object-file.c

/*
 * GIT - The information manager from hell
 *
 * Copyright (C) Linus Torvalds, 2005
 *
 * This handles basic git object files - packing, unpacking,
 * creation etc.
 */

#define USE_THE_REPOSITORY_VARIABLE
#define DISABLE_SIGN_COMPARE_WARNINGS

#include "git-compat-util.h"
#include "bulk-checkin.h"
#include "convert.h"
#include "dir.h"
#include "environment.h"
#include "fsck.h"
#include "gettext.h"
#include "hex.h"
#include "loose.h"
#include "object-file-convert.h"
#include "object-file.h"
#include "object-store.h"
#include "oidtree.h"
#include "pack.h"
#include "packfile.h"
#include "path.h"
#include "setup.h"
#include "streaming.h"

/* The maximum size for an object header. */
#define MAX_HEADER_LEN 32

static int get_conv_flags(unsigned flags)
{
	if (flags & INDEX_RENORMALIZE)
		return CONV_EOL_RENORMALIZE;
	else if (flags & INDEX_WRITE_OBJECT)
		return global_conv_flags_eol | CONV_WRITE_OBJECT;
	else
		return 0;
}

static void fill_loose_path(struct strbuf *buf, const struct object_id *oid)
{
	int i;
	for (i = 0; i < the_hash_algo->rawsz; i++) {
		static char hex[] = "0123456789abcdef";
		unsigned int val = oid->hash[i];
		strbuf_addch(buf, hex[val >> 4]);
		strbuf_addch(buf, hex[val & 0xf]);
		if (!i)
			strbuf_addch(buf, '/');
	}
}

const char *odb_loose_path(struct object_directory *odb,
			   struct strbuf *buf,
			   const struct object_id *oid)
{
	strbuf_reset(buf);
	strbuf_addstr(buf, odb->path);
	strbuf_addch(buf, '/');
	fill_loose_path(buf, oid);
	return buf->buf;
}

/* Returns 1 if we have successfully freshened the file, 0 otherwise. */
static int freshen_file(const char *fn)
{
	return !utime(fn, NULL);
}

/*
 * All of the check_and_freshen functions return 1 if the file exists and was
 * freshened (if freshening was requested), 0 otherwise. If they return
 * 0, you should not assume that it is safe to skip a write of the object (it
 * either does not exist on disk, or has a stale mtime and may be subject to
 * pruning).
 */
int check_and_freshen_file(const char *fn, int freshen)
{
	if (access(fn, F_OK))
		return 0;
	if (freshen && !freshen_file(fn))
		return 0;
	return 1;
}

static int check_and_freshen_odb(struct object_directory *odb,
				 const struct object_id *oid,
				 int freshen)
{
	static struct strbuf path = STRBUF_INIT;
	odb_loose_path(odb, &path, oid);
	return check_and_freshen_file(path.buf, freshen);
}

static int check_and_freshen_local(const struct object_id *oid, int freshen)
{
	return check_and_freshen_odb(the_repository->objects->odb, oid, freshen);
}

static int check_and_freshen_nonlocal(const struct object_id *oid, int freshen)
{
	struct object_directory *odb;

	prepare_alt_odb(the_repository);
	for (odb = the_repository->objects->odb->next; odb; odb = odb->next) {
		if (check_and_freshen_odb(odb, oid, freshen))
			return 1;
	}
	return 0;
}

static int check_and_freshen(const struct object_id *oid, int freshen)
{
	return check_and_freshen_local(oid, freshen) ||
	       check_and_freshen_nonlocal(oid, freshen);
}

int has_loose_object_nonlocal(const struct object_id *oid)
{
	return check_and_freshen_nonlocal(oid, 0);
}

int has_loose_object(const struct object_id *oid)
{
	return check_and_freshen(oid, 0);
}

static int format_object_header_literally(char *str, size_t size,
					  const char *type, size_t objsize)
{
	return xsnprintf(str, size, "%s %"PRIuMAX, type, (uintmax_t)objsize) + 1;
}

int format_object_header(char *str, size_t size, enum object_type type,
			 size_t objsize)
{
	const char *name = type_name(type);

	if (!name)
		BUG("could not get a type name for 'enum object_type' value %d", type);

	return format_object_header_literally(str, size, name, objsize);
}

int check_object_signature(struct repository *r, const struct object_id *oid,
			   void *buf, unsigned long size,
			   enum object_type type)
{
	const struct git_hash_algo *algo =
		oid->algo ? &hash_algos[oid->algo] : r->hash_algo;
	struct object_id real_oid;

	hash_object_file(algo, buf, size, type, &real_oid);

	return !oideq(oid, &real_oid) ? -1 : 0;
}

int stream_object_signature(struct repository *r, const struct object_id *oid)
{
	struct object_id real_oid;
	unsigned long size;
	enum object_type obj_type;
	struct git_istream *st;
	struct git_hash_ctx c;
	char hdr[MAX_HEADER_LEN];
	int hdrlen;

	st = open_istream(r, oid, &obj_type, &size, NULL);
	if (!st)
		return -1;

	/* Generate the header */
	hdrlen = format_object_header(hdr, sizeof(hdr), obj_type, size);

	/* Sha1.. */
	r->hash_algo->init_fn(&c);
	git_hash_update(&c, hdr, hdrlen);
	for (;;) {
		char buf[1024 * 16];
		ssize_t readlen = read_istream(st, buf, sizeof(buf));

		if (readlen < 0) {
			close_istream(st);
			return -1;
		}
		if (!readlen)
			break;
		git_hash_update(&c, buf, readlen);
	}
	git_hash_final_oid(&real_oid, &c);
	close_istream(st);
	return !oideq(oid, &real_oid) ? -1 : 0;
}

/*
 * Find "oid" as a loose object in the local repository or in an alternate.
 * Returns 0 on success, negative on failure.
 *
 * The "path" out-parameter will give the path of the object we found (if any).
 * Note that it may point to static storage and is only valid until another
 * call to stat_loose_object().
 */
static int stat_loose_object(struct repository *r, const struct object_id *oid,
			     struct stat *st, const char **path)
{
	struct object_directory *odb;
	static struct strbuf buf = STRBUF_INIT;

	prepare_alt_odb(r);
	for (odb = r->objects->odb; odb; odb = odb->next) {
		*path = odb_loose_path(odb, &buf, oid);
		if (!lstat(*path, st))
			return 0;
	}

	return -1;
}

/*
 * Like stat_loose_object(), but actually open the object and return the
 * descriptor. See the caveats on the "path" parameter above.
 */
static int open_loose_object(struct repository *r,
			     const struct object_id *oid, const char **path)
{
	int fd;
	struct object_directory *odb;
	int most_interesting_errno = ENOENT;
	static struct strbuf buf = STRBUF_INIT;

	prepare_alt_odb(r);
	for (odb = r->objects->odb; odb; odb = odb->next) {
		*path = odb_loose_path(odb, &buf, oid);
		fd = git_open(*path);
		if (fd >= 0)
			return fd;

		if (most_interesting_errno == ENOENT)
			most_interesting_errno = errno;
	}
	errno = most_interesting_errno;
	return -1;
}

static int quick_has_loose(struct repository *r,
			   const struct object_id *oid)
{
	struct object_directory *odb;

	prepare_alt_odb(r);
	for (odb = r->objects->odb; odb; odb = odb->next) {
		if (oidtree_contains(odb_loose_cache(odb, oid), oid))
			return 1;
	}
	return 0;
}

