帮助复制内存 [英] help on copying memory

问题描述

我对C ++还是很陌生，谁能帮助我解决内存复制问题(目标的无效指针):

切出的代码如下所示:

I am quite new to C++, could anyone help me to fix memory copy issue (invalid pointer of destination):

cut out code looks like this:

int cWrapper::EncryptRun(const unsigned char *data, NewCamDData *cd, int len, bool UseMsgId, comm_type_t commType)
{
	memcpy(desKey , cd->desKey, 16);	
	int sz = sizeof(DES_key_schedule);
	memcpy(&ks1, &cd->ks1, sz);
	memcpy(&ks2, &cd->ks2, sz);

unsigned char netbuf[CWS_NETMSGSIZE];
memset(&netbuf[2],0,cdLen+2);
memcpy(&netbuf[cdLen+4],data,len);
netbuf[cdLen+4+1]=(data[1]&0xf0)|(((len-3)>>8)&0x0f);
netbuf[cdLen+4+2]=(len-3)&0xff;
//...assign values

//this is where the problem is for the data pointer
memcpy(&data,&netbuf,len);
}

数据指向一个240字节的数组，而netbuf是要复制到数据的新字节数组.

为了完成通话，我添加了调用该通话的方法:

data points to an array of 240 bytes, and netbuf is new byte array to be copied to data.

To complete calls, I am adding the method which calls this:

DllExport int CALLBACK EncryptA(NewCamDData *cd, unsigned char *pBuffer, int len, bool UseMsgId, comm_type_t commType)
{
    //cw assigned in class initialisation:
    cw = new cWrapper(525);
    int ret = cw->EncryptRun(pBuffer, cd, len, UseMsgId, commType);
    return ret; //*pBuffer;
}

从VB.NET调用此方法.

调试向我显示了此信息:

This method called from VB.NET.

debugging shows me this:

?netbuf
0x0038ebec ""
    [0]: 0 <-first byte of array
    [1]: 48 '0'
    [2]: 169 '©'
?data
0x0280aee4 "€	¤+ØÔ­&§Hœõ­Røî°¶l-áþ«…"
?sizeof(data)
4
?*data
128 '€' <-first byte of array

推荐答案

使用

memcpy(data, netbuf, len);

因为data和netbuf已经是指针.
但是，这将产生编译器错误，因为目标data被声明为const.由于不使用cd的事实，我认为

because data and netbuf are already pointers.
However, this will produce a compiler error, because the destination data is declared as const. Due to the fact that cd is not used, I assume that

memcpy(cd, netbuf, len)

是你想要的.

为确保不会发生缓冲区溢出，您还可以添加一些检查:

is what you want.

To be sure that no buffer overflows occur, you may also add some checks:

ASSERT(cdLen + 4 + len <= CWS_NETMSGSIZE);
ASSERT(cdLen + 7 <= CWS_NETMSGSIZE);
// This only when copying to cd
ASSERT(len <= sizeof(NewCamDData));

memcpy(data,netbuf,len);

我认为，这就是您应该打电话的方式.要这样调用，数据参数声明应为"unsigned char * data"，不应为常量指针！.

还要确保-

i think, this is how you should call. To call like this the data parameter declaration should be "unsigned char *data" should not be a constant pointer!.

Also make sure -

CWS_NETMSGSIZE>=len.

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