usage reasonable, and we can generally (for a 4G or smaller
	 * packfile) quit after two rounds of radix-sorting.
	 */
#define DIGIT_SIZE (16)
#define BUCKETS (1 << DIGIT_SIZE)
	/*
	 * We want to know the bucket that a[i] will go into when we are using
	 * the digit that is N bits from the (least significant) end.
	 */
#define BUCKET_FOR(a, i, bits) (((a)[(i)].offset >> (bits)) & (BUCKETS-1))

	/*
	 * We need O(n) temporary storage. Rather than do an extra copy of the
	 * partial results into "entries", we sort back and forth between the
	 * real array and temporary storage. In each iteration of the loop, we
	 * keep track of them with alias pointers, always sorting from "from"
	 * to "to".
	 */
	struct revindex_entry *tmp, *from, *to;
	int bits;
	unsigned *pos;

	ALLOC_ARRAY(pos, BUCKETS);
	ALLOC_ARRAY(tmp, n);
	from = entries;
	to = tmp;

	/*
	 * If (max >> bits) is zero, then we know that the radix digit we are
	 * on (and any higher) will be zero for all entries, and our loop will
	 * be a no-op, as everybody lands in the same zero-th bucket.
	 */
	for (bits = 0; max >> bits; bits += DIGIT_SIZE) {
		unsigned i;

		memset(pos, 0, BUCKETS * sizeof(*pos));

		/*
		 * We want pos[i] to store the index of the last element that
		 * will go in bucket "i" (actually one past the last element).
		 * To do this, we first count the items that will go in each
		 * bucket, which gives us a relative offset from the last
		 * bucket. We can then cumulatively add the index from the
		 * previous bucket to get the true index.
		 */
		for (i = 0; i < n; i++)
			pos[BUCKET_FOR(from, i, bits)]++;
		for (i = 1; i < BUCKETS; i++)
			pos[i] += pos[i-1];

		/*
		 * Now we can drop the elements into their correct buckets (in
		 * our temporary array).  We iterate the pos counter backwards
		 * to avoid using an extra index to count up. And since we are
		 * going backwards there, we must also go backwards through the
		 * array itself, to keep the sort stable.
		 *
		 * Note that we use an unsigned iterator to make sure we can
		 * handle 2^32-1 objects, even on a 32-bit system. But this
		 * means we cannot use the more obvious "i >= 0" loop condition
		 * for counting backwards, and must instead check for
		 * wrap-around with UINT_MAX.
		 */
		for (i = n - 1; i != UINT_MAX; i--)
			to[--pos[BUCKET_FOR(from, i, bits)]] = from[i];

		/*
		 * Now "to" contains the most sorted list, so we swap "from" and
		 * "to" for the next iteration.
		 */
		SWAP(from, to);
	}

	/*
	 * If we ended with our data in the original array, great. If not,
	 * we have to move it back from the temporary storage.
	 */
	if (from != entries)
		COPY_ARRAY(entries, tmp, n);
	free(tmp);
	free(pos);

#undef BUCKET_FOR
#undef BUCKETS
#undef DIGIT_SIZE
}

/*
 * Ordered list of offsets of objects in the pack.
 */
static void create_pack_revindex(struct packed_git *p)
{
	const unsigned num_ent = p->num_objects;
	unsigned i;
	const char *index = p->index_data;
	const unsigned hashsz = the_hash_algo->rawsz;

	ALLOC_ARRAY(p->revindex, num_ent + 1);
	index += 4 * 256;

	if (p->index_version > 1) {
		const uint32_t *off_32 =
			(uint32_t *)(index + 8 + (size_t)p->num_objects * (hashsz + 4));
		const uint32_t *off_64 = off_32 + p->num_objects;
		for (i = 0; i < num_ent; i++) {
			const uint32_t off = ntohl(*off_32++);
			if (!(off & 0x80000000)) {
				p->revindex[i].offset = off;
			} else {
				p->revindex[i].offset = get_be64(off_64);
				off_64 += 2;
			}
			p->revindex[i].nr = i;
		}
	} else {
		for (i = 0; i < num_ent; i++) {
			const uint32_t hl = *((uint32_t *)(index + (hashsz + 4) * i));
			p->revindex[i].offset = ntohl(hl);
			p->revindex[i].nr = i;
		}
	}

