add method to Write ConnectionClose frames

frames/connection_close_frame.go

@@ -3,6 +3,7 @@ package frames
 import (
 	"bytes"
 	"errors"
+	"math"
 
 	"github.com/lucas-clemente/quic-go/utils"
 )
@@ -13,12 +14,7 @@ type ConnectionCloseFrame struct {
 	ReasonPhrase string
 }
 
-// Write writes an ACK frame.
-func (f *ConnectionCloseFrame) Write(b *bytes.Buffer) error {
-	return errors.New("ConnectionCloseFrame: Write not yet implemented")
-}
-
-// ParseConnectionCloseFrame reads an ACK frame
+// ParseConnectionCloseFrame reads a CONNECTION_CLOSE frame
 func ParseConnectionCloseFrame(r *bytes.Reader) (*ConnectionCloseFrame, error) {
 	frame := &ConnectionCloseFrame{}
 
@@ -49,3 +45,22 @@ func ParseConnectionCloseFrame(r *bytes.Reader) (*ConnectionCloseFrame, error) {
 
 	return frame, nil
 }
+
+// Write writes an CONNECTION_CLOSE frame.
+func (f *ConnectionCloseFrame) Write(b *bytes.Buffer) error {
+	b.WriteByte(0x02)
+	utils.WriteUint32(b, f.ErrorCode)
+
+	if len(f.ReasonPhrase) > math.MaxUint16 {
+		return errors.New("ConnectionFrame: ReasonPhrase too long")
+	}
+
+	reasonPhraseLen := uint16(len(f.ReasonPhrase))
+	utils.WriteUint16(b, reasonPhraseLen)
+
+	for i := 0; i < int(reasonPhraseLen); i++ {
+		b.WriteByte(uint8(f.ReasonPhrase[i]))
+	}
+
+	return nil
+}