添加 github.com/pion/dtls 代码

dtls-2.0.9/pkg/protocol/recordlayer/header.go

@@ -0,0 +1,61 @@
+package recordlayer
+
+import (
+	"encoding/binary"
+
+	"github.com/pion/dtls/v2/internal/util"
+	"github.com/pion/dtls/v2/pkg/protocol"
+)
+
+// Header implements a TLS RecordLayer header
+type Header struct {
+	ContentType    protocol.ContentType
+	ContentLen     uint16
+	Version        protocol.Version
+	Epoch          uint16
+	SequenceNumber uint64 // uint48 in spec
+}
+
+// RecordLayer enums
+const (
+	HeaderSize        = 13
+	MaxSequenceNumber = 0x0000FFFFFFFFFFFF
+)
+
+// Marshal encodes a TLS RecordLayer Header to binary
+func (h *Header) Marshal() ([]byte, error) {
+	if h.SequenceNumber > MaxSequenceNumber {
+		return nil, errSequenceNumberOverflow
+	}
+
+	out := make([]byte, HeaderSize)
+	out[0] = byte(h.ContentType)
+	out[1] = h.Version.Major
+	out[2] = h.Version.Minor
+	binary.BigEndian.PutUint16(out[3:], h.Epoch)
+	util.PutBigEndianUint48(out[5:], h.SequenceNumber)
+	binary.BigEndian.PutUint16(out[HeaderSize-2:], h.ContentLen)
+	return out, nil
+}
+
+// Unmarshal populates a TLS RecordLayer Header from binary
+func (h *Header) Unmarshal(data []byte) error {
+	if len(data) < HeaderSize {
+		return errBufferTooSmall
+	}
+	h.ContentType = protocol.ContentType(data[0])
+	h.Version.Major = data[1]
+	h.Version.Minor = data[2]
+	h.Epoch = binary.BigEndian.Uint16(data[3:])
+
+	// SequenceNumber is stored as uint48, make into uint64
+	seqCopy := make([]byte, 8)
+	copy(seqCopy[2:], data[5:11])
+	h.SequenceNumber = binary.BigEndian.Uint64(seqCopy)
+
+	if !h.Version.Equal(protocol.Version1_0) && !h.Version.Equal(protocol.Version1_2) {
+		return errUnsupportedProtocolVersion
+	}
+
+	return nil
+}