/*
 * Map and close the given loose object fd. The path argument is used for
 * error reporting.
 */
static void *map_fd(int fd, const char *path, unsigned long *size)
{
	void *map = NULL;
	struct stat st;

	if (!fstat(fd, &st)) {
		*size = xsize_t(st.st_size);
		if (!*size) {
			/* mmap() is forbidden on empty files */
			error(_("object file %s is empty"), path);
			close(fd);
			return NULL;
		}
		map = xmmap(NULL, *size, PROT_READ, MAP_PRIVATE, fd, 0);
	}
	close(fd);
	return map;
}

void *map_loose_object(struct repository *r,
		       const struct object_id *oid,
		       unsigned long *size)
{
	const char *p;
	int fd = open_loose_object(r, oid, &p);

	if (fd < 0)
		return NULL;
	return map_fd(fd, p, size);
}

enum unpack_loose_header_result unpack_loose_header(git_zstream *stream,
						    unsigned char *map,
						    unsigned long mapsize,
						    void *buffer,
						    unsigned long bufsiz,
						    struct strbuf *header)
{
	int status;

	/* Get the data stream */
	memset(stream, 0, sizeof(*stream));
	stream->next_in = map;
	stream->avail_in = mapsize;
	stream->next_out = buffer;
	stream->avail_out = bufsiz;

	git_inflate_init(stream);
	obj_read_unlock();
	status = git_inflate(stream, 0);
	obj_read_lock();
	if (status != Z_OK && status != Z_STREAM_END)
		return ULHR_BAD;

	/*
	 * Check if entire header is unpacked in the first iteration.
	 */
	if (memchr(buffer, '\0', stream->next_out - (unsigned char *)buffer))
		return ULHR_OK;

	/*
	 * We have a header longer than MAX_HEADER_LEN. The "header"
	 * here is only non-NULL when we run "cat-file
	 * --allow-unknown-type".
	 */
	if (!header)
		return ULHR_TOO_LONG;

	/*
	 * buffer[0..bufsiz] was not large enough.  Copy the partial
	 * result out to header, and then append the result of further
	 * reading the stream.
	 */
	strbuf_add(header, buffer, stream->next_out - (unsigned char *)buffer);

	do {
		stream->next_out = buffer;
		stream->avail_out = bufsiz;

		obj_read_unlock();
		status = git_inflate(stream, 0);
		obj_read_lock();
		strbuf_add(header, buffer, stream->next_out - (unsigned char *)buffer);
		if (memchr(buffer, '\0', stream->next_out - (unsigned char *)buffer))
			return 0;
	} while (status == Z_OK);
	return ULHR_BAD;
}

static void *unpack_loose_rest(git_zstream *stream,
			       void *buffer, unsigned long size,
			       const struct object_id *oid)
{
	int bytes = strlen(buffer) + 1;
	unsigned char *buf = xmallocz(size);
	unsigned long n;
	int status = Z_OK;

	n = stream->total_out - bytes;
	if (n > size)
		n = size;
	memcpy(buf, (char *) buffer + bytes, n);
	bytes = n;
	if (bytes <= size) {
		/*
		 * The above condition must be (bytes <= size), not
		 * (bytes < size).  In other words, even though we
		 * expect no more output and set avail_out to zero,
		 * the input zlib stream may have bytes that express
		 * "this concludes the stream", and we *do* want to
		 * eat that input.
		 *
		 * Otherwise we would not be able to test that we
		 * consumed all the input to reach the expected size;
		 * we also want to check that zlib tells us that all
		 * went well with status == Z_STREAM_END at the end.
		 */
		stream->next_out = buf + bytes;
		stream->avail_out = size - bytes;
		while (status == Z_OK) {
			obj_read_unlock();
			status = git_inflate(stream, Z_FINISH);
			obj_read_lock();
		}
	}

	if (status != Z_STREAM_END) {
		error(_("corrupt loose object '%s'"), oid_to_hex(oid));
		FREE_AND_NULL(buf);
	} else if (stream->avail_in) {
		error(_("garbage at end of loose object '%s'"),
		      oid_to_hex(oid));
		FREE_AND_NULL(buf);
	}

	return buf;
}

/*
 * We used to just use "sscanf()", but that's actually way
 * too permissive for what we want to check. So do an anal
 * object header parse by hand.
 */
int parse_loose_header(const char *hdr, struct object_info *oi)
{
	const char *type_buf = hdr;
	size_t size;
	int type, type_len = 0;

	/*
	 * The type can be of any size but is followed by
	 * a space.
	 */
	for (;;) {
		char c = *hdr++;
		if (!c)
			return -1;
		if (c == ' ')
			break;
		type_len++;
	}

	type = type_from_string_gently(type_buf, type_len, 1);
	if (oi->type_name)
		strbuf_add(oi->type_name, type_buf, type_len);
	if (oi->typep)
		*oi->typep = type;

	/*
	 * The length must follow immediately, and be in canonical
	 * decimal format (ie "010" is not valid).
	 */
	size = *hdr++ - '0';
	if (size > 9)
		return -1;
	if (size) {
		for (;;) {
			unsigned long c = *hdr - '0';
			if (c > 9)
				break;
			hdr++;
			size = st_add(st_mult(size, 10), c);
		}
	}

	if (oi->sizep)
		*oi->sizep = cast_size_t_to_ulong(size);

	/*
	 * The length must be followed by a zero byte
	 */
	if (*hdr)
		return -1;

	/*
	 * The format is valid, but the type may still be bogus. The
	 * Caller needs to check its oi->typep.
	 */
	return 0;
}

int loose_object_info(struct repository *r,
		      const struct object_id *oid,
		      struct object_info *oi, int flags)
{
	int status = 0;
	int fd;
	unsigned long mapsize;
	const char *path;
	void *map;
	git_zstream stream;
	char hdr[MAX_HEADER_LEN];
	struct strbuf hdrbuf = STRBUF_INIT;
	unsigned long size_scratch;
	enum object_type type_scratch;
	int allow_unknown = flags & OBJECT_INFO_ALLOW_UNKNOWN_TYPE;

	if (oi->delta_base_oid)
		oidclr(oi->delta_base_oid, the_repository->hash_algo);

