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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
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
}
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