c++ java 结构体通讯

最新推荐文章于 2023-08-21 20:09:55 发布

涂鸦c

最新推荐文章于 2023-08-21 20:09:55 发布

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文章标签： java c++ 开发语言

本文链接：https://blog.youkuaiyun.com/qq_16377055/article/details/129860934

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文章详细介绍了在C++和Java中char类型的字节长度差异，并展示了如何进行数据转换，特别是在网络通信中，如何将数据序列化为字节数组。代码示例涵盖了int、byte、char等类型的转换方法，以及大小端字节序的处理。

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C++与java的char字节长度不一

java

udpdata mytestdata = new udpdata( 4,("hello").toCharArray(),("world").getBytes(),true,7);
ByteArrayOutputStream ostream = new ByteArrayOutputStream();
DataOutputStream out = new DataOutputStream(ostream);
out.write(dataconvert.intToByteLittle(mytestdata.getiNumber()));
out.write(dataconvert.getBytes(mytestdata.getArrchResult()));
out.write(mytestdata.getArrchCode());
out.write(dataconvert.BoolToByte(mytestdata.getbOutLimit_Flag()));
out.write(dataconvert.intToByteLittle(mytestdata.getiMark()));
out.flush();
byte[] mydata = ostream.toByteArray();
Log.i("udp", "数据-------------------:" + mydata.length);

dataconvert.java

package com.example.myapp.datastruct;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;

public class dataconvert {
    /**
     * 将int转为高字节在前，低字节在后的byte数组（大端）
     * @param n int
     * @return byte[]
     */
    public static byte[] intToByteBig(int n) {
        byte[] b = new byte[4];
        b[3] = (byte) (n & 0xff);
        b[2] = (byte) (n >> 8 & 0xff);
        b[1] = (byte) (n >> 16 & 0xff);
        b[0] = (byte) (n >> 24 & 0xff);
        return b;
    }
    /**
     * 将int转为低字节在前，高字节在后的byte数组（小端）
     * @param n int
     * @return byte[]
     */
    public static byte[] intToByteLittle(int n) {
        byte[] b = new byte[4];
        b[0] = (byte) (n & 0xff);
        b[1] = (byte) (n >> 8 & 0xff);
        b[2] = (byte) (n >> 16 & 0xff);
        b[3] = (byte) (n >> 24 & 0xff);
        return b;
    }
    /**
     * byte数组到int的转换(小端)
     * @param bytes
     * @return
     */
    public static int bytes2IntLittle(byte[] bytes )
    {
        int int1=bytes[0]&0xff;
        int int2=(bytes[1]&0xff)<<8;
        int int3=(bytes[2]&0xff)<<16;
        int int4=(bytes[3]&0xff)<<24;

        return int1|int2|int3|int4;
    }
    /**
     * byte数组到int的转换(大端)
     * @param bytes
     * @return
     */
    public static int bytes2IntBig(byte[] bytes )
    {
        int int1=bytes[3]&0xff;
        int int2=(bytes[2]&0xff)<<8;
        int int3=(bytes[1]&0xff)<<16;
        int int4=(bytes[0]&0xff)<<24;

        return int1|int2|int3|int4;
    }
    /**
     * 将short转为高字节在前，低字节在后的byte数组（大端）
     * @param n short
     * @return byte[]
     */
    public static byte[] shortToByteBig(short n) {
        byte[] b = new byte[2];
        b[1] = (byte) (n & 0xff);
        b[0] = (byte) (n >> 8 & 0xff);
        return b;
    }

