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

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

void reset_pack_idx_option(struct pack_idx_option *opts)
{
	memset(opts, 0, sizeof(*opts));
	opts->version = 2;
	opts->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);
}

static int cmp_uint32(const void *a_, const void *b_)
{
	uint32_t a = *((uint32_t *)a_);
	uint32_t b = *((uint32_t *)b_);

	return (a < b) ? -1 : (a != b);
}

static int need_large_offset(off_t offset, const struct pack_idx_option *opts)
{
	uint32_t ofsval;

	if ((offset >> 31) || (opts->off32_limit < offset))
		return 1;
	if (!opts->anomaly_nr)
		return 0;
	ofsval = offset;
	return !!bsearch(&ofsval, opts->anomaly, opts->anomaly_nr,
			 sizeof(ofsval), cmp_uint32);
}

/*
 * 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, const struct pack_idx_option *opts,
			   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 (opts->flags & WRITE_IDX_VERIFY) {
		assert(index_name);
		f = sha1fd_check(index_name);
	} else {
		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 = need_large_offset(last_obj_offset, opts) ? 2 : opts->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;

			offset = (need_large_offset(obj->offset, opts)
				  ? (0x80000000 | nr_large_offset++)
				  : obj->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;
			uint32_t split[2];

			if (!need_large_offset(offset, opts))
				continue;
			split[0] = htonl(offset >> 32);
			split[1] = htonl(offset & 0xffffffff);
			sha1write(f, split, 8);
			nr_large_offset--;
		}
	}

