位集合

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

unsigned character_offset(unsigned bit_number);
unsigned bit_offset(unsigned bit_number);

/**
 * 将位集合中指定的位设置为0
 */
void
set_bit(char bit_array[], unsigned bit_number)
{
        bit_array[character_offset(bit_number)] |= 
                1 << bit_offset(bit_number);
}

void
clear_bit(char bit_array[], unsigned bit_number)
{
        bit_array[character_offset(bit_number)] &=
                ~(1 << bit_offset(bit_number));
}

void
assign_bit(char bit_array[], unsigned bit_number, int value){
        if(value != 0){
                set_bit(bit_array, bit_number);
        }else{
                clear_bit(bit_array, bit_number);
        }
}

int test_bit(char bit_array[], unsigned bit_number)
{
        return (
                        bit_array[character_offset(bit_number)]
                        & 1 << bit_offset(bit_number)
                ) != 0;
}

unsigned
character_offset(unsigned bit_number)
{
        return bit_number / CHAR_BIT;
}

unsigned
bit_offset(unsigned bit_number)
{
        return bit_number % CHAR_BIT;
}

int
main()
{
        char bit_array[10];
        memset(bit_array, 0, 10);
        set_bit(bit_array, 2);
        if(test_bit(bit_array, 2)){
                printf("2-ok\n");
        }
        if(test_bit(bit_array, 3)){
                printf("3-ok\n");
        }
}