ccitt.cpp

CRC-CCITT码: G(x)=X16+X12+X5+1 多项式为 0x08408 用VC++写的DLL 用VB调用的 有调用实例

// ccitt.cpp : Defines the initialization routines for the DLL.
//

#include "stdafx.h"
#include "ccitt.h"


#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif


#define POLYNOMIAL 0x08408 

//
//	Note!
//
//		If this DLL is dynamically linked against the MFC
//		DLLs, any functions exported from this DLL which
//		call into MFC must have the AFX_MANAGE_STATE macro
//		added at the very beginning of the function.
//
//		For example:
//
//		extern "C" BOOL PASCAL EXPORT ExportedFunction()
//		{
//			AFX_MANAGE_STATE(AfxGetStaticModuleState());
//			// normal function body here
//		}
//
//		It is very important that this macro appear in each
//		function, prior to any calls into MFC.  This means that
//		it must appear as the first statement within the 
//		function, even before any object variable declarations
//		as their constructors may generate calls into the MFC
//		DLL.
//
//		Please see MFC Technical Notes 33 and 58 for additional
//		details.
//

/////////////////////////////////////////////////////////////////////////////
// CCcittApp

BEGIN_MESSAGE_MAP(CCcittApp, CWinApp)
	//{{AFX_MSG_MAP(CCcittApp)
		// NOTE - the ClassWizard will add and remove mapping macros here.
		//    DO NOT EDIT what you see in these blocks of generated code!
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CCcittApp construction

CCcittApp::CCcittApp()
{
	// TODO: add construction code here,
	// Place all significant initialization in InitInstance
}

/////////////////////////////////////////////////////////////////////////////
// The one and only CCcittApp object

CCcittApp theApp;



extern "C" _declspec(dllexport) unsigned int __stdcall getcrc16d(unsigned char *bufdata,unsigned int sizedata)
//返回低位字节
{
unsigned int CRC,i;
unsigned char j;
CRC=0;
for(i=0;i<sizedata;i++)
	{
	CRC^=bufdata[i];
	for(j=0;j<8;j++)
		{
		if(CRC&0X0001) {CRC>>=1;CRC^=POLYNOMIAL;}
		else CRC>>=1;
		}
	}
return((CRC & 0xff));
}

extern "C" _declspec(dllexport) unsigned int __stdcall getcrc16g(unsigned char *bufdata,unsigned int sizedata)
//返回高位字节
{
unsigned int CRC,i;
unsigned char j;
CRC=0;
for(i=0;i<sizedata;i++)
	{
	CRC^=bufdata[i];
	for(j=0;j<8;j++)
		{
		if(CRC&0X0001) {CRC>>=1;CRC^=POLYNOMIAL;}
		else CRC>>=1;
		}
	}
return(((CRC & 0xff00) / 0x100));
}


extern "C" _declspec(dllexport) unsigned int __stdcall getcrc16(unsigned char *bufdata,unsigned int sizedata)
//返回两位字节
{
unsigned int CRC,i;
unsigned char j;
CRC=0;
for(i=0;i<sizedata;i++)
	{
	CRC^=bufdata[i];
	for(j=0;j<8;j++)
		{
		if(CRC&0X0001) {CRC>>=1;CRC^=POLYNOMIAL;}
		else CRC>>=1;
		}
	}
return(CRC);
}