Add "named object array" concept

We've had this notion of a "object_list" for a long time, which eventually
grew a "name" member because some users (notably git-rev-list) wanted to
name each object as it is generated.

That object_list is great for some things, but it isn't all that wonderful
for others, and the "name" member is generally not used by everybody.

This patch splits the users of the object_list array up into two: the
traditional list users, who want the list-like format, and who don't
actually use or want the name. And another class of users that really used
the list as an extensible array, and generally wanted to name the objects.

The patch is fairly straightforward, but it's also biggish. Most of it
really just cleans things up: switching the revision parsing and listing
over to the array makes things like the builtin-diff usage much simpler
(we now see exactly how many members the array has, and we don't get the
objects reversed from the order they were on the command line).

One of the main reasons for doing this at all is that the malloc overhead
of the simple object list was actually pretty high, and the array is just
a lot denser. So this patch brings down memory usage by git-rev-list by
just under 3% (on top of all the other memory use optimizations) on the
mozilla archive.

It does add more lines than it removes, and more importantly, it adds a
whole new infrastructure for maintaining lists of objects, but on the
other hand, the new dynamic array code is pretty obvious. The change to
builtin-diff-tree.c shows a fairly good example of why an array interface
is sometimes more natural, and just much simpler for everybody.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 14 insertions, 12 deletions

diff --git a/builtin-diff.c b/builtin-diff.c
index 6ac3d4b8c..99a2f7660 100644
--- a/builtin-diff.c
+++ b/builtin-diff.c
@@ -50,7 +50,7 @@ static int builtin_diff_files(struct rev_info *revs,
 	 * specified rev.max_count is reasonable (0 <= n <= 3), and
 	 * there is no other revision filtering parameter.
 	 */
-	if (revs->pending_objects ||
+	if (revs->pending.nr ||
 	    revs->min_age != -1 ||
 	    revs->max_age != -1 ||
 	    3 < revs->max_count)
@@ -172,7 +172,7 @@ static int builtin_diff_index(struct rev_info *revs,
 	 * Make sure there is one revision (i.e. pending object),
 	 * and there is no revision filtering parameters.
 	 */
-	if (!revs->pending_objects || revs->pending_objects->next ||
+	if (revs->pending.nr != 1 ||
 	    revs->max_count != -1 || revs->min_age != -1 ||
 	    revs->max_age != -1)
 		usage(builtin_diff_usage);
@@ -181,10 +181,10 @@ static int builtin_diff_index(struct rev_info *revs,
 
 static int builtin_diff_tree(struct rev_info *revs,
 			     int argc, const char **argv,
-			     struct object_list *ent)
+			     struct object_array_entry *ent)
 {
 	const unsigned char *(sha1[2]);
-	int swap = 1;
+	int swap = 0;
 	while (1 < argc) {
 		const char *arg = argv[1];
 		if (!strcmp(arg, "--raw"))
@@ -195,10 +195,10 @@ static int builtin_diff_tree(struct rev_info *revs,
 	}
 
 	/* We saw two trees, ent[0] and ent[1].
-	 * unless ent[0] is unintesting, they are swapped
+	 * if ent[1] is unintesting, they are swapped
 	 */
-	if (ent[0].item->flags & UNINTERESTING)
-		swap = 0;
+	if (ent[1].item->flags & UNINTERESTING)
+		swap = 1;
 	sha1[swap] = ent[0].item->sha1;
 	sha1[1-swap] = ent[1].item->sha1;
 	diff_tree_sha1(sha1[0], sha1[1], "", &revs->diffopt);
@@ -208,7 +208,7 @@ static int builtin_diff_tree(struct rev_info *revs,
 
 static int builtin_diff_combined(struct rev_info *revs,
 				 int argc, const char **argv,
-				 struct object_list *ent,
+				 struct object_array_entry *ent,
 				 int ents)
 {
 	const unsigned char (*parent)[20];
@@ -242,13 +242,14 @@ void add_head(struct rev_info *revs)
 	obj = parse_object(sha1);
 	if (!obj)
 		return;
-	add_object(obj, &revs->pending_objects, NULL, "HEAD");
+	add_pending_object(revs, obj, "HEAD");
 }
 
 int cmd_diff(int argc, const char **argv, char **envp)
 {
+	int i;
 	struct rev_info rev;
-	struct object_list *list, ent[100];
+	struct object_array_entry ent[100];
 	int ents = 0, blobs = 0, paths = 0;
 	const char *path = NULL;
 	struct blobinfo blob[2];
@@ -281,7 +282,7 @@ int cmd_diff(int argc, const char **argv, char **envp)
 	/* Do we have --cached and not have a pending object, then
 	 * default to HEAD by hand.  Eek.
 	 */
-	if (!rev.pending_objects) {
+	if (!rev.pending.nr) {
 		int i;
 		for (i = 1; i < argc; i++) {
 			const char *arg = argv[i];
@@ -294,7 +295,8 @@ int cmd_diff(int argc, const char **argv, char **envp)
 		}
 	}
 
-	for (list = rev.pending_objects; list; list = list->next) {
+	for (i = 0; i < rev.pending.nr; i++) {
+		struct object_array_entry *list = rev.pending.objects+i;
 		struct object *obj = list->item;
 		const char *name = list->name;
 		int flags = (obj->flags & UNINTERESTING);