指针之6.5

/*
 * Sieve of Dratosthense -- compute prime numbers using a bit array
 * 2010-11-20
 */

 

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include "bitarray.h"    // 在第五章编程练习中开发的位数组函数


#define        MAX_VALUE        10000
#define        MAX_BIT_NUMBER        ( ( MAX_VALUE - 3 ) / 2 )
#define        SIZE            ( MAX_BIT_NUMBER / CHAR_BIT + 1 )

int main(void)
{
    char    sieve[ SIZE ];
    int        number;
    int        bit_number;
    char    *sp;

    for( sp = sieve; sp < &sieve[ SIZE ]; )
        *sp++ = 0xff;

    for( number =3; number <= MAX_VALUE; number += 2 )
    {
        bit_number = ( number - 3 ) / 2;

        if( !test_bit( sieve, bit_number ) )
            continue;
    }

    printf( "2\n" );
    for( bit_number = 0,number = 3;
        number <= MAX_VALUE;
        bit_number += 1, number += 2 )
    {
        if( test_bit( sieve, bit_number ) )
            printf( "%d\n", number );
    }

    return EXIT_SUCCESS;
}