1 files changed, 21 insertions, 0 deletions
diff --git a/src/string/strlen.c b/src/string/strlen.c
new file mode 100644
index 00000000..936fb5cf
--- /dev/null
+++ b/src/string/strlen.c
@@ -0,0 +1,21 @@
+#include <string.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <limits.h>
+
+#define ALIGN (sizeof(size_t)-1)
+#define ONES ((size_t)-1/UCHAR_MAX)
+#define HIGHS (ONES * (UCHAR_MAX/2+1))
+#define HASZERO(x) ((x)-ONES & ~(x) & HIGHS)
+
+size_t strlen(const char *s)
+{
+	const char *a = s;
+	const size_t *w;
+	for (; ((uintptr_t)s & ALIGN) && *s; s++);
+	if (*s) {
+		for (w = (const void *)s; !HASZERO(*w); w++);
+		for (s = (const void *)w; *s; s++);
+	}
+	return s-a;
+}