builtin/unpack-objects.c - jrn/git - Git at Google

 #include "builtin.h"
 #include "cache.h"
 #include "bulk-checkin.h"
 #include "config.h"
 #include "object-store.h"
 #include "object.h"
 #include "delta.h"
 #include "pack.h"
 #include "blob.h"
 #include "commit.h"
 #include "tag.h"
 #include "tree.h"
 #include "tree-walk.h"
 #include "progress.h"
 #include "decorate.h"
 #include "fsck.h"

 static int dry_run, quiet, recover, has_errors, strict;
 static const char unpack_usage[] = "git unpack-objects [-n] [-q] [-r] [--strict]";

 /* We always read in 4kB chunks. */
 static unsigned char buffer[4096];
 static unsigned int offset, len;
 static off_t consumed_bytes;
 static off_t max_input_size;
 static git_hash_ctx ctx;
 static struct fsck_options fsck_options = FSCK_OPTIONS_STRICT;
 static struct progress *progress;

 /*
  * When running under --strict mode, objects whose reachability are
  * suspect are kept in core without getting written in the object
  * store.
  */
 struct obj_buffer {
 	char *buffer;
 	unsigned long size;
 };

 static struct decoration obj_decorate;

 static struct obj_buffer *lookup_object_buffer(struct object *base)
 {
 	return lookup_decoration(&obj_decorate, base);
 }

 static void add_object_buffer(struct object *object, char *buffer, unsigned long size)
 {
 	struct obj_buffer *obj;
 	CALLOC_ARRAY(obj, 1);
 	obj->buffer = buffer;
 	obj->size = size;
 	if (add_decoration(&obj_decorate, object, obj))
 		die("object %s tried to add buffer twice!", oid_to_hex(&object->oid));
 }

 /*
  * Make sure at least "min" bytes are available in the buffer, and
  * return the pointer to the buffer.
  */
 static void *fill(int min)
 {
 	if (min <= len)
 		return buffer + offset;
 	if (min > sizeof(buffer))
 		die("cannot fill %d bytes", min);
 	if (offset) {
 		the_hash_algo->update_fn(&ctx, buffer, offset);
 		memmove(buffer, buffer + offset, len);
 		offset = 0;
 	}
 	do {
 		ssize_t ret = xread(0, buffer + len, sizeof(buffer) - len);
 		if (ret <= 0) {
 			if (!ret)
 				die("early EOF");
 			die_errno("read error on input");
 		}
 		len += ret;
 	} while (len < min);
 	return buffer;
 }

 static void use(int bytes)
 {
 	if (bytes > len)
 		die("used more bytes than were available");
 	len -= bytes;
 	offset += bytes;

 	/* make sure off_t is sufficiently large not to wrap */
 	if (signed_add_overflows(consumed_bytes, bytes))
 		die("pack too large for current definition of off_t");
 	consumed_bytes += bytes;
 	if (max_input_size && consumed_bytes > max_input_size)
 		die(_("pack exceeds maximum allowed size"));
 	display_throughput(progress, consumed_bytes);
 }

 /*
  * Decompress zstream from the standard input into a newly
  * allocated buffer of specified size and return the buffer.
  * The caller is responsible to free the returned buffer.
  *
  * But for dry_run mode, "get_data()" is only used to check the
  * integrity of data, and the returned buffer is not used at all.
  * Therefore, in dry_run mode, "get_data()" will release the small
  * allocated buffer which is reused to hold temporary zstream output
  * and return NULL instead of returning garbage data.
  */
 static void *get_data(unsigned long size)
 {
 	git_zstream stream;
 	unsigned long bufsize = dry_run && size > 8192 ? 8192 : size;
 	void *buf = xmallocz(bufsize);

 	memset(&stream, 0, sizeof(stream));

 	stream.next_out = buf;
 	stream.avail_out = bufsize;
 	stream.next_in = fill(1);
 	stream.avail_in = len;
 	git_inflate_init(&stream);

 	for (;;) {
 		int ret = git_inflate(&stream, 0);
 		use(len - stream.avail_in);
 		if (stream.total_out == size && ret == Z_STREAM_END)
 			break;
 		if (ret != Z_OK) {
 			error("inflate returned %d", ret);
 			FREE_AND_NULL(buf);
 			if (!recover)
 				exit(1);
 			has_errors = 1;
 			break;
 		}
 		stream.next_in = fill(1);
 		stream.avail_in = len;
 		if (dry_run) {
 			/* reuse the buffer in dry_run mode */
 			stream.next_out = buf;
 			stream.avail_out = bufsize > size - stream.total_out ?
 						   size - stream.total_out :
 						   bufsize;
 		}
 	}
 	git_inflate_end(&stream);
 	if (dry_run)
 		FREE_AND_NULL(buf);
 	return buf;
 }

 struct delta_info {
 	struct object_id base_oid;
 	unsigned nr;
 	off_t base_offset;
 	unsigned long size;
 	void *delta;
 	struct delta_info *next;
 };

 static struct delta_info *delta_list;

 static void add_delta_to_list(unsigned nr, const struct object_id *base_oid,
 			      off_t base_offset,
 			      void *delta, unsigned long size)
 {
 	struct delta_info *info = xmalloc(sizeof(*info));

 	oidcpy(&info->base_oid, base_oid);
 	info->base_offset = base_offset;
 	info->size = size;
 	info->delta = delta;
 	info->nr = nr;
 	info->next = delta_list;
 	delta_list = info;
 }

 struct obj_info {
 	off_t offset;
 	struct object_id oid;
 	struct object *obj;
 };

