#include <stdio.h>
#include <string.h>
#include <windows.h>

/* All function indices in FastCRC.dll can be found in:*/
/* FastCRC Library Help (FastCRC Library Run-Time Dynamic Linking page) */
#define CRC32_INIT_INDEX          101
#define CRC32_UPDATE_INDEX        102
#define CRC32_FINAL_INDEX         104
#define CRC32_CALCULATE_INDEX     105

#define FCRC_CONVERTTOHEX32_INDEX 51

/* This constant can be found in FastCRC.h */
#define FCRC_MAXHEXSIZE           9

/* Declare pointer types for each function you need to use */
typedef void          ( _stdcall *PINIT )( unsigned long* );
typedef void          ( _stdcall *PUPDATE )( unsigned long*, const void*, unsigned int );
typedef unsigned long ( _stdcall *PFINAL )( unsigned long* );
typedef unsigned long ( _stdcall *PCALCULATE )( const void*, unsigned int );

typedef void          ( _stdcall *PCONVERTTOHEX32 )( char*, unsigned long, int );

int main()
{
    PINIT           pInit;
    PUPDATE         pUpdate;
    PFINAL          pFinal;
    PCALCULATE      pCalculate;

    PCONVERTTOHEX32 pConvertToHex32;

    char buff[ 256 ];

    unsigned long checksum;
    char          checksumhex[ FCRC_MAXHEXSIZE ]; /*0 terminated*/

    unsigned long crcvar;

    /*****Load FastCRC.dll*************/
    HMODULE hModule = LoadLibrary( "FastCRC.dll" );
    if( !hModule )
    {
        printf( "Could not load FastCRC.dll library" );
        return 1;
    }

    /*****Get all function addresses*****/
    pInit           = (PINIT)GetProcAddress( hModule, (LPCSTR)CRC32_INIT_INDEX );
    pUpdate         = (PUPDATE)GetProcAddress( hModule, (LPCSTR)CRC32_UPDATE_INDEX );
    pFinal          = (PFINAL)GetProcAddress( hModule, (LPCSTR)CRC32_FINAL_INDEX );
    pCalculate      = (PCALCULATE)GetProcAddress( hModule, (LPCSTR)CRC32_CALCULATE_INDEX );

    pConvertToHex32 = (PCONVERTTOHEX32)GetProcAddress( hModule, (LPCSTR)FCRC_CONVERTTOHEX32_INDEX );

    do
    {
        /*****Get the string from the user****************************************/

        printf( "\nEnter a string: " );
        gets( buff );

        printf( "\nDigest for \"%s\":", buff );

        /*****Calculate the checksum using Calculate******************************/

        printf( "\nCalculated using Calculate:           " );

        checksum = ( *pCalculate )( buff, strlen( buff ) );

        ( *pConvertToHex32 )( checksumhex, checksum, 0 );

        printf( "%s", checksumhex );

        /*****Initialize the context before calling Update, Final, or FinalHex****/

        ( *pInit )( &crcvar );

        /*****Calculate the checksum using Update and Final***********************/

        printf( "\nCalculated using Update and Final:    " );

        ( *pUpdate )( &crcvar, buff, strlen( buff ) );
        checksum = ( *pFinal )( &crcvar ); /* Final reinitializes the crcvar for the next use */

        ( *pConvertToHex32 )( checksumhex, checksum, 1 );

        printf( "%s", checksumhex );

        /*****Continue?***********************************************************/

        printf( "\nContinue (Y/N)?" );
        gets( buff );

    }while( *buff == 'y' || *buff == 'Y' );

    FreeLibrary( hModule );

    return 0;
}