sha1_file.c: rename to use dash in file name

This is more consistent with the project style. The majority of Git's
source files use dashes in preference to underscores in their file names.

Signed-off-by: Stefan Beller <sbeller@google.com>

1 files changed, 2254 insertions, 0 deletions

diff --git a/sha1-file.c b/sha1-file.c
new file mode 100644
index 0000000..77ccaab
--- /dev/null
+++ b/sha1-file.c
@@ -0,0 +1,2254 @@
+/*
+ * GIT - The information manager from hell
+ *
+ * Copyright (C) Linus Torvalds, 2005
+ *
+ * This handles basic git sha1 object files - packing, unpacking,
+ * creation etc.
+ */
+#include "cache.h"
+#include "config.h"
+#include "string-list.h"
+#include "lockfile.h"
+#include "delta.h"
+#include "pack.h"
+#include "blob.h"
+#include "commit.h"
+#include "run-command.h"
+#include "tag.h"
+#include "tree.h"
+#include "tree-walk.h"
+#include "refs.h"
+#include "pack-revindex.h"
+#include "sha1-lookup.h"
+#include "bulk-checkin.h"
+#include "repository.h"
+#include "streaming.h"
+#include "dir.h"
+#include "list.h"
+#include "mergesort.h"
+#include "quote.h"
+#include "packfile.h"
+#include "fetch-object.h"
+#include "object-store.h"
+
+/* The maximum size for an object header. */
+#define MAX_HEADER_LEN 32
+
+const unsigned char null_sha1[GIT_MAX_RAWSZ];
+const struct object_id null_oid;
+const struct object_id empty_tree_oid = {
+	EMPTY_TREE_SHA1_BIN_LITERAL
+};
+const struct object_id empty_blob_oid = {
+	EMPTY_BLOB_SHA1_BIN_LITERAL
+};
+
+static void git_hash_sha1_init(git_hash_ctx *ctx)
+{
+	git_SHA1_Init(&ctx->sha1);
+}
+
+static void git_hash_sha1_update(git_hash_ctx *ctx, const void *data, size_t len)
+{
+	git_SHA1_Update(&ctx->sha1, data, len);
+}
+
+static void git_hash_sha1_final(unsigned char *hash, git_hash_ctx *ctx)
+{
+	git_SHA1_Final(hash, &ctx->sha1);
+}
+
+static void git_hash_unknown_init(git_hash_ctx *ctx)
+{
+	die("trying to init unknown hash");
+}
+
+static void git_hash_unknown_update(git_hash_ctx *ctx, const void *data, size_t len)
+{
+	die("trying to update unknown hash");
+}
+
+static void git_hash_unknown_final(unsigned char *hash, git_hash_ctx *ctx)
+{
+	die("trying to finalize unknown hash");
+}
+
+const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
+	{
+		NULL,
+		0x00000000,
+		0,
+		0,
+		git_hash_unknown_init,
+		git_hash_unknown_update,
+		git_hash_unknown_final,
+		NULL,
+		NULL,
+	},
+	{
+		"sha-1",
+		/* "sha1", big-endian */
+		0x73686131,
+		GIT_SHA1_RAWSZ,
+		GIT_SHA1_HEXSZ,
+		git_hash_sha1_init,
+		git_hash_sha1_update,
+		git_hash_sha1_final,
+		&empty_tree_oid,
+		&empty_blob_oid,
+	},
+};
+
+/*
+ * This is meant to hold a *small* number of objects that you would
+ * want read_sha1_file() to be able to return, but yet you do not want
+ * to write them into the object store (e.g. a browse-only
+ * application).
+ */
+static struct cached_object {
+	unsigned char sha1[20];
+	enum object_type type;
+	void *buf;
+	unsigned long size;
+} *cached_objects;
+static int cached_object_nr, cached_object_alloc;
+
+static struct cached_object empty_tree = {
+	EMPTY_TREE_SHA1_BIN_LITERAL,
+	OBJ_TREE,
+	"",
+	0
+};
+
+static struct cached_object *find_cached_object(const unsigned char *sha1)
+{
+	int i;
+	struct cached_object *co = cached_objects;
+
+	for (i = 0; i < cached_object_nr; i++, co++) {
+		if (!hashcmp(co->sha1, sha1))
+			return co;
+	}
+	if (!hashcmp(sha1, empty_tree.sha1))
+		return &empty_tree;
+	return NULL;
+}
+
+
+static int get_conv_flags(unsigned flags)
+{
+	if (flags & HASH_RENORMALIZE)
+		return CONV_EOL_RENORMALIZE;
+	else if (flags & HASH_WRITE_OBJECT)
+	  return global_conv_flags_eol;
+	else
+		return 0;
+}
+
+
+int mkdir_in_gitdir(const char *path)
+{
+	if (mkdir(path, 0777)) {
+		int saved_errno = errno;
+		struct stat st;
+		struct strbuf sb = STRBUF_INIT;
+
+		if (errno != EEXIST)
+			return -1;
+		/*
+		 * Are we looking at a path in a symlinked worktree
+		 * whose original repository does not yet have it?
+		 * e.g. .git/rr-cache pointing at its original
+		 * repository in which the user hasn't performed any
+		 * conflict resolution yet?
+		 */
+		if (lstat(path, &st) || !S_ISLNK(st.st_mode) ||
+		    strbuf_readlink(&sb, path, st.st_size) ||
+		    !is_absolute_path(sb.buf) ||
+		    mkdir(sb.buf, 0777)) {
+			strbuf_release(&sb);
+			errno = saved_errno;
+			return -1;
+		}
+		strbuf_release(&sb);
+	}
+	return adjust_shared_perm(path);
+}
+
+enum scld_error safe_create_leading_directories(char *path)
+{
+	char *next_component = path + offset_1st_component(path);
+	enum scld_error ret = SCLD_OK;
+
+	while (ret == SCLD_OK && next_component) {
+		struct stat st;
+		char *slash = next_component, slash_character;
+
+		while (*slash && !is_dir_sep(*slash))
+			slash++;
+
+		if (!*slash)
+			break;
+
+		next_component = slash + 1;
+		while (is_dir_sep(*next_component))
+			next_component++;
+		if (!*next_component)
+			break;
+
+		slash_character = *slash;
+		*slash = '\0';
+		if (!stat(path, &st)) {
+			/* path exists */
+			if (!S_ISDIR(st.st_mode)) {
+				errno = ENOTDIR;
+				ret = SCLD_EXISTS;
+			}
+		} else if (mkdir(path, 0777)) {
+			if (errno == EEXIST &&
+			    !stat(path, &st) && S_ISDIR(st.st_mode))
+				; /* somebody created it since we checked */
+			else if (errno == ENOENT)
+				/*
+				 * Either mkdir() failed because
+				 * somebody just pruned the containing
+				 * directory, or stat() failed because
+				 * the file that was in our way was
+				 * just removed.  Either way, inform
+				 * the caller that it might be worth
+				 * trying again:
+				 */
+				ret = SCLD_VANISHED;
+			else
+				ret = SCLD_FAILED;
+		} else if (adjust_shared_perm(path)) {
+			ret = SCLD_PERMS;
+		}
+		*slash = slash_character;
+	}
+	return ret;
+}
+
+enum scld_error safe_create_leading_directories_const(const char *path)
+{
+	int save_errno;
+	/* path points to cache entries, so xstrdup before messing with it */
+	char *buf = xstrdup(path);
+	enum scld_error result = safe_create_leading_directories(buf);
+
+	save_errno = errno;
+	free(buf);
+	errno = save_errno;
+	return result;
+}
+
+int raceproof_create_file(const char *path, create_file_fn fn, void *cb)
+{
+	/*
+	 * The number of times we will try to remove empty directories
+	 * in the way of path. This is only 1 because if another
+	 * process is racily creating directories that conflict with
+	 * us, we don't want to fight against them.