	/*
	 * This knows the pack format -- the hash trailer
	 * follows immediately after the last object data.
	 */
	p->revindex[num_ent].offset = p->pack_size - hashsz;
	p->revindex[num_ent].nr = -1;
	sort_revindex(p->revindex, num_ent, p->pack_size);
}

static int create_pack_revindex_in_memory(struct packed_git *p)
{
	if (git_env_bool(GIT_TEST_REV_INDEX_DIE_IN_MEMORY, 0))
		die("dying as requested by '%s'",
		    GIT_TEST_REV_INDEX_DIE_IN_MEMORY);
	if (open_pack_index(p))
		return -1;
	create_pack_revindex(p);
	return 0;
}

static char *pack_revindex_filename(struct packed_git *p)
{
	size_t len;
	if (!strip_suffix(p->pack_name, ".pack", &len))
		BUG("pack_name does not end in .pack");
	return xstrfmt("%.*s.rev", (int)len, p->pack_name);
}

#define RIDX_HEADER_SIZE (12)
#define RIDX_MIN_SIZE (RIDX_HEADER_SIZE + (2 * the_hash_algo->rawsz))

struct revindex_header {
	uint32_t signature;
	uint32_t version;
	uint32_t hash_id;
};

static int load_revindex_from_disk(char *revindex_name,
				   uint32_t num_objects,
				   const uint32_t **data_p, size_t *len_p)
{
	int fd, ret = 0;
	struct stat st;
	void *data = NULL;
	size_t revindex_size;
	struct revindex_header *hdr;

	fd = git_open(revindex_name);

	if (fd < 0) {
		ret = -1;
		goto cleanup;
	}
	if (fstat(fd, &st)) {
		ret = error_errno(_("failed to read %s"), revindex_name);
		goto cleanup;
	}

	revindex_size = xsize_t(st.st_size);

	if (revindex_size < RIDX_MIN_SIZE) {
		ret = error(_("reverse-index file %s is too small"), revindex_name);
		goto cleanup;
	}

	if (revindex_size - RIDX_MIN_SIZE != st_mult(sizeof(uint32_t), num_objects)) {
		ret = error(_("reverse-index file %s is corrupt"), revindex_name);
		goto cleanup;
	}

	data = xmmap(NULL, revindex_size, PROT_READ, MAP_PRIVATE, fd, 0);
	hdr = data;

	if (ntohl(hdr->signature) != RIDX_SIGNATURE) {
		ret = error(_("reverse-index file %s has unknown signature"), revindex_name);
		goto cleanup;
	}
	if (ntohl(hdr->version) != 1) {
		ret = error(_("reverse-index file %s has unsupported version %"PRIu32),
			    revindex_name, ntohl(hdr->version));
		goto cleanup;
	}
	if (!(ntohl(hdr->hash_id) == 1 || ntohl(hdr->hash_id) == 2)) {
		ret = error(_("reverse-index file %s has unsupported hash id %"PRIu32),
			    revindex_name, ntohl(hdr->hash_id));
		goto cleanup;
	}

cleanup:
	if (ret) {
		if (data)
			munmap(data, revindex_size);
	} else {
		*len_p = revindex_size;
		*data_p = (const uint32_t *)data;
	}

	if (fd >= 0)
		close(fd);
	return ret;
}

static int load_pack_revindex_from_disk(struct packed_git *p)
{
	char *revindex_name;
	int ret;
	if (open_pack_index(p))
		return -1;

	revindex_name = pack_revindex_filename(p);

	ret = load_revindex_from_disk(revindex_name,
				      p->num_objects,
				      &p->revindex_map,
				      &p->revindex_size);
	if (ret)
		goto cleanup;

	p->revindex_data = (const uint32_t *)((const char *)p->revindex_map + RIDX_HEADER_SIZE);

cleanup:
	free(revindex_name);
	return ret;
}

int load_pack_revindex(struct packed_git *p)
{
	if (p->revindex || p->revindex_data)
		return 0;

	if (!load_pack_revindex_from_disk(p))
		return 0;
	else if (!create_pack_revindex_in_memory(p))
		return 0;
	return -1;
}

