Merge branch 'mh/object-code-cleanup'

* mh/object-code-cleanup:
  sha1_file.c: document a bunch of functions defined in the file
  sha1_file_name(): declare to return a const string
  find_pack_entry(): document last_found_pack
  replace_object: use struct members instead of an array

cache.h

@@ -660,9 +660,28 @@ extern char *git_path(const char *fmt, ...) __attribute__((format (printf, 1, 2)
 extern char *git_path_submodule(const char *path, const char *fmt, ...)
 	__attribute__((format (printf, 2, 3)));
 
-extern char *sha1_file_name(const unsigned char *sha1);
+/*
+ * Return the name of the file in the local object database that would
+ * be used to store a loose object with the specified sha1.  The
+ * return value is a pointer to a statically allocated buffer that is
+ * overwritten each time the function is called.
+ */
+extern const char *sha1_file_name(const unsigned char *sha1);
+
+/*
+ * Return the name of the (local) packfile with the specified sha1 in
+ * its name.  The return value is a pointer to memory that is
+ * overwritten each time this function is called.
+ */
 extern char *sha1_pack_name(const unsigned char *sha1);
+
+/*
+ * Return the name of the (local) pack index file with the specified
+ * sha1 in its name.  The return value is a pointer to memory that is
+ * overwritten each time this function is called.
+ */
 extern char *sha1_pack_index_name(const unsigned char *sha1);
+
 extern const char *find_unique_abbrev(const unsigned char *sha1, int);
 extern const unsigned char null_sha1[20];
 
@@ -822,7 +841,19 @@ extern int check_sha1_signature(const unsigned char *sha1, void *buf, unsigned l
 extern int move_temp_to_file(const char *tmpfile, const char *filename);
 
 extern int has_sha1_pack(const unsigned char *sha1);
+
+/*
+ * Return true iff we have an object named sha1, whether local or in
+ * an alternate object database, and whether packed or loose.  This
+ * function does not respect replace references.
+ */
 extern int has_sha1_file(const unsigned char *sha1);
+
+/*
+ * Return true iff an alternate object database has a loose object
+ * with the specified name.  This function does not respect replace
+ * references.
+ */
 extern int has_loose_object_nonlocal(const unsigned char *sha1);
 
 extern int has_pack_index(const unsigned char *sha1);
@@ -1086,17 +1117,46 @@ extern struct packed_git *find_sha1_pack(const unsigned char *sha1,
 					 struct packed_git *packs);
 
 extern void pack_report(void);
+
+/*
+ * mmap the index file for the specified packfile (if it is not
+ * already mmapped).  Return 0 on success.
+ */
 extern int open_pack_index(struct packed_git *);
+
+/*
+ * munmap the index file for the specified packfile (if it is
+ * currently mmapped).
+ */
 extern void close_pack_index(struct packed_git *);
+
 extern unsigned char *use_pack(struct packed_git *, struct pack_window **, off_t, unsigned long *);
 extern void close_pack_windows(struct packed_git *);
 extern void unuse_pack(struct pack_window **);
 extern void free_pack_by_name(const char *);
 extern void clear_delta_base_cache(void);
 extern struct packed_git *add_packed_git(const char *, int, int);
-extern const unsigned char *nth_packed_object_sha1(struct packed_git *, uint32_t);
-extern off_t nth_packed_object_offset(const struct packed_git *, uint32_t);
-extern off_t find_pack_entry_one(const unsigned char *, struct packed_git *);
+
+/*
+ * Return the SHA-1 of the nth object within the specified packfile.
+ * Open the index if it is not already open.  The return value points
+ * at the SHA-1 within the mmapped index.  Return NULL if there is an
+ * error.
+ */
+extern const unsigned char *nth_packed_object_sha1(struct packed_git *, uint32_t n);
+
+/*
+ * Return the offset of the nth object within the specified packfile.
+ * The index must already be opened.
+ */
+extern off_t nth_packed_object_offset(const struct packed_git *, uint32_t n);
+
+/*
+ * If the object named sha1 is present in the specified packfile,
+ * return its offset within the packfile; otherwise, return 0.
+ */
+extern off_t find_pack_entry_one(const unsigned char *sha1, struct packed_git *);
+
 extern int is_pack_valid(struct packed_git *);
 extern void *unpack_entry(struct packed_git *, off_t, enum object_type *, unsigned long *);
 extern unsigned long unpack_object_header_buffer(const unsigned char *buf, unsigned long len, enum object_type *type, unsigned long *sizep);

http.c

@@ -1390,7 +1390,7 @@ struct http_object_request *new_http_object_request(const char *base_url,
 	unsigned char *sha1)
 {
 	char *hex = sha1_to_hex(sha1);
-	char *filename;
+	const char *filename;
 	char prevfile[PATH_MAX];
 	int prevlocal;
 	char prev_buf[PREV_BUF_SIZE];

replace_object.c

@@ -3,8 +3,13 @@
 #include "refs.h"
 #include "commit.h"
 
