implement parsing of stream frames

frame.go

@@ -0,0 +1,72 @@
+package quic
+
+import (
+	"bytes"
+	"io/ioutil"
+)
+
+// A StreamFrame of QUIC
+type StreamFrame struct {
+	FinBit            bool
+	DataLengthPresent bool
+	OffsetLength      uint8
+	StreamIDLength    uint8
+	StreamID          uint32
+	Offset            uint64
+	DataLength        uint16
+	Data              []byte
+}
+
+// ParseStreamFrame reads a stream frame. The type byte must not have been read yet.
+func ParseStreamFrame(r *bytes.Reader) (*StreamFrame, error) {
+	frame := &StreamFrame{}
+
+	typeByte, err := r.ReadByte()
+	if err != nil {
+		return nil, err
+	}
+	frame.FinBit = typeByte&0x40 > 0
+	frame.DataLengthPresent = typeByte&0x20 > 0
+	frame.OffsetLength = typeByte & 0x1C >> 2
+	if frame.OffsetLength != 0 {
+		frame.OffsetLength++
+	}
+	frame.StreamIDLength = typeByte&0x03 + 1
+
+	sid, err := readUint64(r, frame.StreamIDLength)
+	if err != nil {
+		return nil, err
+	}
+	frame.StreamID = uint32(sid)
+
+	frame.Offset, err = readUint64(r, frame.OffsetLength)
+	if err != nil {
+		return nil, err
+	}
+
+	if frame.DataLengthPresent {
+		var b1, b2 byte
+		if b1, err = r.ReadByte(); err != nil {
+			return nil, err
+		}
+		if b2, err = r.ReadByte(); err != nil {
+			return nil, err
+		}
+		frame.DataLength = uint16(b1) + uint16(b2)<<8
+	}
+
+	if frame.DataLength == 0 {
+		// The rest of the packet is data
+		frame.Data, err = ioutil.ReadAll(r)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		frame.Data = make([]byte, frame.DataLength)
+		if _, err := r.Read(frame.Data); err != nil {
+			return nil, err
+		}
+	}
+
+	return frame, nil
+}