int load_midx_revindex(struct multi_pack_index *m)
{
	struct strbuf revindex_name = STRBUF_INIT;
	int ret;
	if (m->revindex_data)
		return 0;

	trace2_data_string("load_midx_revindex", the_repository,
			   "source", "rev");

	get_midx_rev_filename(&revindex_name, m);

	ret = load_revindex_from_disk(revindex_name.buf,
				      m->num_objects,
				      &m->revindex_map,
				      &m->revindex_len);
	if (ret)
		goto cleanup;

	m->revindex_data = (const uint32_t *)((const char *)m->revindex_map + RIDX_HEADER_SIZE);

cleanup:
	strbuf_release(&revindex_name);
	return ret;
}

int close_midx_revindex(struct multi_pack_index *m)
{
	if (!m || !m->revindex_map)
		return 0;

	munmap((void*)m->revindex_map, m->revindex_len);

	m->revindex_map = NULL;
	m->revindex_data = NULL;
	m->revindex_len = 0;

	return 0;
}

int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos)
{
	unsigned lo, hi;

	if (load_pack_revindex(p) < 0)
		return -1;

	lo = 0;
	hi = p->num_objects + 1;

	do {
		const unsigned mi = lo + (hi - lo) / 2;
		off_t got = pack_pos_to_offset(p, mi);

		if (got == ofs) {
			*pos = mi;
			return 0;
		} else if (ofs < got)
			hi = mi;
		else
			lo = mi + 1;
	} while (lo < hi);

	error("bad offset for revindex");
	return -1;
}

uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos)
{
	if (!(p->revindex || p->revindex_data))
		BUG("pack_pos_to_index: reverse index not yet loaded");
	if (p->num_objects <= pos)
		BUG("pack_pos_to_index: out-of-bounds object at %"PRIu32, pos);

	if (p->revindex)
		return p->revindex[pos].nr;
	else
		return get_be32(p->revindex_data + pos);
}

off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos)
{
	if (!(p->revindex || p->revindex_data))
		BUG("pack_pos_to_index: reverse index not yet loaded");
	if (p->num_objects < pos)
		BUG("pack_pos_to_offset: out-of-bounds object at %"PRIu32, pos);

	if (p->revindex)
		return p->revindex[pos].offset;
	else if (pos == p->num_objects)
		return p->pack_size - the_hash_algo->rawsz;
	else
		return nth_packed_object_offset(p, pack_pos_to_index(p, pos));
}

uint32_t pack_pos_to_midx(struct multi_pack_index *m, uint32_t pos)
{
	if (!m->revindex_data)
		BUG("pack_pos_to_midx: reverse index not yet loaded");
	if (m->num_objects <= pos)
		BUG("pack_pos_to_midx: out-of-bounds object at %"PRIu32, pos);
	return get_be32(m->revindex_data + pos);
}

struct midx_pack_key {
	uint32_t pack;
	off_t offset;

	uint32_t preferred_pack;
	struct multi_pack_index *midx;
};

static int midx_pack_order_cmp(const void *va, const void *vb)
{
	const struct midx_pack_key *key = va;
	struct multi_pack_index *midx = key->midx;

	uint32_t versus = pack_pos_to_midx(midx, (uint32_t*)vb - (const uint32_t *)midx->revindex_data);
	uint32_t versus_pack = nth_midxed_pack_int_id(midx, versus);
	off_t versus_offset;

	uint32_t key_preferred = key->pack == key->preferred_pack;
	uint32_t versus_preferred = versus_pack == key->preferred_pack;

	/*
	 * First, compare the preferred-ness, noting that the preferred pack
	 * comes first.
	 */
	if (key_preferred && !versus_preferred)
		return -1;
	else if (!key_preferred && versus_preferred)
		return 1;

	/* Then, break ties first by comparing the pack IDs. */
	if (key->pack < versus_pack)
		return -1;
	else if (key->pack > versus_pack)
		return 1;

