如何将结构对象分配给char * [英] How to assign struct object into char *

问题描述

朋友，
现在我正在使用TCP/IP开发套接字程序.现在的问题是，我想从服务器和客户端传输结构数据，我想使用相同的结构接收相同的数据.

服务器端:
步骤1:使用CFile对象"pCustInfoFile" struct obj"oModeld传递以从文件读取daa.
步骤2:现在，我将此结构obj"oModel"分配给char * Buff.
步骤3:使用strncpy函数，将数据从oMdel复制到Buff.
步骤4:使用Socket obj"pSocket"，将数据发送到客户端.

服务器端代码供您参考:

Hi friends,
Right now i am developing socket program using TCP/IP. Now problem is, I want to transmit structure data from server and in client, i want to receive same data using same structure.

Server Side:
Step1: Using CFile object "pCustInfoFile" struct obj "oModeld passed to read daa from file.
Step2: Now i Assign this struct obj "oModel" into char *Buff.
Step3: using strncpy function, copied data from oMdel in to Buff.
Step4: Using Socket obj "pSocket", the data sent to client side.

Server side code for your reference:

if(pCustInfoFile->Open(FName,CFile::modeRead))
{
   SModelInfo *oModel;  //"SModelInfo" is a structure
   char *Buff;
   oModel = new SModelInfo;
   pCustInfoFile->Read(oModel,sizeof(SModelInfo));
   
   strncpy(Buff,(char*)&oModel,sizeof(SModelInfo));
   pSocket->Send(Buff,sizeof(Buff));

}

客户端:

步骤1:使用大小和数据相同的char buff从客户端接收.
步骤2:oModel =(SModelInfo *)buff;
步骤3:如果将oModel->名称分配给sName(sName = oModel->名称)变量，则值(Name)不会得到

Client Side:

Step1: Using char buff with same size and data is receives in client side.
Step2: oModel = (SModelInfo*)buff;
Step3: If assigning oModel->Name to sName (sName = oModel->Name)variable then the value(Name) is not getting

int br=Receive(buff,sizeof(SModelInfo));
SModelInfo *oModel;
oModel = (SModelInfo*)buff;
CString sName;
sName = oModel->Name;

帮助我解决此问题.

谢谢与问候
S.Shanmuga Raja

Help me to fix this problem.

Thanks and Regards
S.Shanmuga Raja

推荐答案

在服务器端，您声明了Buff指针，但没有将其指向特定的内存.尝试为Buff分配内存.像这样的东西:

In the server side, you declared the Buff pointer but, didn''t point it to a specific memory. Try to allocate memory for Buff. Something like:

char *Buff = new char[sizeof(SModelInfo)];

而且，为什么要使用strncpy和指向SModelInfo的指针(您将oModel声明为指针...).尝试在堆栈中声明oModel.像这样的东西:

And, why do you use strncpy with the pointer to the pointer to SModelInfo (you declared oModel as a pointer...). Try to declare oModel in the stack instead. Something like:

SModelInfo oModel;
pCustInfoFile->Read(&oModel,sizeof(SModelInfo));

另一个问题:尝试更改Send函数以使用struct大小.像这样的东西:

Another issue: Try to change the Send function to use the struct size. Something like:

pSocket->Send(Buff,sizeof(SModelInfo));

在下面的代码中，您尝试将其从结构oModel复制到Buff，但是该指针尚未初始化，因此将损坏某些内存或导致内存访问错误.

In the following code you are trying to copy from the structure oModel to Buff, but that pointer has not been initialised so you will corrupt some memory or cause a memory access error.

char *Buff;
oModel = new SModelInfo;
pCustInfoFile->Read(oModel,sizeof(SModelInfo));

strncpy(Buff,(char*)&oModel,sizeof(SModelInfo));

它应该显示为

It should read

char *Buff;
oModel = new SModelInfo;
pCustInfoFile->Read(oModel,sizeof(SModelInfo));
Buff = new char[sizeof(SModelInfo)]; // allocate space for buffer
strncpy(Buff,(char*)oModel,sizeof(SModelInfo));

在下面的代码中，您将创建一个指针，并使用new对其进行初始化，然后立即使用其他指针覆盖它，从而丢失先前分配的块.

In the following code you create a pointer, initialise it with new and then immediately overwrite it with a different pointer thus losing the previously allocated block.

SModelInfo *oModel1;
oModel1 = new SModelInfo;
oModel1 = (SModelInfo*)buff;

应该是

This should be

SModelInfo *oModel1 = (SModelInfo*)buff; // just point at the existing buffer.

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