1 files changed, 27 insertions, 0 deletions
diff --git a/swap.c b/swap.c
new file mode 100644
index 0000000..626abb0
--- /dev/null
+++ b/swap.c
@@ -0,0 +1,27 @@
+#include <stddef.h>
+#include <stdint.h>
+
+#include "common.h"
+
+void swap(char *a, char *b, size_t width)
+{
+#ifdef __GNUC__
+	typedef uint32_t __attribute__((__may_alias__)) u32;
+
+	if ((uintptr_t)a % 4 == 0 && (uintptr_t)b % 4 == 0) {
+		for (; width >= 4; width -= 4) {
+			uint32_t tmp = *((u32*)a);
+			*((u32*)a) = *((u32*)b);
+			*((u32*)b) = tmp;
+			a += 4;
+			b += 4;
+		}
+	}
+#endif
+
+	while (width--) {
+		char tmp = *a;
+		*a++ = *b;
+		*b++ = tmp;
+	}
+}