Move base16 and base32 specific bits to their own file.

base16.go

@@ -0,0 +1,21 @@
+package multibase
+
+func hexEncodeToStringUpper(src []byte) string {
+	dst := make([]byte, len(src)*2)
+	hexEncodeUpper(dst, src)
+	return string(dst)
+}
+
+var hextableUpper = [16]byte{
+	'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+	'A', 'B', 'C', 'D', 'E', 'F',
+}
+
+func hexEncodeUpper(dst, src []byte) int {
+	for i, v := range src {
+		dst[i*2] = hextableUpper[v>>4]
+		dst[i*2+1] = hextableUpper[v&0x0f]
+	}
+
+	return len(src) * 2
+}