    /**
     * 将short转为低字节在前，高字节在后的byte数组(小端)
     * @param n short
     * @return byte[]
     */
    public static byte[] shortToByteLittle(short n) {
        byte[] b = new byte[2];
        b[0] = (byte) (n & 0xff);
        b[1] = (byte) (n >> 8 & 0xff);
        return b;
    }
    /**
     *  读取小端byte数组为short
     * @param b
     * @return
     */
    public static short byteToShortLittle(byte[] b) {
        return (short) (((b[1] << 8) | b[0] & 0xff));
    }
    /**
     *  读取大端byte数组为short
     * @param b
     * @return
     */
    public static short byteToShortBig(byte[] b) {
        return (short) (((b[0] << 8) | b[1] & 0xff));
    }
    /**
     * long类型转byte[] (大端)
     * @param n
     * @return
     */
    public static byte[] longToBytesBig(long n) {
        byte[] b = new byte[8];
        b[7] = (byte) (n & 0xff);
        b[6] = (byte) (n >> 8  & 0xff);
        b[5] = (byte) (n >> 16 & 0xff);
        b[4] = (byte) (n >> 24 & 0xff);
        b[3] = (byte) (n >> 32 & 0xff);
        b[2] = (byte) (n >> 40 & 0xff);
        b[1] = (byte) (n >> 48 & 0xff);
        b[0] = (byte) (n >> 56 & 0xff);
        return b;
    }
    /**
     * long类型转byte[] (小端)
     * @param n
     * @return
     */
    public static byte[] longToBytesLittle(long n) {
        byte[] b = new byte[8];
        b[0] = (byte) (n & 0xff);
        b[1] = (byte) (n >> 8  & 0xff);
        b[2] = (byte) (n >> 16 & 0xff);
        b[3] = (byte) (n >> 24 & 0xff);
        b[4] = (byte) (n >> 32 & 0xff);
        b[5] = (byte) (n >> 40 & 0xff);
        b[6] = (byte) (n >> 48 & 0xff);
        b[7] = (byte) (n >> 56 & 0xff);
        return b;
    }
    /**
     * byte[]转long类型(小端)
     * @param array
     * @return
     */
    public static long bytesToLongLittle( byte[] array )
    {
        return ((((long) array[ 0] & 0xff) << 0)
                | (((long) array[ 1] & 0xff) << 8)
                | (((long) array[ 2] & 0xff) << 16)
                | (((long) array[ 3] & 0xff) << 24)
                | (((long) array[ 4] & 0xff) << 32)
                | (((long) array[ 5] & 0xff) << 40)
                | (((long) array[ 6] & 0xff) << 48)
                | (((long) array[ 7] & 0xff) << 56));
    }

    /**
     * byte[]转long类型(大端)
     * @param array
     * @return
     */
    public static long bytesToLongBig( byte[] array )
    {
        return ((((long) array[ 0] & 0xff) << 56)
                | (((long) array[ 1] & 0xff) << 48)
                | (((long) array[ 2] & 0xff) << 40)
                | (((long) array[ 3] & 0xff) << 32)
                | (((long) array[ 4] & 0xff) << 24)
                | (((long) array[ 5] & 0xff) << 16)
                | (((long) array[ 6] & 0xff) << 8)
                | (((long) array[ 7] & 0xff) << 0));
    }


    public static byte[] getBytes(char[] chars) {
        Charset cs = Charset.forName("UTF-8");
        CharBuffer cb = CharBuffer.allocate(chars.length);
        cb.put(chars);
        cb.flip();
        ByteBuffer bb = cs.encode(cb);
        return bb.array();
    }

    public static byte BoolToByte(boolean b){
        byte a ;
        a = (byte) (b?0x01:0x00);
        return a;
    }

}

c++

#define BYTE unsigned char
#pragma pack(1)  //指定一字节对齐
struct Test_data{
    int iNumber;
    char arrchResult[90];
    char arrchCode[12];
    bool bOutLimit_Flag;
    int iMark;
    //BYTE byteResultType;
};
#pragma pack()  //取消指定对齐，恢复缺省对齐

Test_data datagram;
        //接收
        char rcData[1024];
        memset(rcData,0,1024);
        m_receiver->readDatagram(rcData,1024);
        memcpy(&datagram,rcData,sizeof(Test_data));

        qDebug()<<"size:"<<sizeof(datagram);

        ui->textEdit->append(QString::number(datagram.iNumber));
        ui->textEdit->append((char*)datagram.arrchResult);
        ui->textEdit->append((char*)datagram.arrchCode);

        ui->textEdit->append(datagram.bOutLimit_Flag?"true":"false");
        ui->textEdit->append(QString::number(datagram.iMark));