feat: impl. new protol design & new head

gold/head/flags.go

@@ -1,41 +1,37 @@
 package head
 
 import (
-	"encoding/binary"
 	"fmt"
 )
 
-type PacketFlags uint16
+const (
+	hasmorebit FlagsProto = 0x20 << iota
+	nofragbit
+	topbit //TODO: 改为 trans 标记
+)
 
-func (pf PacketFlags) String() string {
-	return fmt.Sprintf("%04x", uint16(pf))
+const (
+	impossiblebit = hasmorebit | nofragbit
+	flagsbit      = topbit | impossiblebit
+	protobit      = ^flagsbit
+)
+
+type FlagsProto uint8
+
+func (pf FlagsProto) String() string {
+	return fmt.Sprintf("%02x", uint8(pf))
 }
 
-func (pf PacketFlags) IsValid() bool {
-	return pf&0x8000 == 0
+func (pf FlagsProto) IsValid() bool {
+	return pf&topbit == 0 &&
+		pf&impossiblebit != impossiblebit &&
+		pf.Proto() < ProtoTop
 }
 
-func (pf PacketFlags) DontFrag() bool {
-	return pf&0x4000 == 0x4000
+func (pf FlagsProto) HasMore() bool {
+	return pf&hasmorebit != 0
 }
 
-func (pf PacketFlags) NoFrag() bool {
-	return pf == 0x4000
-}
-
-func (pf PacketFlags) IsSingle() bool {
-	return pf == 0
-}
-
-func (pf PacketFlags) ZeroOffset() bool {
-	return pf&0x1fff == 0
-}
-
-func (pf PacketFlags) Offset() uint16 {
-	return uint16(pf << 3)
-}
-
-// Flags extract flags from raw data
-func Flags(data []byte) PacketFlags {
-	return PacketFlags(binary.LittleEndian.Uint16(data[10:12]))
+func (pf FlagsProto) NoFrag() bool {
+	return pf&nofragbit != 0
 }