+	 */
+	int remove_directories_remaining = 1;
+
+	/*
+	 * The number of times that we will try to create the
+	 * directories containing path. We are willing to attempt this
+	 * more than once, because another process could be trying to
+	 * clean up empty directories at the same time as we are
+	 * trying to create them.
+	 */
+	int create_directories_remaining = 3;
+
+	/* A scratch copy of path, filled lazily if we need it: */
+	struct strbuf path_copy = STRBUF_INIT;
+
+	int ret, save_errno;
+
+	/* Sanity check: */
+	assert(*path);
+
+retry_fn:
+	ret = fn(path, cb);
+	save_errno = errno;
+	if (!ret)
+		goto out;
+
+	if (errno == EISDIR && remove_directories_remaining-- > 0) {
+		/*
+		 * A directory is in the way. Maybe it is empty; try
+		 * to remove it:
+		 */
+		if (!path_copy.len)
+			strbuf_addstr(&path_copy, path);
+
+		if (!remove_dir_recursively(&path_copy, REMOVE_DIR_EMPTY_ONLY))
+			goto retry_fn;
+	} else if (errno == ENOENT && create_directories_remaining-- > 0) {
+		/*
+		 * Maybe the containing directory didn't exist, or
+		 * maybe it was just deleted by a process that is
+		 * racing with us to clean up empty directories. Try
+		 * to create it:
+		 */
+		enum scld_error scld_result;
+
+		if (!path_copy.len)
+			strbuf_addstr(&path_copy, path);
+
+		do {
+			scld_result = safe_create_leading_directories(path_copy.buf);
+			if (scld_result == SCLD_OK)
+				goto retry_fn;
+		} while (scld_result == SCLD_VANISHED && create_directories_remaining-- > 0);
+	}
+
+out:
+	strbuf_release(&path_copy);
+	errno = save_errno;
+	return ret;
+}
+
+static void fill_sha1_path(struct strbuf *buf, const unsigned char *sha1)
+{
+	int i;
+	for (i = 0; i < 20; i++) {
+		static char hex[] = "0123456789abcdef";
+		unsigned int val = sha1[i];
+		strbuf_addch(buf, hex[val >> 4]);
+		strbuf_addch(buf, hex[val & 0xf]);
+		if (!i)
+			strbuf_addch(buf, '/');
+	}
+}
+
+void sha1_file_name(struct repository *r, struct strbuf *buf, const unsigned char *sha1)
+{
+	strbuf_addstr(buf, r->objects->objectdir);
+	strbuf_addch(buf, '/');
+	fill_sha1_path(buf, sha1);
+}
+
+struct strbuf *alt_scratch_buf(struct alternate_object_database *alt)
+{
+	strbuf_setlen(&alt->scratch, alt->base_len);
+	return &alt->scratch;
+}
+
+static const char *alt_sha1_path(struct alternate_object_database *alt,
+				 const unsigned char *sha1)
+{
+	struct strbuf *buf = alt_scratch_buf(alt);
+	fill_sha1_path(buf, sha1);
+	return buf->buf;
+}
+
+/*
+ * Return non-zero iff the path is usable as an alternate object database.
+ */
+static int alt_odb_usable(struct raw_object_store *o,
+			  struct strbuf *path,
+			  const char *normalized_objdir)
+{
+	struct alternate_object_database *alt;
+
+	/* Detect cases where alternate disappeared */
+	if (!is_directory(path->buf)) {
+		error("object directory %s does not exist; "
+		      "check .git/objects/info/alternates.",
+		      path->buf);
+		return 0;
+	}
+
+	/*
+	 * Prevent the common mistake of listing the same
+	 * thing twice, or object directory itself.
+	 */
+	for (alt = o->alt_odb_list; alt; alt = alt->next) {
+		if (!fspathcmp(path->buf, alt->path))
+			return 0;
+	}
+	if (!fspathcmp(path->buf, normalized_objdir))
+		return 0;
+
+	return 1;
+}
+
+/*
+ * Prepare alternate object database registry.
+ *
+ * The variable alt_odb_list points at the list of struct
+ * alternate_object_database.  The elements on this list come from
+ * non-empty elements from colon separated ALTERNATE_DB_ENVIRONMENT
+ * environment variable, and $GIT_OBJECT_DIRECTORY/info/alternates,
+ * whose contents is similar to that environment variable but can be
+ * LF separated.  Its base points at a statically allocated buffer that
+ * contains "/the/directory/corresponding/to/.git/objects/...", while
+ * its name points just after the slash at the end of ".git/objects/"
+ * in the example above, and has enough space to hold 40-byte hex
+ * SHA1, an extra slash for the first level indirection, and the
+ * terminating NUL.
+ */
+static void read_info_alternates(struct repository *r,
+				 const char *relative_base,
+				 int depth);
+static int link_alt_odb_entry(struct repository *r, const char *entry,
+	const char *relative_base, int depth, const char *normalized_objdir)
+{
+	struct alternate_object_database *ent;
+	struct strbuf pathbuf = STRBUF_INIT;
+
+	if (!is_absolute_path(entry) && relative_base) {
+		strbuf_realpath(&pathbuf, relative_base, 1);
+		strbuf_addch(&pathbuf, '/');
+	}
+	strbuf_addstr(&pathbuf, entry);
+
+	if (strbuf_normalize_path(&pathbuf) < 0 && relative_base) {
+		error("unable to normalize alternate object path: %s",
+		      pathbuf.buf);
+		strbuf_release(&pathbuf);
+		return -1;
+	}
+
+	/*
+	 * The trailing slash after the directory name is given by
+	 * this function at the end. Remove duplicates.
+	 */
+	while (pathbuf.len && pathbuf.buf[pathbuf.len - 1] == '/')
+		strbuf_setlen(&pathbuf, pathbuf.len - 1);
+
+	if (!alt_odb_usable(r->objects, &pathbuf, normalized_objdir)) {
+		strbuf_release(&pathbuf);
+		return -1;
+	}
+
+	ent = alloc_alt_odb(pathbuf.buf);
+
+	/* add the alternate entry */
+	*r->objects->alt_odb_tail = ent;
+	r->objects->alt_odb_tail = &(ent->next);
+	ent->next = NULL;
+
+	/* recursively add alternates */
+	read_info_alternates(r, pathbuf.buf, depth + 1);
+
+	strbuf_release(&pathbuf);
+	return 0;
+}
+
+static const char *parse_alt_odb_entry(const char *string,
+				       int sep,
+				       struct strbuf *out)
+{
+	const char *end;
+
+	strbuf_reset(out);
+
+	if (*string == '#') {
+		/* comment; consume up to next separator */
+		end = strchrnul(string, sep);
+	} else if (*string == '"' && !unquote_c_style(out, string, &end)) {
+		/*
+		 * quoted path; unquote_c_style has copied the
+		 * data for us and set "end". Broken quoting (e.g.,
+		 * an entry that doesn't end with a quote) falls
+		 * back to the unquoted case below.
+		 */
+	} else {
+		/* normal, unquoted path */
+		end = strchrnul(string, sep);
+		strbuf_add(out, string, end - string);
+	}
+
+	if (*end)
+		end++;
+	return end;
+}
+
+static void link_alt_odb_entries(struct repository *r, const char *alt,
+				 int sep, const char *relative_base, int depth)
+{
+	struct strbuf objdirbuf = STRBUF_INIT;
+	struct strbuf entry = STRBUF_INIT;
+
+	if (!alt || !*alt)
+		return;
+
+	if (depth > 5) {
+		error("%s: ignoring alternate object stores, nesting too deep.",
+				relative_base);
+		return;
+	}
+
+	strbuf_add_absolute_path(&objdirbuf, r->objects->objectdir);
+	if (strbuf_normalize_path(&objdirbuf) < 0)
+		die("unable to normalize object directory: %s",
+		    objdirbuf.buf);
+
+	while (*alt) {
+		alt = parse_alt_odb_entry(alt, sep, &entry);
+		if (!entry.len)
+			continue;
+		link_alt_odb_entry(r, entry.buf,
+				   relative_base, depth, objdirbuf.buf);
+	}
+	strbuf_release(&entry);
+	strbuf_release(&objdirbuf);
+}
+
+static void read_info_alternates(struct repository *r,
+				 const char *relative_base,
+				 int depth)
+{
+	char *path;
+	struct strbuf buf = STRBUF_INIT;
+
+	path = xstrfmt("%s/info/alternates", relative_base);
+	if (strbuf_read_file(&buf, path, 1024) < 0) {
+		warn_on_fopen_errors(path);
+		free(path);
+		return;
+	}
+
+	link_alt_odb_entries(r, buf.buf, '\n', relative_base, depth);
+	strbuf_release(&buf);
+	free(path);
+}
+
+struct alternate_object_database *alloc_alt_odb(const char *dir)
+{
+	struct alternate_object_database *ent;
+
+	FLEX_ALLOC_STR(ent, path, dir);
+	strbuf_init(&ent->scratch, 0);
+	strbuf_addf(&ent->scratch, "%s/", dir);
+	ent->base_len = ent->scratch.len;
+
+	return ent;
+}
+
+void add_to_alternates_file(const char *reference)
+{
+	struct lock_file lock = LOCK_INIT;
+	char *alts = git_pathdup("objects/info/alternates");
+	FILE *in, *out;
+	int found = 0;
+
+	hold_lock_file_for_update(&lock, alts, LOCK_DIE_ON_ERROR);
+	out = fdopen_lock_file(&lock, "w");
+	if (!out)
+		die_errno("unable to fdopen alternates lockfile");
+
+	in = fopen(alts, "r");
+	if (in) {
+		struct strbuf line = STRBUF_INIT;
+
+		while (strbuf_getline(&line, in) != EOF) {
+			if (!strcmp(reference, line.buf)) {
+				found = 1;
+				break;
+			}
+			fprintf_or_die(out, "%s\n", line.buf);
+		}
+
+		strbuf_release(&line);
+		fclose(in);
+	}
+	else if (errno != ENOENT)
+		die_errno("unable to read alternates file");
+
+	if (found) {
+		rollback_lock_file(&lock);
+	} else {
+		fprintf_or_die(out, "%s\n", reference);
+		if (commit_lock_file(&lock))
+			die_errno("unable to move new alternates file into place");
+		if (the_repository->objects->alt_odb_tail)
+			link_alt_odb_entries(the_repository, reference,
+					     '\n', NULL, 0);
+	}
+	free(alts);
+}
+
+void add_to_alternates_memory(const char *reference)
+{
+	/*
+	 * Make sure alternates are initialized, or else our entry may be
+	 * overwritten when they are.
+	 */
+	prepare_alt_odb(the_repository);
+
+	link_alt_odb_entries(the_repository, reference,
+			     '\n', NULL, 0);
+}
+
+/*
+ * Compute the exact path an alternate is at and returns it. In case of
+ * error NULL is returned and the human readable error is added to `err`
+ * `path` may be relative and should point to $GITDIR.
+ * `err` must not be null.
+ */
+char *compute_alternate_path(const char *path, struct strbuf *err)
+{
+	char *ref_git = NULL;
+	const char *repo, *ref_git_s;
+	int seen_error = 0;
+
+	ref_git_s = real_path_if_valid(path);
+	if (!ref_git_s) {
+		seen_error = 1;
+		strbuf_addf(err, _("path '%s' does not exist"), path);
+		goto out;
+	} else
+		/*
+		 * Beware: read_gitfile(), real_path() and mkpath()
+		 * return static buffer
+		 */
+		ref_git = xstrdup(ref_git_s);
+
+	repo = read_gitfile(ref_git);
+	if (!repo)
+		repo = read_gitfile(mkpath("%s/.git", ref_git));
+	if (repo) {
+		free(ref_git);
+		ref_git = xstrdup(repo);
+	}
+
+	if (!repo && is_directory(mkpath("%s/.git/objects", ref_git))) {
+		char *ref_git_git = mkpathdup("%s/.git", ref_git);
+		free(ref_git);
+		ref_git = ref_git_git;
+	} else if (!is_directory(mkpath("%s/objects", ref_git))) {
+		struct strbuf sb = STRBUF_INIT;
+		seen_error = 1;
+		if (get_common_dir(&sb, ref_git)) {
+			strbuf_addf(err,
+				    _("reference repository '%s' as a linked "
+				      "checkout is not supported yet."),
+				    path);
+			goto out;
+		}
+
+		strbuf_addf(err, _("reference repository '%s' is not a "
+					"local repository."), path);
+		goto out;
+	}
+
+	if (!access(mkpath("%s/shallow", ref_git), F_OK)) {
+		strbuf_addf(err, _("reference repository '%s' is shallow"),
+			    path);
+		seen_error = 1;
+		goto out;
+	}
+
+	if (!access(mkpath("%s/info/grafts", ref_git), F_OK)) {
+		strbuf_addf(err,
+			    _("reference repository '%s' is grafted"),
+			    path);
+		seen_error = 1;
+		goto out;
+	}
+
+out:
+	if (seen_error) {
+		FREE_AND_NULL(ref_git);
+	}
+
+	return ref_git;
+}
+
+int foreach_alt_odb(alt_odb_fn fn, void *cb)
+{
+	struct alternate_object_database *ent;
+	int r = 0;
+
+	prepare_alt_odb(the_repository);
+	for (ent = the_repository->objects->alt_odb_list; ent; ent = ent->next) {
+		r = fn(ent, cb);
+		if (r)
+			break;
+	}
+	return r;
+}
+
+void prepare_alt_odb(struct repository *r)
+{
+	if (r->objects->alt_odb_tail)
+		return;
+
+	r->objects->alt_odb_tail = &r->objects->alt_odb_list;
+	link_alt_odb_entries(r, r->objects->alternate_db, PATH_SEP, NULL, 0);
+
+	read_info_alternates(r, r->objects->objectdir, 0);
+}
+
+/* Returns 1 if we have successfully freshened the file, 0 otherwise. */
+static int freshen_file(const char *fn)
+{
+	struct utimbuf t;
+	t.actime = t.modtime = time(NULL);
+	return !utime(fn, &t);
+}
+
+/*
+ * 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_local(const unsigned char *sha1, int freshen)
+{
+	static struct strbuf buf = STRBUF_INIT;
+
+	strbuf_reset(&buf);
+	sha1_file_name(the_repository, &buf, sha1);
+
+	return check_and_freshen_file(buf.buf, freshen);
+}
+
+static int check_and_freshen_nonlocal(const unsigned char *sha1, int freshen)
+{
+	struct alternate_object_database *alt;
+	prepare_alt_odb(the_repository);
+	for (alt = the_repository->objects->alt_odb_list; alt; alt = alt->next) {
+		const char *path = alt_sha1_path(alt, sha1);
+		if (check_and_freshen_file(path, freshen))
+			return 1;
+	}
+	return 0;
+}
+
+static int check_and_freshen(const unsigned char *sha1, int freshen)
+{
+	return check_and_freshen_local(sha1, freshen) ||
+	       check_and_freshen_nonlocal(sha1, freshen);
+}
+
+int has_loose_object_nonlocal(const unsigned char *sha1)
+{
+	return check_and_freshen_nonlocal(sha1, 0);
+}
+
+static int has_loose_object(const unsigned char *sha1)
+{
+	return check_and_freshen(sha1, 0);
+}
+
+static void mmap_limit_check(size_t length)
+{
+	static size_t limit = 0;
+	if (!limit) {
+		limit = git_env_ulong("GIT_MMAP_LIMIT", 0);
+		if (!limit)
+			limit = SIZE_MAX;
+	}
+	if (length > limit)
+		die("attempting to mmap %"PRIuMAX" over limit %"PRIuMAX,
+		    (uintmax_t)length, (uintmax_t)limit);
+}
+
+void *xmmap_gently(void *start, size_t length,
+		  int prot, int flags, int fd, off_t offset)
+{
+	void *ret;
+
+	mmap_limit_check(length);
+	ret = mmap(start, length, prot, flags, fd, offset);
+	if (ret == MAP_FAILED) {
+		if (!length)
+			return NULL;
+		release_pack_memory(length);
+		ret = mmap(start, length, prot, flags, fd, offset);
+	}
+	return ret;
+}
+
+void *xmmap(void *start, size_t length,
+	int prot, int flags, int fd, off_t offset)
+{
+	void *ret = xmmap_gently(start, length, prot, flags, fd, offset);
+	if (ret == MAP_FAILED)
+		die_errno("mmap failed");
+	return ret;
+}
+
+/*
+ * With an in-core object data in "map", rehash it to make sure the
+ * object name actually matches "sha1" to detect object corruption.
