1 files changed, 31 insertions, 0 deletions
diff --git a/lib/libc/memmove.c b/lib/libc/memmove.c
new file mode 100644
index 0000000..5c2b661
--- /dev/null
+++ b/lib/libc/memmove.c
@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2013-2018, Arm Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <string.h>
+
+void *memmove(void *dst, const void *src, size_t len)
+{
+	/*
+	 * The following test makes use of unsigned arithmetic overflow to
+	 * more efficiently test the condition !(src <= dst && dst < str+len).
+	 * It also avoids the situation where the more explicit test would give
+	 * incorrect results were the calculation str+len to overflow (though
+	 * that issue is probably moot as such usage is probably undefined
+	 * behaviour and a bug anyway.
+	 */
+	if ((size_t)dst - (size_t)src >= len) {
+		/* destination not in source data, so can safely use memcpy */
+		return memcpy(dst, src, len);
+	} else {
+		/* copy backwards... */
+		const char *end = dst;
+		const char *s = (const char *)src + len;
+		char *d = (char *)dst + len;
+		while (d != end)
+			*--d = *--s;
+	}
+	return dst;
+}