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

#include "cache.h"
#include "pack.h"
#include "csum-file.h"

uint32_t pack_idx_default_version = 2;
uint32_t pack_idx_off32_limit = 0x7fffffff;

static int sha1_compare(const void *_a, const void *_b)
{
	struct pack_idx_entry *a = *(struct pack_idx_entry **)_a;
	struct pack_idx_entry *b = *(struct pack_idx_entry **)_b;
	return hashcmp(a->sha1, b->sha1);
}

/*
 * On entry *sha1 contains the pack content SHA1 hash, on exit it is
 * the SHA1 hash of sorted object names. The objects array passed in
 * will be sorted by SHA1 on exit.
 */
const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects,
			   int nr_objects, unsigned char *sha1)
{
	struct sha1file *f;
	struct pack_idx_entry **sorted_by_sha, **list, **last;
	off_t last_obj_offset = 0;
	uint32_t array[256];
	int i, fd;
	git_SHA_CTX ctx;
	uint32_t index_version;

	if (nr_objects) {
		sorted_by_sha = objects;
		list = sorted_by_sha;
		last = sorted_by_sha + nr_objects;
		for (i = 0; i < nr_objects; ++i) {
			if (objects[i]->offset > last_obj_offset)
				last_obj_offset = objects[i]->offset;
		}
		qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
		      sha1_compare);
	}
	else
		sorted_by_sha = list = last = NULL;

	if (!index_name) {
		static char tmpfile[PATH_MAX];
		fd = odb_mkstemp(tmpfile, sizeof(tmpfile), "pack/tmp_idx_XXXXXX");
		index_name = xstrdup(tmpfile);
	} else {
		unlink(index_name);
		fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
	}
	if (fd < 0)
		die_errno("unable to create '%s'", index_name);
	f = sha1fd(fd, index_name);

	/* if last object's offset is >= 2^31 we should use index V2 */
	index_version = (last_obj_offset >> 31) ? 2 : pack_idx_default_version;

	/* index versions 2 and above need a header */
	if (index_version >= 2) {
		struct pack_idx_header hdr;
		hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
		hdr.idx_version = htonl(index_version);
		sha1write(f, &hdr, sizeof(hdr));
	}

	/*
	 * Write the first-level table (the list is sorted,
	 * but we use a 256-entry lookup to be able to avoid
	 * having to do eight extra binary search iterations).
	 */
	for (i = 0; i < 256; i++) {
		struct pack_idx_entry **next = list;
		while (next < last) {
			struct pack_idx_entry *obj = *next;
			if (obj->sha1[0] != i)
				break;
			next++;
		}
		array[i] = htonl(next - sorted_by_sha);
		list = next;
	}
	sha1write(f, array, 256 * 4);

	/* compute the SHA1 hash of sorted object names. */
	git_SHA1_Init(&ctx);

	/*
	 * Write the actual SHA1 entries..
	 */
	list = sorted_by_sha;
	for (i = 0; i < nr_objects; i++) {
		struct pack_idx_entry *obj = *list++;
		if (index_version < 2) {
			uint32_t offset = htonl(obj->offset);
			sha1write(f, &offset, 4);
		}
		sha1write(f, obj->sha1, 20);
		git_SHA1_Update(&ctx, obj->sha1, 20);
	}

	if (index_version >= 2) {
		unsigned int nr_large_offset = 0;

		/* write the crc32 table */
		list = sorted_by_sha;
		for (i = 0; i < nr_objects; i++) {
			struct pack_idx_entry *obj = *list++;
			uint32_t crc32_val = htonl(obj->crc32);
			sha1write(f, &crc32_val, 4);
		}

		/* write the 32-bit offset table */
		list = sorted_by_sha;
		for (i = 0; i < nr_objects; i++) {
			struct pack_idx_entry *obj = *list++;
			uint32_t offset = (obj->offset <= pack_idx_off32_limit) ?
				obj->offset : (0x80000000 | nr_large_offset++);
			offset = htonl(offset);
			sha1write(f, &offset, 4);
		}

