Add encoding decoding of header

pdu/pdu.go

@@ -2,6 +2,7 @@ package pdu
 
 type (
 	PDU interface {
+		EncodeInto(*[]byte)
 		Encode() []byte
 		Decode([]byte)
 	}
@@ -19,12 +20,23 @@ type (
 )
 
 func (p *PDU_HEADER) Encode() []byte {
-    // Encode PDU_HEADER fields to byte slice
+	buf := make([]byte, 16)
-    // (For simplicity, we assume little-endian encoding)
+	EncodeUint32(buf[0:4], p.command_length)
-    buf := make([]byte, 16)
+	EncodeUint32(buf[4:8], p.command_id)
-    encodeUint32(buf[0:4], p.command_length)
+	EncodeUint32(buf[8:12], p.command_status)
-    encodeUint32(buf[4:8], p.command_id)
+	EncodeUint32(buf[12:16], p.sequence_number)
-    encodeUint32(buf[8:12], p.command_status)
+	return buf
-    encodeUint32(buf[12:16], p.sequence_number)
+}
-    return buf
+func (p *PDU_HEADER) EncodeInto(buf *[]byte) {
+	bufVal := *buf
+	EncodeUint32(bufVal[0:4], p.command_length)
+	EncodeUint32(bufVal[4:8], p.command_id)
+	EncodeUint32(bufVal[8:12], p.command_status)
+	EncodeUint32(bufVal[12:16], p.sequence_number)
+}
+func (p *PDU_HEADER) Decode(data []byte) {
+	p.command_length = DecodeUint32(data[0:4])
+	p.command_id = DecodeUint32(data[4:8])
+	p.command_status = DecodeUint32(data[8:12])
+	p.sequence_number = DecodeUint32(data[12:16])
 }

pdu/util.go

@@ -1 +1,14 @@
 package pdu
+
+// EncodeUint32 encodes a uint32 into a byte slice in big-endian order
+func EncodeUint32(b []byte, i uint32) {
+	b[0] = byte(i >> 24)
+	b[1] = byte(i >> 16)
+	b[2] = byte(i >> 8)
+	b[3] = byte(i)
+}
+
+// DecodeUint32 decodes a uint32 from a byte slice in big-endian order
+func DecodeUint32(b []byte) uint32 {
+	return uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3])
+}