implement memmove

src/string.c

@@ -29,5 +29,19 @@ void *memcpy(void *restrict dst, const void *restrict src, usize n)
 
 void *memmove(void *dst, const void *src, usize n)
 {
-	/* TODO: Moves memory area, allowing overlap. As though an array is used. */
+	const u8 *ssrc = src;
+	u8       *sdst = dst;
+
+	/* If the destination is before, or equal to the source,
+	 * we needn't worry about accidentally overriding the source
+	 * before it is written to the destination. */
+	if (sdst > ssrc) {
+		sdst += n;
+		ssrc += n;
+		while (n--) *(--sdst) = *(--ssrc);
+	} else {
+		while (n--) *(sdst++) = *(ssrc++);
+	}
+
+	return dst;
 }