+ * With "map" == NULL, try reading the object named with "sha1" using
+ * the streaming interface and rehash it to do the same.
+ */
+int check_object_signature(const struct object_id *oid, void *map,
+			   unsigned long size, const char *type)
+{
+	struct object_id real_oid;
+	enum object_type obj_type;
+	struct git_istream *st;
+	git_hash_ctx c;
+	char hdr[MAX_HEADER_LEN];
+	int hdrlen;
+
+	if (map) {
+		hash_object_file(map, size, type, &real_oid);
+		return oidcmp(oid, &real_oid) ? -1 : 0;
+	}
+
+	st = open_istream(oid, &obj_type, &size, NULL);
+	if (!st)
+		return -1;
+
+	/* Generate the header */
+	hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %lu", type_name(obj_type), size) + 1;
+
+	/* Sha1.. */
+	the_hash_algo->init_fn(&c);
+	the_hash_algo->update_fn(&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;
+		the_hash_algo->update_fn(&c, buf, readlen);
+	}
+	the_hash_algo->final_fn(real_oid.hash, &c);
+	close_istream(st);
+	return oidcmp(oid, &real_oid) ? -1 : 0;
+}
+
+int git_open_cloexec(const char *name, int flags)
+{
+	int fd;
+	static int o_cloexec = O_CLOEXEC;
+
+	fd = open(name, flags | o_cloexec);
+	if ((o_cloexec & O_CLOEXEC) && fd < 0 && errno == EINVAL) {
+		/* Try again w/o O_CLOEXEC: the kernel might not support it */
+		o_cloexec &= ~O_CLOEXEC;
+		fd = open(name, flags | o_cloexec);
+	}
+
+#if defined(F_GETFD) && defined(F_SETFD) && defined(FD_CLOEXEC)
+	{
+		static int fd_cloexec = FD_CLOEXEC;
+
+		if (!o_cloexec && 0 <= fd && fd_cloexec) {
+			/* Opened w/o O_CLOEXEC?  try with fcntl(2) to add it */
+			int flags = fcntl(fd, F_GETFD);
+			if (fcntl(fd, F_SETFD, flags | fd_cloexec))
+				fd_cloexec = 0;
+		}
+	}
+#endif
+	return fd;
+}
+
+/*
+ * Find "sha1" 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 sha1_file_name(), etc.
+ */
+static int stat_sha1_file(struct repository *r, const unsigned char *sha1,
+			  struct stat *st, const char **path)
+{
+	struct alternate_object_database *alt;
+	static struct strbuf buf = STRBUF_INIT;
+
+	strbuf_reset(&buf);
+	sha1_file_name(r, &buf, sha1);
+	*path = buf.buf;
+
+	if (!lstat(*path, st))
+		return 0;
+
+	prepare_alt_odb(r);
+	errno = ENOENT;
+	for (alt = r->objects->alt_odb_list; alt; alt = alt->next) {
+		*path = alt_sha1_path(alt, sha1);
+		if (!lstat(*path, st))
+			return 0;
+	}
+
+	return -1;
+}
+
+/*
+ * Like stat_sha1_file(), but actually open the object and return the
+ * descriptor. See the caveats on the "path" parameter above.
+ */
+static int open_sha1_file(struct repository *r,
+			  const unsigned char *sha1, const char **path)
+{
+	int fd;
+	struct alternate_object_database *alt;
+	int most_interesting_errno;
+	static struct strbuf buf = STRBUF_INIT;
+
+	strbuf_reset(&buf);
+	sha1_file_name(r, &buf, sha1);
+	*path = buf.buf;
+
+	fd = git_open(*path);
+	if (fd >= 0)
+		return fd;
+	most_interesting_errno = errno;
+
+	prepare_alt_odb(r);
+	for (alt = r->objects->alt_odb_list; alt; alt = alt->next) {
+		*path = alt_sha1_path(alt, sha1);
+		fd = git_open(*path);
+		if (fd >= 0)
+			return fd;
+		if (most_interesting_errno == ENOENT)
+			most_interesting_errno = errno;
+	}
+	errno = most_interesting_errno;
+	return -1;
+}
+
+/*
+ * Map the loose object at "path" if it is not NULL, or the path found by
+ * searching for a loose object named "sha1".
+ */
+static void *map_sha1_file_1(struct repository *r, const char *path,
+			     const unsigned char *sha1, unsigned long *size)
+{
+	void *map;
+	int fd;
+
+	if (path)
+		fd = git_open(path);
+	else
+		fd = open_sha1_file(r, sha1, &path);
+	map = NULL;
+	if (fd >= 0) {
+		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);
+				return NULL;
+			}
+			map = xmmap(NULL, *size, PROT_READ, MAP_PRIVATE, fd, 0);
+		}
+		close(fd);
+	}
+	return map;
+}
+
+void *map_sha1_file(struct repository *r,
+		    const unsigned char *sha1, unsigned long *size)
+{
+	return map_sha1_file_1(r, NULL, sha1, size);
+}
+
+static int unpack_sha1_short_header(git_zstream *stream,
+				    unsigned char *map, unsigned long mapsize,
+				    void *buffer, unsigned long bufsiz)
+{
+	/* 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);
+	return git_inflate(stream, 0);
+}
+
+int unpack_sha1_header(git_zstream *stream,
+		       unsigned char *map, unsigned long mapsize,
+		       void *buffer, unsigned long bufsiz)
+{
+	int status = unpack_sha1_short_header(stream, map, mapsize,
+					      buffer, bufsiz);
+
+	if (status < Z_OK)
+		return status;
+
+	/* Make sure we have the terminating NUL */
+	if (!memchr(buffer, '\0', stream->next_out - (unsigned char *)buffer))
+		return -1;
+	return 0;
+}
+
+static int unpack_sha1_header_to_strbuf(git_zstream *stream, unsigned char *map,
+					unsigned long mapsize, void *buffer,
+					unsigned long bufsiz, struct strbuf *header)
+{
+	int status;
+
+	status = unpack_sha1_short_header(stream, map, mapsize, buffer, bufsiz);
+	if (status < Z_OK)
+		return -1;
+
+	/*
+	 * Check if entire header is unpacked in the first iteration.
