import (

    "bytes"

    "encoding/binary"

)

const (

    // 支持数据最大长度为 2 << 61

    // DataLengthOfLenth = 8

    // 支持数据最大长度为 2 << 30

    DataLengthOfLenth = 4

)

//通讯协议处理，主要处理封包和解包的过程

type Protocol struct {

    // 包头

    header string

    // 包头长度

    headerLen int

}

func NewProtocol(packetHeader string) *Protocol {

    return &Protocol{

        header:    packetHeader,

        headerLen: len([]byte(packetHeader)),

    }

}

func (self *Protocol) ReSet(header string) {

    self.header = header

    self.headerLen = len([]byte(header))

}

//封包

func (self *Protocol) Packet(message []byte) []byte {

    return append(append([]byte(self.header), IntToBytes(len(message))...), message...)

}

//解包

func (self *Protocol) Unpack(buffer []byte) (readerSlice [][]byte, bufferOver []byte) {

    length := len(buffer)

    var i int

    for i = 0; i < length; i = i + 1 {

        if length < i+self.headerLen+DataLengthOfLenth {

            break

        }

        if string(buffer[i:i+self.headerLen]) == self.header {

            messageLength := BytesToInt(buffer[i+self.headerLen : i+self.headerLen+DataLengthOfLenth])

            if length < i+self.headerLen+DataLengthOfLenth+messageLength {

                break

            }

            data := buffer[i+self.headerLen+DataLengthOfLenth : i+self.headerLen+DataLengthOfLenth+messageLength]

            readerSlice = append(readerSlice, data)

            i += self.headerLen + DataLengthOfLenth + messageLength - 1

        }

    }

    if i == length {

        bufferOver = make([]byte, 0)

        return

    }

    bufferOver = buffer[i:]

    return

}

//整形转换成字节

// func IntToBytes(n int) []byte {

//     x := int64(n)

//     bytesBuffer := bytes.NewBuffer([]byte{})

//     binary.Write(bytesBuffer, binary.BigEndian, x)

//     return bytesBuffer.Bytes()

// }

// //字节转换成整形

// func BytesToInt(b []byte) int {

//     bytesBuffer := bytes.NewBuffer(b)

//     var x int64

//     binary.Read(bytesBuffer, binary.BigEndian, &x)

//     return int(x)

// }

//整形转换成字节

func IntToBytes(n int) []byte {

    x := int32(n)

    bytesBuffer := bytes.NewBuffer([]byte{})

    binary.Write(bytesBuffer, binary.LittleEndian, x)

    return bytesBuffer.Bytes()

}

//字节转换成整形

func BytesToInt(b []byte) int {

    bytesBuffer := bytes.NewBuffer(b)

    var x int32

    binary.Read(bytesBuffer, binary.LittleEndian, &x)

    return int(x)

}