index: write out the tree cache extension

Keeping the cache around after read-tree is only one part of the
optimisation opportunities. In order to share the cache between program
instances, we need to write the TREE extension to the index.

Do so, taking the opportunity to rename 'entries' to 'entry_count' to
match the name given in the format description. The included test is
rather trivial, but works as a sanity check.

1 files changed, 56 insertions, 4 deletions

diff --git a/src/tree-cache.c b/src/tree-cache.c
index 1eb046d33..48dc46a40 100644
--- a/src/tree-cache.c
+++ b/src/tree-cache.c
@@ -31,7 +31,7 @@ void git_tree_cache_invalidate_path(git_tree_cache *tree, const char *path)
 	if (tree == NULL)
 		return;
 
-	tree->entries = -1;
+	tree->entry_count = -1;
 
 	while (ptr != NULL) {
 		end = strchr(ptr, '/');
@@ -43,7 +43,7 @@ void git_tree_cache_invalidate_path(git_tree_cache *tree, const char *path)
 		if (tree == NULL) /* We don't have that tree */
 			return;
 
-		tree->entries = -1;
+		tree->entry_count = -1;
 		ptr = end + 1;
 	}
 }
@@ -93,7 +93,7 @@ static int read_tree_internal(git_tree_cache **out,
 	if (git__strtol32(&count, buffer, &buffer, 10) < 0)
 		goto corrupted;
 
-	tree->entries = count;
+	tree->entry_count = count;
 
 	if (*buffer != ' ' || ++buffer >= buffer_end)
 		goto corrupted;
@@ -108,7 +108,7 @@ static int read_tree_internal(git_tree_cache **out,
 		goto corrupted;
 
 	/* The SHA1 is only there if it's not invalidated */
-	if (tree->entries >= 0) {
+	if (tree->entry_count >= 0) {
 		/* 160-bit SHA-1 for this tree and it's children */
 		if (buffer + GIT_OID_RAWSZ > buffer_end)
 			goto corrupted;
@@ -244,3 +244,55 @@ int git_tree_cache_new(git_tree_cache **out, const char *name, git_pool *pool)
 	*out = tree;
 	return 0;
 }
+
+/**
+ * Recursively recalculate the total entry count, which we need to
+ * write out to the index
+ */
+static void recount_entries(git_tree_cache *tree)
+{
+	size_t i;
+	ssize_t entry_count;
+	git_tree_cache *child;
+
+	for (i = 0; i < tree->children_count; i++)
+		recount_entries(tree->children[i]);
+
+	if (tree->entry_count == -1)
+		return;
+
+	entry_count = 0;
+	for (i = 0; i < tree->children_count; i++) {
+		child = tree->children[i];
+
+		if (child->entry_count == -1)
+			continue;
+
+		entry_count += tree->children[i]->children_count;
+	}
+
+	tree->entry_count = entry_count;
+}
+
+static void write_tree(git_buf *out, git_tree_cache *tree)
+{
+	size_t i;
+
+	git_buf_printf(out, "%s%c%zd %"PRIuZ"\n", tree->name, 0, tree->entry_count, tree->children_count);
+
+	if (tree->entry_count == -1)
+		return;
+
+	git_buf_put(out, (const char *) &tree->oid, GIT_OID_RAWSZ);
+
+	for (i = 0; i < tree->children_count; i++)
+		write_tree(out, tree->children[i]);
+}
+
+int git_tree_cache_write(git_buf *out, git_tree_cache *tree)
+{
+	recount_entries(tree);
+	write_tree(out, tree);
+
+	return git_buf_oom(out) ? -1 : 0;
+}