+	 */
+	if (memchr(buffer, '\0', stream->next_out - (unsigned char *)buffer))
+		return 0;
+
+	/*
+	 * 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);
+	stream->next_out = buffer;
+	stream->avail_out = bufsiz;
+
+	do {
+		status = git_inflate(stream, 0);
+		strbuf_add(header, buffer, stream->next_out - (unsigned char *)buffer);
+		if (memchr(buffer, '\0', stream->next_out - (unsigned char *)buffer))
+			return 0;
+		stream->next_out = buffer;
+		stream->avail_out = bufsiz;
+	} while (status != Z_STREAM_END);
+	return -1;
+}
+
+static void *unpack_sha1_rest(git_zstream *stream, void *buffer, unsigned long size, const unsigned char *sha1)
+{
+	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)
+			status = git_inflate(stream, Z_FINISH);
+	}
+	if (status == Z_STREAM_END && !stream->avail_in) {
+		git_inflate_end(stream);
+		return buf;
+	}
+
+	if (status < 0)
+		error("corrupt loose object '%s'", sha1_to_hex(sha1));
+	else if (stream->avail_in)
+		error("garbage at end of loose object '%s'",
+		      sha1_to_hex(sha1));
+	free(buf);
+	return NULL;
+}
+
+/*
+ * 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.
+ */
+static int parse_sha1_header_extended(const char *hdr, struct object_info *oi,
+			       unsigned int flags)
+{
+	const char *type_buf = hdr;
+	unsigned long 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);
+	/*
+	 * Set type to 0 if its an unknown object and
+	 * we're obtaining the type using '--allow-unknown-type'
+	 * option.
+	 */
+	if ((flags & OBJECT_INFO_ALLOW_UNKNOWN_TYPE) && (type < 0))
+		type = 0;
+	else if (type < 0)
+		die("invalid object type");
+	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 = size * 10 + c;
+		}
+	}
+
+	if (oi->sizep)
+		*oi->sizep = size;
+
+	/*
+	 * The length must be followed by a zero byte
+	 */
+	return *hdr ? -1 : type;
+}
+
+int parse_sha1_header(const char *hdr, unsigned long *sizep)
+{
+	struct object_info oi = OBJECT_INFO_INIT;
+
+	oi.sizep = sizep;
+	return parse_sha1_header_extended(hdr, &oi, 0);
+}
+
+static int sha1_loose_object_info(struct repository *r,
+				  const unsigned char *sha1,
+				  struct object_info *oi, int flags)
+{
+	int status = 0;
+	unsigned long mapsize;
+	void *map;
+	git_zstream stream;
+	char hdr[MAX_HEADER_LEN];
+	struct strbuf hdrbuf = STRBUF_INIT;
+	unsigned long size_scratch;
+
+	if (oi->delta_base_sha1)
+		hashclr(oi->delta_base_sha1);
+
+	/*
+	 * 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) {
+		const char *path;
+		struct stat st;
+		if (stat_sha1_file(r, sha1, &st, &path) < 0)
+			return -1;
+		if (oi->disk_sizep)
+			*oi->disk_sizep = st.st_size;
+		return 0;
+	}
+
+	map = map_sha1_file(r, sha1, &mapsize);
+	if (!map)
+		return -1;
+
+	if (!oi->sizep)
+		oi->sizep = &size_scratch;
+
+	if (oi->disk_sizep)
+		*oi->disk_sizep = mapsize;
+	if ((flags & OBJECT_INFO_ALLOW_UNKNOWN_TYPE)) {
+		if (unpack_sha1_header_to_strbuf(&stream, map, mapsize, hdr, sizeof(hdr), &hdrbuf) < 0)
+			status = error("unable to unpack %s header with --allow-unknown-type",
+				       sha1_to_hex(sha1));
+	} else if (unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr)) < 0)
+		status = error("unable to unpack %s header",
+			       sha1_to_hex(sha1));
+	if (status < 0)
+		; /* Do nothing */
+	else if (hdrbuf.len) {
+		if ((status = parse_sha1_header_extended(hdrbuf.buf, oi, flags)) < 0)
+			status = error("unable to parse %s header with --allow-unknown-type",
+				       sha1_to_hex(sha1));
+	} else if ((status = parse_sha1_header_extended(hdr, oi, flags)) < 0)
+		status = error("unable to parse %s header", sha1_to_hex(sha1));
+
+	if (status >= 0 && oi->contentp) {
+		*oi->contentp = unpack_sha1_rest(&stream, hdr,
+						 *oi->sizep, sha1);
+		if (!*oi->contentp) {
+			git_inflate_end(&stream);
+			status = -1;
+		}
+	} else
+		git_inflate_end(&stream);
+
+	munmap(map, mapsize);
+	if (status && oi->typep)
+		*oi->typep = status;
+	if (oi->sizep == &size_scratch)
+		oi->sizep = NULL;
+	strbuf_release(&hdrbuf);
+	oi->whence = OI_LOOSE;
+	return (status < 0) ? status : 0;
+}
+
+int fetch_if_missing = 1;
+
+int oid_object_info_extended(const struct object_id *oid, struct object_info *oi, unsigned flags)
+{
+	static struct object_info blank_oi = OBJECT_INFO_INIT;
+	struct pack_entry e;
+	int rtype;
+	const struct object_id *real = oid;
+	int already_retried = 0;
+
+	if (flags & OBJECT_INFO_LOOKUP_REPLACE)
+		real = lookup_replace_object(oid);
+
+	if (is_null_oid(real))
+		return -1;
+
+	if (!oi)
+		oi = &blank_oi;
+
+	if (!(flags & OBJECT_INFO_SKIP_CACHED)) {
+		struct cached_object *co = find_cached_object(real->hash);
+		if (co) {
+			if (oi->typep)
+				*(oi->typep) = co->type;
+			if (oi->sizep)
+				*(oi->sizep) = co->size;
+			if (oi->disk_sizep)
+				*(oi->disk_sizep) = 0;
+			if (oi->delta_base_sha1)
+				hashclr(oi->delta_base_sha1);
+			if (oi->type_name)
+				strbuf_addstr(oi->type_name, type_name(co->type));
+			if (oi->contentp)
+				*oi->contentp = xmemdupz(co->buf, co->size);
+			oi->whence = OI_CACHED;
+			return 0;
+		}
+	}
+
+	while (1) {
+		if (find_pack_entry(the_repository, real->hash, &e))
+			break;
+
+		if (flags & OBJECT_INFO_IGNORE_LOOSE)
+			return -1;
+
+		/* Most likely it's a loose object. */
+		if (!sha1_loose_object_info(the_repository, real->hash, oi, flags))
+			return 0;
+
+		/* Not a loose object; someone else may have just packed it. */
+		if (!(flags & OBJECT_INFO_QUICK)) {
+			reprepare_packed_git(the_repository);
+			if (find_pack_entry(the_repository, real->hash, &e))
+				break;
+		}
+
+		/* Check if it is a missing object */
+		if (fetch_if_missing && repository_format_partial_clone &&
+		    !already_retried) {
+			/*
+			 * TODO Investigate haveing fetch_object() return
+			 * TODO error/success and stopping the music here.
+			 */
+			fetch_object(repository_format_partial_clone, real->hash);
+			already_retried = 1;
+			continue;
+		}
+
+		return -1;
+	}
+
+	if (oi == &blank_oi)
+		/*
+		 * We know that the caller doesn't actually need the
+		 * information below, so return early.
