Add rpc request/response for handshake

mtproto/rpc/rpc_handshake_response.go

@@ -0,0 +1,53 @@
+package rpc
+
+import (
+	"bytes"
+
+	"github.com/juju/errors"
+)
+
+const rpcHandshakeResponseLength = rpcHandshakeRequestLength
+
+type RPCHandshakeResponse struct {
+	Type      [rpcHandshakeTagLength]byte
+	Flags     [rpcHandshakeFlagsLength]byte
+	SenderPID [rpcHandshakeSenderPIDLength]byte
+	PeerPID   [rpcHandshakePeerPIDLength]byte
+}
+
+func (r *RPCHandshakeResponse) Bytes() *bytes.Buffer {
+	buf := &bytes.Buffer{}
+	buf.Grow(rpcHandshakeResponseLength)
+
+	buf.Write(r.Type[:])
+	buf.Write(r.Flags[:])
+	buf.Write(r.SenderPID[:])
+	buf.Write(r.PeerPID[:])
+
+	return buf
+}
+
+func (r *RPCHandshakeResponse) Valid(req *RPCHandshakeRequest) error {
+	if r.Type != rpcHandshakeTag {
+		return errors.New("Unexpected handshake tag")
+	}
+	if r.PeerPID != rpcHandshakeSenderPID {
+		return errors.New("Incorrect sender PID")
+	}
+
+	return nil
+}
+
+func NewRPCHandshakeResponse(data []byte) (*RPCHandshakeResponse, error) {
+	if len(data) != rpcHandshakeResponseLength {
+		return nil, errors.New("Incorrect handshake response length")
+	}
+
+	resp := RPCHandshakeResponse{}
+	copy(resp.Type[:], data[:4])
+	copy(resp.Flags[:], data[4:8])
+	copy(resp.SenderPID[:], data[8:20])
+	copy(resp.PeerPID[:], data[20:])
+
+	return &resp, nil
+}