		/* write the large offset table */
		list = sorted_by_sha;
		while (nr_large_offset) {
			struct pack_idx_entry *obj = *list++;
			uint64_t offset = obj->offset;
			if (offset > pack_idx_off32_limit) {
				uint32_t split[2];
				split[0] = htonl(offset >> 32);
				split[1] = htonl(offset & 0xffffffff);
				sha1write(f, split, 8);
				nr_large_offset--;
			}
		}
	}

	sha1write(f, sha1, 20);
	sha1close(f, NULL, CSUM_FSYNC);
	git_SHA1_Final(sha1, &ctx);
	return index_name;
}

/*
 * Update pack header with object_count and compute new SHA1 for pack data
 * associated to pack_fd, and write that SHA1 at the end.  That new SHA1
 * is also returned in new_pack_sha1.
 *
 * If partial_pack_sha1 is non null, then the SHA1 of the existing pack
 * (without the header update) is computed and validated against the
 * one provided in partial_pack_sha1.  The validation is performed at
 * partial_pack_offset bytes in the pack file.  The SHA1 of the remaining
 * data (i.e. from partial_pack_offset to the end) is then computed and
 * returned in partial_pack_sha1.
 *
 * Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
 * partial_pack_sha1 can refer to the same buffer if the caller is not
 * interested in the resulting SHA1 of pack data above partial_pack_offset.
 */
void fixup_pack_header_footer(int pack_fd,
			 unsigned char *new_pack_sha1,
			 const char *pack_name,
			 uint32_t object_count,
			 unsigned char *partial_pack_sha1,
			 off_t partial_pack_offset)
{
	int aligned_sz, buf_sz = 8 * 1024;
	git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
	struct pack_header hdr;
	char *buf;

	git_SHA1_Init(&old_sha1_ctx);
	git_SHA1_Init(&new_sha1_ctx);

	if (lseek(pack_fd, 0, SEEK_SET) != 0)
		die_errno("Failed seeking to start of '%s'", pack_name);
	if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
		die_errno("Unable to reread header of '%s'", pack_name);
	if (lseek(pack_fd, 0, SEEK_SET) != 0)
		die_errno("Failed seeking to start of '%s'", pack_name);
	git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
	hdr.hdr_entries = htonl(object_count);
	git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
	write_or_die(pack_fd, &hdr, sizeof(hdr));
	partial_pack_offset -= sizeof(hdr);

	buf = xmalloc(buf_sz);
	aligned_sz = buf_sz - sizeof(hdr);
	for (;;) {
		ssize_t m, n;
		m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
			partial_pack_offset : aligned_sz;
		n = xread(pack_fd, buf, m);
		if (!n)
			break;
		if (n < 0)
			die_errno("Failed to checksum '%s'", pack_name);
		git_SHA1_Update(&new_sha1_ctx, buf, n);

		aligned_sz -= n;
		if (!aligned_sz)
			aligned_sz = buf_sz;

		if (!partial_pack_sha1)
			continue;

		git_SHA1_Update(&old_sha1_ctx, buf, n);
		partial_pack_offset -= n;
		if (partial_pack_offset == 0) {
			unsigned char sha1[20];
			git_SHA1_Final(sha1, &old_sha1_ctx);
			if (hashcmp(sha1, partial_pack_sha1) != 0)
				die("Unexpected checksum for %s "
				    "(disk corruption?)", pack_name);
			/*
			 * Now let's compute the SHA1 of the remainder of the
			 * pack, which also means making partial_pack_offset
			 * big enough not to matter anymore.
			 */
			git_SHA1_Init(&old_sha1_ctx);
			partial_pack_offset = ~partial_pack_offset;
			partial_pack_offset -= MSB(partial_pack_offset, 1);
		}
	}
	free(buf);

	if (partial_pack_sha1)
		git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
	git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
	write_or_die(pack_fd, new_pack_sha1, 20);
	fsync_or_die(pack_fd, pack_name);
}

char *index_pack_lockfile(int ip_out)
{
	char packname[46];

	/*
	 * The first thing we expect from index-pack's output
	 * is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
	 * %40s is the newly created pack SHA1 name.  In the "keep"
	 * case, we need it to remove the corresponding .keep file
	 * later on.  If we don't get that then tough luck with it.
	 */
	if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n' &&
	    memcmp(packname, "keep\t", 5) == 0) {
		char path[PATH_MAX];
		packname[45] = 0;
		snprintf(path, sizeof(path), "%s/pack/pack-%s.keep",
			 get_object_directory(), packname + 5);
		return xstrdup(path);
	}
	return NULL;
}