 /* Remember to update object flag allocation in object.h */
 #define FLAG_OPEN (1u<<20)
 #define FLAG_WRITTEN (1u<<21)

 static struct obj_info *obj_list;
 static unsigned nr_objects;

 /*
  * Called only from check_object() after it verified this object
  * is Ok.
  */
 static void write_cached_object(struct object *obj, struct obj_buffer *obj_buf)
 {
 	struct object_id oid;

 	if (write_object_file(obj_buf->buffer, obj_buf->size,
 			      obj->type, &oid) < 0)
 		die("failed to write object %s", oid_to_hex(&obj->oid));
 	obj->flags |= FLAG_WRITTEN;
 }

 /*
  * At the very end of the processing, write_rest() scans the objects
  * that have reachability requirements and calls this function.
  * Verify its reachability and validity recursively and write it out.
  */
 static int check_object(struct object *obj, enum object_type type,
 			void *data, struct fsck_options *options)
 {
 	struct obj_buffer *obj_buf;

 	if (!obj)
 		return 1;

 	if (obj->flags & FLAG_WRITTEN)
 		return 0;

 	if (type != OBJ_ANY && obj->type != type)
 		die("object type mismatch");

 	if (!(obj->flags & FLAG_OPEN)) {
 		unsigned long size;
 		int type = oid_object_info(the_repository, &obj->oid, &size);
 		if (type != obj->type || type <= 0)
 			die("object of unexpected type");
 		obj->flags |= FLAG_WRITTEN;
 		return 0;
 	}

 	obj_buf = lookup_object_buffer(obj);
 	if (!obj_buf)
 		die("Whoops! Cannot find object '%s'", oid_to_hex(&obj->oid));
 	if (fsck_object(obj, obj_buf->buffer, obj_buf->size, &fsck_options))
 		die("fsck error in packed object");
 	fsck_options.walk = check_object;
 	if (fsck_walk(obj, NULL, &fsck_options))
 		die("Error on reachable objects of %s", oid_to_hex(&obj->oid));
 	write_cached_object(obj, obj_buf);
 	return 0;
 }

 static void write_rest(void)
 {
 	unsigned i;
 	for (i = 0; i < nr_objects; i++) {
 		if (obj_list[i].obj)
 			check_object(obj_list[i].obj, OBJ_ANY, NULL, NULL);
 	}
 }

 static void added_object(unsigned nr, enum object_type type,
 			 void *data, unsigned long size);

 /*
  * Write out nr-th object from the list, now we know the contents
  * of it.  Under --strict, this buffers structured objects in-core,
  * to be checked at the end.
  */
 static void write_object(unsigned nr, enum object_type type,
 			 void *buf, unsigned long size)
 {
 	if (!strict) {
 		if (write_object_file(buf, size, type,
 				      &obj_list[nr].oid) < 0)
 			die("failed to write object");
 		added_object(nr, type, buf, size);
 		free(buf);
 		obj_list[nr].obj = NULL;
 	} else if (type == OBJ_BLOB) {
 		struct blob *blob;
 		if (write_object_file(buf, size, type,
 				      &obj_list[nr].oid) < 0)
 			die("failed to write object");
 		added_object(nr, type, buf, size);
 		free(buf);

 		blob = lookup_blob(the_repository, &obj_list[nr].oid);
 		if (blob)
 			blob->object.flags |= FLAG_WRITTEN;
 		else
 			die("invalid blob object");
 		obj_list[nr].obj = NULL;
 	} else {
 		struct object *obj;
 		int eaten;
 		hash_object_file(the_hash_algo, buf, size, type,
 				 &obj_list[nr].oid);
 		added_object(nr, type, buf, size);
 		obj = parse_object_buffer(the_repository, &obj_list[nr].oid,
 					  type, size, buf,
 					  &eaten);
 		if (!obj)
 			die("invalid %s", type_name(type));
 		add_object_buffer(obj, buf, size);
 		obj->flags |= FLAG_OPEN;
 		obj_list[nr].obj = obj;
 	}
 }

 static void resolve_delta(unsigned nr, enum object_type type,
 			  void *base, unsigned long base_size,
 			  void *delta, unsigned long delta_size)
 {
 	void *result;
 	unsigned long result_size;

 	result = patch_delta(base, base_size,
 			     delta, delta_size,
 			     &result_size);
 	if (!result)
 		die("failed to apply delta");
 	free(delta);
 	write_object(nr, type, result, result_size);
 }