	/* Finally, break ties by comparing offsets within a pack. */
	versus_offset = nth_midxed_offset(midx, versus);
	if (key->offset < versus_offset)
		return -1;
	else if (key->offset > versus_offset)
		return 1;

	return 0;
}

int midx_to_pack_pos(struct multi_pack_index *m, uint32_t at, uint32_t *pos)
{
	struct midx_pack_key key;
	uint32_t *found;

	if (!m->revindex_data)
		BUG("midx_to_pack_pos: reverse index not yet loaded");
	if (m->num_objects <= at)
		BUG("midx_to_pack_pos: out-of-bounds object at %"PRIu32, at);

	key.pack = nth_midxed_pack_int_id(m, at);
	key.offset = nth_midxed_offset(m, at);
	key.midx = m;
	/*
	 * The preferred pack sorts first, so determine its identifier by
	 * looking at the first object in pseudo-pack order.
	 *
	 * Note that if no --preferred-pack is explicitly given when writing a
	 * multi-pack index, then whichever pack has the lowest identifier
	 * implicitly is preferred (and includes all its objects, since ties are
	 * broken first by pack identifier).
	 */
	key.preferred_pack = nth_midxed_pack_int_id(m, pack_pos_to_midx(m, 0));

	found = bsearch(&key, m->revindex_data, m->num_objects,
			sizeof(*m->revindex_data), midx_pack_order_cmp);

	if (!found)
		return error("bad offset for revindex");

