Question

我收到了需要在代码中实现的功能。该功能正在其自身的自测器上运行。这是与struct相关联的（如果需要，我可以制作一个可执行的示例）：

    #define STEERINGCMD_MSG_BUFFERLENGTH    40

typedef struct GLOBAL_MSG
{
    u1 starter;
    u1 frameID;
    u1 length;
    u1 msgData[STEERINGCMD_MSG_BUFFERLENGTH];
    u4 CRYPTO;
};

GLOBAL_MSG  steeringCmdMsg;

struct SteeringData
{
    int                 isL1;
    int                 isL5;
    unsigned long long  CoPR;
    unsigned long long  CoPA;
    unsigned long long  CaPR;
    unsigned long long  CaPA;

};

void generateNextSteeringCmdMsg(SteeringData stData)
{
    steeringCmdMsg.starter = 0xAA;
    steeringCmdMsg.frameID = 68;
    steeringCmdMsg.length = STEERINGCMD_MSG_BUFFERLENGTH;

    if()
    {
        steeringCmdMsg.msgData[0] = 0x0F;
    }
    else if( )
    {
        steeringCmdMsg.msgData[0] = 0xF0;
    }
    steeringCmdMsg.msgData[1] = stData.CoPR & 0xFF;
    steeringCmdMsg.msgData[2] = stData.CoPR >> 8 & 0xFF;
    steeringCmdMsg.msgData[3] = stData.CoPR >> 16 & 0xFF;
    steeringCmdMsg.msgData[4] = stData.CoPR >> 24 & 0xFF;
    steeringCmdMsg.msgData[5] = stData.CoPR >> 32 & 0xFF;
    steeringCmdMsg.msgData[6] = stData.CoPR >> 40 & 0xFF;
    steeringCmdMsg.msgData[7] = stData.CoPR >> 48 & 0xFF;
    steeringCmdMsg.msgData[8] = stData.CoPR >> 56 & 0xFF;
    steeringCmdMsg.msgData[9] = stData.CoPA & 0xFF;
    steeringCmdMsg.msgData[10] = stData.CoPA >> 8 & 0xFF;
    steeringCmdMsg.msgData[11] = stData.CoPA >> 16 & 0xFF;
    steeringCmdMsg.msgData[12] = stData.CoPA >> 24 & 0xFF;
    steeringCmdMsg.msgData[13] = stData.CoPA >> 32 & 0xFF;
    steeringCmdMsg.msgData[14] = stData.CoPA >> 40 & 0xFF;
    steeringCmdMsg.msgData[15] = stData.CoPA >> 48 & 0xFF;
    steeringCmdMsg.msgData[16] = stData.CoPA >> 56 & 0xFF;
    steeringCmdMsg.msgData[17] = stData.CaPR & 0xFF;
    steeringCmdMsg.msgData[18] = stData.CaPR >> 8 & 0xFF;
    steeringCmdMsg.msgData[19] = stData.CaPR >> 16 & 0xFF;
    steeringCmdMsg.msgData[20] = stData.CaPR >> 24 & 0xFF;
    steeringCmdMsg.msgData[21] = stData.CaPR >> 32 & 0xFF;
    steeringCmdMsg.msgData[22] = stData.CaPR >> 40 & 0xFF;
    steeringCmdMsg.msgData[23] = stData.CaPR >> 48 & 0xFF;
    steeringCmdMsg.msgData[24] = stData.CaPR >> 56 & 0xFF;
    steeringCmdMsg.msgData[25] = stData.CaPA & 0xFF;
    steeringCmdMsg.msgData[26] = stData.CaPA >> 8 & 0xFF;
    steeringCmdMsg.msgData[27] = stData.CaPA >> 16 & 0xFF;
    steeringCmdMsg.msgData[28] = stData.CaPA >> 24 & 0xFF;
    steeringCmdMsg.msgData[29] = stData.CaPA >> 32 & 0xFF;
    steeringCmdMsg.msgData[30] = stData.CaPA >> 40 & 0xFF;
    steeringCmdMsg.msgData[31] = stData.CaPA >> 48 & 0xFF;
    steeringCmdMsg.msgData[32] = stData.CaPA >> 56 & 0xFF;

    char* actMsg =(char*) &steeringCmdMsg;
    steeringCmdMsg.crc32 = calculateCRYPTOForBuf(actMsg, STEERINGCMD_MSG_BUFFERLENGTH - 4);
}

void getSteeringMsg(i1 msg[STEERINGCMD_MSG_BUFFERLENGTH])
{
    char* actMsgData =(char*) &steeringCmdMsg.msgData;
    msg[0] =  steeringCmdMsg.starter;
    msg[1] =  steeringCmdMsg.frameID;
    msg[2] =  steeringCmdMsg.length;
    memcpy( &msg[3], actMsgData, STEERINGCMD_MSG_BUFFERLENGTH - 7);

    msg[39] = steeringCmdMsg.CRYPTO >>24;
    msg[38] = steeringCmdMsg.CRYPTO >>16;
    msg[37] = steeringCmdMsg.CRYPTO >>8;
    msg[36] = steeringCmdMsg.CRYPTO;

}

//used like this in the main
int main {

    i1 tmpMsg[STEERINGCMD_MSG_BUFFERLENGTH + 1];
    memset(tmpMsg, 0, STEERINGCMD_MSG_BUFFERLENGTH + 1);
    generateNextSteeringCmdMsg(steeringDataL1);
    getSteeringMsg(tmpMsg);
    write(tmpMsg, STEERINGCMD_MSG_BUFFERLENGTH);

    return 0;
}

上下文： 我的设备需要以二进制形式接收我们所谓的“ steering msg”，其中包含基本标头和SteeringData中包含的所有参数结构。最后，将所有参数串联在msgData中，我计算出我们所谓的CRYPTO。并将其添加到邮件末尾。

问题是，在此代码中，stData.CoPR / CoPA ...是无符号的long long（大小= 8），而在我的代码中，这是一个double（struct.CoPR-不能修改，因为来自结构）。

所以我正在寻找修改此功能并用我的double结构替换此unsigned long的最佳方法。一种简单的强制转换，或另一种直接将我的double结构转换为char数组的方法。但是我不知道在哪里看，什么是最最安全最安全的方法。

随时要求更多解释，谢谢！

双精度，无符号long long和char数组[C程序]

0 个答案: