Implement a part of submit encode

pdu/submit.go

@@ -1,5 +1,7 @@
 package pdu
 
+import "fmt"
+
 type (
 	SUBMIT_SM struct {
 		header                 PDU_HEADER
@@ -58,16 +60,28 @@ type (
 	SUBMIT_MULTI_RESP struct{}
 )
 
-func (p *SUBMIT_SM) Encode() []byte {
-	return []byte{}
+func (p *SUBMIT_SM) Encode() ([]byte, error) {
+	buf := make([]byte, p.Size())
+	err := p.EncodeInto(&buf)
+	return buf, err
 }
-func (p *SUBMIT_SM) EncodeInto(buf *[]byte) {
+func (p *SUBMIT_SM) EncodeInto(buf *[]byte) error {
+	if buf == nil {
+		return fmt.Errorf("cannot encode SUBMIT_SM, buffer is nil")
+	}
+	if len(*buf) < int(p.Size()) {
+		return fmt.Errorf("cannot encode SUBMIT_SM, buffer too small (%d, required %d)", len(*buf), p.Size())
+	}
+
+	p.header.EncodeInto(buf)
+
+	return nil
 }
 func (p *SUBMIT_SM) Decode(data []byte) {
 }
 func (p *SUBMIT_SM) Size() uint32 {
 	var size uint32
-	size += 16 // header
+	size += p.header.Size()
 	size += uint32(len(p.service_type) * 1)
 	size += 1 // source_addr_ton
 	size += 1 // source_addr_npi