/*
 * The per-object header is a pretty dense thing, which is
 *  - first byte: low four bits are "size", then three bits of "type",
 *    and the high bit is "size continues".
 *  - each byte afterwards: low seven bits are size continuation,
 *    with the high bit being "size continues"
 */
int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr)
{
	int n = 1;
	unsigned char c;

	if (type < OBJ_COMMIT || type > OBJ_REF_DELTA)
		die("bad type %d", type);

	c = (type << 4) | (size & 15);
	size >>= 4;
	while (size) {
		*hdr++ = c | 0x80;
		c = size & 0x7f;
		size >>= 7;
		n++;
	}
	*hdr = c;
	return n;
}
Commit	Line	Data
8b0eca7c DH	1	#include "cache.h"
8b0eca7c DH	2	#include "pack.h"
aa7e44bf GB	3	#include "csum-file.h"
aa7e44bf GB	4
c0a5e2d4	5	uint32_t pack_idx_default_version = 2;
aa7e44bf GB	6	uint32_t pack_idx_off32_limit = 0x7fffffff;
	7
	8	static int sha1_compare(const void _a, const void _b)
	9	{
	10	struct pack_idx_entry a = (struct pack_idx_entry **)_a;
	11	struct pack_idx_entry b = (struct pack_idx_entry **)_b;
	12	return hashcmp(a->sha1, b->sha1);
	13	}
	14
	15	/*
	16	* On entry *sha1 contains the pack content SHA1 hash, on exit it is
	17	* the SHA1 hash of sorted object names. The objects array passed in
	18	* will be sorted by SHA1 on exit.
	19	*/
3bb72562 LT	20	const char write_idx_file(const char index_name, struct pack_idx_entry **objects,
3bb72562 LT	21	int nr_objects, unsigned char *sha1)
aa7e44bf GB	22	{
	23	struct sha1file *f;
	24	struct pack_idx_entry sorted_by_sha, list, **last;
	25	off_t last_obj_offset = 0;
	26	uint32_t array[256];
	27	int i, fd;
9126f009	28	git_SHA_CTX ctx;
aa7e44bf GB	29	uint32_t index_version;
	30
	31	if (nr_objects) {
	32	sorted_by_sha = objects;
	33	list = sorted_by_sha;
	34	last = sorted_by_sha + nr_objects;
	35	for (i = 0; i < nr_objects; ++i) {
	36	if (objects[i]->offset > last_obj_offset)
	37	last_obj_offset = objects[i]->offset;
	38	}
	39	qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
	40	sha1_compare);
	41	}
	42	else
	43	sorted_by_sha = list = last = NULL;
	44
	45	if (!index_name) {
	46	static char tmpfile[PATH_MAX];
6e180cdc	47	fd = odb_mkstemp(tmpfile, sizeof(tmpfile), "pack/tmp_idx_XXXXXX");
aa7e44bf GB	48	index_name = xstrdup(tmpfile);
	49	} else {
	50	unlink(index_name);
	51	fd = open(index_name, O_CREAT\|O_EXCL\|O_WRONLY, 0600);
	52	}
	53	if (fd < 0)
d824cbba	54	die_errno("unable to create '%s'", index_name);
aa7e44bf GB	55	f = sha1fd(fd, index_name);
	56
	57	/* if last object's offset is >= 2^31 we should use index V2 */
	58	index_version = (last_obj_offset >> 31) ? 2 : pack_idx_default_version;
	59
	60	/* index versions 2 and above need a header */
	61	if (index_version >= 2) {
	62	struct pack_idx_header hdr;
	63	hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
	64	hdr.idx_version = htonl(index_version);
	65	sha1write(f, &hdr, sizeof(hdr));
	66	}
	67
	68	/*
	69	* Write the first-level table (the list is sorted,
	70	* but we use a 256-entry lookup to be able to avoid
	71	* having to do eight extra binary search iterations).
	72	*/
	73	for (i = 0; i < 256; i++) {
	74	struct pack_idx_entry **next = list;
	75	while (next < last) {
	76	struct pack_idx_entry obj = next;
	77	if (obj->sha1[0] != i)
	78	break;
	79	next++;
	80	}
	81	array[i] = htonl(next - sorted_by_sha);
	82	list = next;
	83	}
	84	sha1write(f, array, 256 * 4);
	85
	86	/* compute the SHA1 hash of sorted object names. */
9126f009	87	git_SHA1_Init(&ctx);