+		 */
+		return 0;
+	rtype = packed_object_info(e.p, e.offset, oi);
+	if (rtype < 0) {
+		mark_bad_packed_object(e.p, real->hash);
+		return oid_object_info_extended(real, oi, 0);
+	} else if (oi->whence == OI_PACKED) {
+		oi->u.packed.offset = e.offset;
+		oi->u.packed.pack = e.p;
+		oi->u.packed.is_delta = (rtype == OBJ_REF_DELTA ||
+					 rtype == OBJ_OFS_DELTA);
+	}
+
+	return 0;
+}
+
+/* returns enum object_type or negative */
+int oid_object_info(const struct object_id *oid, unsigned long *sizep)
+{
+	enum object_type type;
+	struct object_info oi = OBJECT_INFO_INIT;
+
+	oi.typep = &type;
+	oi.sizep = sizep;
+	if (oid_object_info_extended(oid, &oi,
+				     OBJECT_INFO_LOOKUP_REPLACE) < 0)
+		return -1;
+	return type;
+}
+
+static void *read_object(const unsigned char *sha1, enum object_type *type,
+			 unsigned long *size)
+{
+	struct object_id oid;
+	struct object_info oi = OBJECT_INFO_INIT;
+	void *content;
+	oi.typep = type;
+	oi.sizep = size;
+	oi.contentp = &content;
+
+	hashcpy(oid.hash, sha1);
+
+	if (oid_object_info_extended(&oid, &oi, 0) < 0)
+		return NULL;
+	return content;
+}
+
+int pretend_object_file(void *buf, unsigned long len, enum object_type type,
+			struct object_id *oid)
+{
+	struct cached_object *co;
+
+	hash_object_file(buf, len, type_name(type), oid);
+	if (has_sha1_file(oid->hash) || find_cached_object(oid->hash))
+		return 0;
+	ALLOC_GROW(cached_objects, cached_object_nr + 1, cached_object_alloc);
+	co = &cached_objects[cached_object_nr++];
+	co->size = len;
+	co->type = type;
+	co->buf = xmalloc(len);
+	memcpy(co->buf, buf, len);
+	hashcpy(co->sha1, oid->hash);
+	return 0;
+}
+
+/*
+ * This function dies on corrupt objects; the callers who want to
+ * deal with them should arrange to call read_object() and give error
+ * messages themselves.
+ */
+void *read_object_file_extended(const struct object_id *oid,
+				enum object_type *type,
+				unsigned long *size,
+				int lookup_replace)
+{
+	void *data;
+	const struct packed_git *p;
+	const char *path;
+	struct stat st;
+	const struct object_id *repl = lookup_replace ? lookup_replace_object(oid)
+						      : oid;
+
+	errno = 0;
+	data = read_object(repl->hash, type, size);
+	if (data)
+		return data;
+
+	if (errno && errno != ENOENT)
+		die_errno("failed to read object %s", oid_to_hex(oid));
+
+	/* die if we replaced an object with one that does not exist */
+	if (repl != oid)
+		die("replacement %s not found for %s",
+		    oid_to_hex(repl), oid_to_hex(oid));
+
+	if (!stat_sha1_file(the_repository, repl->hash, &st, &path))
+		die("loose object %s (stored in %s) is corrupt",
+		    oid_to_hex(repl), path);
+
+	if ((p = has_packed_and_bad(repl->hash)) != NULL)
+		die("packed object %s (stored in %s) is corrupt",
+		    oid_to_hex(repl), p->pack_name);
+
+	return NULL;
+}
+
+void *read_object_with_reference(const struct object_id *oid,
+				 const char *required_type_name,
+				 unsigned long *size,
+				 struct object_id *actual_oid_return)
+{
+	enum object_type type, required_type;
+	void *buffer;
+	unsigned long isize;
+	struct object_id actual_oid;
+
+	required_type = type_from_string(required_type_name);
+	oidcpy(&actual_oid, oid);
+	while (1) {
+		int ref_length = -1;
+		const char *ref_type = NULL;
+
+		buffer = read_object_file(&actual_oid, &type, &isize);
+		if (!buffer)
+			return NULL;
+		if (type == required_type) {
+			*size = isize;
+			if (actual_oid_return)
+				oidcpy(actual_oid_return, &actual_oid);
+			return buffer;
+		}
+		/* Handle references */
+		else if (type == OBJ_COMMIT)
+			ref_type = "tree ";
+		else if (type == OBJ_TAG)
+			ref_type = "object ";
+		else {
+			free(buffer);
+			return NULL;
+		}
+		ref_length = strlen(ref_type);
+
+		if (ref_length + GIT_SHA1_HEXSZ > isize ||
+		    memcmp(buffer, ref_type, ref_length) ||
+		    get_oid_hex((char *) buffer + ref_length, &actual_oid)) {
+			free(buffer);
+			return NULL;
+		}
+		free(buffer);
+		/* Now we have the ID of the referred-to object in
+		 * actual_oid.  Check again. */
+	}
+}
+
+static void write_object_file_prepare(const void *buf, unsigned long len,
+				      const char *type, struct object_id *oid,
+				      char *hdr, int *hdrlen)
+{
+	git_hash_ctx c;
+
+	/* Generate the header */
+	*hdrlen = xsnprintf(hdr, *hdrlen, "%s %lu", type, len)+1;
+
+	/* Sha1.. */
+	the_hash_algo->init_fn(&c);
+	the_hash_algo->update_fn(&c, hdr, *hdrlen);
+	the_hash_algo->update_fn(&c, buf, len);
+	the_hash_algo->final_fn(oid->hash, &c);
+}
+
+/*
+ * Move the just written object into its final resting place.