	*pos = found - m->revindex_data;
	return 0;
}
Commit	Line	Data
3449f8c4 NP	1	#include "cache.h"
3449f8c4 NP	2	#include "pack-revindex.h"
a80d72db	3	#include "object-store.h"
4828ce98	4	#include "packfile.h"
ec8e7760	5	#include "config.h"
f894081d	6	#include "midx.h"
3449f8c4	7
d5bc7c60 TB	8	struct revindex_entry {
	9	off_t offset;
	10	unsigned int nr;
	11	};
	12
3449f8c4 NP	13	/*
	14	* Pack index for existing packs give us easy access to the offsets into
	15	* corresponding pack file where each object's data starts, but the entries
	16	* do not store the size of the compressed representation (uncompressed
	17	* size is easily available by examining the pack entry header). It is
	18	* also rather expensive to find the sha1 for an object given its offset.
	19	*
f4015337 JK	20	* The pack index file is sorted by object name mapping to offset;
f4015337 JK	21	* this revindex array is a list of offset/index_nr pairs
3449f8c4 NP	22	* ordered by offset, so if you know the offset of an object, next offset
	23	* is where its packed representation ends and the index_nr can be used to
	24	* get the object sha1 from the main index.
	25	*/
	26
8b8dfd51 JK	27	/*
	28	* This is a least-significant-digit radix sort.
	29	*
	30	* It sorts each of the "n" items in "entries" by its offset field. The "max"
	31	* parameter must be at least as large as the largest offset in the array,
	32	* and lets us quit the sort early.
	33	*/
	34	static void sort_revindex(struct revindex_entry *entries, unsigned n, off_t max)
3449f8c4	35	{
8b8dfd51 JK	36	/*
	37	* We use a "digit" size of 16 bits. That keeps our memory
	38	* usage reasonable, and we can generally (for a 4G or smaller
	39	* packfile) quit after two rounds of radix-sorting.
	40	*/
	41	#define DIGIT_SIZE (16)
	42	#define BUCKETS (1 << DIGIT_SIZE)
	43	/*
	44	* We want to know the bucket that a[i] will go into when we are using
	45	* the digit that is N bits from the (least significant) end.
	46	*/
	47	#define BUCKET_FOR(a, i, bits) (((a)[(i)].offset >> (bits)) & (BUCKETS-1))
	48
	49	/*
	50	* We need O(n) temporary storage. Rather than do an extra copy of the
	51	* partial results into "entries", we sort back and forth between the
	52	* real array and temporary storage. In each iteration of the loop, we
	53	* keep track of them with alias pointers, always sorting from "from"
	54	* to "to".
	55	*/
b32fa95f	56	struct revindex_entry tmp, from, *to;
8b8dfd51	57	int bits;
b32fa95f JK	58	unsigned *pos;
	59
	60	ALLOC_ARRAY(pos, BUCKETS);
	61	ALLOC_ARRAY(tmp, n);
	62	from = entries;
	63	to = tmp;
8b8dfd51 JK	64
	65	/*
	66	* If (max >> bits) is zero, then we know that the radix digit we are
	67	* on (and any higher) will be zero for all entries, and our loop will
	68	* be a no-op, as everybody lands in the same zero-th bucket.
	69	*/
	70	for (bits = 0; max >> bits; bits += DIGIT_SIZE) {
8b8dfd51 JK	71	unsigned i;
	72
	73	memset(pos, 0, BUCKETS * sizeof(*pos));
	74
	75	/*
	76	* We want pos[i] to store the index of the last element that
	77	* will go in bucket "i" (actually one past the last element).
	78	* To do this, we first count the items that will go in each
	79	* bucket, which gives us a relative offset from the last
	80	* bucket. We can then cumulatively add the index from the
	81	* previous bucket to get the true index.
	82	*/
	83	for (i = 0; i < n; i++)
	84	pos[BUCKET_FOR(from, i, bits)]++;
	85	for (i = 1; i < BUCKETS; i++)
	86	pos[i] += pos[i-1];
	87
	88	/*
	89	* Now we can drop the elements into their correct buckets (in
	90	* our temporary array). We iterate the pos counter backwards
	91	* to avoid using an extra index to count up. And since we are
	92	* going backwards there, we must also go backwards through the
	93	* array itself, to keep the sort stable.
	94	*
	95	* Note that we use an unsigned iterator to make sure we can
