crc.cpp

Skin, zip, unzip, md5, crc32, drag and drop

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>


unsigned long CRCTable[ 256 ];

#define SEPARATOR "/"
#define FILENAME_SIZE 260



#define MSDOS 1
#define Mob 512
#include <stdarg.h>
#include <dos.h>



#define FILE_INFO                 struct find_t
#define FIND_FIRST( n, i )        _dos_findfirst( (n), _A_SUBDIR, (i) )
#define FIND_NEXT( info )         _dos_findnext( ( info ) )
#define FILE_NAME( info )         ( ( info ).name )


unsigned long CalculateFileCRC( FILE *file );
void BuildCRCTable( void );
unsigned long CalculateBufferCRC( unsigned int count, unsigned long crc, void *buffer );
unsigned long CheckFiles( char *na);

#define CRC32_POLYNOMIAL     0xEDB88320L
#define defi                 0x7c211d96L



unsigned long CheckFiles( char *na)
{
    FILE *crc_file;
    FILE *test_file;
    unsigned long crc;


   BuildCRCTable();

        test_file = fopen( na, "rb" );
       if ( test_file != NULL ) {
          
            crc = CalculateFileCRC( test_file );
            fclose( test_file );
			return crc;
          
        }
		return NULL;
  
}


/*
 * This routine is responsible for actually performing the
 * calculation of the 32 bit CRC for the entire file.  We
 * precondition the CRC value with all 1's, then invert every bit
 * after the entire file has been done.  This gives us a CRC value
 * that corresponds with the values calculated by PKZIP and ARJ.
 * The actual calculation consists of reading in blocks from the
 * file, then updating the CRC with the value for that block.  The
 * CRC work is done by another the CalculateBufferCRC routine.
 */

unsigned long CalculateFileCRC( FILE *file )

{
    unsigned long crc;
    int count;
    unsigned char buffer[ Mob+1 ];
    int i;

    crc = 0xFFFFFFFFL;
    i = 0;
    for ( ; ; ) {
        count = fread( buffer, 1, Mob, file );

		//if ( ( i++ % 32 ) == 0 )  { } //putc( '.', stdout );
        if ( count == 0 )   break;


        crc = CalculateBufferCRC( count, crc, buffer );
    }
   // putc( ' ', stdout );
    return( crc ^= 0xFFFFFFFFL );
}



void BuildCRCTable()
{
    int i;
    int j;
    unsigned long crc;

    for ( i = 0; i <= 255 ; i++ ) {
        crc = i;
        for ( j = 8 ; j > 0; j-- ) {
            if ( crc & 1 )
                crc = ( crc >> 1 ) ^ CRC32_POLYNOMIAL;
            else
                crc >>= 1;
        }
        CRCTable[ i ] = crc;
    }
}



unsigned long CalculateBufferCRC( unsigned int count, unsigned long crc, void *buffer )

{
    unsigned char *p;
    unsigned long temp1;
    unsigned long temp2;

    p = (unsigned char*) buffer;
    while ( count-- != 0 ) {
        temp1 = ( crc >> 8 ) & 0x00FFFFFFL;
        temp2 = CRCTable[ ( (int) crc ^ *p++ ) & 0xff ];
        crc = temp1 ^ temp2;
    }
    return( crc );
}