implement parsing, writing and logging of CRYPTO frames

internal/wire/crypto_frame.go

@@ -0,0 +1,71 @@
+package wire
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/utils"
+)
+
+// A CryptoFrame is a CRYPTO frame
+type CryptoFrame struct {
+	Offset protocol.ByteCount
+	Data   []byte
+}
+
+func parseCryptoFrame(r *bytes.Reader, _ protocol.VersionNumber) (*CryptoFrame, error) {
+	if _, err := r.ReadByte(); err != nil {
+		return nil, err
+	}
+
+	frame := &CryptoFrame{}
+	offset, err := utils.ReadVarInt(r)
+	if err != nil {
+		return nil, err
+	}
+	frame.Offset = protocol.ByteCount(offset)
+	dataLen, err := utils.ReadVarInt(r)
+	if err != nil {
+		return nil, err
+	}
+	if dataLen > uint64(r.Len()) {
+		return nil, io.EOF
+	}
+	if dataLen != 0 {
+		frame.Data = make([]byte, dataLen)
+		if _, err := io.ReadFull(r, frame.Data); err != nil {
+			// this should never happen, since we already checked the dataLen earlier
+			return nil, err
+		}
+	}
+	return frame, nil
+}
+
+func (f *CryptoFrame) Write(b *bytes.Buffer, _ protocol.VersionNumber) error {
+	b.WriteByte(0x18)
+	utils.WriteVarInt(b, uint64(f.Offset))
+	utils.WriteVarInt(b, uint64(len(f.Data)))
+	b.Write(f.Data)
+	return nil
+}
+
+// Length of a written frame
+func (f *CryptoFrame) Length(_ protocol.VersionNumber) protocol.ByteCount {
+	return 1 + utils.VarIntLen(uint64(f.Offset)) + utils.VarIntLen(uint64(len(f.Data))) + protocol.ByteCount(len(f.Data))
+}
+
+// MaxDataLen returns the maximum data length
+func (f *CryptoFrame) MaxDataLen(maxSize protocol.ByteCount) protocol.ByteCount {
+	// pretend that the data size will be 1 bytes
+	// if it turns out that varint encoding the length will consume 2 bytes, we need to adjust the data length afterwards
+	headerLen := 1 + utils.VarIntLen(uint64(f.Offset)) + 1
+	if headerLen > maxSize {
+		return 0
+	}
+	maxDataLen := maxSize - headerLen
+	if utils.VarIntLen(uint64(maxDataLen)) != 1 {
+		maxDataLen--
+	}
+	return maxDataLen
+}