	/*
	 * If we don't care about type or size, then we don't
	 * need to look inside the object at all. Note that we
	 * do not optimize out the stat call, even if the
	 * caller doesn't care about the disk-size, since our
	 * return value implicitly indicates whether the
	 * object even exists.
	 */
	if (!oi->typep && !oi->type_name && !oi->sizep && !oi->contentp) {
		struct stat st;
		if (!oi->disk_sizep && (flags & OBJECT_INFO_QUICK))
			return quick_has_loose(r, oid) ? 0 : -1;
		if (stat_loose_object(r, oid, &st, &path) < 0)
			return -1;
		if (oi->disk_sizep)
			*oi->disk_sizep = st.st_size;
		return 0;
	}

	fd = open_loose_object(r, oid, &path);
	if (fd < 0) {
		if (errno != ENOENT)
			error_errno(_("unable to open loose object %s"), oid_to_hex(oid));
		return -1;
	}
	map = map_fd(fd, path, &mapsize);
	if (!map)
		return -1;

	if (!oi->sizep)
		oi->sizep = &size_scratch;
	if (!oi->typep)
		oi->typep = &type_scratch;

	if (oi->disk_sizep)
		*oi->disk_sizep = mapsize;

	switch (unpack_loose_header(&stream, map, mapsize, hdr, sizeof(hdr),
				    allow_unknown ? &hdrbuf : NULL)) {
	case ULHR_OK:
		if (parse_loose_header(hdrbuf.len ? hdrbuf.buf : hdr, oi) < 0)
			status = error(_("unable to parse %s header"), oid_to_hex(oid));
		else if (!allow_unknown && *oi->typep < 0)
			die(_("invalid object type"));

		if (!oi->contentp)
			break;
		if (hdrbuf.len)
			BUG("unpacking content with unknown types not yet supported");
		*oi->contentp = unpack_loose_rest(&stream, hdr, *oi->sizep, oid);
		if (*oi->contentp)
			goto cleanup;

		status = -1;
		break;
	case ULHR_BAD:
		status = error(_("unable to unpack %s header"),
			       oid_to_hex(oid));
		break;
	case ULHR_TOO_LONG:
		status = error(_("header for %s too long, exceeds %d bytes"),
			       oid_to_hex(oid), MAX_HEADER_LEN);
		break;
	}

	if (status && (flags & OBJECT_INFO_DIE_IF_CORRUPT))
		die(_("loose object %s (stored in %s) is corrupt"),
		    oid_to_hex(oid), path);

cleanup:
	git_inflate_end(&stream);
	munmap(map, mapsize);
	if (oi->sizep == &size_scratch)
		oi->sizep = NULL;
	strbuf_release(&hdrbuf);
	if (oi->typep == &type_scratch)
		oi->typep = NULL;
	oi->whence = OI_LOOSE;
	return status;
}

static void hash_object_body(const struct git_hash_algo *algo, struct git_hash_ctx *c,
			     const void *buf, unsigned long len,
			     struct object_id *oid,
			     char *hdr, int *hdrlen)
{
	algo->init_fn(c);
	git_hash_update(c, hdr, *hdrlen);
	git_hash_update(c, buf, len);
	git_hash_final_oid(oid, c);
}

static void write_object_file_prepare(const struct git_hash_algo *algo,
				      const void *buf, unsigned long len,
				      enum object_type type, struct object_id *oid,
				      char *hdr, int *hdrlen)
{
	struct git_hash_ctx c;

	/* Generate the header */
	*hdrlen = format_object_header(hdr, *hdrlen, type, len);

	/* Sha1.. */
	hash_object_body(algo, &c, buf, len, oid, hdr, hdrlen);
}

static void write_object_file_prepare_literally(const struct git_hash_algo *algo,
				      const void *buf, unsigned long len,
				      const char *type, struct object_id *oid,
				      char *hdr, int *hdrlen)
{
	struct git_hash_ctx c;

	*hdrlen = format_object_header_literally(hdr, *hdrlen, type, len);
	hash_object_body(algo, &c, buf, len, oid, hdr, hdrlen);
}

#define CHECK_COLLISION_DEST_VANISHED -2

static int check_collision(const char *source, const char *dest)
{
	char buf_source[4096], buf_dest[4096];
	int fd_source = -1, fd_dest = -1;
	int ret = 0;

	fd_source = open(source, O_RDONLY);
	if (fd_source < 0) {
		ret = error_errno(_("unable to open %s"), source);
		goto out;
	}

	fd_dest = open(dest, O_RDONLY);
	if (fd_dest < 0) {
		if (errno != ENOENT)
			ret = error_errno(_("unable to open %s"), dest);
		else
			ret = CHECK_COLLISION_DEST_VANISHED;
		goto out;
	}

	while (1) {
		ssize_t sz_a, sz_b;

		sz_a = read_in_full(fd_source, buf_source, sizeof(buf_source));
		if (sz_a < 0) {
			ret = error_errno(_("unable to read %s"), source);
			goto out;
		}

		sz_b = read_in_full(fd_dest, buf_dest, sizeof(buf_dest));
		if (sz_b < 0) {
			ret = error_errno(_("unable to read %s"), dest);
			goto out;
		}

		if (sz_a != sz_b || memcmp(buf_source, buf_dest, sz_a)) {
			ret = error(_("files '%s' and '%s' differ in contents"),
				    source, dest);
			goto out;
		}

		if (sz_a < sizeof(buf_source))
			break;
	}

out:
	if (fd_source > -1)
		close(fd_source);
	if (fd_dest > -1)
		close(fd_dest);
	return ret;
}

/*
 * Move the just written object into its final resting place.
 */
int finalize_object_file(const char *tmpfile, const char *filename)
{
	return finalize_object_file_flags(tmpfile, filename, 0);
}

int finalize_object_file_flags(const char *tmpfile, const char *filename,
			       enum finalize_object_file_flags flags)
{
	unsigned retries = 0;
	int ret;

retry:
	ret = 0;

	if (object_creation_mode == OBJECT_CREATION_USES_RENAMES)
		goto try_rename;
	else if (link(tmpfile, filename))
		ret = errno;
	else
		unlink_or_warn(tmpfile);