+ */
+int finalize_object_file(const char *tmpfile, const char *filename)
+{
+	int ret = 0;
+
+	if (object_creation_mode == OBJECT_CREATION_USES_RENAMES)
+		goto try_rename;
+	else if (link(tmpfile, filename))
+		ret = errno;
+
+	/*
+	 * 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) {
+	try_rename:
+		if (!rename(tmpfile, filename))
+			goto out;
+		ret = errno;
+	}
+	unlink_or_warn(tmpfile);
+	if (ret) {
+		if (ret != EEXIST) {
+			return error_errno("unable to write sha1 filename %s", filename);
+		}
+		/* FIXME!!! Collision check here ? */
+	}
+
+out:
+	if (adjust_shared_perm(filename))
+		return error("unable to set permission to '%s'", filename);
+	return 0;
+}
+
+static int write_buffer(int fd, const void *buf, size_t len)
+{
+	if (write_in_full(fd, buf, len) < 0)
+		return error_errno("file write error");
+	return 0;
+}
+
+int hash_object_file(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(buf, len, type, oid, hdr, &hdrlen);
+	return 0;
+}
+
+/* Finalize a file on disk, and close it. */
+static void close_sha1_file(int fd)
+{
+	if (fsync_object_files)
+		fsync_or_die(fd, "sha1 file");
+	if (close(fd) != 0)
+		die_errno("error when closing sha1 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(tmp->buf))
+			return -1;
+
+		/* Try again */
+		strbuf_addstr(tmp, "/tmp_obj_XXXXXX");
+		fd = git_mkstemp_mode(tmp->buf, 0444);
+	}
+	return fd;
+}
+
+static int write_loose_object(const struct object_id *oid, char *hdr,
+			      int hdrlen, const void *buf, unsigned long len,
+			      time_t mtime)
+{
+	int fd, ret;
+	unsigned char compressed[4096];
+	git_zstream stream;
+	git_hash_ctx c;
+	struct object_id parano_oid;
+	static struct strbuf tmp_file = STRBUF_INIT;
+	static struct strbuf filename = STRBUF_INIT;
+
+	strbuf_reset(&filename);
+	sha1_file_name(the_repository, &filename, oid->hash);
+
+	fd = create_tmpfile(&tmp_file, filename.buf);
+	if (fd < 0) {
+		if (errno == EACCES)
+			return error("insufficient permission for adding an object to repository database %s", get_object_directory());
+		else
+			return error_errno("unable to create temporary file");
+	}
+
+	/* Set it up */
+	git_deflate_init(&stream, zlib_compression_level);
+	stream.next_out = compressed;
+	stream.avail_out = sizeof(compressed);
+	the_hash_algo->init_fn(&c);
+
+	/* First header.. */
+	stream.next_in = (unsigned char *)hdr;
+	stream.avail_in = hdrlen;
+	while (git_deflate(&stream, 0) == Z_OK)
+		; /* nothing */
+	the_hash_algo->update_fn(&c, hdr, hdrlen);
+
+	/* Then the data itself.. */
+	stream.next_in = (void *)buf;
+	stream.avail_in = len;
+	do {
+		unsigned char *in0 = stream.next_in;
+		ret = git_deflate(&stream, Z_FINISH);
+		the_hash_algo->update_fn(&c, in0, stream.next_in - in0);
+		if (write_buffer(fd, compressed, stream.next_out - compressed) < 0)
+			die("unable to write sha1 file");
+		stream.next_out = compressed;
+		stream.avail_out = 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 = git_deflate_end_gently(&stream);
+	if (ret != Z_OK)
+		die("deflateEnd on object %s failed (%d)", oid_to_hex(oid),
+		    ret);
+	the_hash_algo->final_fn(parano_oid.hash, &c);
+	if (oidcmp(oid, &parano_oid) != 0)
+		die("confused by unstable object source data for %s",
+		    oid_to_hex(oid));
+
+	close_sha1_file(fd);
+
+	if (mtime) {
+		struct utimbuf utb;
+		utb.actime = mtime;
+		utb.modtime = mtime;
+		if (utime(tmp_file.buf, &utb) < 0)
+			warning_errno("failed utime() on %s", tmp_file.buf);
+	}
+
+	return finalize_object_file(tmp_file.buf, filename.buf);
+}
+
+static int freshen_loose_object(const unsigned char *sha1)
+{
+	return check_and_freshen(sha1, 1);
+}
+
+static int freshen_packed_object(const unsigned char *sha1)
+{
+	struct pack_entry e;
+	if (!find_pack_entry(the_repository, sha1, &e))
+		return 0;
+	if (e.p->freshened)
+		return 1;
+	if (!freshen_file(e.p->pack_name))
+		return 0;
+	e.p->freshened = 1;
+	return 1;
+}
+
+int write_object_file(const void *buf, unsigned long len, const char *type,
+		      struct object_id *oid)
+{
+	char hdr[MAX_HEADER_LEN];
+	int hdrlen = sizeof(hdr);
+
+	/* 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(buf, len, type, oid, hdr, &hdrlen);
+	if (freshen_packed_object(oid->hash) || freshen_loose_object(oid->hash))
+		return 0;
+	return write_loose_object(oid, hdr, hdrlen, buf, len, 0);
+}
+
+int hash_object_file_literally(const void *buf, unsigned long len,
+			       const char *type, struct object_id *oid,
+			       unsigned flags)
+{
+	char *header;
+	int hdrlen, status = 0;
+
+	/* 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(buf, len, type, oid, header, &hdrlen);
+
+	if (!(flags & HASH_WRITE_OBJECT))
+		goto cleanup;
+	if (freshen_packed_object(oid->hash) || freshen_loose_object(oid->hash))
+		goto cleanup;
+	status = write_loose_object(oid, header, hdrlen, buf, len, 0);
+
+cleanup:
+	free(header);
+	return status;
+}
+
+int force_object_loose(const struct object_id *oid, time_t mtime)
+{
+	void *buf;
+	unsigned long len;
+	enum object_type type;
+	char hdr[MAX_HEADER_LEN];
+	int hdrlen;
+	int ret;
+
+	if (has_loose_object(oid->hash))
+		return 0;
+	buf = read_object(oid->hash, &type, &len);
+	if (!buf)
+		return error("cannot read sha1_file for %s", oid_to_hex(oid));
+	hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %lu", type_name(type), len) + 1;
+	ret = write_loose_object(oid, hdr, hdrlen, buf, len, mtime);
+	free(buf);
+
+	return ret;
+}
+
+int has_sha1_file_with_flags(const unsigned char *sha1, int flags)
+{
+	struct object_id oid;
+	if (!startup_info->have_repository)
+		return 0;
+	hashcpy(oid.hash, sha1);
+	return oid_object_info_extended(&oid, NULL,
+					flags | OBJECT_INFO_SKIP_CACHED) >= 0;
+}
+
+int has_object_file(const struct object_id *oid)
+{
+	return has_sha1_file(oid->hash);
+}
+
+int has_object_file_with_flags(const struct object_id *oid, int flags)
+{
+	return has_sha1_file_with_flags(oid->hash, flags);
+}
+
+static void check_tree(const void *buf, size_t size)
+{
+	struct tree_desc desc;
+	struct name_entry entry;
+
+	init_tree_desc(&desc, buf, size);
+	while (tree_entry(&desc, &entry))
+		/* do nothing
+		 * tree_entry() will die() on malformed entries */
+		;
+}
+
+static void check_commit(const void *buf, size_t size)
+{
+	struct commit c;
+	memset(&c, 0, sizeof(c));
+	if (parse_commit_buffer(&c, buf, size))
+		die("corrupt commit");
+}
+
+static void check_tag(const void *buf, size_t size)
+{
+	struct tag t;
+	memset(&t, 0, sizeof(t));
+	if (parse_tag_buffer(&t, buf, size))
+		die("corrupt tag");
+}
+
+static int index_mem(struct object_id *oid, void *buf, size_t size,
+		     enum object_type type,
+		     const char *path, unsigned flags)
+{
+	int ret, re_allocated = 0;
+	int write_object = flags & HASH_WRITE_OBJECT;
+
+	if (!type)
+		type = OBJ_BLOB;
+
+	/*
+	 * Convert blobs to git internal format
+	 */
+	if ((type == OBJ_BLOB) && path) {
+		struct strbuf nbuf = STRBUF_INIT;
+		if (convert_to_git(&the_index, path, buf, size, &nbuf,
+				   get_conv_flags(flags))) {
+			buf = strbuf_detach(&nbuf, &size);
+			re_allocated = 1;
+		}
+	}
+	if (flags & HASH_FORMAT_CHECK) {
+		if (type == OBJ_TREE)
+			check_tree(buf, size);
+		if (type == OBJ_COMMIT)
+			check_commit(buf, size);
+		if (type == OBJ_TAG)
+			check_tag(buf, size);
+	}
+
+	if (write_object)
+		ret = write_object_file(buf, size, type_name(type), oid);
+	else
+		ret = hash_object_file(buf, size, type_name(type), oid);
+	if (re_allocated)
+		free(buf);
+	return ret;
+}
+
+static int index_stream_convert_blob(struct object_id *oid, int fd,
+				     const char *path, unsigned flags)
+{
+	int ret;
+	const int write_object = flags & HASH_WRITE_OBJECT;
+	struct strbuf sbuf = STRBUF_INIT;
+
+	assert(path);
+	assert(would_convert_to_git_filter_fd(path));
+
+	convert_to_git_filter_fd(&the_index, path, fd, &sbuf,
+				 get_conv_flags(flags));
+
+	if (write_object)
+		ret = write_object_file(sbuf.buf, sbuf.len, type_name(OBJ_BLOB),
+					oid);
+	else
+		ret = hash_object_file(sbuf.buf, sbuf.len, type_name(OBJ_BLOB),
+				       oid);
+	strbuf_release(&sbuf);
+	return ret;
+}
+
+static int index_pipe(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(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 object_id *oid, int fd, size_t size,
+		      enum object_type type, const char *path,
+		      unsigned flags)
+{
+	int ret;
+
+	if (!size) {
+		ret = index_mem(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(oid, buf, size, type, path, flags);
+		free(buf);
+	} else {
+		void *buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
+		ret = index_mem(oid, buf, size, type, path, flags);
+		munmap(buf, size);
+	}
+	return ret;
+}
+
+/*
+ * This creates one packfile per large blob unless bulk-checkin
+ * machinery is "plugged".
