Extract bits from byte stream

main.c

#include <stdio.h>
#include <stdlib.h>

/*
Starting at position <position> extract <length> older bits.

Example:

bit number:
7 6 5 4 3 2 1 0 | 15 14 13 12 11 10 9 8 | 23 22 21 20 19 18 17 16
----------
bit value:
1 0 0 0 0 0 0 1   1  0  0  0  0  0  0 1   1  0  0  0  0  0  0  0

For the above sol(stream, 5, 3) should return 1100 and sol(stream, 0, 2) should
return 001
*/

unsigned int sol(unsigned char *stream,
                 unsigned position,
                 unsigned length)
{
	static const unsigned masks[8] = {1, 3, 7, 15, 31, 63, 127, 255};

	unsigned int result = stream[position / 8];

	result = result >> (position % 8);

	if ((position + length) / 8 > (position / 8))
		{
			result = result | (stream[position / 8 + 1] << 8 -
			                   (position % 8));
		}

	result = result & masks[length];
	return result;
}

int main(void)
{
	int i1 = 8421761;

        printf("%u\n", sol((unsigned char *) &i1, 5, 3));

	printf("%u\n", sol((unsigned char *) &i1, 2, 6));

	printf("%u\n", sol((unsigned char *) &i1, 0, 2));
	exit(0);
}