	/*
	 * Coda hack - coda doesn't like cross-directory links,
	 * so we fall back to a rename, which will mean that it
	 * won't be able to check collisions, but that's not a
	 * big deal.
	 *
	 * The same holds for FAT formatted media.
	 *
	 * When this succeeds, we just return.  We have nothing
	 * left to unlink.
	 */
	if (ret && ret != EEXIST) {
		struct stat st;

	try_rename:
		if (!stat(filename, &st))
			ret = EEXIST;
		else if (!rename(tmpfile, filename))
			goto out;
		else
			ret = errno;
	}
	if (ret) {
		if (ret != EEXIST) {
			int saved_errno = errno;
			unlink_or_warn(tmpfile);
			errno = saved_errno;
			return error_errno(_("unable to write file %s"), filename);
		}
		if (!(flags & FOF_SKIP_COLLISION_CHECK)) {
			ret = check_collision(tmpfile, filename);
			if (ret == CHECK_COLLISION_DEST_VANISHED) {
				if (retries++ > 5)
					return error(_("unable to write repeatedly vanishing file %s"),
						     filename);
				goto retry;
			}
			else if (ret)
				return -1;
		}
		unlink_or_warn(tmpfile);
	}

out:
	if (adjust_shared_perm(the_repository, filename))
		return error(_("unable to set permission to '%s'"), filename);
	return 0;
}

static void hash_object_file_literally(const struct git_hash_algo *algo,
				       const void *buf, unsigned long len,
				       const char *type, struct object_id *oid)
{
	char hdr[MAX_HEADER_LEN];
	int hdrlen = sizeof(hdr);

	write_object_file_prepare_literally(algo, buf, len, type, oid, hdr, &hdrlen);
}

void hash_object_file(const struct git_hash_algo *algo, const void *buf,
		      unsigned long len, enum object_type type,
		      struct object_id *oid)
{
	hash_object_file_literally(algo, buf, len, type_name(type), oid);
}

/* Finalize a file on disk, and close it. */
static void close_loose_object(int fd, const char *filename)
{
	if (the_repository->objects->odb->will_destroy)
		goto out;

	if (batch_fsync_enabled(FSYNC_COMPONENT_LOOSE_OBJECT))
		fsync_loose_object_bulk_checkin(fd, filename);
	else if (fsync_object_files > 0)
		fsync_or_die(fd, filename);
	else
		fsync_component_or_die(FSYNC_COMPONENT_LOOSE_OBJECT, fd,
				       filename);

out:
	if (close(fd) != 0)
		die_errno(_("error when closing loose object file"));
}

/* Size of directory component, including the ending '/' */
static inline int directory_size(const char *filename)
{
	const char *s = strrchr(filename, '/');
	if (!s)
		return 0;
	return s - filename + 1;
}

/*
 * This creates a temporary file in the same directory as the final
 * 'filename'
 *
 * We want to avoid cross-directory filename renames, because those
 * can have problems on various filesystems (FAT, NFS, Coda).
 */
static int create_tmpfile(struct strbuf *tmp, const char *filename)
{
	int fd, dirlen = directory_size(filename);

	strbuf_reset(tmp);
	strbuf_add(tmp, filename, dirlen);
	strbuf_addstr(tmp, "tmp_obj_XXXXXX");
	fd = git_mkstemp_mode(tmp->buf, 0444);
	if (fd < 0 && dirlen && errno == ENOENT) {
		/*
		 * Make sure the directory exists; note that the contents
		 * of the buffer are undefined after mkstemp returns an
		 * error, so we have to rewrite the whole buffer from
		 * scratch.
		 */
		strbuf_reset(tmp);
		strbuf_add(tmp, filename, dirlen - 1);
		if (mkdir(tmp->buf, 0777) && errno != EEXIST)
			return -1;
		if (adjust_shared_perm(the_repository, tmp->buf))
			return -1;

		/* Try again */
		strbuf_addstr(tmp, "/tmp_obj_XXXXXX");
		fd = git_mkstemp_mode(tmp->buf, 0444);
	}
	return fd;
}

/**
 * Common steps for loose object writers to start writing loose
 * objects:
 *
 * - Create tmpfile for the loose object.
 * - Setup zlib stream for compression.
 * - Start to feed header to zlib stream.
 *
 * Returns a "fd", which should later be provided to
 * end_loose_object_common().
 */
static int start_loose_object_common(struct strbuf *tmp_file,
				     const char *filename, unsigned flags,
				     git_zstream *stream,
				     unsigned char *buf, size_t buflen,
				     struct git_hash_ctx *c, struct git_hash_ctx *compat_c,
				     char *hdr, int hdrlen)
{
	struct repository *repo = the_repository;
	const struct git_hash_algo *algo = repo->hash_algo;
	const struct git_hash_algo *compat = repo->compat_hash_algo;
	int fd;

	fd = create_tmpfile(tmp_file, filename);
	if (fd < 0) {
		if (flags & WRITE_OBJECT_FILE_SILENT)
			return -1;
		else if (errno == EACCES)
			return error(_("insufficient permission for adding "
				       "an object to repository database %s"),
				     repo_get_object_directory(the_repository));
		else
			return error_errno(
				_("unable to create temporary file"));
	}

	/*  Setup zlib stream for compression */
	git_deflate_init(stream, zlib_compression_level);
	stream->next_out = buf;
	stream->avail_out = buflen;
	algo->init_fn(c);
	if (compat && compat_c)
		compat->init_fn(compat_c);

	/*  Start to feed header to zlib stream */
	stream->next_in = (unsigned char *)hdr;
	stream->avail_in = hdrlen;
	while (git_deflate(stream, 0) == Z_OK)
		; /* nothing */
	git_hash_update(c, hdr, hdrlen);
	if (compat && compat_c)
		git_hash_update(compat_c, hdr, hdrlen);

	return fd;
}

/**
 * Common steps for the inner git_deflate() loop for writing loose
 * objects. Returns what git_deflate() returns.
 */
static int write_loose_object_common(struct git_hash_ctx *c, struct git_hash_ctx *compat_c,
				     git_zstream *stream, const int flush,
				     unsigned char *in0, const int fd,
				     unsigned char *compressed,
				     const size_t compressed_len)
{
	struct repository *repo = the_repository;
	const struct git_hash_algo *compat = repo->compat_hash_algo;
	int ret;

	ret = git_deflate(stream, flush ? Z_FINISH : 0);
	git_hash_update(c, in0, stream->next_in - in0);
	if (compat && compat_c)
		git_hash_update(compat_c, in0, stream->next_in - in0);
	if (write_in_full(fd, compressed, stream->next_out - compressed) < 0)
		die_errno(_("unable to write loose object file"));
	stream->next_out = compressed;
	stream->avail_out = compressed_len;

	return ret;
}

/**
 * Common steps for loose object writers to end writing loose objects:
 *
 * - End the compression of zlib stream.
 * - Get the calculated oid to "oid".
 */
static int end_loose_object_common(struct git_hash_ctx *c, struct git_hash_ctx *compat_c,
				   git_zstream *stream, struct object_id *oid,
				   struct object_id *compat_oid)
{
	struct repository *repo = the_repository;
	const struct git_hash_algo *compat = repo->compat_hash_algo;
	int ret;

