feat(head): use uniform head extract & crc64 -> md5

gold/head/flags.go

@@ -0,0 +1,34 @@
+package head
+
+import "encoding/binary"
+
+type PacketFlags uint16
+
+func (pf PacketFlags) IsValid() bool {
+	return pf&0x8000 == 0
+}
+
+func (pf PacketFlags) DontFrag() bool {
+	return pf&0x4000 == 0x4000
+}
+
+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]))
+}