 /*
  * We now know the contents of an object (which is nr-th in the pack);
  * resolve all the deltified objects that are based on it.
  */
 static void added_object(unsigned nr, enum object_type type,
 			 void *data, unsigned long size)
 {
 	struct delta_info **p = &delta_list;
 	struct delta_info *info;

 	while ((info = *p) != NULL) {
 		if (oideq(&info->base_oid, &obj_list[nr].oid) ||
 		    info->base_offset == obj_list[nr].offset) {
 			*p = info->next;
 			p = &delta_list;
 			resolve_delta(info->nr, type, data, size,
 				      info->delta, info->size);
 			free(info);
 			continue;
 		}
 		p = &info->next;
 	}
 }

 static void unpack_non_delta_entry(enum object_type type, unsigned long size,
 				   unsigned nr)
 {
 	void *buf = get_data(size);

 	if (buf)
 		write_object(nr, type, buf, size);
 }

 struct input_zstream_data {
 	git_zstream *zstream;
 	unsigned char buf[8192];
 	int status;
 };

 static const void *feed_input_zstream(struct input_stream *in_stream,
 				      unsigned long *readlen)
 {
 	struct input_zstream_data *data = in_stream->data;
 	git_zstream *zstream = data->zstream;
 	void *in = fill(1);

 	if (in_stream->is_finished) {
 		*readlen = 0;
 		return NULL;
 	}

 	zstream->next_out = data->buf;
 	zstream->avail_out = sizeof(data->buf);
 	zstream->next_in = in;
 	zstream->avail_in = len;

 	data->status = git_inflate(zstream, 0);

 	in_stream->is_finished = data->status != Z_OK;
 	use(len - zstream->avail_in);
 	*readlen = sizeof(data->buf) - zstream->avail_out;

 	return data->buf;
 }

 static void stream_blob(unsigned long size, unsigned nr)
 {
 	git_zstream zstream = { 0 };
 	struct input_zstream_data data = { 0 };
 	struct input_stream in_stream = {
 		.read = feed_input_zstream,
 		.data = &data,
 	};
 	struct obj_info *info = &obj_list[nr];

 	data.zstream = &zstream;
 	git_inflate_init(&zstream);

 	if (stream_loose_object(&in_stream, size, &info->oid))
 		die(_("failed to write object in stream"));

 	if (data.status != Z_STREAM_END)
 		die(_("inflate returned (%d)"), data.status);
 	git_inflate_end(&zstream);

 	if (strict) {
 		struct blob *blob = lookup_blob(the_repository, &info->oid);

 		if (!blob)
 			die(_("invalid blob object from stream"));
 		blob->object.flags |= FLAG_WRITTEN;
 	}
 	info->obj = NULL;
 }

 static int resolve_against_held(unsigned nr, const struct object_id *base,
 				void *delta_data, unsigned long delta_size)
 {
 	struct object *obj;
 	struct obj_buffer *obj_buffer;
 	obj = lookup_object(the_repository, base);
 	if (!obj)
 		return 0;
 	obj_buffer = lookup_object_buffer(obj);
 	if (!obj_buffer)
 		return 0;
 	resolve_delta(nr, obj->type, obj_buffer->buffer,
 		      obj_buffer->size, delta_data, delta_size);
 	return 1;
 }

 static void unpack_delta_entry(enum object_type type, unsigned long delta_size,
 			       unsigned nr)
 {
 	void *delta_data, *base;
 	unsigned long base_size;
 	struct object_id base_oid;

 	if (type == OBJ_REF_DELTA) {
 		oidread(&base_oid, fill(the_hash_algo->rawsz));
 		use(the_hash_algo->rawsz);
 		delta_data = get_data(delta_size);
 		if (!delta_data)
 			return;
 		if (has_object_file(&base_oid))
 			; /* Ok we have this one */
 		else if (resolve_against_held(nr, &base_oid,
 					      delta_data, delta_size))
 			return; /* we are done */
 		else {
 			/* cannot resolve yet --- queue it */
 			oidclr(&obj_list[nr].oid);
 			add_delta_to_list(nr, &base_oid, 0, delta_data, delta_size);
 			return;
 		}
 	} else {
 		unsigned base_found = 0;
 		unsigned char *pack, c;
 		off_t base_offset;
 		unsigned lo, mid, hi;

 		pack = fill(1);
 		c = *pack;
 		use(1);
 		base_offset = c & 127;
 		while (c & 128) {
 			base_offset += 1;
 			if (!base_offset || MSB(base_offset, 7))
 				die("offset value overflow for delta base object");
 			pack = fill(1);
 			c = *pack;
 			use(1);
 			base_offset = (base_offset << 7) + (c & 127);
 		}
 		base_offset = obj_list[nr].offset - base_offset;
 		if (base_offset <= 0 || base_offset >= obj_list[nr].offset)
 			die("offset value out of bound for delta base object");