	ret = git_deflate_end_gently(stream);
	if (ret != Z_OK)
		return ret;
	git_hash_final_oid(oid, c);
	if (compat && compat_c)
		git_hash_final_oid(compat_oid, compat_c);

	return Z_OK;
}

static int write_loose_object(const struct object_id *oid, char *hdr,
			      int hdrlen, const void *buf, unsigned long len,
			      time_t mtime, unsigned flags)
{
	int fd, ret;
	unsigned char compressed[4096];
	git_zstream stream;
	struct git_hash_ctx c;
	struct object_id parano_oid;
	static struct strbuf tmp_file = STRBUF_INIT;
	static struct strbuf filename = STRBUF_INIT;

	if (batch_fsync_enabled(FSYNC_COMPONENT_LOOSE_OBJECT))
		prepare_loose_object_bulk_checkin();

	odb_loose_path(the_repository->objects->odb, &filename, oid);

	fd = start_loose_object_common(&tmp_file, filename.buf, flags,
				       &stream, compressed, sizeof(compressed),
				       &c, NULL, hdr, hdrlen);
	if (fd < 0)
		return -1;

	/* Then the data itself.. */
	stream.next_in = (void *)buf;
	stream.avail_in = len;
	do {
		unsigned char *in0 = stream.next_in;

		ret = write_loose_object_common(&c, NULL, &stream, 1, in0, fd,
						compressed, sizeof(compressed));
	} while (ret == Z_OK);

	if (ret != Z_STREAM_END)
		die(_("unable to deflate new object %s (%d)"), oid_to_hex(oid),
		    ret);
	ret = end_loose_object_common(&c, NULL, &stream, &parano_oid, NULL);
	if (ret != Z_OK)
		die(_("deflateEnd on object %s failed (%d)"), oid_to_hex(oid),
		    ret);
	if (!oideq(oid, &parano_oid))
		die(_("confused by unstable object source data for %s"),
		    oid_to_hex(oid));

	close_loose_object(fd, tmp_file.buf);

	if (mtime) {
		struct utimbuf utb;
		utb.actime = mtime;
		utb.modtime = mtime;
		if (utime(tmp_file.buf, &utb) < 0 &&
		    !(flags & WRITE_OBJECT_FILE_SILENT))
			warning_errno(_("failed utime() on %s"), tmp_file.buf);
	}

	return finalize_object_file_flags(tmp_file.buf, filename.buf,
					  FOF_SKIP_COLLISION_CHECK);
}

static int freshen_loose_object(const struct object_id *oid)
{
	return check_and_freshen(oid, 1);
}

static int freshen_packed_object(const struct object_id *oid)
{
	struct pack_entry e;
	if (!find_pack_entry(the_repository, oid, &e))
		return 0;
	if (e.p->is_cruft)
		return 0;
	if (e.p->freshened)
		return 1;
	if (!freshen_file(e.p->pack_name))
		return 0;
	e.p->freshened = 1;
	return 1;
}

int stream_loose_object(struct input_stream *in_stream, size_t len,
			struct object_id *oid)
{
	const struct git_hash_algo *compat = the_repository->compat_hash_algo;
	struct object_id compat_oid;
	int fd, ret, err = 0, flush = 0;
	unsigned char compressed[4096];
	git_zstream stream;
	struct git_hash_ctx c, compat_c;
	struct strbuf tmp_file = STRBUF_INIT;
	struct strbuf filename = STRBUF_INIT;
	int dirlen;
	char hdr[MAX_HEADER_LEN];
	int hdrlen;

	if (batch_fsync_enabled(FSYNC_COMPONENT_LOOSE_OBJECT))
		prepare_loose_object_bulk_checkin();

	/* Since oid is not determined, save tmp file to odb path. */
	strbuf_addf(&filename, "%s/", repo_get_object_directory(the_repository));
	hdrlen = format_object_header(hdr, sizeof(hdr), OBJ_BLOB, len);

	/*
	 * Common steps for write_loose_object and stream_loose_object to
	 * start writing loose objects:
	 *
	 *  - Create tmpfile for the loose object.
	 *  - Setup zlib stream for compression.
	 *  - Start to feed header to zlib stream.
	 */
	fd = start_loose_object_common(&tmp_file, filename.buf, 0,
				       &stream, compressed, sizeof(compressed),
				       &c, &compat_c, hdr, hdrlen);
	if (fd < 0) {
		err = -1;
		goto cleanup;
	}

	/* Then the data itself.. */
	do {
		unsigned char *in0 = stream.next_in;

		if (!stream.avail_in && !in_stream->is_finished) {
			const void *in = in_stream->read(in_stream, &stream.avail_in);
			stream.next_in = (void *)in;
			in0 = (unsigned char *)in;
			/* All data has been read. */
			if (in_stream->is_finished)
				flush = 1;
		}
		ret = write_loose_object_common(&c, &compat_c, &stream, flush, in0, fd,
						compressed, sizeof(compressed));
		/*
		 * Unlike write_loose_object(), we do not have the entire
		 * buffer. If we get Z_BUF_ERROR due to too few input bytes,
		 * then we'll replenish them in the next input_stream->read()
		 * call when we loop.
		 */
	} while (ret == Z_OK || ret == Z_BUF_ERROR);

	if (stream.total_in != len + hdrlen)
		die(_("write stream object %ld != %"PRIuMAX), stream.total_in,
		    (uintmax_t)len + hdrlen);

	/*
	 * Common steps for write_loose_object and stream_loose_object to
	 * end writing loose object:
	 *
	 *  - End the compression of zlib stream.
	 *  - Get the calculated oid.
	 */
	if (ret != Z_STREAM_END)
		die(_("unable to stream deflate new object (%d)"), ret);
	ret = end_loose_object_common(&c, &compat_c, &stream, oid, &compat_oid);
	if (ret != Z_OK)
		die(_("deflateEnd on stream object failed (%d)"), ret);
	close_loose_object(fd, tmp_file.buf);

	if (freshen_packed_object(oid) || freshen_loose_object(oid)) {
		unlink_or_warn(tmp_file.buf);
		goto cleanup;
	}

	odb_loose_path(the_repository->objects->odb, &filename, oid);