aa7e44bf GB	88
	89	/*
	90	* Write the actual SHA1 entries..
	91	*/
	92	list = sorted_by_sha;
	93	for (i = 0; i < nr_objects; i++) {
	94	struct pack_idx_entry obj = list++;
	95	if (index_version < 2) {
	96	uint32_t offset = htonl(obj->offset);
	97	sha1write(f, &offset, 4);
	98	}
	99	sha1write(f, obj->sha1, 20);
9126f009	100	git_SHA1_Update(&ctx, obj->sha1, 20);
aa7e44bf GB	101	}
	102
	103	if (index_version >= 2) {
	104	unsigned int nr_large_offset = 0;
	105
	106	/* write the crc32 table */
	107	list = sorted_by_sha;
	108	for (i = 0; i < nr_objects; i++) {
	109	struct pack_idx_entry obj = list++;
	110	uint32_t crc32_val = htonl(obj->crc32);
	111	sha1write(f, &crc32_val, 4);
	112	}
	113
	114	/* write the 32-bit offset table */
	115	list = sorted_by_sha;
	116	for (i = 0; i < nr_objects; i++) {
	117	struct pack_idx_entry obj = list++;
	118	uint32_t offset = (obj->offset <= pack_idx_off32_limit) ?
	119	obj->offset : (0x80000000 \| nr_large_offset++);
	120	offset = htonl(offset);
	121	sha1write(f, &offset, 4);
	122	}
	123
	124	/* write the large offset table */
	125	list = sorted_by_sha;
	126	while (nr_large_offset) {
	127	struct pack_idx_entry obj = list++;
	128	uint64_t offset = obj->offset;
	129	if (offset > pack_idx_off32_limit) {
	130	uint32_t split[2];
	131	split[0] = htonl(offset >> 32);
	132	split[1] = htonl(offset & 0xffffffff);
	133	sha1write(f, split, 8);
	134	nr_large_offset--;
	135	}
	136	}
	137	}
	138
	139	sha1write(f, sha1, 20);
4c81b03e	140	sha1close(f, NULL, CSUM_FSYNC);
9126f009	141	git_SHA1_Final(sha1, &ctx);
aa7e44bf GB	142	return index_name;
aa7e44bf GB	143	}
8b0eca7c	144
abeb40e5 NP	145	/*
	146	* Update pack header with object_count and compute new SHA1 for pack data
	147	* associated to pack_fd, and write that SHA1 at the end. That new SHA1
	148	* is also returned in new_pack_sha1.
	149	*
	150	* If partial_pack_sha1 is non null, then the SHA1 of the existing pack
	151	* (without the header update) is computed and validated against the
	152	* one provided in partial_pack_sha1. The validation is performed at
	153	* partial_pack_offset bytes in the pack file. The SHA1 of the remaining
	154	* data (i.e. from partial_pack_offset to the end) is then computed and
	155	* returned in partial_pack_sha1.
	156	*
	157	* Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
	158	* partial_pack_sha1 can refer to the same buffer if the caller is not
	159	* interested in the resulting SHA1 of pack data above partial_pack_offset.
	160	*/
8b0eca7c	161	void fixup_pack_header_footer(int pack_fd,
abeb40e5	162	unsigned char *new_pack_sha1,
8b0eca7c	163	const char *pack_name,
abeb40e5 NP	164	uint32_t object_count,
	165	unsigned char *partial_pack_sha1,
	166	off_t partial_pack_offset)
8b0eca7c	167	{
d35825da	168	int aligned_sz, buf_sz = 8 * 1024;
9126f009	169	git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
8b0eca7c DH	170	struct pack_header hdr;
	171	char *buf;
	172
9126f009 NP	173	git_SHA1_Init(&old_sha1_ctx);
9126f009 NP	174	git_SHA1_Init(&new_sha1_ctx);
abeb40e5	175
8b0eca7c	176	if (lseek(pack_fd, 0, SEEK_SET) != 0)
d824cbba	177	die_errno("Failed seeking to start of '%s'", pack_name);
8b0eca7c	178	if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
d824cbba	179	die_errno("Unable to reread header of '%s'", pack_name);
8b0eca7c	180	if (lseek(pack_fd, 0, SEEK_SET) != 0)
d824cbba	181	die_errno("Failed seeking to start of '%s'", pack_name);
9126f009	182	git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