+/*
+ * An array of replacements.  The array is kept sorted by the original
+ * sha1.
+ */
 static struct replace_object {
-	unsigned char sha1[2][20];
+	unsigned char original[20];
+	unsigned char replacement[20];
 } **replace_object;
 
 static int replace_object_alloc, replace_object_nr;
@@ -12,7 +17,7 @@ static int replace_object_alloc, replace_object_nr;
 static const unsigned char *replace_sha1_access(size_t index, void *table)
 {
 	struct replace_object **replace = table;
-	return replace[index]->sha1[0];
+	return replace[index]->original;
 }
 
 static int replace_object_pos(const unsigned char *sha1)
@@ -24,7 +29,7 @@ static int replace_object_pos(const unsigned char *sha1)
 static int register_replace_object(struct replace_object *replace,
 				   int ignore_dups)
 {
-	int pos = replace_object_pos(replace->sha1[0]);
+	int pos = replace_object_pos(replace->original);
 
 	if (0 <= pos) {
 		if (ignore_dups)
@@ -60,14 +65,14 @@ static int register_replace_ref(const char *refname,
 	const char *hash = slash ? slash + 1 : refname;
 	struct replace_object *repl_obj = xmalloc(sizeof(*repl_obj));
 
-	if (strlen(hash) != 40 || get_sha1_hex(hash, repl_obj->sha1[0])) {
+	if (strlen(hash) != 40 || get_sha1_hex(hash, repl_obj->original)) {
 		free(repl_obj);
 		warning("bad replace ref name: %s", refname);
 		return 0;
 	}
 
 	/* Copy sha1 from the read ref */
-	hashcpy(repl_obj->sha1[1], sha1);
+	hashcpy(repl_obj->replacement, sha1);
 
 	/* Register new object */
 	if (register_replace_object(repl_obj, 1))
@@ -107,7 +112,7 @@ const unsigned char *do_lookup_replace_object(const unsigned char *sha1)
 
 		pos = replace_object_pos(cur);
 		if (0 <= pos)
-			cur = replace_object[pos]->sha1[1];
+			cur = replace_object[pos]->replacement;
 	} while (0 <= pos);
 
 	return cur;

sha1_file.c

@@ -60,6 +60,12 @@ static struct cached_object empty_tree = {
 	0
 };
 
+/*
+ * A pointer to the last packed_git in which an object was found.
+ * When an object is sought, we look in this packfile first, because
+ * objects that are looked up at similar times are often in the same
+ * packfile as one another.
+ */
 static struct packed_git *last_found_pack;
 
 static struct cached_object *find_cached_object(const unsigned char *sha1)
@@ -178,17 +184,7 @@ static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
 	}
 }
 
-/*
- * NOTE! This returns a statically allocated buffer, so you have to be
- * careful about using it. Do an "xstrdup()" if you need to save the
- * filename.
- *
- * Also note that this returns the location for creating.  Reading
- * SHA1 file can happen from any alternate directory listed in the
- * DB_ENVIRONMENT environment variable if it is not found in
- * the primary object database.
- */
-char *sha1_file_name(const unsigned char *sha1)
+const char *sha1_file_name(const unsigned char *sha1)
 {
 	static char buf[PATH_MAX];
 	const char *objdir;
@@ -208,6 +204,11 @@ char *sha1_file_name(const unsigned char *sha1)
 	return buf;
 }
 
