// Copyright (c) 1999  Microsoft Corporation.  All Rights Reserved.
#ifndef crc32_h
#define crc32_h

// initial CRC should be 0xffffffff
class CRC32
{
public:
	CRC32( DWORD in) : m_crc32( in ) {};
	CRC32() : m_crc32( 0xffffffff ) {};
	CRC32( const CRC32& in ) : m_crc32( in.m_crc32 ) {};
	CRC32(const void* pPtr, unsigned dwNumBytes);
	template <class T>
	CRC32(const T* pPtr) : m_crc32(  0xffffffff )
		{ Update( pPtr ); }

	DWORD		Update( BYTE bNextByte );
	DWORD		Update( const void* pPtr, unsigned dwNumBytes );

	// template version for adding a structure, data type, or class
	// do not add classes with virtual functions
	template <class T>
	DWORD		Update( const T* pPtr )
				{ return Update( pPtr, sizeof(*pPtr));}

	// a conversion operator is used instead of a 'Get' method so
	// that you can use declarations like " DWORD myCRC = CRC32(ptr,len)"
	//
	//	This class can be used like a function or as an object
	//
	//	For example:
	//		CRC32 myCRC32;
	//		myCRC32.Update( ptr, len );
	//		DWORD myValue = myCRC32;
	//
	//		CRC32 myCRC32(ptr1, len1 );
	//		myCRC32.Update(ptr2, len2 );
	//
	//		DWORD myValue = CRC32(ptr, len )
	//
	operator	DWORD() const	{ return m_crc32; };

protected:
	DWORD		m_crc32;
};

#endif // CRC32