8b0eca7c	183	hdr.hdr_entries = htonl(object_count);
9126f009	184	git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
8b0eca7c	185	write_or_die(pack_fd, &hdr, sizeof(hdr));
abeb40e5	186	partial_pack_offset -= sizeof(hdr);
8b0eca7c DH	187
8b0eca7c DH	188	buf = xmalloc(buf_sz);
d35825da	189	aligned_sz = buf_sz - sizeof(hdr);
8b0eca7c	190	for (;;) {
abeb40e5	191	ssize_t m, n;
d35825da NP	192	m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
d35825da NP	193	partial_pack_offset : aligned_sz;
abeb40e5	194	n = xread(pack_fd, buf, m);
8b0eca7c DH	195	if (!n)
	196	break;
	197	if (n < 0)
d824cbba	198	die_errno("Failed to checksum '%s'", pack_name);
9126f009	199	git_SHA1_Update(&new_sha1_ctx, buf, n);
abeb40e5	200
d35825da NP	201	aligned_sz -= n;
	202	if (!aligned_sz)
	203	aligned_sz = buf_sz;
	204
abeb40e5 NP	205	if (!partial_pack_sha1)
	206	continue;
	207
9126f009	208	git_SHA1_Update(&old_sha1_ctx, buf, n);
abeb40e5 NP	209	partial_pack_offset -= n;
	210	if (partial_pack_offset == 0) {
	211	unsigned char sha1[20];
9126f009	212	git_SHA1_Final(sha1, &old_sha1_ctx);
abeb40e5 NP	213	if (hashcmp(sha1, partial_pack_sha1) != 0)
	214	die("Unexpected checksum for %s "
	215	"(disk corruption?)", pack_name);
	216	/*
	217	* Now let's compute the SHA1 of the remainder of the
	218	* pack, which also means making partial_pack_offset
	219	* big enough not to matter anymore.
	220	*/
9126f009	221	git_SHA1_Init(&old_sha1_ctx);
abeb40e5 NP	222	partial_pack_offset = ~partial_pack_offset;
	223	partial_pack_offset -= MSB(partial_pack_offset, 1);
	224	}
8b0eca7c DH	225	}
	226	free(buf);
	227
abeb40e5	228	if (partial_pack_sha1)
9126f009 NP	229	git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
9126f009 NP	230	git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
abeb40e5	231	write_or_die(pack_fd, new_pack_sha1, 20);
0c68d386	232	fsync_or_die(pack_fd, pack_name);
8b0eca7c	233	}
106764e6 SP	234
	235	char *index_pack_lockfile(int ip_out)
	236	{
106764e6 SP	237	char packname[46];
	238
	239	/*
6e180cdc	240	* The first thing we expect from index-pack's output
106764e6 SP	241	* is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
	242	* %40s is the newly created pack SHA1 name. In the "keep"
	243	* case, we need it to remove the corresponding .keep file
	244	* later on. If we don't get that then tough luck with it.
	245	*/
c697ad14 HO	246	if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n' &&
c697ad14 HO	247	memcmp(packname, "keep\t", 5) == 0) {
106764e6 SP	248	char path[PATH_MAX];
	249	packname[45] = 0;
	250	snprintf(path, sizeof(path), "%s/pack/pack-%s.keep",
	251	get_object_directory(), packname + 5);
	252	return xstrdup(path);
	253	}
	254	return NULL;
	255	}
f965c525 NP	256
	257	/*
	258	* The per-object header is a pretty dense thing, which is
	259	* - first byte: low four bits are "size", then three bits of "type",
	260	* and the high bit is "size continues".
	261	* - each byte afterwards: low seven bits are size continuation,
	262	* with the high bit being "size continues"
	263	*/
	264	int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr)
	265	{
	266	int n = 1;
	267	unsigned char c;
	268
	269	if (type < OBJ_COMMIT \|\| type > OBJ_REF_DELTA)
	270	die("bad type %d", type);
	271
	272	c = (type << 4) \| (size & 15);
	273	size >>= 4;
	274	while (size) {
	275	*hdr++ = c \| 0x80;
	276	c = size & 0x7f;
	277	size >>= 7;
	278	n++;
	279	}
	280	*hdr = c;
	281	return n;
	282	}