 		delta_data = get_data(delta_size);
 		if (!delta_data)
 			return;
 		lo = 0;
 		hi = nr;
 		while (lo < hi) {
 			mid = lo + (hi - lo) / 2;
 			if (base_offset < obj_list[mid].offset) {
 				hi = mid;
 			} else if (base_offset > obj_list[mid].offset) {
 				lo = mid + 1;
 			} else {
 				oidcpy(&base_oid, &obj_list[mid].oid);
 				base_found = !is_null_oid(&base_oid);
 				break;
 			}
 		}
 		if (!base_found) {
 			/*
 			 * The delta base object is itself a delta that
 			 * has not been resolved yet.
 			 */
 			oidclr(&obj_list[nr].oid);
 			add_delta_to_list(nr, null_oid(), base_offset,
 					  delta_data, delta_size);
 			return;
 		}
 	}

 	if (resolve_against_held(nr, &base_oid, delta_data, delta_size))
 		return;

 	base = read_object_file(&base_oid, &type, &base_size);
 	if (!base) {
 		error("failed to read delta-pack base object %s",
 		      oid_to_hex(&base_oid));
 		if (!recover)
 			exit(1);
 		has_errors = 1;
 		return;
 	}
 	resolve_delta(nr, type, base, base_size, delta_data, delta_size);
 	free(base);
 }

 static void unpack_one(unsigned nr)
 {
 	unsigned shift;
 	unsigned char *pack;
 	unsigned long size, c;
 	enum object_type type;

 	obj_list[nr].offset = consumed_bytes;

 	pack = fill(1);
 	c = *pack;
 	use(1);
 	type = (c >> 4) & 7;
 	size = (c & 15);
 	shift = 4;
 	while (c & 0x80) {
 		pack = fill(1);
 		c = *pack;
 		use(1);
 		size += (c & 0x7f) << shift;
 		shift += 7;
 	}

 	switch (type) {
 	case OBJ_BLOB:
 		if (!dry_run && size > big_file_threshold) {
 			stream_blob(size, nr);
 			return;
 		}
 		/* fallthrough */
 	case OBJ_COMMIT:
 	case OBJ_TREE:
 	case OBJ_TAG:
 		unpack_non_delta_entry(type, size, nr);
 		return;
 	case OBJ_REF_DELTA:
 	case OBJ_OFS_DELTA:
 		unpack_delta_entry(type, size, nr);
 		return;
 	default:
 		error("bad object type %d", type);
 		has_errors = 1;
 		if (recover)
 			return;
 		exit(1);
 	}
 }

 static void unpack_all(void)
 {
 	int i;
 	struct pack_header *hdr = fill(sizeof(struct pack_header));

 	nr_objects = ntohl(hdr->hdr_entries);

 	if (ntohl(hdr->hdr_signature) != PACK_SIGNATURE)
 		die("bad pack file");
 	if (!pack_version_ok(hdr->hdr_version))
 		die("unknown pack file version %"PRIu32,
 			ntohl(hdr->hdr_version));
 	use(sizeof(struct pack_header));

 	if (!quiet)
 		progress = start_progress(_("Unpacking objects"), nr_objects);
 	CALLOC_ARRAY(obj_list, nr_objects);
 	begin_odb_transaction();
 	for (i = 0; i < nr_objects; i++) {
 		unpack_one(i);
 		display_progress(progress, i + 1);
 	}
 	end_odb_transaction();
 	stop_progress(&progress);

 	if (delta_list)
 		die("unresolved deltas left after unpacking");
 }

 int cmd_unpack_objects(int argc, const char **argv, const char *prefix)
 {
 	int i;
 	struct object_id oid;

 	read_replace_refs = 0;

 	git_config(git_default_config, NULL);

 	quiet = !isatty(2);

 	for (i = 1 ; i < argc; i++) {
 		const char *arg = argv[i];

 		if (*arg == '-') {
 			if (!strcmp(arg, "-n")) {
 				dry_run = 1;
 				continue;
 			}
 			if (!strcmp(arg, "-q")) {
 				quiet = 1;
 				continue;
 			}
 			if (!strcmp(arg, "-r")) {
 				recover = 1;
 				continue;
 			}
 			if (!strcmp(arg, "--strict")) {
 				strict = 1;
 				continue;
 			}
 			if (skip_prefix(arg, "--strict=", &arg)) {
 				strict = 1;
 				fsck_set_msg_types(&fsck_options, arg);
 				continue;
 			}
 			if (starts_with(arg, "--pack_header=")) {
 				struct pack_header *hdr;
 				char *c;

 				hdr = (struct pack_header *)buffer;
 				hdr->hdr_signature = htonl(PACK_SIGNATURE);
 				hdr->hdr_version = htonl(strtoul(arg + 14, &c, 10));
 				if (*c != ',')
 					die("bad %s", arg);
 				hdr->hdr_entries = htonl(strtoul(c + 1, &c, 10));
 				if (*c)
 					die("bad %s", arg);
 				len = sizeof(*hdr);
 				continue;
 			}
 			if (skip_prefix(arg, "--max-input-size=", &arg)) {
 				max_input_size = strtoumax(arg, NULL, 10);
 				continue;
 			}
 			usage(unpack_usage);
 		}