	/* We finally know the object path, and create the missing dir. */
	dirlen = directory_size(filename.buf);
	if (dirlen) {
		struct strbuf dir = STRBUF_INIT;
		strbuf_add(&dir, filename.buf, dirlen);

		if (safe_create_dir_in_gitdir(the_repository, dir.buf) &&
		    errno != EEXIST) {
			err = error_errno(_("unable to create directory %s"), dir.buf);
			strbuf_release(&dir);
			goto cleanup;
		}
		strbuf_release(&dir);
	}

	err = finalize_object_file_flags(tmp_file.buf, filename.buf,
					 FOF_SKIP_COLLISION_CHECK);
	if (!err && compat)
		err = repo_add_loose_object_map(the_repository, oid, &compat_oid);
cleanup:
	strbuf_release(&tmp_file);
	strbuf_release(&filename);
	return err;
}

int write_object_file_flags(const void *buf, unsigned long len,
			    enum object_type type, struct object_id *oid,
			    struct object_id *compat_oid_in, unsigned flags)
{
	struct repository *repo = the_repository;
	const struct git_hash_algo *algo = repo->hash_algo;
	const struct git_hash_algo *compat = repo->compat_hash_algo;
	struct object_id compat_oid;
	char hdr[MAX_HEADER_LEN];
	int hdrlen = sizeof(hdr);

	/* Generate compat_oid */
	if (compat) {
		if (compat_oid_in)
			oidcpy(&compat_oid, compat_oid_in);
		else if (type == OBJ_BLOB)
			hash_object_file(compat, buf, len, type, &compat_oid);
		else {
			struct strbuf converted = STRBUF_INIT;
			convert_object_file(the_repository, &converted, algo, compat,
					    buf, len, type, 0);
			hash_object_file(compat, converted.buf, converted.len,
					 type, &compat_oid);
			strbuf_release(&converted);
		}
	}

	/* Normally if we have it in the pack then we do not bother writing
	 * it out into .git/objects/??/?{38} file.
	 */
	write_object_file_prepare(algo, buf, len, type, oid, hdr, &hdrlen);
	if (freshen_packed_object(oid) || freshen_loose_object(oid))
		return 0;
	if (write_loose_object(oid, hdr, hdrlen, buf, len, 0, flags))
		return -1;
	if (compat)
		return repo_add_loose_object_map(repo, oid, &compat_oid);
	return 0;
}

int write_object_file_literally(const void *buf, unsigned long len,
				const char *type, struct object_id *oid,
				unsigned flags)
{
	char *header;
	struct repository *repo = the_repository;
	const struct git_hash_algo *algo = repo->hash_algo;
	const struct git_hash_algo *compat = repo->compat_hash_algo;
	struct object_id compat_oid;
	int hdrlen, status = 0;
	int compat_type = -1;

	if (compat) {
		compat_type = type_from_string_gently(type, -1, 1);
		if (compat_type == OBJ_BLOB)
			hash_object_file(compat, buf, len, compat_type,
					 &compat_oid);
		else if (compat_type != -1) {
			struct strbuf converted = STRBUF_INIT;
			convert_object_file(the_repository,
					    &converted, algo, compat,
					    buf, len, compat_type, 0);
			hash_object_file(compat, converted.buf, converted.len,
					 compat_type, &compat_oid);
			strbuf_release(&converted);
		}
	}

	/* type string, SP, %lu of the length plus NUL must fit this */
	hdrlen = strlen(type) + MAX_HEADER_LEN;
	header = xmalloc(hdrlen);
	write_object_file_prepare_literally(the_hash_algo, buf, len, type,
					    oid, header, &hdrlen);

	if (!(flags & WRITE_OBJECT_FILE_PERSIST))
		goto cleanup;
	if (freshen_packed_object(oid) || freshen_loose_object(oid))
		goto cleanup;
	status = write_loose_object(oid, header, hdrlen, buf, len, 0, 0);
	if (compat_type != -1)
		return repo_add_loose_object_map(repo, oid, &compat_oid);

cleanup:
	free(header);
	return status;
}

int force_object_loose(const struct object_id *oid, time_t mtime)
{
	struct repository *repo = the_repository;
	const struct git_hash_algo *compat = repo->compat_hash_algo;
	void *buf;
	unsigned long len;
	struct object_info oi = OBJECT_INFO_INIT;
	struct object_id compat_oid;
	enum object_type type;
	char hdr[MAX_HEADER_LEN];
	int hdrlen;
	int ret;

	if (has_loose_object(oid))
		return 0;
	oi.typep = &type;
	oi.sizep = &len;
	oi.contentp = &buf;
	if (oid_object_info_extended(the_repository, oid, &oi, 0))
		return error(_("cannot read object for %s"), oid_to_hex(oid));
	if (compat) {
		if (repo_oid_to_algop(repo, oid, compat, &compat_oid))
			return error(_("cannot map object %s to %s"),
				     oid_to_hex(oid), compat->name);
	}
	hdrlen = format_object_header(hdr, sizeof(hdr), type, len);
	ret = write_loose_object(oid, hdr, hdrlen, buf, len, mtime, 0);
	if (!ret && compat)
		ret = repo_add_loose_object_map(the_repository, oid, &compat_oid);
	free(buf);

	return ret;
}

/*
 * We can't use the normal fsck_error_function() for index_mem(),
 * because we don't yet have a valid oid for it to report. Instead,
 * report the minimal fsck error here, and rely on the caller to
 * give more context.
 */
static int hash_format_check_report(struct fsck_options *opts UNUSED,
				    void *fsck_report UNUSED,
				    enum fsck_msg_type msg_type UNUSED,
				    enum fsck_msg_id msg_id UNUSED,
				    const char *message)
{
	error(_("object fails fsck: %s"), message);
	return 1;
}

static int index_mem(struct index_state *istate,
		     struct object_id *oid,
		     const void *buf, size_t size,
		     enum object_type type,
		     const char *path, unsigned flags)
{
	struct strbuf nbuf = STRBUF_INIT;
	int ret = 0;
	int write_object = flags & INDEX_WRITE_OBJECT;

	if (!type)
		type = OBJ_BLOB;

	/*
	 * Convert blobs to git internal format
	 */
	if ((type == OBJ_BLOB) && path) {
		if (convert_to_git(istate, path, buf, size, &nbuf,
				   get_conv_flags(flags))) {
			buf = nbuf.buf;
			size = nbuf.len;
		}
	}
	if (flags & INDEX_FORMAT_CHECK) {
		struct fsck_options opts = FSCK_OPTIONS_DEFAULT;

		opts.strict = 1;
		opts.error_func = hash_format_check_report;
		if (fsck_buffer(null_oid(the_hash_algo), type, buf, size, &opts))
			die(_("refusing to create malformed object"));
		fsck_finish(&opts);
	}

	if (write_object)
		ret = write_object_file(buf, size, type, oid);
	else
		hash_object_file(the_hash_algo, buf, size, type, oid);

	strbuf_release(&nbuf);
	return ret;
}

static int index_stream_convert_blob(struct index_state *istate,
				     struct object_id *oid,
				     int fd,
				     const char *path,
				     unsigned flags)
{
	int ret = 0;
	const int write_object = flags & INDEX_WRITE_OBJECT;
	struct strbuf sbuf = STRBUF_INIT;

	assert(path);
	ASSERT(would_convert_to_git_filter_fd(istate, path));

	convert_to_git_filter_fd(istate, path, fd, &sbuf,
				 get_conv_flags(flags));

	if (write_object)
		ret = write_object_file(sbuf.buf, sbuf.len, OBJ_BLOB,
					oid);
	else
		hash_object_file(the_hash_algo, sbuf.buf, sbuf.len, OBJ_BLOB,
				 oid);
	strbuf_release(&sbuf);
	return ret;
}

static int index_pipe(struct index_state *istate, struct object_id *oid,
		      int fd, enum object_type type,
		      const char *path, unsigned flags)
{
	struct strbuf sbuf = STRBUF_INIT;
	int ret;

	if (strbuf_read(&sbuf, fd, 4096) >= 0)
		ret = index_mem(istate, oid, sbuf.buf, sbuf.len, type, path, flags);
	else
		ret = -1;
	strbuf_release(&sbuf);
	return ret;
}

