Initial signer rewrite in Go

datastructures/signerresponse.go

@@ -0,0 +1,63 @@
+package datastructures
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+)
+
+type SignerResponse struct {
+	Version   uint8
+	Action    Action
+	Reserved1 uint8
+	Reserved2 uint8
+	Content1  string
+	Content2  string
+	Content3  string
+}
+
+func SignerResponseFromData(lengthBytes []byte, blockData []byte, checkSum byte) (*SignerResponse, error) {
+	headerLength := decode24BitLength(lengthBytes)
+	headerBytes := blockData[3 : 3+headerLength]
+
+	contentBytes := blockData[3+headerLength:]
+	content1Length := decode24BitLength(contentBytes[0:3])
+	content1 := string(contentBytes[3 : 3+content1Length])
+
+	content2Offset := 3 + content1Length
+	content2Length := decode24BitLength(contentBytes[content2Offset : content2Offset+3])
+	content2 := string(contentBytes[3+content2Offset : 3+content2Offset+content2Length])
+
+	content3Offset := 3 + content2Offset + content2Length
+	content3Length := decode24BitLength(contentBytes[content3Offset : content3Offset+3])
+	content3 := string(contentBytes[3+content3Offset : 3+content3Offset+content3Length])
+
+	calculated := CalculateXorCheckSum([][]byte{lengthBytes, blockData})
+	if checkSum != calculated {
+		return nil, errors.New(fmt.Sprintf("invalid checksum expected 0x%x got 0x%x", calculated, checkSum))
+	}
+
+	return &SignerResponse{
+		Version:   headerBytes[0],
+		Action:    Action(headerBytes[1]),
+		Reserved1: headerBytes[2],
+		Reserved2: headerBytes[3],
+		Content1:  content1,
+		Content2:  content2,
+		Content3:  content3,
+	}, nil
+}
+
+func (r SignerResponse) Serialize() []byte {
+	headerBytes := []byte{r.Version, byte(r.Action), r.Reserved1, r.Reserved2}
+	content1Bytes := []byte(r.Content1)
+	content2Bytes := []byte(r.Content2)
+	content3Bytes := []byte(r.Content3)
+	blockBytes := bytes.Join([][]byte{
+		encode24BitLength(headerBytes), headerBytes,
+		encode24BitLength(content1Bytes), content1Bytes,
+		encode24BitLength(content2Bytes), content2Bytes,
+		encode24BitLength(content3Bytes), content3Bytes,
+	}, []byte{})
+	return bytes.Join([][]byte{encode24BitLength(blockBytes), blockBytes}, []byte{})
+}