1 files changed, 356 insertions, 130 deletions

diff --git a/sha1_file.c b/sha1_file.c
index 309e87d987..ec957db5e1 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -26,14 +26,7 @@
 #include "mru.h"
 #include "list.h"
 #include "mergesort.h"
-
-#ifndef O_NOATIME
-#if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
-#define O_NOATIME 01000000
-#else
-#define O_NOATIME 0
-#endif
-#endif
+#include "quote.h"
 
 #define SZ_FMT PRIuMAX
 static inline uintmax_t sz_fmt(size_t s) { return s; }
@@ -172,36 +165,42 @@ enum scld_error safe_create_leading_directories_const(const char *path)
 	return result;
 }
 
-static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
+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];
-		char *pos = pathbuf + i*2 + (i > 0);
-		*pos++ = hex[val >> 4];
-		*pos = hex[val & 0xf];
+		strbuf_addch(buf, hex[val >> 4]);
+		strbuf_addch(buf, hex[val & 0xf]);
+		if (!i)
+			strbuf_addch(buf, '/');
 	}
 }
 
 const char *sha1_file_name(const unsigned char *sha1)
 {
-	static char buf[PATH_MAX];
-	const char *objdir;
-	int len;
+	static struct strbuf buf = STRBUF_INIT;
+
+	strbuf_reset(&buf);
+	strbuf_addf(&buf, "%s/", get_object_directory());
 
-	objdir = get_object_directory();
-	len = strlen(objdir);
+	fill_sha1_path(&buf, sha1);
+	return buf.buf;
+}
+
+struct strbuf *alt_scratch_buf(struct alternate_object_database *alt)
+{
+	strbuf_setlen(&alt->scratch, alt->base_len);
+	return &alt->scratch;
+}
 
-	/* '/' + sha1(2) + '/' + sha1(38) + '\0' */
-	if (len + 43 > PATH_MAX)
-		die("insanely long object directory %s", objdir);
-	memcpy(buf, objdir, len);
-	buf[len] = '/';
-	buf[len+3] = '/';
-	buf[len+42] = '\0';
-	fill_sha1_path(buf + len + 1, sha1);
-	return buf;
+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;
 }
 
 /*
@@ -235,6 +234,35 @@ struct alternate_object_database *alt_odb_list;
 static struct alternate_object_database **alt_odb_tail;
 
 /*
+ * Return non-zero iff the path is usable as an alternate object database.
+ */
+static int alt_odb_usable(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 = 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
@@ -253,59 +281,34 @@ static int link_alt_odb_entry(const char *entry, const char *relative_base,
 	int depth, const char *normalized_objdir)
 {
 	struct alternate_object_database *ent;
-	struct alternate_object_database *alt;
-	size_t pfxlen, entlen;
 	struct strbuf pathbuf = STRBUF_INIT;
 
 	if (!is_absolute_path(entry) && relative_base) {
-		strbuf_addstr(&pathbuf, real_path(relative_base));
+		strbuf_realpath(&pathbuf, relative_base, 1);
 		strbuf_addch(&pathbuf, '/');
 	}
 	strbuf_addstr(&pathbuf, entry);
 
-	normalize_path_copy(pathbuf.buf, pathbuf.buf);
-
-	pfxlen = strlen(pathbuf.buf);
+	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 (pfxlen && pathbuf.buf[pfxlen-1] == '/')
-		pfxlen -= 1;
-
-	entlen = st_add(pfxlen, 43); /* '/' + 2 hex + '/' + 38 hex + NUL */
-	ent = xmalloc(st_add(sizeof(*ent), entlen));
-	memcpy(ent->base, pathbuf.buf, pfxlen);
-	strbuf_release(&pathbuf);
-
-	ent->name = ent->base + pfxlen + 1;
-	ent->base[pfxlen + 3] = '/';
-	ent->base[pfxlen] = ent->base[entlen-1] = 0;
+	while (pathbuf.len && pathbuf.buf[pathbuf.len - 1] == '/')
+		strbuf_setlen(&pathbuf, pathbuf.len - 1);
 