 		/* We don't take any non-flag arguments now.. Maybe some day */
 		usage(unpack_usage);
 	}
 	the_hash_algo->init_fn(&ctx);
 	unpack_all();
 	the_hash_algo->update_fn(&ctx, buffer, offset);
 	the_hash_algo->final_oid_fn(&oid, &ctx);
 	if (strict) {
 		write_rest();
 		if (fsck_finish(&fsck_options))
 			die(_("fsck error in pack objects"));
 	}
 	if (!hasheq(fill(the_hash_algo->rawsz), oid.hash))
 		die("final sha1 did not match");
 	use(the_hash_algo->rawsz);

 	/* Write the last part of the buffer to stdout */
 	while (len) {
 		int ret = xwrite(1, buffer + offset, len);
 		if (ret <= 0)
 			break;
 		len -= ret;
 		offset += ret;
 	}

 	/* All done */
 	return has_errors;
 }
	#include "builtin.h"
	#include "cache.h"
	#include "bulk-checkin.h"
	#include "config.h"
	#include "object-store.h"
	#include "object.h"
	#include "delta.h"
	#include "pack.h"
	#include "blob.h"
	#include "commit.h"
	#include "tag.h"
	#include "tree.h"
	#include "tree-walk.h"
	#include "progress.h"
	#include "decorate.h"
	#include "fsck.h"

	static int dry_run, quiet, recover, has_errors, strict;
	static const char unpack_usage[] = "git unpack-objects [-n] [-q] [-r] [--strict]";

	/* We always read in 4kB chunks. */
	static unsigned char buffer[4096];
	static unsigned int offset, len;
	static off_t consumed_bytes;
	static off_t max_input_size;
	static git_hash_ctx ctx;
	static struct fsck_options fsck_options = FSCK_OPTIONS_STRICT;
	static struct progress *progress;

	/*
	* When running under --strict mode, objects whose reachability are
	* suspect are kept in core without getting written in the object
	* store.
	*/
	struct obj_buffer {
	char *buffer;
	unsigned long size;
	};

	static struct decoration obj_decorate;

	static struct obj_buffer lookup_object_buffer(struct object base)
	{
	return lookup_decoration(&obj_decorate, base);
	}

	static void add_object_buffer(struct object object, char buffer, unsigned long size)
	{
	struct obj_buffer *obj;
	CALLOC_ARRAY(obj, 1);
	obj->buffer = buffer;
	obj->size = size;
	if (add_decoration(&obj_decorate, object, obj))
	die("object %s tried to add buffer twice!", oid_to_hex(&object->oid));
	}

	/*
	* Make sure at least "min" bytes are available in the buffer, and
	* return the pointer to the buffer.
	*/
	static void *fill(int min)
	{
	if (min <= len)
	return buffer + offset;
	if (min > sizeof(buffer))
	die("cannot fill %d bytes", min);
	if (offset) {
	the_hash_algo->update_fn(&ctx, buffer, offset);
	memmove(buffer, buffer + offset, len);
	offset = 0;
	}
	do {
	ssize_t ret = xread(0, buffer + len, sizeof(buffer) - len);
	if (ret <= 0) {
	if (!ret)
	die("early EOF");
	die_errno("read error on input");
	}
	len += ret;
	} while (len < min);
	return buffer;
	}

	static void use(int bytes)
	{
	if (bytes > len)
	die("used more bytes than were available");
	len -= bytes;
	offset += bytes;

	/* make sure off_t is sufficiently large not to wrap */
	if (signed_add_overflows(consumed_bytes, bytes))
	die("pack too large for current definition of off_t");
	consumed_bytes += bytes;
	if (max_input_size && consumed_bytes > max_input_size)
	die(_("pack exceeds maximum allowed size"));
	display_throughput(progress, consumed_bytes);
	}

	/*
	* Decompress zstream from the standard input into a newly
	* allocated buffer of specified size and return the buffer.
	* The caller is responsible to free the returned buffer.
	*
	* But for dry_run mode, "get_data()" is only used to check the
	* integrity of data, and the returned buffer is not used at all.
	* Therefore, in dry_run mode, "get_data()" will release the small
	* allocated buffer which is reused to hold temporary zstream output
	* and return NULL instead of returning garbage data.
	*/
	static void *get_data(unsigned long size)
	{
	git_zstream stream;
	unsigned long bufsize = dry_run && size > 8192 ? 8192 : size;
	void *buf = xmallocz(bufsize);

	memset(&stream, 0, sizeof(stream));

	stream.next_out = buf;
	stream.avail_out = bufsize;
	stream.next_in = fill(1);
	stream.avail_in = len;
	git_inflate_init(&stream);

	for (;;) {
	int ret = git_inflate(&stream, 0);
	use(len - stream.avail_in);
	if (stream.total_out == size && ret == Z_STREAM_END)
	break;
	if (ret != Z_OK) {
	error("inflate returned %d", ret);
	FREE_AND_NULL(buf);
	if (!recover)
	exit(1);
	has_errors = 1;
	break;
	}
	stream.next_in = fill(1);
	stream.avail_in = len;
	if (dry_run) {
	/* reuse the buffer in dry_run mode */
	stream.next_out = buf;
	stream.avail_out = bufsize > size - stream.total_out ?
	size - stream.total_out :
	bufsize;
	}
	}
	git_inflate_end(&stream);
	if (dry_run)
	FREE_AND_NULL(buf);
	return buf;
	}

