1 files changed, 41 insertions, 0 deletions
diff --git a/lib/util/file_cmp.c b/lib/util/file_cmp.c
new file mode 100644
index 0000000..2aa0cc2
--- /dev/null
+++ b/lib/util/file_cmp.c
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * file_cmp.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+
+#include "util/util.h"
+#include "sqfs/io.h"
+
+#include <string.h>
+
+int check_file_range_equal(sqfs_file_t *file, void *scratch, size_t scratch_sz,
+			   sqfs_u64 loc_a, sqfs_u64 loc_b, sqfs_u64 size)
+{
+	sqfs_u8 *ptr_a = scratch, *ptr_b = ptr_a + scratch_sz / 2;
+	int ret;
+
+	while (size > 0) {
+		size_t diff = scratch_sz / 2;
+		diff = (sqfs_u64)diff > size ? size : diff;
+
+		ret = file->read_at(file, loc_a, ptr_a, diff);
+		if (ret != 0)
+			return ret;
+
+		ret = file->read_at(file, loc_b, ptr_b, diff);
+		if (ret != 0)
+			return ret;
+
+		if (memcmp(ptr_a, ptr_b, diff) != 0)
+			return 1;
+
+		size -= diff;
+		loc_a += diff;
+		loc_b += diff;
+	}
+
+	return 0;
+}