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-rw-r--r--lib/util/is_memory_zero.c54
1 files changed, 54 insertions, 0 deletions
diff --git a/lib/util/is_memory_zero.c b/lib/util/is_memory_zero.c
new file mode 100644
index 0000000..3974ee2
--- /dev/null
+++ b/lib/util/is_memory_zero.c
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * is_memory_zero.c
+ *
+ * Copyright (C) 2021 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+#include "util.h"
+
+#include <stdint.h>
+
+#define U64THRESHOLD (128)
+
+static bool test_u8(const unsigned char *blob, size_t size)
+{
+ while (size--) {
+ if (*(blob++) != 0)
+ return false;
+ }
+
+ return true;
+}
+
+bool is_memory_zero(const void *blob, size_t size)
+{
+ const sqfs_u64 *u64ptr;
+ size_t diff;
+
+ if (size < U64THRESHOLD)
+ return test_u8(blob, size);
+
+ diff = (uintptr_t)blob % sizeof(sqfs_u64);
+
+ if (diff != 0) {
+ diff = sizeof(sqfs_u64) - diff;
+
+ if (!test_u8(blob, diff))
+ return false;
+
+ blob = (const char *)blob + diff;
+ size -= diff;
+ }
+
+ u64ptr = blob;
+
+ while (size >= sizeof(sqfs_u64)) {
+ if (*(u64ptr++) != 0)
+ return false;
+
+ size -= sizeof(sqfs_u64);
+ }
+
+ return test_u8((const unsigned char *)u64ptr, size);
+}