	struct delta_info {
	struct object_id base_oid;
	unsigned nr;
	off_t base_offset;
	unsigned long size;
	void *delta;
	struct delta_info *next;
	};

	static struct delta_info *delta_list;

	static void add_delta_to_list(unsigned nr, const struct object_id *base_oid,
	off_t base_offset,
	void *delta, unsigned long size)
	{
	struct delta_info info = xmalloc(sizeof(info));

	oidcpy(&info->base_oid, base_oid);
	info->base_offset = base_offset;
	info->size = size;
	info->delta = delta;
	info->nr = nr;
	info->next = delta_list;
	delta_list = info;
	}

	struct obj_info {
	off_t offset;
	struct object_id oid;
	struct object *obj;
	};

	/* Remember to update object flag allocation in object.h */
	#define FLAG_OPEN (1u<<20)
	#define FLAG_WRITTEN (1u<<21)

	static struct obj_info *obj_list;
	static unsigned nr_objects;

	/*
	* Called only from check_object() after it verified this object
	* is Ok.
	*/
	static void write_cached_object(struct object obj, struct obj_buffer obj_buf)
	{
	struct object_id oid;

	if (write_object_file(obj_buf->buffer, obj_buf->size,
	obj->type, &oid) < 0)
	die("failed to write object %s", oid_to_hex(&obj->oid));
	obj->flags \|= FLAG_WRITTEN;
	}

	/*
	* At the very end of the processing, write_rest() scans the objects
	* that have reachability requirements and calls this function.
	* Verify its reachability and validity recursively and write it out.
	*/
	static int check_object(struct object *obj, enum object_type type,
	void data, struct fsck_options options)
	{
	struct obj_buffer *obj_buf;

	if (!obj)
	return 1;

	if (obj->flags & FLAG_WRITTEN)
	return 0;

	if (type != OBJ_ANY && obj->type != type)
	die("object type mismatch");

	if (!(obj->flags & FLAG_OPEN)) {
	unsigned long size;
	int type = oid_object_info(the_repository, &obj->oid, &size);
	if (type != obj->type \|\| type <= 0)
	die("object of unexpected type");
	obj->flags \|= FLAG_WRITTEN;
	return 0;
	}

	obj_buf = lookup_object_buffer(obj);
	if (!obj_buf)
	die("Whoops! Cannot find object '%s'", oid_to_hex(&obj->oid));
	if (fsck_object(obj, obj_buf->buffer, obj_buf->size, &fsck_options))
	die("fsck error in packed object");
	fsck_options.walk = check_object;
	if (fsck_walk(obj, NULL, &fsck_options))
	die("Error on reachable objects of %s", oid_to_hex(&obj->oid));
	write_cached_object(obj, obj_buf);
	return 0;
	}

	static void write_rest(void)
	{
	unsigned i;
	for (i = 0; i < nr_objects; i++) {
	if (obj_list[i].obj)
	check_object(obj_list[i].obj, OBJ_ANY, NULL, NULL);
	}
	}

	static void added_object(unsigned nr, enum object_type type,
	void *data, unsigned long size);

	/*
	* Write out nr-th object from the list, now we know the contents
	* of it. Under --strict, this buffers structured objects in-core,
	* to be checked at the end.
	*/
	static void write_object(unsigned nr, enum object_type type,
	void *buf, unsigned long size)
	{
	if (!strict) {
	if (write_object_file(buf, size, type,
	&obj_list[nr].oid) < 0)
	die("failed to write object");
	added_object(nr, type, buf, size);
	free(buf);
	obj_list[nr].obj = NULL;
	} else if (type == OBJ_BLOB) {
	struct blob *blob;
	if (write_object_file(buf, size, type,
	&obj_list[nr].oid) < 0)
	die("failed to write object");
	added_object(nr, type, buf, size);
	free(buf);

	blob = lookup_blob(the_repository, &obj_list[nr].oid);
	if (blob)
	blob->object.flags \|= FLAG_WRITTEN;
	else
	die("invalid blob object");
	obj_list[nr].obj = NULL;
	} else {
	struct object *obj;
	int eaten;
	hash_object_file(the_hash_algo, buf, size, type,
	&obj_list[nr].oid);
	added_object(nr, type, buf, size);
	obj = parse_object_buffer(the_repository, &obj_list[nr].oid,
	type, size, buf,
	&eaten);
	if (!obj)
	die("invalid %s", type_name(type));
	add_object_buffer(obj, buf, size);
	obj->flags \|= FLAG_OPEN;
	obj_list[nr].obj = obj;
	}
	}

	static void resolve_delta(unsigned nr, enum object_type type,
	void *base, unsigned long base_size,
	void *delta, unsigned long delta_size)
	{
	void *result;
	unsigned long result_size;

	result = patch_delta(base, base_size,
	delta, delta_size,
	&result_size);
	if (!result)
	die("failed to apply delta");
	free(delta);
	write_object(nr, type, result, result_size);
	}

