1 files changed, 116 insertions, 0 deletions
diff --git a/tree-walk.c b/tree-walk.c
new file mode 100644
index 0000000000..0735f4046d
--- /dev/null
+++ b/tree-walk.c
@@ -0,0 +1,116 @@
+#include "cache.h"
+#include "tree-walk.h"
+
+void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1)
+{
+	unsigned long size = 0;
+	void *buf = NULL;
+
+	if (sha1) {
+		buf = read_object_with_reference(sha1, "tree", &size, NULL);
+		if (!buf)
+			die("unable to read tree %s", sha1_to_hex(sha1));
+	}
+	desc->size = size;
+	desc->buf = buf;
+	return buf;
+}
+
+static int entry_compare(struct name_entry *a, struct name_entry *b)
+{
+	return base_name_compare(
+			a->path, a->pathlen, a->mode,
+			b->path, b->pathlen, b->mode);
+}
+
+static void entry_clear(struct name_entry *a)
+{
+	memset(a, 0, sizeof(*a));
+}
+
+static void entry_extract(struct tree_desc *t, struct name_entry *a)
+{
+	a->sha1 = tree_entry_extract(t, &a->path, &a->mode);
+	a->pathlen = strlen(a->path);
+}
+
+void update_tree_entry(struct tree_desc *desc)
+{
+	void *buf = desc->buf;
+	unsigned long size = desc->size;
+	int len = strlen(buf) + 1 + 20;
+
+	if (size < len)
+		die("corrupt tree file");
+	desc->buf = buf + len;
+	desc->size = size - len;
+}
+
+const unsigned char *tree_entry_extract(struct tree_desc *desc, const char **pathp, unsigned int *modep)
+{
+	void *tree = desc->buf;
+	unsigned long size = desc->size;
+	int len = strlen(tree)+1;
+	const unsigned char *sha1 = tree + len;
+	const char *path = strchr(tree, ' ');
+	unsigned int mode;
+
+	if (!path || size < len + 20 || sscanf(tree, "%o", &mode) != 1)
+		die("corrupt tree file");
+	*pathp = path+1;
+	*modep = canon_mode(mode);
+	return sha1;
+}
+
+void traverse_trees(int n, struct tree_desc *t, const char *base, traverse_callback_t callback)
+{
+	struct name_entry *entry = xmalloc(n*sizeof(*entry));
+
+	for (;;) {
+		struct name_entry entry[3];
+		unsigned long mask = 0;
+		int i, last;
+
+		last = -1;
+		for (i = 0; i < n; i++) {
+			if (!t[i].size)
+				continue;
+			entry_extract(t+i, entry+i);
+			if (last >= 0) {
+				int cmp = entry_compare(entry+i, entry+last);
+
+				/*
+				 * Is the new name bigger than the old one?
+				 * Ignore it
+				 */
+				if (cmp > 0)
+					continue;
+				/*
+				 * Is the new name smaller than the old one?
+				 * Ignore all old ones
+				 */
+				if (cmp < 0)
+					mask = 0;
+			}
+			mask |= 1ul << i;
+			last = i;
+		}
+		if (!mask)
+			break;
+
+		/*
+		 * Update the tree entries we've walked, and clear
+		 * all the unused name-entries.
+		 */
+		for (i = 0; i < n; i++) {
+			if (mask & (1ul << i)) {
+				update_tree_entry(t+i);
+				continue;
+			}
+			entry_clear(entry + i);
+		}
+		callback(n, mask, entry, base);
+	}
+	free(entry);
+}
+