-	/* Detect cases where alternate disappeared */
-	if (!is_directory(ent->base)) {
-		error("object directory %s does not exist; "
-		      "check .git/objects/info/alternates.",
-		      ent->base);
-		free(ent);
+	if (!alt_odb_usable(&pathbuf, normalized_objdir)) {
+		strbuf_release(&pathbuf);
 		return -1;
 	}
 
-	/* Prevent the common mistake of listing the same
-	 * thing twice, or object directory itself.
-	 */
-	for (alt = alt_odb_list; alt; alt = alt->next) {
-		if (pfxlen == alt->name - alt->base - 1 &&
-		    !memcmp(ent->base, alt->base, pfxlen)) {
-			free(ent);
-			return -1;
-		}
-	}
-	if (!fspathcmp(ent->base, normalized_objdir)) {
-		free(ent);
-		return -1;
-	}
+	ent = alloc_alt_odb(pathbuf.buf);
 
 	/* add the alternate entry */
 	*alt_odb_tail = ent;
@@ -313,20 +316,46 @@ static int link_alt_odb_entry(const char *entry, const char *relative_base,
 	ent->next = NULL;
 
 	/* recursively add alternates */
-	read_info_alternates(ent->base, depth + 1);
-
-	ent->base[pfxlen] = '/';
+	read_info_alternates(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(const char *alt, int len, int sep,
 				 const char *relative_base, int depth)
 {
-	struct string_list entries = STRING_LIST_INIT_NODUP;
-	char *alt_copy;
-	int i;
 	struct strbuf objdirbuf = STRBUF_INIT;
+	struct strbuf entry = STRBUF_INIT;
 
 	if (depth > 5) {
 		error("%s: ignoring alternate object stores, nesting too deep.",
@@ -335,23 +364,17 @@ static void link_alt_odb_entries(const char *alt, int len, int sep,
 	}
 
 	strbuf_add_absolute_path(&objdirbuf, get_object_directory());
-	normalize_path_copy(objdirbuf.buf, objdirbuf.buf);
+	if (strbuf_normalize_path(&objdirbuf) < 0)
+		die("unable to normalize object directory: %s",
+		    objdirbuf.buf);
 
-	alt_copy = xmemdupz(alt, len);
-	string_list_split_in_place(&entries, alt_copy, sep, -1);
-	for (i = 0; i < entries.nr; i++) {
-		const char *entry = entries.items[i].string;
-		if (entry[0] == '\0' || entry[0] == '#')
+	while (*alt) {
+		alt = parse_alt_odb_entry(alt, sep, &entry);
+		if (!entry.len)
 			continue;
-		if (!is_absolute_path(entry) && depth) {
-			error("%s: ignoring relative alternate object store %s",
-					relative_base, entry);
-		} else {
-			link_alt_odb_entry(entry, relative_base, depth, objdirbuf.buf);
-		}
+		link_alt_odb_entry(entry.buf, relative_base, depth, objdirbuf.buf);
 	}
-	string_list_clear(&entries, 0);
-	free(alt_copy);
+	strbuf_release(&entry);
 	strbuf_release(&objdirbuf);
 }
 
@@ -364,7 +387,7 @@ void read_info_alternates(const char * relative_base, int depth)
 	int fd;
 
 	path = xstrfmt("%s/info/alternates", relative_base);
-	fd = git_open_noatime(path);
+	fd = git_open(path);
 	free(path);
 	if (fd < 0)
 		return;
@@ -381,6 +404,18 @@ void read_info_alternates(const char * relative_base, int depth)
 	munmap(map, mapsz);
 }
 