	/*
	* We now know the contents of an object (which is nr-th in the pack);
	* resolve all the deltified objects that are based on it.
	*/
	static void added_object(unsigned nr, enum object_type type,
	void *data, unsigned long size)
	{
	struct delta_info **p = &delta_list;
	struct delta_info *info;

	while ((info = *p) != NULL) {
	if (oideq(&info->base_oid, &obj_list[nr].oid) \|\|
	info->base_offset == obj_list[nr].offset) {
	*p = info->next;
	p = &delta_list;
	resolve_delta(info->nr, type, data, size,
	info->delta, info->size);
	free(info);
	continue;
	}
	p = &info->next;
	}
	}

	static void unpack_non_delta_entry(enum object_type type, unsigned long size,
	unsigned nr)
	{
	void *buf = get_data(size);

	if (buf)
	write_object(nr, type, buf, size);
	}

	struct input_zstream_data {
	git_zstream *zstream;
	unsigned char buf[8192];
	int status;
	};

	static const void feed_input_zstream(struct input_stream in_stream,
	unsigned long *readlen)
	{
	struct input_zstream_data *data = in_stream->data;
	git_zstream *zstream = data->zstream;
	void *in = fill(1);

	if (in_stream->is_finished) {
	*readlen = 0;
	return NULL;
	}

	zstream->next_out = data->buf;
	zstream->avail_out = sizeof(data->buf);
	zstream->next_in = in;
	zstream->avail_in = len;

	data->status = git_inflate(zstream, 0);

	in_stream->is_finished = data->status != Z_OK;
	use(len - zstream->avail_in);
	*readlen = sizeof(data->buf) - zstream->avail_out;

	return data->buf;
	}

	static void stream_blob(unsigned long size, unsigned nr)
	{
	git_zstream zstream = { 0 };
	struct input_zstream_data data = { 0 };
	struct input_stream in_stream = {
	.read = feed_input_zstream,
	.data = &data,
	};
	struct obj_info *info = &obj_list[nr];

	data.zstream = &zstream;
	git_inflate_init(&zstream);

	if (stream_loose_object(&in_stream, size, &info->oid))
	die(_("failed to write object in stream"));

	if (data.status != Z_STREAM_END)
	die(_("inflate returned (%d)"), data.status);
	git_inflate_end(&zstream);

	if (strict) {
	struct blob *blob = lookup_blob(the_repository, &info->oid);

	if (!blob)
	die(_("invalid blob object from stream"));
	blob->object.flags \|= FLAG_WRITTEN;
	}
	info->obj = NULL;
	}

	static int resolve_against_held(unsigned nr, const struct object_id *base,
	void *delta_data, unsigned long delta_size)
	{
	struct object *obj;
	struct obj_buffer *obj_buffer;
	obj = lookup_object(the_repository, base);
	if (!obj)
	return 0;
	obj_buffer = lookup_object_buffer(obj);
	if (!obj_buffer)
	return 0;
	resolve_delta(nr, obj->type, obj_buffer->buffer,
	obj_buffer->size, delta_data, delta_size);
	return 1;
	}

	static void unpack_delta_entry(enum object_type type, unsigned long delta_size,
	unsigned nr)
	{
	void delta_data, base;
	unsigned long base_size;
	struct object_id base_oid;

	if (type == OBJ_REF_DELTA) {
	oidread(&base_oid, fill(the_hash_algo->rawsz));
	use(the_hash_algo->rawsz);
	delta_data = get_data(delta_size);
	if (!delta_data)
	return;
	if (has_object_file(&base_oid))
	; /* Ok we have this one */
	else if (resolve_against_held(nr, &base_oid,
	delta_data, delta_size))
	return; /* we are done */
	else {
	/* cannot resolve yet --- queue it */
	oidclr(&obj_list[nr].oid);
	add_delta_to_list(nr, &base_oid, 0, delta_data, delta_size);
	return;
	}
	} else {
	unsigned base_found = 0;
	unsigned char *pack, c;
	off_t base_offset;
	unsigned lo, mid, hi;

	pack = fill(1);
	c = *pack;
	use(1);
	base_offset = c & 127;
	while (c & 128) {
	base_offset += 1;
	if (!base_offset \|\| MSB(base_offset, 7))
	die("offset value overflow for delta base object");
	pack = fill(1);
	c = *pack;
	use(1);
	base_offset = (base_offset << 7) + (c & 127);
	}
	base_offset = obj_list[nr].offset - base_offset;
	if (base_offset <= 0 \|\| base_offset >= obj_list[nr].offset)
	die("offset value out of bound for delta base object");

	delta_data = get_data(delta_size);
	if (!delta_data)
	return;
	lo = 0;
	hi = nr;
	while (lo < hi) {
	mid = lo + (hi - lo) / 2;
	if (base_offset < obj_list[mid].offset) {
	hi = mid;
	} else if (base_offset > obj_list[mid].offset) {
	lo = mid + 1;
	} else {
	oidcpy(&base_oid, &obj_list[mid].oid);
	base_found = !is_null_oid(&base_oid);
	break;
	}
	}
	if (!base_found) {
	/*
	* The delta base object is itself a delta that
	* has not been resolved yet.
	*/
	oidclr(&obj_list[nr].oid);
	add_delta_to_list(nr, null_oid(), base_offset,
	delta_data, delta_size);
	return;
	}
	}