+/*
+ * Return the name of the pack or index file with the specified sha1
+ * in its filename.  *base and *name are scratch space that must be
+ * provided by the caller.  which should be "pack" or "idx".
+ */
 static char *sha1_get_pack_name(const unsigned char *sha1,
 				char **name, char **base, const char *which)
 {
@@ -436,8 +437,7 @@ void prepare_alt_odb(void)
 
 static int has_loose_object_local(const unsigned char *sha1)
 {
-	char *name = sha1_file_name(sha1);
-	return !access(name, F_OK);
+	return !access(sha1_file_name(sha1), F_OK);
 }
 
 int has_loose_object_nonlocal(const unsigned char *sha1)
@@ -489,7 +489,12 @@ void pack_report(void)
 		sz_fmt(pack_mapped), sz_fmt(peak_pack_mapped));
 }
 
-static int check_packed_git_idx(const char *path,  struct packed_git *p)
+/*
+ * Open and mmap the index file at path, perform a couple of
+ * consistency checks, then record its information to p.  Return 0 on
+ * success.
+ */
+static int check_packed_git_idx(const char *path, struct packed_git *p)
 {
 	void *idx_map;
 	struct pack_idx_header *hdr;
@@ -1412,17 +1417,15 @@ int git_open_noatime(const char *name)
 
 static int stat_sha1_file(const unsigned char *sha1, struct stat *st)
 {
-	char *name = sha1_file_name(sha1);
 	struct alternate_object_database *alt;
 
-	if (!lstat(name, st))
+	if (!lstat(sha1_file_name(sha1), st))
 		return 0;
 
 	prepare_alt_odb();
 	errno = ENOENT;
 	for (alt = alt_odb_list; alt; alt = alt->next) {
-		name = alt->name;
-		fill_sha1_path(name, sha1);
+		fill_sha1_path(alt->name, sha1);
 		if (!lstat(alt->base, st))
 			return 0;
 	}
@@ -1433,18 +1436,16 @@ static int stat_sha1_file(const unsigned char *sha1, struct stat *st)
 static int open_sha1_file(const unsigned char *sha1)
 {
 	int fd;
-	char *name = sha1_file_name(sha1);
 	struct alternate_object_database *alt;
 
-	fd = git_open_noatime(name);
+	fd = git_open_noatime(sha1_file_name(sha1));
 	if (fd >= 0)
 		return fd;
 
 	prepare_alt_odb();
 	errno = ENOENT;
 	for (alt = alt_odb_list; alt; alt = alt->next) {
-		name = alt->name;
-		fill_sha1_path(name, sha1);
+		fill_sha1_path(alt->name, sha1);
 		fd = git_open_noatime(alt->base);
 		if (fd >= 0)
 			return fd;
@@ -2446,6 +2447,10 @@ static int fill_pack_entry(const unsigned char *sha1,
 	return 1;
 }
 
+/*
+ * Iff a pack file contains the object named by sha1, return true and
+ * store its location to e.
+ */
 static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e)
 {
 	struct packed_git *p;
@@ -2458,11 +2463,13 @@ static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e)
 		return 1;
 
 	for (p = packed_git; p; p = p->next) {
-		if (p == last_found_pack || !fill_pack_entry(sha1, e, p))
-			continue;
+		if (p == last_found_pack)
+			continue; /* we already checked this one */
 
-		last_found_pack = p;
-		return 1;
+		if (fill_pack_entry(sha1, e, p)) {
+			last_found_pack = p;
+			return 1;
+		}
 	}
 	return 0;
 }
@@ -2677,7 +2684,6 @@ void *read_sha1_file_extended(const unsigned char *sha1,
 			      unsigned flag)
 {
 	void *data;
-	char *path;
 	const struct packed_git *p;
 	const unsigned char *repl = lookup_replace_object_extended(sha1, flag);
 
@@ -2695,7 +2701,8 @@ void *read_sha1_file_extended(const unsigned char *sha1,
 		    sha1_to_hex(repl), sha1_to_hex(sha1));
 
 	if (has_loose_object(repl)) {
-		path = sha1_file_name(sha1);
+		const char *path = sha1_file_name(sha1);
+
 		die("loose object %s (stored in %s) is corrupt",
 		    sha1_to_hex(repl), path);
 	}
@@ -2893,10 +2900,9 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
 	git_zstream stream;
 	git_SHA_CTX c;
 	unsigned char parano_sha1[20];
-	char *filename;
 	static char tmp_file[PATH_MAX];
+	const char *filename = sha1_file_name(sha1);
 
-	filename = sha1_file_name(sha1);
 	fd = create_tmpfile(tmp_file, sizeof(tmp_file), filename);
 	if (fd < 0) {
 		if (errno == EACCES)