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
+}

frame_test.go

@@ -0,0 +1,40 @@
+package quic
+
+import (
+	"bytes"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Frame", func() {
+	Context("when parsing", func() {
+		It("accepts sample frame", func() {
+			b := bytes.NewReader([]byte{0xa0, 0x1, 0x06, 0x00, 'f', 'o', 'o', 'b', 'a', 'r'})
+			frame, err := ParseStreamFrame(b)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(frame.FinBit).To(BeFalse())
+			Expect(frame.DataLengthPresent).To(BeTrue())
+			Expect(frame.OffsetLength).To(BeZero())
+			Expect(frame.StreamIDLength).To(Equal(uint8(1)))
+			Expect(frame.StreamID).To(Equal(uint32(1)))
+			Expect(frame.Offset).To(BeZero())
+			Expect(frame.DataLength).To(Equal(uint16(6)))
+			Expect(frame.Data).To(Equal([]byte("foobar")))
+		})
+
+		It("accepts frame without datalength", func() {
+			b := bytes.NewReader([]byte{0x80, 0x1, 'f', 'o', 'o', 'b', 'a', 'r'})
+			frame, err := ParseStreamFrame(b)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(frame.FinBit).To(BeFalse())
+			Expect(frame.DataLengthPresent).To(BeFalse())
+			Expect(frame.OffsetLength).To(BeZero())
+			Expect(frame.StreamIDLength).To(Equal(uint8(1)))
+			Expect(frame.StreamID).To(Equal(uint32(1)))
+			Expect(frame.Offset).To(BeZero())
+			Expect(frame.DataLength).To(Equal(uint16(0)))
+			Expect(frame.Data).To(Equal([]byte("foobar")))
+		})
+	})
+})