enhance(crc):CRC系列校验算法增加使用大端序或者小端序输出的功能。

types/endian.go

@@ -0,0 +1,28 @@
+package types
+
+import "fmt"
+
+type Endian string
+
+const (
+	BigEndian    Endian = "big"
+	LittleEndian Endian = "little"
+)
+
+func (e *Endian) String() string {
+	return string(*e)
+}
+
+func (e *Endian) Set(s string) error {
+	switch s {
+	case "big", "little":
+		*e = Endian(s)
+		return nil
+	default:
+		return fmt.Errorf("不支持的字节序：%s", s)
+	}
+}
+
+func (e *Endian) Type() string {
+	return "Endian"
+}