make api.Channel as interface

[govpp.git] / codec / msg_codec.go

diff --git a/codec/msg_codec.go b/codec/msg_codec.go
new file mode 100644 (file)
index 0000000..7ba8771
--- /dev/null
+++ b/codec/msg_codec.go
@@ -0,0 +1,141 @@
+// Copyright (c) 2017 Cisco and/or its affiliates.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at:
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package codec
+
+import (
+       "bytes"
+       "errors"
+       "fmt"
+       "reflect"
+
+       "git.fd.io/govpp.git/api"
+       "github.com/lunixbochs/struc"
+)
+
+// MsgCodec provides encoding and decoding functionality of `api.Message` structs into/from
+// binary format as accepted by VPP.
+type MsgCodec struct{}
+
+// VppRequestHeader struct contains header fields implemented by all VPP requests.
+type VppRequestHeader struct {
+       VlMsgID     uint16
+       ClientIndex uint32
+       Context     uint32
+}
+
+// VppReplyHeader struct contains header fields implemented by all VPP replies.
+type VppReplyHeader struct {
+       VlMsgID uint16
+       Context uint32
+}
+
+// VppEventHeader struct contains header fields implemented by all VPP events.
+type VppEventHeader struct {
+       VlMsgID uint16
+       Context uint32
+}
+
+// VppOtherHeader struct contains header fields implemented by other VPP messages (not requests nor replies).
+type VppOtherHeader struct {
+       VlMsgID uint16
+}
+
+const (
+       vppRequestHeaderSize = 10 // size of a VPP request header
+       vppReplyHeaderSize   = 6  // size of a VPP reply header
+       vppEventHeaderSize   = 6  // size of a VPP event header
+       vppOtherHeaderSize   = 2  // size of the header of other VPP messages
+)
+
+// EncodeMsg encodes provided `Message` structure into its binary-encoded data representation.
+func (*MsgCodec) EncodeMsg(msg api.Message, msgID uint16) ([]byte, error) {
+       if msg == nil {
+               return nil, errors.New("nil message passed in")
+       }
+
+       buf := new(bytes.Buffer)
+
+       // encode message header
+       var header interface{}
+       if msg.GetMessageType() == api.RequestMessage {
+               header = &VppRequestHeader{VlMsgID: msgID}
+       } else if msg.GetMessageType() == api.ReplyMessage {
+               header = &VppReplyHeader{VlMsgID: msgID}
+       } else if msg.GetMessageType() == api.EventMessage {
+               header = &VppEventHeader{VlMsgID: msgID}
+       } else {
+               header = &VppOtherHeader{VlMsgID: msgID}
+       }
+       err := struc.Pack(buf, header)
+       if err != nil {
+               return nil, fmt.Errorf("unable to encode message: header: %v, error %v", header, err)
+       }
+
+       // encode message content
+       if reflect.Indirect(reflect.ValueOf(msg)).NumField() > 0 {
+               err := struc.Pack(buf, msg)
+               if err != nil {
+                       return nil, fmt.Errorf("unable to encode message: header %v, error %v", header, err)
+               }
+       }
+
+       return buf.Bytes(), nil
+}
+
+// DecodeMsg decodes binary-encoded data of a message into provided `Message` structure.
+func (*MsgCodec) DecodeMsg(data []byte, msg api.Message) error {
+       if msg == nil {
+               return errors.New("nil message passed in")
+       }
+
+       buf := bytes.NewReader(data)
+
+       // check which header is expected
+       var header interface{}
+       if msg.GetMessageType() == api.RequestMessage {
+               header = &VppRequestHeader{}
+       } else if msg.GetMessageType() == api.ReplyMessage {
+               header = &VppReplyHeader{}
+       } else if msg.GetMessageType() == api.EventMessage {
+               header = &VppEventHeader{}
+       } else {
+               header = &VppOtherHeader{}
+       }
+
+       // decode message header
+       err := struc.Unpack(buf, header)
+       if err != nil {
+               return fmt.Errorf("unable to decode message: data %v, error %v", data, err)
+       }
+
+       // get rid of the message header
+       if msg.GetMessageType() == api.RequestMessage {
+               buf = bytes.NewReader(data[vppRequestHeaderSize:])
+       } else if msg.GetMessageType() == api.ReplyMessage {
+               buf = bytes.NewReader(data[vppReplyHeaderSize:])
+       } else if msg.GetMessageType() == api.EventMessage {
+               buf = bytes.NewReader(data[vppEventHeaderSize:])
+       } else {
+               buf = bytes.NewReader(data[vppOtherHeaderSize:])
+       }
+
+       // decode message content
+       err = struc.Unpack(buf, msg)
+       if err != nil {
+               return fmt.Errorf("unable to decode message: data %v, error %v", data, err)
+       }
+
+       return nil
+}