fsck: actually fsck blob data

Because fscking a blob has always been a noop, we didn't
bother passing around the blob data. In preparation for
content-level checks, let's fix up a few things:

  1. The fsck_object() function just returns success for any
     blob. Let's a noop fsck_blob(), which we can fill in
     with actual logic later.

  2. The fsck_loose() function in builtin/fsck.c
     just threw away blob content after loading it. Let's
     hold onto it until after we've called fsck_object().

     The easiest way to do this is to just drop the
     parse_loose_object() helper entirely. Incidentally,
     this also fixes a memory leak: if we successfully
     loaded the object data but did not parse it, we would
     have left the function without freeing it.

  3. When fsck_loose() loads the object data, it
     does so with a custom read_loose_object() helper. This
     function streams any blobs, regardless of size, under
     the assumption that we're only checking the sha1.

     Instead, let's actually load blobs smaller than
     big_file_threshold, as the normal object-reading
     code-paths would do. This lets us fsck small files, and
     a NULL return is an indication that the blob was so big
     that it needed to be streamed, and we can pass that
     information along to fsck_blob().

Signed-off-by: Jeff King <peff@peff.net>

builtin/fsck.c

@@ -337,7 +337,7 @@ static void check_connectivity(void)
 	}
 }
 
-static int fsck_obj(struct object *obj)
+static int fsck_obj(struct object *obj, void *buffer, unsigned long size)
 {
 	int err;
 
@@ -351,7 +351,7 @@ static int fsck_obj(struct object *obj)
 
 	if (fsck_walk(obj, NULL, &fsck_obj_options))
 		objerror(obj, "broken links");
-	err = fsck_object(obj, NULL, 0, &fsck_obj_options);
+	err = fsck_object(obj, buffer, size, &fsck_obj_options);
 	if (err)
 		goto out;
 
@@ -396,7 +396,7 @@ static int fsck_obj_buffer(const struct object_id *oid, enum object_type type,
 	}
 	obj->flags &= ~(REACHABLE | SEEN);
 	obj->flags |= HAS_OBJ;
-	return fsck_obj(obj);
+	return fsck_obj(obj, buffer, size);
 }
 
 static int default_refs;
@@ -504,44 +504,42 @@ static void get_default_heads(void)
 	}
 }
 
-static struct object *parse_loose_object(const struct object_id *oid,
-					 const char *path)
-{
-	struct object *obj;
-	void *contents;
-	enum object_type type;
-	unsigned long size;
-	int eaten;
-
-	if (read_loose_object(path, oid->hash, &type, &size, &contents) < 0)
-		return NULL;
-
-	if (!contents && type != OBJ_BLOB)
-		die("BUG: read_loose_object streamed a non-blob");
-
-	obj = parse_object_buffer(oid, type, size, contents, &eaten);
-
-	if (!eaten)
-		free(contents);
-	return obj;
-}
-
 static int fsck_loose(const struct object_id *oid, const char *path, void *data)
 {
-	struct object *obj = parse_loose_object(oid, path);
+	struct object *obj;
+	enum object_type type;
+	unsigned long size;
+	void *contents;
+	int eaten;
 
-	if (!obj) {
+	if (read_loose_object(path, oid->hash, &type, &size, &contents) < 0) {
 		errors_found |= ERROR_OBJECT;
 		error("%s: object corrupt or missing: %s",
 		      oid_to_hex(oid), path);
 		return 0; /* keep checking other objects */
 	}
 
+	if (!contents && type != OBJ_BLOB)
+		BUG("read_loose_object streamed a non-blob");
+
+	obj = parse_object_buffer(oid, type, size, contents, &eaten);
+	if (!obj) {
+		errors_found |= ERROR_OBJECT;
+		error("%s: object could not be parsed: %s",
+		      oid_to_hex(oid), path);
+		if (!eaten)
+			free(contents);
+		return 0; /* keep checking other objects */
+	}
+
 	obj->flags &= ~(REACHABLE | SEEN);
 	obj->flags |= HAS_OBJ;
-	if (fsck_obj(obj))
+	if (fsck_obj(obj, contents, size))
 		errors_found |= ERROR_OBJECT;
-	return 0;
+
+	if (!eaten)
+		free(contents);
+	return 0; /* keep checking other objects, even if we saw an error */
 }
 
 static int fsck_cruft(const char *basename, const char *path, void *data)

fsck.c

@@ -899,6 +899,12 @@ static int fsck_tag(struct tag *tag, const char *data,
 	return fsck_tag_buffer(tag, data, size, options);
 }
 
+static int fsck_blob(struct blob *blob, const char *buf,
+		     unsigned long size, struct fsck_options *options)
+{
+	return 0;
+}
+
 int fsck_object(struct object *obj, void *data, unsigned long size,
 	struct fsck_options *options)
 {
@@ -906,7 +912,7 @@ int fsck_object(struct object *obj, void *data, unsigned long size,
 		return report(options, obj, FSCK_MSG_BAD_OBJECT_SHA1, "no valid object to fsck");
 
 	if (obj->type == OBJ_BLOB)
-		return 0;
+		return fsck_blob((struct blob *)obj, data, size, options);
 	if (obj->type == OBJ_TREE)
 		return fsck_tree((struct tree *) obj, options);
 	if (obj->type == OBJ_COMMIT)

sha1_file.c

@@ -2209,7 +2209,7 @@ int read_loose_object(const char *path,
 		goto out;
 	}
 
-	if (*type == OBJ_BLOB) {
+	if (*type == OBJ_BLOB && *size > big_file_threshold) {
 		if (check_stream_sha1(&stream, hdr, *size, path, expected_sha1) < 0)
 			goto out;
 	} else {