+ *
+ * This also bypasses the usual "convert-to-git" dance, and that is on
+ * purpose. We could write a streaming version of the converting
+ * functions and insert that before feeding the data to fast-import
+ * (or equivalent in-core API described above). However, that is
+ * somewhat complicated, as we do not know the size of the filter
+ * result, which we need to know beforehand when writing a git object.
+ * Since the primary motivation for trying to stream from the working
+ * tree file and to avoid mmaping it in core is to deal with large
+ * binary blobs, they generally do not want to get any conversion, and
+ * callers should avoid this code path when filters are requested.
+ */
+static int index_stream(struct object_id *oid, int fd, size_t size,
+			enum object_type type, const char *path,
+			unsigned flags)
+{
+	return index_bulk_checkin(oid, fd, size, type, path, flags);
+}
+
+int index_fd(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(path))
+		ret = index_stream_convert_blob(oid, fd, path, flags);
+	else if (!S_ISREG(st->st_mode))
+		ret = index_pipe(oid, fd, type, path, flags);
+	else if (st->st_size <= big_file_threshold || type != OBJ_BLOB ||
+		 (path && would_convert_to_git(&the_index, path)))
+		ret = index_core(oid, fd, xsize_t(st->st_size), type, path,
+				 flags);
+	else
+		ret = index_stream(oid, fd, xsize_t(st->st_size), type, path,
+				   flags);
+	close(fd);
+	return ret;
+}
+
+int index_path(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(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 & HASH_WRITE_OBJECT))
+			hash_object_file(sb.buf, sb.len, blob_type, oid);
+		else if (write_object_file(sb.buf, sb.len, blob_type, oid))
+			rc = error("%s: failed to insert into database", path);
+		strbuf_release(&sb);
+		break;
+	case S_IFDIR:
+		return resolve_gitlink_ref(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;
+}
+
+void assert_oid_type(const struct object_id *oid, enum object_type expect)
+{
+	enum object_type type = oid_object_info(oid, NULL);
+	if (type < 0)
+		die("%s is not a valid object", oid_to_hex(oid));
+	if (type != expect)
+		die("%s is not a valid '%s' object", oid_to_hex(oid),
+		    type_name(expect));
+}
+
+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(dir))) {
+		size_t namelen;
+		if (is_dot_or_dotdot(de->d_name))
+			continue;
+
+		namelen = strlen(de->d_name);
+		strbuf_setlen(path, baselen);
+		strbuf_add(path, de->d_name, namelen);
+		if (namelen == GIT_SHA1_HEXSZ - 2 &&
+		    !hex_to_bytes(oid.hash + 1, de->d_name,
+				  GIT_SHA1_RAWSZ - 1)) {
+			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;
+}
+
+struct loose_alt_odb_data {
+	each_loose_object_fn *cb;
+	void *data;
+};
+
+static int loose_from_alt_odb(struct alternate_object_database *alt,
+			      void *vdata)
+{
+	struct loose_alt_odb_data *data = vdata;
+	struct strbuf buf = STRBUF_INIT;
+	int r;
+
+	strbuf_addstr(&buf, alt->path);
+	r = for_each_loose_file_in_objdir_buf(&buf,
+					      data->cb, NULL, NULL,
+					      data->data);
+	strbuf_release(&buf);
+	return r;
+}
+
+int for_each_loose_object(each_loose_object_fn cb, void *data, unsigned flags)
+{
+	struct loose_alt_odb_data alt;
+	int r;
+
+	r = for_each_loose_file_in_objdir(get_object_directory(),
+					  cb, NULL, NULL, data);
+	if (r)
+		return r;
+
+	if (flags & FOR_EACH_OBJECT_LOCAL_ONLY)
+		return 0;
+
+	alt.cb = cb;
+	alt.data = data;
+	return foreach_alt_odb(loose_from_alt_odb, &alt);
+}
+
+static int check_stream_sha1(git_zstream *stream,
+			     const char *hdr,
+			     unsigned long size,
+			     const char *path,
+			     const unsigned char *expected_sha1)
+{
+	git_hash_ctx c;
+	unsigned char real_sha1[GIT_MAX_RAWSZ];
+	unsigned char buf[4096];
+	unsigned long total_read;
+	int status = Z_OK;
+
+	the_hash_algo->init_fn(&c);
+	the_hash_algo->update_fn(&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_sha1_rest for details.
+	 */
+	while (total_read <= size &&
+	       (status == Z_OK || status == Z_BUF_ERROR)) {
+		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);
+		the_hash_algo->update_fn(&c, buf, stream->next_out - buf);
+		total_read += stream->next_out - buf;
+	}
+	git_inflate_end(stream);
+
+	if (status != Z_STREAM_END) {
+		error("corrupt loose object '%s'", sha1_to_hex(expected_sha1));
+		return -1;
+	}
+	if (stream->avail_in) {
+		error("garbage at end of loose object '%s'",
+		      sha1_to_hex(expected_sha1));
+		return -1;
+	}
+
+	the_hash_algo->final_fn(real_sha1, &c);
+	if (hashcmp(expected_sha1, real_sha1)) {
+		error("sha1 mismatch for %s (expected %s)", path,
+		      sha1_to_hex(expected_sha1));
+		return -1;
+	}
+
+	return 0;
+}
+
+int read_loose_object(const char *path,
+		      const struct object_id *expected_oid,
+		      enum object_type *type,
+		      unsigned long *size,
+		      void **contents)
+{
+	int ret = -1;
+	void *map = NULL;
+	unsigned long mapsize;
+	git_zstream stream;
+	char hdr[MAX_HEADER_LEN];
+
+	*contents = NULL;
+
+	map = map_sha1_file_1(the_repository, path, NULL, &mapsize);
+	if (!map) {
+		error_errno("unable to mmap %s", path);
+		goto out;
+	}
+
+	if (unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr)) < 0) {
+		error("unable to unpack header of %s", path);
+		goto out;
+	}
+
+	*type = parse_sha1_header(hdr, size);
+	if (*type < 0) {
+		error("unable to parse header of %s", path);
+		git_inflate_end(&stream);
+		goto out;
+	}
+
+	if (*type == OBJ_BLOB) {
+		if (check_stream_sha1(&stream, hdr, *size, path, expected_oid->hash) < 0)
+			goto out;
+	} else {
+		*contents = unpack_sha1_rest(&stream, hdr, *size, expected_oid->hash);
+		if (!*contents) {
+			error("unable to unpack contents of %s", path);
+			git_inflate_end(&stream);
+			goto out;
+		}
+		if (check_object_signature(expected_oid, *contents,
+					 *size, type_name(*type))) {
+			error("sha1 mismatch for %s (expected %s)", path,
+			      oid_to_hex(expected_oid));
+			free(*contents);
+			goto out;
+		}
+	}
+
+	ret = 0; /* everything checks out */
+
+out:
+	if (map)
+		munmap(map, mapsize);
+	return ret;
+}