[PATCH] delta check

This adds knowledge of delta objects to fsck-cache and various object
parsing code.  A new switch to git-fsck-cache is provided to display the
maximum delta depth found in a repository.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 115 insertions, 0 deletions

diff --git a/delta.c b/delta.c
new file mode 100644
index 000000000..05ef7fd6e
--- /dev/null
+++ b/delta.c
@@ -0,0 +1,115 @@
+#include "object.h"
+#include "blob.h"
+#include "tree.h"
+#include "commit.h"
+#include "tag.h"
+#include "delta.h"
+#include "cache.h"
+#include <string.h>
+
+/* the delta object definition (it can alias any other object) */
+struct delta {
+	union {
+		struct object object;
+		struct blob blob;
+		struct tree tree;
+		struct commit commit;
+		struct tag tag;
+	} u;
+};
+
+struct delta *lookup_delta(unsigned char *sha1)
+{
+	struct object *obj = lookup_object(sha1);
+	if (!obj) {
+		struct delta *ret = xmalloc(sizeof(struct delta));
+		memset(ret, 0, sizeof(struct delta));
+		created_object(sha1, &ret->u.object);
+		return ret;
+	}
+	return (struct delta *) obj;
+}
+
+int parse_delta_buffer(struct delta *item, void *buffer, unsigned long size)
+{
+	struct object *reference;
+	struct object_list *p;
+
+	if (item->u.object.delta)
+		return 0;
+	item->u.object.delta = 1;
+	if (size <= 20)
+		return -1;
+	reference = lookup_object(buffer);
+	if (!reference) {
+		struct delta *ref = xmalloc(sizeof(struct delta));
+		memset(ref, 0, sizeof(struct delta));
+		created_object(buffer, &ref->u.object);
+		reference = &ref->u.object;
+	}
+
+	p = xmalloc(sizeof(*p));
+	p->item = &item->u.object;
+	p->next = reference->attached_deltas;
+	reference->attached_deltas = p;
+	return 0;
+}
+
+int process_deltas(void *src, unsigned long src_size, const char *src_type,
+		   struct object_list *delta_list)
+{
+	int deepest = 0;
+	do {
+		struct object *obj = delta_list->item;
+		static char type[10];
+		void *map, *delta, *buf;
+		unsigned long map_size, delta_size, buf_size;
+		map = map_sha1_file(obj->sha1, &map_size);
+		if (!map)
+			continue;
+		delta = unpack_sha1_file(map, map_size, type, &delta_size);
+		munmap(map, map_size);
+		if (!delta)
+			continue;
+		if (strcmp(type, "delta") || delta_size <= 20) {
+			free(delta);
+			continue;
+		}
+		buf = patch_delta(src, src_size,
+				  delta+20, delta_size-20,
+				  &buf_size);
+		free(delta);
+		if (!buf)
+			continue;
+		if (check_sha1_signature(obj->sha1, buf, buf_size, src_type) < 0)
+			printf("sha1 mismatch for delta %s\n", sha1_to_hex(obj->sha1));
+		if (obj->type && obj->type != src_type) {
+			error("got %s when expecting %s for delta %s",
+			      src_type, obj->type, sha1_to_hex(obj->sha1));
+			free(buf);
+			continue;
+		}
+		obj->type = src_type;
+		if (src_type == blob_type) {
+			parse_blob_buffer((struct blob *)obj, buf, buf_size);
+		} else if (src_type == tree_type) {
+			parse_tree_buffer((struct tree *)obj, buf, buf_size);
+		} else if (src_type == commit_type) {
+			parse_commit_buffer((struct commit *)obj, buf, buf_size);
+		} else if (src_type == tag_type) {
+			parse_tag_buffer((struct tag *)obj, buf, buf_size);
+		} else {
+			error("unknown object type %s", src_type);
+			free(buf);
+			continue;
+		}
+		if (obj->attached_deltas) {
+			int depth = process_deltas(buf, buf_size, src_type,
+						   obj->attached_deltas);
+			if (deepest < depth)
+				deepest = depth;
+		}
+		free(buf);
+	} while ((delta_list = delta_list->next));
+	return deepest + 1;
+}