在VC中使用DLL一般都是采用動態(tài)聲明的方式，函數說明中給出的是Delphi的函數原型，
在VC中聲明時只要注意一下類型的對應即可,Delphi中的longint類型對應VC中的int類型
Delphi中的Pchar對應VC中的char* ，下面給出主要函數的聲明：
在使用的文件的cpp中聲明一個句柄：
HINSTANCE hinstDLL;
用來標識導入的動態(tài)鏈接庫。
1)、按下例說明聲明相關各個函數：(在cpp文件的頭處聲明)
typedef int (_stdcall *pOpen)(int nport, int BaudRate, int DataBits, char* Parity, int StopBits, char* User);
typedef int (_stdcall *pClose)(int nport);
typedef int (_stdcall *pSetDelay)(int nport);
typedef int (_stdcall *pComTrue)(int nport);
typedef int (_stdcall *pComWork)(int nport);
typedef int (_stdcall *pMS)(int nport, int node);
typedef int (_stdcall *pSC)(int nport, int node, int State);
typedef int (_stdcall *pMM)(int nport, int node);
typedef int (_stdcall *pTS)(int nport, int node);
typedef int (_stdcall *pReadInt)(int nport, int node, int address, int Count, char* Order, int* RxdBuffer);
typedef int (_stdcall *pReadTc)(int nport, int node, int address, int Count, int* RxdBuffer);
typedef int (_stdcall *pWriteInt)(int nport, int node, int address, int Count, char* Order, int* TxdBuffer);
typedef int (_stdcall *pSetF)(int nport, int node, int address, int Bit, char* Order);
typedef int (_stdcall *pReSetF)(int nport, int node, int address, int Bit, char* Order);
typedef int (_stdcall *pCancelF)(int nport, int node, int address, int Bit, char* Order);
typedef int (_stdcall *pCancelAllF)(int nport, int node);
typedef int (_stdcall *pSet)(int nport, int node, int address, int Bit, char* Order);
typedef int (_stdcall *pReSet)(int nport, int node, int address, int Bit, char* Order);
typedef int (_stdcall *pReadBit)(int nport, int node, int address, int Bit, int Count, char* Order, int* RxdBuffer);
typedef int (_stdcall *pReadDInt)(int nport, int node, int address, int Count,int* RxdBuffer);
typedef int (_stdcall *pReadFloat)(int nport, int node, int address, int Count, float* RxdBuffer);
typedef int (_stdcall *pWriteDInt)(int nport, int node, int address, int Count, int* TxdBuffer);
typedef int (_stdcall *pWriteFloat)(int nport, int node, int address, int Count, float* TxdBuffer);
typedef int (_stdcall *pBitBin)(int value, int Bitaddress);
typedef int (_stdcall *p32I_16h)(int value);
typedef int (_stdcall *p32I_16l)(int value);
typedef int (_stdcall *p16I_32I)(int valueH, int valueL);
typedef int (_stdcall *p32f_16h)(float value);
typedef int (_stdcall *p32f_16l)(float value);
typedef float (_stdcall *p16I_32f)(int valueH, int valueL);
2)、建立動態(tài)鏈接庫的新函數名：(在cpp文件的頭處聲明)
pOpen mOpen;
pClose mClose;
pSetDelay mSetDelay;
pComTrue mComTrue;
pComWork mComWork;
pMS mMS;
pSC mSC;
pMM mMM;
pTS mTS;
pReadInt mReadInt;
pReadTc mReadTc;
pWriteInt mWriteInt;
pSetF mSetF;
pReSetF mReSetF;
pCancelF mCancelF;
pCancelAllF mCancelAllF;
pSet mSet;
pReSet mReSet;
pReadBit mReadBit;
pReadDInt mReadDInt;
