use strict;
use warnings;

use Inline C => 'DATA';

my $vector = "\0" x 100;			# Bit vector with 800 bits
mytest($vector, 12);				# Pass it to Inline C function
print "Result:" . vec($vector, 12, 1) . "\n";	# Prints '1'

__DATA__
__C__

int mytest(SV* sv_vec, unsigned int bit) {

	STRLEN vecbytes; // Length of vector in bytes
	unsigned char *myvec = (unsigned char *) SvPV(sv_vec, vecbytes);

	if (bit/8 >= vecbytes) return 0; // Check in range
	
	if (myvec[bit/8] & 1U<<(bit%8)) return 1; // Test if a bit is set

	myvec[bit/8] |= 1U<<(bit%8); // Set bit (CHANGES $vector)

	return 1;
}