添加 github.com/pion/dtls 代码

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

@@ -0,0 +1,50 @@
+package handshake
+
+import (
+	"encoding/binary"
+
+	"github.com/pion/dtls/v2/internal/util"
+)
+
+// HeaderLength msg_len for Handshake messages assumes an extra
+// 12 bytes for sequence, fragment and version information vs TLS
+const HeaderLength = 12
+
+// Header is the static first 12 bytes of each RecordLayer
+// of type Handshake. These fields allow us to support message loss, reordering, and
+// message fragmentation,
+//
+// https://tools.ietf.org/html/rfc6347#section-4.2.2
+type Header struct {
+	Type            Type
+	Length          uint32 // uint24 in spec
+	MessageSequence uint16
+	FragmentOffset  uint32 // uint24 in spec
+	FragmentLength  uint32 // uint24 in spec
+}
+
+// Marshal encodes the Header
+func (h *Header) Marshal() ([]byte, error) {
+	out := make([]byte, HeaderLength)
+
+	out[0] = byte(h.Type)
+	util.PutBigEndianUint24(out[1:], h.Length)
+	binary.BigEndian.PutUint16(out[4:], h.MessageSequence)
+	util.PutBigEndianUint24(out[6:], h.FragmentOffset)
+	util.PutBigEndianUint24(out[9:], h.FragmentLength)
+	return out, nil
+}
+
+// Unmarshal populates the header from encoded data
+func (h *Header) Unmarshal(data []byte) error {
+	if len(data) < HeaderLength {
+		return errBufferTooSmall
+	}
+
+	h.Type = Type(data[0])
+	h.Length = util.BigEndianUint24(data[1:])
+	h.MessageSequence = binary.BigEndian.Uint16(data[4:])
+	h.FragmentOffset = util.BigEndianUint24(data[6:])
+	h.FragmentLength = util.BigEndianUint24(data[9:])
+	return nil
+}