pReadFloat mReadFloat;
pWriteDInt mWriteDInt;
pWriteFloat mWriteFloat;
pBitBin mBitBin;
p32I_16h m32I_16h;
p32I_16l m32I_16l;
p16I_32I m16I_32I;
p32f_16h m32f_16h;
p32f_16l m32f_16l;
p16I_32f m16I_32f;
3)、導入動態(tài)鏈接庫，如例所示：(在cpp文件的OnInitDialog過程建立)：
hinstDLL = LoadLibrary("Omron_HostLink.dll");
4)、判斷dll文件是否存在并聲明并建立動態(tài)鏈接庫中的函數與新函數名的對應關系，
如下：(在cpp文件的OnInitDialog過程建立)：
if (hinstDLL)
{
mOpen = (pOpen)GetProcAddress (hinstDLL,"OmronComOpen");
mClose = (pClose)GetProcAddress (hinstDLL,"OmronComClose");
mSetDelay = (pSetDelay)GetProcAddress (hinstDLL,"OmronSetDelay");
mComTrue = (pComTrue)GetProcAddress (hinstDLL,"OmronComTrue");
mComWork = (pComWork)GetProcAddress (hinstDLL,"OmronComWork");
mMS = (pMS)GetProcAddress (hinstDLL,"OmronMS");
mSC = (pSC)GetProcAddress (hinstDLL,"OmronSC");
mMM = (pMM)GetProcAddress (hinstDLL,"OmronMM");
mTS= (pTS)GetProcAddress (hinstDLL,"OmronTS");
mReadInt = (pReadInt)GetProcAddress (hinstDLL,"OmronReadInt");
mReadTc = (pReadTc)GetProcAddress (hinstDLL,"OmronReadTc");
mWriteInt = (pWriteInt)GetProcAddress (hinstDLL,"OmronWriteInt");
mSetF = (pSetF)GetProcAddress (hinstDLL,"OmronSetF");
mReSetF = (pReSetF)GetProcAddress (hinstDLL,"OmronReSetF");
mCancelF = (pCancelF)GetProcAddress (hinstDLL,"OmronCancelF");
mCancelAllF = (pCancelAllF)GetProcAddress (hinstDLL,"OmronCancelAllF");
mSet = (pSet)GetProcAddress (hinstDLL,"OmronSet");
mReSet = (pReSet)GetProcAddress (hinstDLL,"OmronReSet");
mReadBit = (pReadBit)GetProcAddress (hinstDLL,"OmronReadBit");
mReadDInt = (pReadDInt)GetProcAddress (hinstDLL,"OmronReadDInt");
mReadFloat = (pReadFloat)GetProcAddress (hinstDLL,"OmronReadFloat");
mWriteDInt = (pWriteDInt)GetProcAddress (hinstDLL,"OmronWriteDInt");
mWriteFloat = (pWriteFloat)GetProcAddress (hinstDLL,"OmronWriteFloat");
mBitBin = (pBitBin)GetProcAddress (hinstDLL,"DecBitBin");
m32I_16h = (p32I_16h)GetProcAddress (hinstDLL,"Int32ToInt_16h");
m32I_16l = (p32I_16l)GetProcAddress (hinstDLL,"Int32ToInt_16l");
m16I_32I= (p16I_32I)GetProcAddress (hinstDLL,"Int16ToInt32");
m32f_16h = (p32f_16h)GetProcAddress (hinstDLL,"Float32ToInt_16h");
m32f_16l = (p32f_16l)GetProcAddress (hinstDLL,"Float32ToInt_16l");
m16I_32f= (p16I_32f)GetProcAddress (hinstDLL,"Int16ToFloat32");
AfxMessageBox("Omron_HostLink.dll已成功載入！");
}
else
{
AfxMessageBox("沒找到Omron_HostLink.dll！");
SendMessage(WM_CLOSE);
}
注：雙引號中為動態(tài)鏈接庫中的原有函數名。
函數中用到了char*型參數，這里介紹下char*與Cstring的相互轉換的函數：
(1)char*->CString
char* sz;
CString str;
str.Format("%s",sz); //可以用此函數將讀取的值轉成字符串
(2) CString -> char*
CString str;
char* sz = str.GetBuffer(0);//可將字符串轉成char*給函數賦值
5）、當不再需要使用DLL時記得關閉串口及釋放動態(tài)鏈接庫，(在OnDestroy事件中釋放)
if(hinstDLL)
{
int k = mComTrue(mnport);
if (k==1)
{
mClose(mnport);
}
FreeLibrary(hinstDLL);
}
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