#define SMALL_FILE_SIZE (32*1024)

static int index_core(struct index_state *istate,
		      struct object_id *oid, int fd, size_t size,
		      enum object_type type, const char *path,
		      unsigned flags)
{
	int ret;

	if (!size) {
		ret = index_mem(istate, oid, "", size, type, path, flags);
	} else if (size <= SMALL_FILE_SIZE) {
		char *buf = xmalloc(size);
		ssize_t read_result = read_in_full(fd, buf, size);
		if (read_result < 0)
			ret = error_errno(_("read error while indexing %s"),
					  path ? path : "<unknown>");
		else if (read_result != size)
			ret = error(_("short read while indexing %s"),
				    path ? path : "<unknown>");
		else
			ret = index_mem(istate, oid, buf, size, type, path, flags);
		free(buf);
	} else {
		void *buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
		ret = index_mem(istate, oid, buf, size, type, path, flags);
		munmap(buf, size);
	}
	return ret;
}

int index_fd(struct index_state *istate, struct object_id *oid,
	     int fd, struct stat *st,
	     enum object_type type, const char *path, unsigned flags)
{
	int ret;

	/*
	 * Call xsize_t() only when needed to avoid potentially unnecessary
	 * die() for large files.
	 */
	if (type == OBJ_BLOB && path && would_convert_to_git_filter_fd(istate, path))
		ret = index_stream_convert_blob(istate, oid, fd, path, flags);
	else if (!S_ISREG(st->st_mode))
		ret = index_pipe(istate, oid, fd, type, path, flags);
	else if (st->st_size <= repo_settings_get_big_file_threshold(the_repository) ||
		 type != OBJ_BLOB ||
		 (path && would_convert_to_git(istate, path)))
		ret = index_core(istate, oid, fd, xsize_t(st->st_size),
				 type, path, flags);
	else
		ret = index_blob_bulk_checkin(oid, fd, xsize_t(st->st_size), path,
					     flags);
	close(fd);
	return ret;
}

int index_path(struct index_state *istate, struct object_id *oid,
	       const char *path, struct stat *st, unsigned flags)
{
	int fd;
	struct strbuf sb = STRBUF_INIT;
	int rc = 0;

	switch (st->st_mode & S_IFMT) {
	case S_IFREG:
		fd = open(path, O_RDONLY);
		if (fd < 0)
			return error_errno("open(\"%s\")", path);
		if (index_fd(istate, oid, fd, st, OBJ_BLOB, path, flags) < 0)
			return error(_("%s: failed to insert into database"),
				     path);
		break;
	case S_IFLNK:
		if (strbuf_readlink(&sb, path, st->st_size))
			return error_errno("readlink(\"%s\")", path);
		if (!(flags & INDEX_WRITE_OBJECT))
			hash_object_file(the_hash_algo, sb.buf, sb.len,
					 OBJ_BLOB, oid);
		else if (write_object_file(sb.buf, sb.len, OBJ_BLOB, oid))
			rc = error(_("%s: failed to insert into database"), path);
		strbuf_release(&sb);
		break;
	case S_IFDIR:
		return repo_resolve_gitlink_ref(the_repository, path, "HEAD", oid);
	default:
		return error(_("%s: unsupported file type"), path);
	}
	return rc;
}

int read_pack_header(int fd, struct pack_header *header)
{
	if (read_in_full(fd, header, sizeof(*header)) != sizeof(*header))
		/* "eof before pack header was fully read" */
		return PH_ERROR_EOF;

	if (header->hdr_signature != htonl(PACK_SIGNATURE))
		/* "protocol error (pack signature mismatch detected)" */
		return PH_ERROR_PACK_SIGNATURE;
	if (!pack_version_ok(header->hdr_version))
		/* "protocol error (pack version unsupported)" */
		return PH_ERROR_PROTOCOL;
	return 0;
}

int for_each_file_in_obj_subdir(unsigned int subdir_nr,
				struct strbuf *path,
				each_loose_object_fn obj_cb,
				each_loose_cruft_fn cruft_cb,
				each_loose_subdir_fn subdir_cb,
				void *data)
{
	size_t origlen, baselen;
	DIR *dir;
	struct dirent *de;
	int r = 0;
	struct object_id oid;

	if (subdir_nr > 0xff)
		BUG("invalid loose object subdirectory: %x", subdir_nr);

	origlen = path->len;
	strbuf_complete(path, '/');
	strbuf_addf(path, "%02x", subdir_nr);

	dir = opendir(path->buf);
	if (!dir) {
		if (errno != ENOENT)
			r = error_errno(_("unable to open %s"), path->buf);
		strbuf_setlen(path, origlen);
		return r;
	}

	oid.hash[0] = subdir_nr;
	strbuf_addch(path, '/');
	baselen = path->len;

	while ((de = readdir_skip_dot_and_dotdot(dir))) {
		size_t namelen;

		namelen = strlen(de->d_name);
		strbuf_setlen(path, baselen);
		strbuf_add(path, de->d_name, namelen);
		if (namelen == the_hash_algo->hexsz - 2 &&
		    !hex_to_bytes(oid.hash + 1, de->d_name,
				  the_hash_algo->rawsz - 1)) {
			oid_set_algo(&oid, the_hash_algo);
			memset(oid.hash + the_hash_algo->rawsz, 0,
			       GIT_MAX_RAWSZ - the_hash_algo->rawsz);
			if (obj_cb) {
				r = obj_cb(&oid, path->buf, data);
				if (r)
					break;
			}
			continue;
		}

		if (cruft_cb) {
			r = cruft_cb(de->d_name, path->buf, data);
			if (r)
				break;
		}
	}
	closedir(dir);

	strbuf_setlen(path, baselen - 1);
	if (!r && subdir_cb)
		r = subdir_cb(subdir_nr, path->buf, data);

