If we want to count the total number of bits in an integer, we can divide that number by two until it becomes zero, counting a bit at each step.
Here is how this can be implemented in C:
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#include <stdio.h>
// Determine the number of bits that the given `number` requires.
unsigned int count_total_bits(unsigned int number)
{
unsigned int bits = 0;
while (number) {
number >>= 1;
++bits;
}
return bits;
}
int main()
{
int numbers[] = {7, 2019, -1, -2};
for (int i = 0; i < 4; i++)
printf("count_total_bits(%4d) = %2d\n", numbers[i], count_total_bits(numbers[i]));
}
At line 8, instead of dividing number by two, we right-shift it by 1 position (since the logical shift operation is not expensive).
Here is the output of the above program:
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count_total_bits( 7) = 3
count_total_bits(2019) = 11
count_total_bits( -1) = 32
count_total_bits( -2) = 32
Want to see more bitwise logic? There’s a whole repository on my GitHub on bit fiddling.
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