	sha1write(f, sha1, 20);
	sha1close(f, NULL, ((opts->flags & WRITE_IDX_VERIFY)
			    ? CSUM_CLOSE : 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
ebcfb379 JH	5	void reset_pack_idx_option(struct pack_idx_option *opts)
	6	{
	7	memset(opts, 0, sizeof(*opts));
	8	opts->version = 2;
	9	opts->off32_limit = 0x7fffffff;
	10	}
aa7e44bf GB	11
	12	static int sha1_compare(const void _a, const void _b)
	13	{
	14	struct pack_idx_entry a = (struct pack_idx_entry **)_a;
	15	struct pack_idx_entry b = (struct pack_idx_entry **)_b;
	16	return hashcmp(a->sha1, b->sha1);
	17	}
	18
3c9fc074 JH	19	static int cmp_uint32(const void a_, const void b_)
	20	{
	21	uint32_t a = ((uint32_t )a_);
	22	uint32_t b = ((uint32_t )b_);
	23
	24	return (a < b) ? -1 : (a != b);
	25	}
	26
fb956c1f JH	27	static int need_large_offset(off_t offset, const struct pack_idx_option *opts)
fb956c1f JH	28	{
3c9fc074 JH	29	uint32_t ofsval;
	30
	31	if ((offset >> 31) \|\| (opts->off32_limit < offset))
	32	return 1;
	33	if (!opts->anomaly_nr)
	34	return 0;
	35	ofsval = offset;
	36	return !!bsearch(&ofsval, opts->anomaly, opts->anomaly_nr,
	37	sizeof(ofsval), cmp_uint32);
fb956c1f JH	38	}
fb956c1f JH	39
aa7e44bf GB	40	/*
	41	* On entry *sha1 contains the pack content SHA1 hash, on exit it is
	42	* the SHA1 hash of sorted object names. The objects array passed in
	43	* will be sorted by SHA1 on exit.
	44	*/
3bb72562	45	const char write_idx_file(const char index_name, struct pack_idx_entry **objects,
ebcfb379 JH	46	int nr_objects, const struct pack_idx_option *opts,
ebcfb379 JH	47	unsigned char *sha1)
aa7e44bf GB	48	{
	49	struct sha1file *f;
	50	struct pack_idx_entry sorted_by_sha, list, **last;
	51	off_t last_obj_offset = 0;
	52	uint32_t array[256];
	53	int i, fd;
9126f009	54	git_SHA_CTX ctx;
aa7e44bf GB	55	uint32_t index_version;
	56
	57	if (nr_objects) {
	58	sorted_by_sha = objects;
	59	list = sorted_by_sha;
	60	last = sorted_by_sha + nr_objects;
	61	for (i = 0; i < nr_objects; ++i) {
	62	if (objects[i]->offset > last_obj_offset)
	63	last_obj_offset = objects[i]->offset;
	64	}
	65	qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
	66	sha1_compare);
	67	}
	68	else
	69	sorted_by_sha = list = last = NULL;
	70
e337a04d JH	71	if (opts->flags & WRITE_IDX_VERIFY) {
	72	assert(index_name);
	73	f = sha1fd_check(index_name);
aa7e44bf	74	} else {
e337a04d JH	75	if (!index_name) {
	76	static char tmpfile[PATH_MAX];
	77	fd = odb_mkstemp(tmpfile, sizeof(tmpfile), "pack/tmp_idx_XXXXXX");
	78	index_name = xstrdup(tmpfile);
	79	} else {
	80	unlink(index_name);
	81	fd = open(index_name, O_CREAT\|O_EXCL\|O_WRONLY, 0600);
	82	}
	83	if (fd < 0)
	84	die_errno("unable to create '%s'", index_name);
	85	f = sha1fd(fd, index_name);
aa7e44bf	86	}
aa7e44bf GB	87
aa7e44bf GB	88	/* if last object's offset is >= 2^31 we should use index V2 */
fb956c1f	89	index_version = need_large_offset(last_obj_offset, opts) ? 2 : opts->version;
aa7e44bf GB	90
	91	/* index versions 2 and above need a header */
	92	if (index_version >= 2) {
	93	struct pack_idx_header hdr;
	94	hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
	95	hdr.idx_version = htonl(index_version);
	96	sha1write(f, &hdr, sizeof(hdr));
	97	}
	98
	99	/*
	100	* Write the first-level table (the list is sorted,
	101	* but we use a 256-entry lookup to be able to avoid
	102	* having to do eight extra binary search iterations).
	103	*/
	104	for (i = 0; i < 256; i++) {
	105	struct pack_idx_entry **next = list;
	106	while (next < last) {
	107	struct pack_idx_entry obj = next;
	108	if (obj->sha1[0] != i)
	109	break;
	110	next++;
	111	}
	112	array[i] = htonl(next - sorted_by_sha);
	113	list = next;
	114	}
	115	sha1write(f, array, 256 * 4);
	116
	117	/* compute the SHA1 hash of sorted object names. */
9126f009	118	git_SHA1_Init(&ctx);
aa7e44bf GB	119
	120	/*
	121	* Write the actual SHA1 entries..
	122	*/
	123	list = sorted_by_sha;
	124	for (i = 0; i < nr_objects; i++) {
	125	struct pack_idx_entry obj = list++;
	126	if (index_version < 2) {
	127	uint32_t offset = htonl(obj->offset);
	128	sha1write(f, &offset, 4);
	129	}
	130	sha1write(f, obj->sha1, 20);
9126f009	131	git_SHA1_Update(&ctx, obj->sha1, 20);
aa7e44bf GB	132	}
	133
	134	if (index_version >= 2) {
	135	unsigned int nr_large_offset = 0;
	136
	137	/* write the crc32 table */
	138	list = sorted_by_sha;
	139	for (i = 0; i < nr_objects; i++) {
	140	struct pack_idx_entry obj = list++;
	141	uint32_t crc32_val = htonl(obj->crc32);
	142	sha1write(f, &crc32_val, 4);
	143	}
	144
	145	/* write the 32-bit offset table */
	146	list = sorted_by_sha;
	147	for (i = 0; i < nr_objects; i++) {
	148	struct pack_idx_entry obj = list++;
fb956c1f JH	149	uint32_t offset;
	150
	151	offset = (need_large_offset(obj->offset, opts)
	152	? (0x80000000 \| nr_large_offset++)
	153	: obj->offset);
aa7e44bf GB	154	offset = htonl(offset);
	155	sha1write(f, &offset, 4);
	156	}
	157
	158	/* write the large offset table */
	159	list = sorted_by_sha;
	160	while (nr_large_offset) {
	161	struct pack_idx_entry obj = list++;
	162	uint64_t offset = obj->offset;
fb956c1f JH	163	uint32_t split[2];
	164
	165	if (!need_large_offset(offset, opts))
	166	continue;
	167	split[0] = htonl(offset >> 32);
	168	split[1] = htonl(offset & 0xffffffff);
	169	sha1write(f, split, 8);
	170	nr_large_offset--;
aa7e44bf GB	171	}
	172	}
	173
	174	sha1write(f, sha1, 20);
e337a04d JH	175	sha1close(f, NULL, ((opts->flags & WRITE_IDX_VERIFY)
