Subject: Re: [PATCH] unpack-trees: don't shift conflicts left and right

From: René Scharfe <[email-masked]>
Date: Tue, 18 Jun 2013 01:26:45 +0200

Am 17.06.2013 22:44, schrieb Junio C Hamano:
> René Scharfe <[email-masked]> writes:
> 
>>> The information is only useful for the unpack_trees callback, and
>>> "info->data" is a more appropriate place to hang such a callback
>>> specific data.
>>>
>>> Perhaps we should use info->data field to point at
>>>
>>> 	struct {
>>>           	struct unpack_trees_options *o;
>>>           	unsigned long df_conflict;
>>> 	};
>>>
>>> and get rid of info->conflicts field?
>>
>> Here's a patch that does so, but it complicates matters quite a bit.
>> Did I miss anything (or rather: add too much)?
> 
> I do not think so.  These bits are needed per recursion level, and
> it cannot be shoved into unpack_trees_options so I suspect that your
> patch is the best we can do.  Or, perhaps we can
> 
>   - add df_conflict to struct unpack_trees_options;
> 
>   - have traverse_info->data point at struct unpack_trees_options as
>     before; and
> 
>   - save the old value of o->df_conflict on the stack of
>     traverse_trees_recursive(), update the field in place, and
>     restore it when the recursion returns???

How about going into the opposite direction and moving df_conflicts
handling more into traverse_tree?  If the function saved the mask
and dirmask in traverse_info then callbacks could calculate the
cumulated d/f conflicts by walking the info chain, similar to how
make_traverse_path works.  That would match the spirit of that
struct.  Below is a patch for that, for illustration.

We could then remove the mask and dirmask parameters from
traverse_callback_t functions, as the callbacks can then get them
through traverse_info.

René

 tree-walk.c    |  2 ++
 tree-walk.h    |  2 +-
 unpack-trees.c | 11 ++++++-----
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/tree-walk.c b/tree-walk.c
index 6e30ef9..dae5db7 100644
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -400,6 +400,8 @@ int traverse_trees(int n, struct tree_desc *t, struct traverse_info *info)
 		}
 		if (!mask)
 			break;
+		info->mask = mask;
+		info->dirmask = dirmask;
 		interesting = prune_traversal(e, info, &base, interesting);
 		if (interesting < 0)
 			break;
diff --git a/tree-walk.h b/tree-walk.h
index ae04b64..e308859 100644
--- a/tree-walk.h
+++ b/tree-walk.h
@@ -46,7 +46,7 @@ struct traverse_info {
 	int pathlen;
 	struct pathspec *pathspec;
 
-	unsigned long df_conflicts;
+	unsigned long mask, dirmask;
 	traverse_callback_t fn;
 	void *data;
 	int show_all_errors;
diff --git a/unpack-trees.c b/unpack-trees.c
index b27f2a6..58210d0 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -445,7 +445,6 @@ static int switch_cache_bottom(struct traverse_info *info)
 }
 
 static int traverse_trees_recursive(int n, unsigned long dirmask,
-				    unsigned long df_conflicts,
 				    struct name_entry *names,
 				    struct traverse_info *info)
 {
@@ -464,7 +463,6 @@ static int traverse_trees_recursive(int n, unsigned long dirmask,
 	newinfo.pathspec = info->pathspec;
 	newinfo.name = *p;
 	newinfo.pathlen += tree_entry_len(p) + 1;
-	newinfo.df_conflicts |= df_conflicts;
 
 	for (i = 0; i < n; i++, dirmask >>= 1) {
 		const unsigned char *sha1 = NULL;
@@ -565,12 +563,16 @@ static int unpack_nondirectories(int n, unsigned long mask,
 {
 	int i;
 	struct unpack_trees_options *o = info->data;
-	unsigned long conflicts = info->df_conflicts | dirmask;
+	unsigned long conflicts = dirmask;
+	const struct traverse_info *previnfo;
 
 	/* Do we have *only* directories? Nothing to do */
 	if (mask == dirmask && !src[0])
 		return 0;
 
+	for (previnfo = info->prev; previnfo; previnfo = previnfo->prev)
+		conflicts |= previnfo->mask & ~previnfo->dirmask;
+
 	/*
 	 * Ok, we've filled in up to any potential index entry in src[0],
 	 * now do the rest.
@@ -820,8 +822,7 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
 			}
 		}
 
-		if (traverse_trees_recursive(n, dirmask, mask & ~dirmask,
-					     names, info) < 0)
+		if (traverse_trees_recursive(n, dirmask, names, info) < 0)
 			return -1;
 		return mask;
 	}