	if (resolve_against_held(nr, &base_oid, delta_data, delta_size))
	return;

	base = read_object_file(&base_oid, &type, &base_size);
	if (!base) {
	error("failed to read delta-pack base object %s",
	oid_to_hex(&base_oid));
	if (!recover)
	exit(1);
	has_errors = 1;
	return;
	}
	resolve_delta(nr, type, base, base_size, delta_data, delta_size);
	free(base);
	}

	static void unpack_one(unsigned nr)
	{
	unsigned shift;
	unsigned char *pack;
	unsigned long size, c;
	enum object_type type;

	obj_list[nr].offset = consumed_bytes;

	pack = fill(1);
	c = *pack;
	use(1);
	type = (c >> 4) & 7;
	size = (c & 15);
	shift = 4;
	while (c & 0x80) {
	pack = fill(1);
	c = *pack;
	use(1);
	size += (c & 0x7f) << shift;
	shift += 7;
	}

	switch (type) {
	case OBJ_BLOB:
	if (!dry_run && size > big_file_threshold) {
	stream_blob(size, nr);
	return;
	}
	/* fallthrough */
	case OBJ_COMMIT:
	case OBJ_TREE:
	case OBJ_TAG:
	unpack_non_delta_entry(type, size, nr);
	return;
	case OBJ_REF_DELTA:
	case OBJ_OFS_DELTA:
	unpack_delta_entry(type, size, nr);
	return;
	default:
	error("bad object type %d", type);
	has_errors = 1;
	if (recover)
	return;
	exit(1);
	}
	}

	static void unpack_all(void)
	{
	int i;
	struct pack_header *hdr = fill(sizeof(struct pack_header));

	nr_objects = ntohl(hdr->hdr_entries);

	if (ntohl(hdr->hdr_signature) != PACK_SIGNATURE)
	die("bad pack file");
	if (!pack_version_ok(hdr->hdr_version))
	die("unknown pack file version %"PRIu32,
	ntohl(hdr->hdr_version));
	use(sizeof(struct pack_header));

	if (!quiet)
	progress = start_progress(_("Unpacking objects"), nr_objects);
	CALLOC_ARRAY(obj_list, nr_objects);
	begin_odb_transaction();
	for (i = 0; i < nr_objects; i++) {
	unpack_one(i);
	display_progress(progress, i + 1);
	}
	end_odb_transaction();
	stop_progress(&progress);

	if (delta_list)
	die("unresolved deltas left after unpacking");
	}

	int cmd_unpack_objects(int argc, const char *argv, const char prefix)
	{
	int i;
	struct object_id oid;

	read_replace_refs = 0;

	git_config(git_default_config, NULL);

	quiet = !isatty(2);

	for (i = 1 ; i < argc; i++) {
	const char *arg = argv[i];

	if (*arg == '-') {
	if (!strcmp(arg, "-n")) {
	dry_run = 1;
	continue;
	}
	if (!strcmp(arg, "-q")) {
	quiet = 1;
	continue;
	}
	if (!strcmp(arg, "-r")) {
	recover = 1;
	continue;
	}
	if (!strcmp(arg, "--strict")) {
	strict = 1;
	continue;
	}
	if (skip_prefix(arg, "--strict=", &arg)) {
	strict = 1;
	fsck_set_msg_types(&fsck_options, arg);
	continue;
	}
	if (starts_with(arg, "--pack_header=")) {
	struct pack_header *hdr;
	char *c;

	hdr = (struct pack_header *)buffer;
	hdr->hdr_signature = htonl(PACK_SIGNATURE);
	hdr->hdr_version = htonl(strtoul(arg + 14, &c, 10));
	if (*c != ',')
	die("bad %s", arg);
	hdr->hdr_entries = htonl(strtoul(c + 1, &c, 10));
	if (*c)
	die("bad %s", arg);
	len = sizeof(*hdr);
	continue;
	}
	if (skip_prefix(arg, "--max-input-size=", &arg)) {
	max_input_size = strtoumax(arg, NULL, 10);
	continue;
	}
	usage(unpack_usage);
	}

	/* We don't take any non-flag arguments now.. Maybe some day */
	usage(unpack_usage);
	}
	the_hash_algo->init_fn(&ctx);
	unpack_all();
	the_hash_algo->update_fn(&ctx, buffer, offset);
	the_hash_algo->final_oid_fn(&oid, &ctx);
	if (strict) {
	write_rest();
	if (fsck_finish(&fsck_options))
	die(_("fsck error in pack objects"));
	}
	if (!hasheq(fill(the_hash_algo->rawsz), oid.hash))
	die("final sha1 did not match");
	use(the_hash_algo->rawsz);

	/* Write the last part of the buffer to stdout */
	while (len) {
	int ret = xwrite(1, buffer + offset, len);
	if (ret <= 0)
	break;
	len -= ret;
	offset += ret;
	}

	/* All done */
	return has_errors;
	}