	96	* handle 2^32-1 objects, even on a 32-bit system. But this
	97	* means we cannot use the more obvious "i >= 0" loop condition
	98	* for counting backwards, and must instead check for
	99	* wrap-around with UINT_MAX.
	100	*/
	101	for (i = n - 1; i != UINT_MAX; i--)
	102	to[--pos[BUCKET_FOR(from, i, bits)]] = from[i];
	103
	104	/*
	105	* Now "to" contains the most sorted list, so we swap "from" and
	106	* "to" for the next iteration.
	107	*/
35d803bc	108	SWAP(from, to);
8b8dfd51 JK	109	}
	110
	111	/*
	112	* If we ended with our data in the original array, great. If not,
	113	* we have to move it back from the temporary storage.
	114	*/
	115	if (from != entries)
45ccef87	116	COPY_ARRAY(entries, tmp, n);
8b8dfd51 JK	117	free(tmp);
	118	free(pos);
	119
	120	#undef BUCKET_FOR
	121	#undef BUCKETS
	122	#undef DIGIT_SIZE
3449f8c4 NP	123	}
	124
	125	/*
	126	* Ordered list of offsets of objects in the pack.
	127	*/
9d98bbf5	128	static void create_pack_revindex(struct packed_git *p)
3449f8c4	129	{
33de80b1	130	const unsigned num_ent = p->num_objects;
012b32bb	131	unsigned i;
3449f8c4	132	const char *index = p->index_data;
fa130802	133	const unsigned hashsz = the_hash_algo->rawsz;
3449f8c4	134
11529ece	135	ALLOC_ARRAY(p->revindex, num_ent + 1);
3449f8c4 NP	136	index += 4 * 256;
	137
	138	if (p->index_version > 1) {
	139	const uint32_t *off_32 =
f86f7695	140	(uint32_t )(index + 8 + (size_t)p->num_objects (hashsz + 4));
3449f8c4 NP	141	const uint32_t *off_64 = off_32 + p->num_objects;
3449f8c4 NP	142	for (i = 0; i < num_ent; i++) {
33de80b1	143	const uint32_t off = ntohl(*off_32++);
3449f8c4	144	if (!(off & 0x80000000)) {
9d98bbf5	145	p->revindex[i].offset = off;
3449f8c4	146	} else {
ad622a25 DS	147	p->revindex[i].offset = get_be64(off_64);
ad622a25 DS	148	off_64 += 2;
3449f8c4	149	}
9d98bbf5	150	p->revindex[i].nr = i;
3449f8c4 NP	151	}
	152	} else {
	153	for (i = 0; i < num_ent; i++) {
33de80b1	154	const uint32_t hl = ((uint32_t )(index + (hashsz + 4) * i));
9d98bbf5 JK	155	p->revindex[i].offset = ntohl(hl);
9d98bbf5 JK	156	p->revindex[i].nr = i;
3449f8c4 NP	157	}
	158	}
	159
fa130802	160	/*
fa130802	161	* This knows the pack format -- the hash trailer
3449f8c4 NP	162	* follows immediately after the last object data.
3449f8c4 NP	163	*/
fa130802	164	p->revindex[num_ent].offset = p->pack_size - hashsz;
9d98bbf5 JK	165	p->revindex[num_ent].nr = -1;
9d98bbf5 JK	166	sort_revindex(p->revindex, num_ent, p->pack_size);
3449f8c4 NP	167	}
3449f8c4 NP	168
2f4ba2a8	169	static int create_pack_revindex_in_memory(struct packed_git *p)
3449f8c4	170	{
ec8e7760 TB	171	if (git_env_bool(GIT_TEST_REV_INDEX_DIE_IN_MEMORY, 0))
	172	die("dying as requested by '%s'",
	173	GIT_TEST_REV_INDEX_DIE_IN_MEMORY);
2f4ba2a8 TB	174	if (open_pack_index(p))
	175	return -1;
	176	create_pack_revindex(p);
4828ce98	177	return 0;
92e5c77c VM	178	}
92e5c77c VM	179
2f4ba2a8 TB	180	static char pack_revindex_filename(struct packed_git p)
	181	{
	182	size_t len;
	183	if (!strip_suffix(p->pack_name, ".pack", &len))
	184	BUG("pack_name does not end in .pack");
	185	return xstrfmt("%.*s.rev", (int)len, p->pack_name);
	186	}
	187
	188	#define RIDX_HEADER_SIZE (12)
	189	#define RIDX_MIN_SIZE (RIDX_HEADER_SIZE + (2 * the_hash_algo->rawsz))
	190
	191	struct revindex_header {
	192	uint32_t signature;
	193	uint32_t version;
	194	uint32_t hash_id;
	195	};
	196
	197	static int load_revindex_from_disk(char *revindex_name,
	198	uint32_t num_objects,
	199	const uint32_t *data_p, size_t len_p)
	200	{
	201	int fd, ret = 0;
	202	struct stat st;
	203	void *data = NULL;
	204	size_t revindex_size;
	205	struct revindex_header *hdr;
	206
	207	fd = git_open(revindex_name);
	208
	209	if (fd < 0) {
	210	ret = -1;
	211	goto cleanup;
	212	}
	213	if (fstat(fd, &st)) {
	214	ret = error_errno(_("failed to read %s"), revindex_name);
	215	goto cleanup;
	216	}
	217