e337a04d JH	176	? CSUM_CLOSE : CSUM_FSYNC));
9126f009	177	git_SHA1_Final(sha1, &ctx);
aa7e44bf GB	178	return index_name;
aa7e44bf GB	179	}
8b0eca7c	180
abeb40e5 NP	181	/*
	182	* Update pack header with object_count and compute new SHA1 for pack data
	183	* associated to pack_fd, and write that SHA1 at the end. That new SHA1
	184	* is also returned in new_pack_sha1.
	185	*
	186	* If partial_pack_sha1 is non null, then the SHA1 of the existing pack
	187	* (without the header update) is computed and validated against the
	188	* one provided in partial_pack_sha1. The validation is performed at
	189	* partial_pack_offset bytes in the pack file. The SHA1 of the remaining
	190	* data (i.e. from partial_pack_offset to the end) is then computed and
	191	* returned in partial_pack_sha1.
	192	*
	193	* Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
	194	* partial_pack_sha1 can refer to the same buffer if the caller is not
	195	* interested in the resulting SHA1 of pack data above partial_pack_offset.
	196	*/
8b0eca7c	197	void fixup_pack_header_footer(int pack_fd,
abeb40e5	198	unsigned char *new_pack_sha1,
8b0eca7c	199	const char *pack_name,
abeb40e5 NP	200	uint32_t object_count,
	201	unsigned char *partial_pack_sha1,
	202	off_t partial_pack_offset)
8b0eca7c	203	{
d35825da	204	int aligned_sz, buf_sz = 8 * 1024;
9126f009	205	git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
8b0eca7c DH	206	struct pack_header hdr;
	207	char *buf;
	208
9126f009 NP	209	git_SHA1_Init(&old_sha1_ctx);
9126f009 NP	210	git_SHA1_Init(&new_sha1_ctx);
abeb40e5	211
8b0eca7c	212	if (lseek(pack_fd, 0, SEEK_SET) != 0)
d824cbba	213	die_errno("Failed seeking to start of '%s'", pack_name);
8b0eca7c	214	if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
d824cbba	215	die_errno("Unable to reread header of '%s'", pack_name);
8b0eca7c	216	if (lseek(pack_fd, 0, SEEK_SET) != 0)
d824cbba	217	die_errno("Failed seeking to start of '%s'", pack_name);
9126f009	218	git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
8b0eca7c	219	hdr.hdr_entries = htonl(object_count);
9126f009	220	git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
8b0eca7c	221	write_or_die(pack_fd, &hdr, sizeof(hdr));
abeb40e5	222	partial_pack_offset -= sizeof(hdr);
8b0eca7c DH	223
8b0eca7c DH	224	buf = xmalloc(buf_sz);
d35825da	225	aligned_sz = buf_sz - sizeof(hdr);
8b0eca7c	226	for (;;) {
abeb40e5	227	ssize_t m, n;
d35825da NP	228	m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
d35825da NP	229	partial_pack_offset : aligned_sz;
abeb40e5	230	n = xread(pack_fd, buf, m);
8b0eca7c DH	231	if (!n)
	232	break;
	233	if (n < 0)
d824cbba	234	die_errno("Failed to checksum '%s'", pack_name);
9126f009	235	git_SHA1_Update(&new_sha1_ctx, buf, n);
abeb40e5	236
d35825da NP	237	aligned_sz -= n;
	238	if (!aligned_sz)
	239	aligned_sz = buf_sz;
	240
abeb40e5 NP	241	if (!partial_pack_sha1)
	242	continue;
	243
9126f009	244	git_SHA1_Update(&old_sha1_ctx, buf, n);
abeb40e5 NP	245	partial_pack_offset -= n;
	246	if (partial_pack_offset == 0) {
	247	unsigned char sha1[20];
9126f009	248	git_SHA1_Final(sha1, &old_sha1_ctx);
abeb40e5 NP	249	if (hashcmp(sha1, partial_pack_sha1) != 0)
	250	die("Unexpected checksum for %s "
	251	"(disk corruption?)", pack_name);
	252	/*
	253	* Now let's compute the SHA1 of the remainder of the
	254	* pack, which also means making partial_pack_offset
	255	* big enough not to matter anymore.
	256	*/
9126f009	257	git_SHA1_Init(&old_sha1_ctx);
abeb40e5 NP	258	partial_pack_offset = ~partial_pack_offset;
	259	partial_pack_offset -= MSB(partial_pack_offset, 1);
	260	}
8b0eca7c DH	261	}
	262	free(buf);
	263
abeb40e5	264	if (partial_pack_sha1)
9126f009 NP	265	git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
9126f009 NP	266	git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
abeb40e5	267	write_or_die(pack_fd, new_pack_sha1, 20);
0c68d386	268	fsync_or_die(pack_fd, pack_name);
8b0eca7c	269	}
106764e6 SP	270
	271	char *index_pack_lockfile(int ip_out)
	272	{
106764e6 SP	273	char packname[46];
	274
	275	/*
6e180cdc	276	* The first thing we expect from index-pack's output
106764e6 SP	277	* is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
	278	* %40s is the newly created pack SHA1 name. In the "keep"
	279	* case, we need it to remove the corresponding .keep file
	280	* later on. If we don't get that then tough luck with it.
	281	*/
c697ad14 HO	282	if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n' &&
c697ad14 HO	283	memcmp(packname, "keep\t", 5) == 0) {
106764e6 SP	284	char path[PATH_MAX];
	285	packname[45] = 0;
	286	snprintf(path, sizeof(path), "%s/pack/pack-%s.keep",
	287	get_object_directory(), packname + 5);
	288	return xstrdup(path);
	289	}
	290	return NULL;
	291	}
f965c525 NP	292
	293	/*
	294	* The per-object header is a pretty dense thing, which is
	295	* - first byte: low four bits are "size", then three bits of "type",
	296	* and the high bit is "size continues".
	297	* - each byte afterwards: low seven bits are size continuation,
	298	* with the high bit being "size continues"
	299	*/
	300	int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr)
	301	{
	302	int n = 1;
	303	unsigned char c;
	304
	305	if (type < OBJ_COMMIT \|\| type > OBJ_REF_DELTA)
	306	die("bad type %d", type);
	307
	308	c = (type << 4) \| (size & 15);
	309	size >>= 4;
	310	while (size) {
	311	*hdr++ = c \| 0x80;
	312	c = size & 0x7f;
	313	size >>= 7;
	314	n++;
	315	}
	316	*hdr = c;
	317	return n;
	318	}