[PATCH 3/8] cache-tree: implement cache_tree_find_path()

["Derrick Stolee via GitGitGadget" <gitgitgadget@xxxxxxxxx>]

From: Derrick Stolee <dstolee@xxxxxxxxxxxxx>

Given a 'struct cache_tree', it may be beneficial to navigate directly
to a node within that corresponds to a given path name. Create
cache_tree_find_path() for this function. It returns NULL when no such
path exists.

The implementation is adapted from do_invalidate_path() which does a
similar search but also modifies the nodes it finds along the way.

This new method is not currently used, but will be in an upcoming
change.

Signed-off-by: Derrick Stolee <derrickstolee@xxxxxxxxxx>
---
 cache-tree.c | 24 ++++++++++++++++++++++++
 cache-tree.h |  2 ++
 2 files changed, 26 insertions(+)

diff --git a/cache-tree.c b/cache-tree.c
index 6752f69d515..23893a7b113 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -100,6 +100,30 @@ struct cache_tree_sub *cache_tree_sub(struct cache_tree *it, const char *path)
 	return find_subtree(it, path, pathlen, 1);
 }
 
+struct cache_tree *cache_tree_find_path(struct cache_tree *it, const char *path)
+{
+	const char *slash;
+	int namelen;
+	struct cache_tree_sub *down;
+
+	if (!it)
+		return NULL;
+	slash = strchrnul(path, '/');
+	namelen = slash - path;
+	it->entry_count = -1;
+	if (!*slash) {
+		int pos;
+		pos = cache_tree_subtree_pos(it, path, namelen);
+		if (0 <= pos)
+			return it->down[pos]->cache_tree;
+		return NULL;
+	}
+	down = find_subtree(it, path, namelen, 0);
+	if (down)
+		return cache_tree_find_path(down->cache_tree, slash + 1);
+	return NULL;
+}
+
 static int do_invalidate_path(struct cache_tree *it, const char *path)
 {
 	/* a/b/c
diff --git a/cache-tree.h b/cache-tree.h
index 8efeccebfc9..f75f8e74dcd 100644
--- a/cache-tree.h
+++ b/cache-tree.h
@@ -29,6 +29,8 @@ struct cache_tree_sub *cache_tree_sub(struct cache_tree *, const char *);
 
 int cache_tree_subtree_pos(struct cache_tree *it, const char *path, int pathlen);
 
+struct cache_tree *cache_tree_find_path(struct cache_tree *it, const char *path);
+
 void cache_tree_write(struct strbuf *, struct cache_tree *root);
 struct cache_tree *cache_tree_read(const char *buffer, unsigned long size);
 
-- 
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