	218	revindex_size = xsize_t(st.st_size);
	219
	220	if (revindex_size < RIDX_MIN_SIZE) {
	221	ret = error(_("reverse-index file %s is too small"), revindex_name);
	222	goto cleanup;
	223	}
	224
	225	if (revindex_size - RIDX_MIN_SIZE != st_mult(sizeof(uint32_t), num_objects)) {
	226	ret = error(_("reverse-index file %s is corrupt"), revindex_name);
	227	goto cleanup;
	228	}
	229
	230	data = xmmap(NULL, revindex_size, PROT_READ, MAP_PRIVATE, fd, 0);
	231	hdr = data;
	232
	233	if (ntohl(hdr->signature) != RIDX_SIGNATURE) {
	234	ret = error(_("reverse-index file %s has unknown signature"), revindex_name);
	235	goto cleanup;
	236	}
	237	if (ntohl(hdr->version) != 1) {
	238	ret = error(_("reverse-index file %s has unsupported version %"PRIu32),
	239	revindex_name, ntohl(hdr->version));
	240	goto cleanup;
	241	}
	242	if (!(ntohl(hdr->hash_id) == 1 \|\| ntohl(hdr->hash_id) == 2)) {
	243	ret = error(_("reverse-index file %s has unsupported hash id %"PRIu32),
244	revindex_name, ntohl(hdr->hash_id));
245	goto cleanup;
246	}
247
248	cleanup:
249	if (ret) {
250	if (data)
251	munmap(data, revindex_size);
252	} else {
253	*len_p = revindex_size;
254	data_p = (const uint32_t )data;
255	}
256
66f52fa2 TB	257	if (fd >= 0)
66f52fa2 TB	258	close(fd);
2f4ba2a8 TB	259	return ret;
	260	}
	261
	262	static int load_pack_revindex_from_disk(struct packed_git *p)
	263	{
	264	char *revindex_name;
	265	int ret;
	266	if (open_pack_index(p))
	267	return -1;
	268
	269	revindex_name = pack_revindex_filename(p);
	270
	271	ret = load_revindex_from_disk(revindex_name,
	272	p->num_objects,
	273	&p->revindex_map,
	274	&p->revindex_size);
	275	if (ret)
	276	goto cleanup;
	277
	278	p->revindex_data = (const uint32_t )((const char )p->revindex_map + RIDX_HEADER_SIZE);
	279
	280	cleanup:
	281	free(revindex_name);
	282	return ret;
	283	}
	284
	285	int load_pack_revindex(struct packed_git *p)
	286	{
	287	if (p->revindex \|\| p->revindex_data)
	288	return 0;
	289
	290	if (!load_pack_revindex_from_disk(p))
	291	return 0;
	292	else if (!create_pack_revindex_in_memory(p))
	293	return 0;
	294	return -1;
	295	}
	296
f894081d TB	297	int load_midx_revindex(struct multi_pack_index *m)
f894081d TB	298	{
60980aed	299	struct strbuf revindex_name = STRBUF_INIT;
f894081d TB	300	int ret;
	301	if (m->revindex_data)
	302	return 0;
	303
09a77999 TB	304	trace2_data_string("load_midx_revindex", the_repository,
	305	"source", "rev");
	306
60980aed	307	get_midx_rev_filename(&revindex_name, m);
f894081d	308
60980aed	309	ret = load_revindex_from_disk(revindex_name.buf,
f894081d TB	310	m->num_objects,
	311	&m->revindex_map,
	312	&m->revindex_len);
	313	if (ret)
	314	goto cleanup;
	315
	316	m->revindex_data = (const uint32_t )((const char )m->revindex_map + RIDX_HEADER_SIZE);
	317
	318	cleanup:
60980aed	319	strbuf_release(&revindex_name);
f894081d TB	320	return ret;
	321	}
	322
	323	int close_midx_revindex(struct multi_pack_index *m)
	324	{
	325	if (!m \|\| !m->revindex_map)
	326	return 0;
	327
	328	munmap((void*)m->revindex_map, m->revindex_len);
	329
	330	m->revindex_map = NULL;
	331	m->revindex_data = NULL;
	332	m->revindex_len = 0;
	333
	334	return 0;
	335	}
	336
8389855a	337	int offset_to_pack_pos(struct packed_git p, off_t ofs, uint32_t pos)
92e5c77c	338	{
8389855a	339	unsigned lo, hi;
8389855a TB	340
	341	if (load_pack_revindex(p) < 0)
	342	return -1;
	343
	344	lo = 0;
	345	hi = p->num_objects + 1;
92e5c77c	346
3449f8c4	347	do {
33de80b1	348	const unsigned mi = lo + (hi - lo) / 2;
e5dcd784 TB	349	off_t got = pack_pos_to_offset(p, mi);
	350
	351	if (got == ofs) {
8389855a TB	352	*pos = mi;
8389855a TB	353	return 0;
e5dcd784	354	} else if (ofs < got)
3449f8c4 NP	355	hi = mi;
	356	else
	357	lo = mi + 1;
	358	} while (lo < hi);
92e5c77c	359
08698b1e	360	error("bad offset for revindex");
92e5c77c VM	361	return -1;
	362	}
	363