+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 = xcalloc(1, sizeof(struct lock_file));
@@ -426,6 +461,17 @@ void add_to_alternates_file(const char *reference)
 	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();
+
+	link_alt_odb_entries(reference, strlen(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`
@@ -566,8 +612,8 @@ static int check_and_freshen_nonlocal(const unsigned char *sha1, int freshen)
 	struct alternate_object_database *alt;
 	prepare_alt_odb();
 	for (alt = alt_odb_list; alt; alt = alt->next) {
-		fill_sha1_path(alt->name, sha1);
-		if (check_and_freshen_file(alt->base, freshen))
+		const char *path = alt_sha1_path(alt, sha1);
+		if (check_and_freshen_file(path, freshen))
 			return 1;
 	}
 	return 0;
@@ -634,7 +680,7 @@ static int check_packed_git_idx(const char *path, struct packed_git *p)
 	struct pack_idx_header *hdr;
 	size_t idx_size;
 	uint32_t version, nr, i, *index;
-	int fd = git_open_noatime(path);
+	int fd = git_open(path);
 	struct stat st;
 
 	if (fd < 0)
@@ -1040,7 +1086,7 @@ static int open_packed_git_1(struct packed_git *p)
 	while (pack_max_fds <= pack_open_fds && close_one_pack())
 		; /* nothing */
 
-	p->pack_fd = git_open_noatime(p->pack_name);
+	p->pack_fd = git_open(p->pack_name);
 	if (p->pack_fd < 0 || fstat(p->pack_fd, &st))
 		return -1;
 	pack_open_fds++;
@@ -1381,6 +1427,32 @@ static void prepare_packed_git_one(char *objdir, int local)
 	strbuf_release(&path);
 }
 
+static int approximate_object_count_valid;
+
+/*
+ * Give a fast, rough count of the number of objects in the repository. This
+ * ignores loose objects completely. If you have a lot of them, then either
+ * you should repack because your performance will be awful, or they are
+ * all unreachable objects about to be pruned, in which case they're not really
+ * interesting as a measure of repo size in the first place.
+ */
+unsigned long approximate_object_count(void)
+{
+	static unsigned long count;
+	if (!approximate_object_count_valid) {
+		struct packed_git *p;
+
+		prepare_packed_git();
+		count = 0;
+		for (p = packed_git; p; p = p->next) {
+			if (open_pack_index(p))
+				continue;
+			count += p->num_objects;
+		}
+	}
+	return count;
+}
+
 static void *get_next_packed_git(const void *p)
 {
 	return ((const struct packed_git *)p)->next;
@@ -1443,11 +1515,8 @@ void prepare_packed_git(void)
 		return;
 	prepare_packed_git_one(get_object_directory(), 1);
 	prepare_alt_odb();
-	for (alt = alt_odb_list; alt; alt = alt->next) {
-		alt->name[-1] = 0;
-		prepare_packed_git_one(alt->base, 0);
-		alt->name[-1] = '/';
-	}
+	for (alt = alt_odb_list; alt; alt = alt->next)
+		prepare_packed_git_one(alt->path, 0);
 	rearrange_packed_git();
 	prepare_packed_git_mru();
 	prepare_packed_git_run_once = 1;
@@ -1455,6 +1524,7 @@ void prepare_packed_git(void)
 
 void reprepare_packed_git(void)
 {
+	approximate_object_count_valid = 0;
 	prepare_packed_git_run_once = 0;
 	prepare_packed_git();
 }
@@ -1533,61 +1603,81 @@ int check_sha1_signature(const unsigned char *sha1, void *map,
 	return hashcmp(sha1, real_sha1) ? -1 : 0;
 }
 
-int git_open_noatime(const char *name)
+int git_open_cloexec(const char *name, int flags)
 {
-	static int sha1_file_open_flag = O_NOATIME;
+	int fd;
+	static int o_cloexec = O_CLOEXEC;
 
-	for (;;) {
-		int fd;
+	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);
+	}
 
-		errno = 0;
-		fd = open(name, O_RDONLY | sha1_file_open_flag);
-		if (fd >= 0)
-			return fd;
+#if defined(F_GETFL) && defined(F_SETFL) && defined(FD_CLOEXEC)
+	{
+		static int fd_cloexec = FD_CLOEXEC;
 