	strbuf_setlen(path, origlen);

	return r;
}

int for_each_loose_file_in_objdir_buf(struct strbuf *path,
			    each_loose_object_fn obj_cb,
			    each_loose_cruft_fn cruft_cb,
			    each_loose_subdir_fn subdir_cb,
			    void *data)
{
	int r = 0;
	int i;

	for (i = 0; i < 256; i++) {
		r = for_each_file_in_obj_subdir(i, path, obj_cb, cruft_cb,
						subdir_cb, data);
		if (r)
			break;
	}

	return r;
}

int for_each_loose_file_in_objdir(const char *path,
				  each_loose_object_fn obj_cb,
				  each_loose_cruft_fn cruft_cb,
				  each_loose_subdir_fn subdir_cb,
				  void *data)
{
	struct strbuf buf = STRBUF_INIT;
	int r;

	strbuf_addstr(&buf, path);
	r = for_each_loose_file_in_objdir_buf(&buf, obj_cb, cruft_cb,
					      subdir_cb, data);
	strbuf_release(&buf);

	return r;
}

int for_each_loose_object(each_loose_object_fn cb, void *data,
			  enum for_each_object_flags flags)
{
	struct object_directory *odb;

	prepare_alt_odb(the_repository);
	for (odb = the_repository->objects->odb; odb; odb = odb->next) {
		int r = for_each_loose_file_in_objdir(odb->path, cb, NULL,
						      NULL, data);
		if (r)
			return r;

		if (flags & FOR_EACH_OBJECT_LOCAL_ONLY)
			break;
	}

	return 0;
}

static int append_loose_object(const struct object_id *oid,
			       const char *path UNUSED,
			       void *data)
{
	oidtree_insert(data, oid);
	return 0;
}

struct oidtree *odb_loose_cache(struct object_directory *odb,
				  const struct object_id *oid)
{
	int subdir_nr = oid->hash[0];
	struct strbuf buf = STRBUF_INIT;
	size_t word_bits = bitsizeof(odb->loose_objects_subdir_seen[0]);
	size_t word_index = subdir_nr / word_bits;
	size_t mask = (size_t)1u << (subdir_nr % word_bits);
	uint32_t *bitmap;

	if (subdir_nr < 0 ||
	    subdir_nr >= bitsizeof(odb->loose_objects_subdir_seen))
		BUG("subdir_nr out of range");

	bitmap = &odb->loose_objects_subdir_seen[word_index];
	if (*bitmap & mask)
		return odb->loose_objects_cache;
	if (!odb->loose_objects_cache) {
		ALLOC_ARRAY(odb->loose_objects_cache, 1);
		oidtree_init(odb->loose_objects_cache);
	}
	strbuf_addstr(&buf, odb->path);
	for_each_file_in_obj_subdir(subdir_nr, &buf,
				    append_loose_object,
				    NULL, NULL,
				    odb->loose_objects_cache);
	*bitmap |= mask;
	strbuf_release(&buf);
	return odb->loose_objects_cache;
}

void odb_clear_loose_cache(struct object_directory *odb)
{
	oidtree_clear(odb->loose_objects_cache);
	FREE_AND_NULL(odb->loose_objects_cache);
	memset(&odb->loose_objects_subdir_seen, 0,
	       sizeof(odb->loose_objects_subdir_seen));
}

static int check_stream_oid(git_zstream *stream,
			    const char *hdr,
			    unsigned long size,
			    const char *path,
			    const struct object_id *expected_oid)
{
	struct git_hash_ctx c;
	struct object_id real_oid;
	unsigned char buf[4096];
	unsigned long total_read;
	int status = Z_OK;

	the_hash_algo->init_fn(&c);
	git_hash_update(&c, hdr, stream->total_out);

	/*
	 * We already read some bytes into hdr, but the ones up to the NUL
	 * do not count against the object's content size.
	 */
	total_read = stream->total_out - strlen(hdr) - 1;

	/*
	 * This size comparison must be "<=" to read the final zlib packets;
	 * see the comment in unpack_loose_rest for details.
	 */
	while (total_read <= size &&
	       (status == Z_OK ||
		(status == Z_BUF_ERROR && !stream->avail_out))) {
		stream->next_out = buf;
		stream->avail_out = sizeof(buf);
		if (size - total_read < stream->avail_out)
			stream->avail_out = size - total_read;
		status = git_inflate(stream, Z_FINISH);
		git_hash_update(&c, buf, stream->next_out - buf);
		total_read += stream->next_out - buf;
	}

	if (status != Z_STREAM_END) {
		error(_("corrupt loose object '%s'"), oid_to_hex(expected_oid));
		return -1;
	}
	if (stream->avail_in) {
		error(_("garbage at end of loose object '%s'"),
		      oid_to_hex(expected_oid));
		return -1;
	}

	git_hash_final_oid(&real_oid, &c);
	if (!oideq(expected_oid, &real_oid)) {
		error(_("hash mismatch for %s (expected %s)"), path,
		      oid_to_hex(expected_oid));
		return -1;
	}

	return 0;
}

int read_loose_object(const char *path,
		      const struct object_id *expected_oid,
		      struct object_id *real_oid,
		      void **contents,
		      struct object_info *oi)
{
	int ret = -1;
	int fd;
	void *map = NULL;
	unsigned long mapsize;
	git_zstream stream;
	char hdr[MAX_HEADER_LEN];
	unsigned long *size = oi->sizep;

	fd = git_open(path);
	if (fd >= 0)
		map = map_fd(fd, path, &mapsize);
	if (!map) {
		error_errno(_("unable to mmap %s"), path);
		goto out;
	}

	if (unpack_loose_header(&stream, map, mapsize, hdr, sizeof(hdr),
				NULL) != ULHR_OK) {
		error(_("unable to unpack header of %s"), path);
		goto out_inflate;
	}

	if (parse_loose_header(hdr, oi) < 0) {
		error(_("unable to parse header of %s"), path);
		goto out_inflate;
	}

	if (*oi->typep == OBJ_BLOB &&
	    *size > repo_settings_get_big_file_threshold(the_repository)) {
		if (check_stream_oid(&stream, hdr, *size, path, expected_oid) < 0)
			goto out_inflate;
	} else {
		*contents = unpack_loose_rest(&stream, hdr, *size, expected_oid);
		if (!*contents) {
			error(_("unable to unpack contents of %s"), path);
			goto out_inflate;
		}
		hash_object_file_literally(the_repository->hash_algo,
					   *contents, *size,
					   oi->type_name->buf, real_oid);
		if (!oideq(expected_oid, real_oid))
			goto out_inflate;
	}

	ret = 0; /* everything checks out */

out_inflate:
	git_inflate_end(&stream);
out:
	if (map)
		munmap(map, mapsize);
	return ret;
}