f33fb6e4 TB	364	uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos)
f33fb6e4 TB	365	{
2f4ba2a8	366	if (!(p->revindex \|\| p->revindex_data))
f33fb6e4 TB	367	BUG("pack_pos_to_index: reverse index not yet loaded");
	368	if (p->num_objects <= pos)
	369	BUG("pack_pos_to_index: out-of-bounds object at %"PRIu32, pos);
2f4ba2a8 TB	370
	371	if (p->revindex)
	372	return p->revindex[pos].nr;
	373	else
	374	return get_be32(p->revindex_data + pos);
f33fb6e4 TB	375	}
	376
	377	off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos)
	378	{
2f4ba2a8	379	if (!(p->revindex \|\| p->revindex_data))
f33fb6e4 TB	380	BUG("pack_pos_to_index: reverse index not yet loaded");
	381	if (p->num_objects < pos)
	382	BUG("pack_pos_to_offset: out-of-bounds object at %"PRIu32, pos);
2f4ba2a8 TB	383
	384	if (p->revindex)
	385	return p->revindex[pos].offset;
	386	else if (pos == p->num_objects)
	387	return p->pack_size - the_hash_algo->rawsz;
	388	else
	389	return nth_packed_object_offset(p, pack_pos_to_index(p, pos));
f33fb6e4	390	}
f894081d TB	391
	392	uint32_t pack_pos_to_midx(struct multi_pack_index *m, uint32_t pos)
	393	{
	394	if (!m->revindex_data)
	395	BUG("pack_pos_to_midx: reverse index not yet loaded");
	396	if (m->num_objects <= pos)
	397	BUG("pack_pos_to_midx: out-of-bounds object at %"PRIu32, pos);
	398	return get_be32(m->revindex_data + pos);
	399	}
	400
	401	struct midx_pack_key {
	402	uint32_t pack;
	403	off_t offset;
	404
	405	uint32_t preferred_pack;
	406	struct multi_pack_index *midx;
	407	};
	408
	409	static int midx_pack_order_cmp(const void va, const void vb)
	410	{
	411	const struct midx_pack_key *key = va;
	412	struct multi_pack_index *midx = key->midx;
	413
	414	uint32_t versus = pack_pos_to_midx(midx, (uint32_t)vb - (const uint32_t )midx->revindex_data);
	415	uint32_t versus_pack = nth_midxed_pack_int_id(midx, versus);
	416	off_t versus_offset;
	417
	418	uint32_t key_preferred = key->pack == key->preferred_pack;
	419	uint32_t versus_preferred = versus_pack == key->preferred_pack;
	420
	421	/*
	422	* First, compare the preferred-ness, noting that the preferred pack
	423	* comes first.
	424	*/
	425	if (key_preferred && !versus_preferred)
	426	return -1;
	427	else if (!key_preferred && versus_preferred)
	428	return 1;
	429
	430	/* Then, break ties first by comparing the pack IDs. */
	431	if (key->pack < versus_pack)
	432	return -1;
	433	else if (key->pack > versus_pack)
	434	return 1;
	435
	436	/* Finally, break ties by comparing offsets within a pack. */
	437	versus_offset = nth_midxed_offset(midx, versus);
	438	if (key->offset < versus_offset)
	439	return -1;
	440	else if (key->offset > versus_offset)
	441	return 1;
	442
	443	return 0;
	444	}
	445
	446	int midx_to_pack_pos(struct multi_pack_index m, uint32_t at, uint32_t pos)
	447	{
	448	struct midx_pack_key key;
	449	uint32_t *found;
	450
	451	if (!m->revindex_data)
	452	BUG("midx_to_pack_pos: reverse index not yet loaded");
	453	if (m->num_objects <= at)
	454	BUG("midx_to_pack_pos: out-of-bounds object at %"PRIu32, at);
455
456	key.pack = nth_midxed_pack_int_id(m, at);
457	key.offset = nth_midxed_offset(m, at);
458	key.midx = m;
459	/*
460	* The preferred pack sorts first, so determine its identifier by
461	* looking at the first object in pseudo-pack order.
462	*
463	* Note that if no --preferred-pack is explicitly given when writing a
464	* multi-pack index, then whichever pack has the lowest identifier
465	* implicitly is preferred (and includes all its objects, since ties are
466	* broken first by pack identifier).
467	*/
468	key.preferred_pack = nth_midxed_pack_int_id(m, pack_pos_to_midx(m, 0));
469
470	found = bsearch(&key, m->revindex_data, m->num_objects,
471	sizeof(*m->revindex_data), midx_pack_order_cmp);
472
473	if (!found)
474	return error("bad offset for revindex");
475
476	*pos = found - m->revindex_data;
477	return 0;
478	}