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// 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
ClientIndex uint32
}
// VppOtherHeader struct contains header fields implemented by other VPP messages (not requests nor replies).
type VppOtherHeader struct {
VlMsgID uint16
}
// 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")
}
// encode message header
var header interface{}
switch msg.GetMessageType() {
case api.RequestMessage:
header = &VppRequestHeader{VlMsgID: msgID}
case api.ReplyMessage:
header = &VppReplyHeader{VlMsgID: msgID}
case api.EventMessage:
header = &VppEventHeader{VlMsgID: msgID}
default:
header = &VppOtherHeader{VlMsgID: msgID}
}
buf := new(bytes.Buffer)
// encode message header
if err := struc.Pack(buf, header); err != nil {
return nil, fmt.Errorf("unable to encode message header: %v, error %v", header, err)
}
// encode message content
if reflect.TypeOf(msg).Elem().NumField() > 0 {
if err := struc.Pack(buf, msg); err != nil {
return nil, fmt.Errorf("unable to encode message data: %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")
}
// check which header is expected
var header interface{}
switch msg.GetMessageType() {
case api.RequestMessage:
header = new(VppRequestHeader)
case api.ReplyMessage:
header = new(VppReplyHeader)
case api.EventMessage:
header = new(VppEventHeader)
default:
header = new(VppOtherHeader)
}
buf := bytes.NewReader(data)
// decode message header
if err := struc.Unpack(buf, header); err != nil {
return fmt.Errorf("unable to decode message header: %+v, error %v", data, err)
}
// decode message content
if err := struc.Unpack(buf, msg); err != nil {
return fmt.Errorf("unable to decode message data: %+v, error %v", data, err)
}
return nil
}
func (*MsgCodec) DecodeMsgContext(data []byte, msg api.Message) (uint32, error) {
if msg == nil {
return 0, errors.New("nil message passed in")
}
var getContext func() uint32
// check which header is expected
var header interface{}
switch msg.GetMessageType() {
case api.RequestMessage:
header = new(VppRequestHeader)
getContext = func() uint32 { return header.(*VppRequestHeader).Context }
case api.ReplyMessage:
header = new(VppReplyHeader)
getContext = func() uint32 { return header.(*VppReplyHeader).Context }
default:
return 0, nil
}
buf := bytes.NewReader(data)
// decode message header
if err := struc.Unpack(buf, header); err != nil {
return 0, fmt.Errorf("decoding message header failed: %v", err)
}
return getContext(), nil
}
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