传递数据结构

Question

我的问题的背景信息：

我有一个基本的 TCP/IP c++ 语言的服务器客户端，

我创建了很多这样的结构（针对不同的包）；

 struct PACKED AddOrderMessageNoMPIDPackage 
    int8_t  code                   //code of package 'A'
    int32_t nanosecond_elapsed;     
    int64_t order_id;                
    int32_t order_book_id;            
    char    side;                     
    int32_t order_book_position;      
    char session[10];

我正在尝试将数据传递到服务器端的结构中；

    A.to_little_endian(); //(Firstly i use `nhton,hnton` fucntions)
    A.code = server.pop();  //Server is a class include pop functions etc
    A.nanosecond_elapsed = server.pop32();
    A.order_book_id = server.pop32();
    for (int i = 0; i < 32; i++) {
    A.symbol[i] = server.pop();}

弹出函数是这样的；

    int32_t TcpServer::pop32(){
    int32_t ch;
    if(::recv(_sockFd, &ch, 4, 0)>0)
    return getLeValue(ch);   // nhton hnton functions

我无法将数据传递到结构中，有人对此有想法吗？

Answer 1

您应该将结构写入字节数组，然后发送字节数组。您永远不应该以二进制方式编写结构，无论是文件还是套接字。另一方面，您读取字节数组，然后将值读回到您的结构中。

下面是一些示例代码，我是如何做到的。 Endianess 和 padding 对这种方法没有问题。与将每个值写入套接字相比，它还为您提供了更好的性能。我用它来发送 UDP 数据报，但它也可以用于通过 TCP 发送它。

您需要如下功能。

virtual MESSAGE_BUFFER * GetMessageAsBinaryPtr()
{
  MESSAGE_BUFFER * binaryMsg = new MESSAGE_BUFFER;
  UINT8 * ptrBuffer = &(*binaryMsg)[0];
  ptrBuffer = this->serializeUInt16(ptrBuffer, this->m_majorVersion);
  ptrBuffer = this->serializeUInt16(ptrBuffer, this->m_minorVersion);
  ptrBuffer = this->serializeUInt32(ptrBuffer, (UINT32)this->m_messageType);
  ptrBuffer = this->serializeUInt64(ptrBuffer, this->m_packetID);
  ptrBuffer = this->serializeDouble(ptrBuffer, this->m_timestamp);
  return binaryMsg;
}

virtual void CreateFromBinary(MESSAGE_BUFFER buffer)
{
  UINT8 * ptrBuffer = &buffer[0];
  ptrBuffer = this->deserializeUInt16FromBuffer(ptrBuffer, &this->m_majorVersion);
  ptrBuffer = this->deserializeUInt16FromBuffer(ptrBuffer, &this->m_minorVersion);

  UINT32 messageType = 0;
  ptrBuffer = this->deserializeUInt32FromBuffer(ptrBuffer, &messageType);
  this->SetMessageType((MessageTypes)messageType);

  ptrBuffer = this->deserializeUInt64FromBuffer(ptrBuffer, &this->m_packetID);
  ptrBuffer = this->deserializeDoubleFromBuffer(ptrBuffer, &this->m_timestamp);
}

inline UINT8 * serializeUInt16(UINT8 * buffer, UINT16 value)
{
  buffer[1] = value;
  buffer[0] = value >> 8;
  return buffer + 2;
}

inline UINT8 * deserializeUInt16FromBuffer(UINT8 * buffer, UINT16 * pOutput)
{
  *pOutput = (*pOutput << 8) + buffer[0];
  *pOutput = (*pOutput << 8) + buffer[1];
  return buffer + 2;
}

编辑：我发现 post 前段时间引导我走上了正确的道路。这里有一些更多的解释： Passing a structure through Sockets in C

传递数据结构

Passing data structures

c++

tcp

tcp-ip