-		/* Might the failure be due to O_NOATIME? */
-		if (errno != ENOENT && sha1_file_open_flag) {
-			sha1_file_open_flag = 0;
-			continue;
+		if (!o_cloexec && 0 <= fd && fd_cloexec) {
+			/* Opened w/o O_CLOEXEC?  try with fcntl(2) to add it */
+			int flags = fcntl(fd, F_GETFL);
+			if (fcntl(fd, F_SETFL, flags | fd_cloexec))
+				fd_cloexec = 0;
 		}
-
-		return -1;
 	}
+#endif
+	return fd;
 }
 
-static int stat_sha1_file(const unsigned char *sha1, struct stat *st)
+/*
+ * 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(const unsigned char *sha1, struct stat *st,
+			  const char **path)
 {
 	struct alternate_object_database *alt;
 
-	if (!lstat(sha1_file_name(sha1), st))
+	*path = sha1_file_name(sha1);
+	if (!lstat(*path, st))
 		return 0;
 
 	prepare_alt_odb();
 	errno = ENOENT;
 	for (alt = alt_odb_list; alt; alt = alt->next) {
-		fill_sha1_path(alt->name, sha1);
-		if (!lstat(alt->base, st))
+		*path = alt_sha1_path(alt, sha1);
+		if (!lstat(*path, st))
 			return 0;
 	}
 
 	return -1;
 }
 
-static int open_sha1_file(const unsigned char *sha1)
+/*
+ * 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(const unsigned char *sha1, const char **path)
 {
 	int fd;
 	struct alternate_object_database *alt;
 	int most_interesting_errno;
 
-	fd = git_open_noatime(sha1_file_name(sha1));
+	*path = sha1_file_name(sha1);
+	fd = git_open(*path);
 	if (fd >= 0)
 		return fd;
 	most_interesting_errno = errno;
 
 	prepare_alt_odb();
 	for (alt = alt_odb_list; alt; alt = alt->next) {
-		fill_sha1_path(alt->name, sha1);
-		fd = git_open_noatime(alt->base);
+		*path = alt_sha1_path(alt, sha1);
+		fd = git_open(*path);
 		if (fd >= 0)
 			return fd;
 		if (most_interesting_errno == ENOENT)
@@ -1597,12 +1687,21 @@ static int open_sha1_file(const unsigned char *sha1)
 	return -1;
 }
 
-void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
+/*
+ * 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(const char *path,
+			     const unsigned char *sha1,
+			     unsigned long *size)
 {
 	void *map;
 	int fd;
 
-	fd = open_sha1_file(sha1);
+	if (path)
+		fd = git_open(path);
+	else
+		fd = open_sha1_file(sha1, &path);
 	map = NULL;
 	if (fd >= 0) {
 		struct stat st;
@@ -1611,7 +1710,7 @@ void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 			*size = xsize_t(st.st_size);
 			if (!*size) {
 				/* mmap() is forbidden on empty files */
-				error("object file %s is empty", sha1_file_name(sha1));
+				error("object file %s is empty", path);
 				return NULL;
 			}
 			map = xmmap(NULL, *size, PROT_READ, MAP_PRIVATE, fd, 0);
@@ -1621,6 +1720,11 @@ void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 	return map;
 }
 
+void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
+{
+	return map_sha1_file_1(NULL, sha1, size);
+}
+
 unsigned long unpack_object_header_buffer(const unsigned char *buf,
 		unsigned long len, enum object_type *type, unsigned long *sizep)
 {
@@ -2267,11 +2371,10 @@ static inline void release_delta_base_cache(struct delta_base_cache_entry *ent)
 
 void clear_delta_base_cache(void)
 {
-	struct hashmap_iter iter;
-	struct delta_base_cache_entry *entry;
-	for (entry = hashmap_iter_first(&delta_base_cache, &iter);
-	     entry;
-	     entry = hashmap_iter_next(&iter)) {
+	struct list_head *lru, *tmp;
+	list_for_each_safe(lru, tmp, &delta_base_cache_lru) {
+		struct delta_base_cache_entry *entry =
+			list_entry(lru, struct delta_base_cache_entry, lru);
 		release_delta_base_cache(entry);
 	}
 }
@@ -2731,8 +2834,9 @@ static int sha1_loose_object_info(const unsigned char *sha1,
 	 * object even exists.
 	 */
 	if (!oi->typep && !oi->typename && !oi->sizep) {
+		const char *path;
 		struct stat st;
-		if (stat_sha1_file(sha1, &st) < 0)
+		if (stat_sha1_file(sha1, &st, &path) < 0)
 			return -1;
 		if (oi->disk_sizep)
 			*oi->disk_sizep = st.st_size;
@@ -2928,6 +3032,8 @@ void *read_sha1_file_extended(const unsigned char *sha1,
 {
 	void *data;
 	const struct packed_git *p;
+	const char *path;
+	struct stat st;
 	const unsigned char *repl = lookup_replace_object_extended(sha1, flag);
 
 	errno = 0;
@@ -2943,12 +3049,9 @@ void *read_sha1_file_extended(const unsigned char *sha1,
 		die("replacement %s not found for %s",
 		    sha1_to_hex(repl), sha1_to_hex(sha1));
 
-	if (has_loose_object(repl)) {
-		const char *path = sha1_file_name(sha1);
-
+	if (!stat_sha1_file(repl, &st, &path))
 		die("loose object %s (stored in %s) is corrupt",
 		    sha1_to_hex(repl), path);
-	}
 
 	if ((p = has_packed_and_bad(repl)) != NULL)
 		die("packed object %s (stored in %s) is corrupt",
@@ -3309,6 +3412,11 @@ 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;
@@ -3648,8 +3756,7 @@ static int loose_from_alt_odb(struct alternate_object_database *alt,
 	struct strbuf buf = STRBUF_INIT;
 	int r;
 
-	/* copy base not including trailing '/' */
-	strbuf_add(&buf, alt->base, alt->name - alt->base - 1);
+	strbuf_addstr(&buf, alt->path);
 	r = for_each_loose_file_in_objdir_buf(&buf,
 					      data->cb, NULL, NULL,
 					      data->data);
@@ -3714,3 +3821,122 @@ int for_each_packed_object(each_packed_object_fn cb, void *data, unsigned flags)
 	}
 	return r ? r : pack_errors;
 }
+
+static int check_stream_sha1(git_zstream *stream,
+			     const char *hdr,
+			     unsigned long size,
+			     const char *path,
+			     const unsigned char *expected_sha1)
+{
+	git_SHA_CTX c;
+	unsigned char real_sha1[GIT_SHA1_RAWSZ];
+	unsigned char buf[4096];
+	unsigned long total_read;
+	int status = Z_OK;
+
+	git_SHA1_Init(&c);
+	git_SHA1_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_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);
+		git_SHA1_Update(&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;
+	}
+
+	git_SHA1_Final(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 unsigned char *expected_sha1,
+		      enum object_type *type,
+		      unsigned long *size,
+		      void **contents)
+{
+	int ret = -1;
+	int fd = -1;
+	void *map = NULL;
+	unsigned long mapsize;
+	git_zstream stream;
+	char hdr[32];
+
+	*contents = NULL;
+
+	map = map_sha1_file_1(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_sha1) < 0)
+			goto out;
+	} else {
+		*contents = unpack_sha1_rest(&stream, hdr, *size, expected_sha1);
+		if (!*contents) {
+			error("unable to unpack contents of %s", path);
+			git_inflate_end(&stream);
+			goto out;
+		}
+		if (check_sha1_signature(expected_sha1, *contents,
+					 *size, typename(*type))) {
+			error("sha1 mismatch for %s (expected %s)", path,
+			      sha1_to_hex(expected_sha1));
+			free(*contents);
+			goto out;
+		}
+	}
+
+	ret = 0; /* everything checks out */
+
+out:
+	if (map)
+		munmap(map, mapsize);
+	if (fd >= 0)
+		close(fd);
+	return ret;
+}