Simple Bitset in Rust

bitset.rs

const BITBLOCK_SIZE		: usize	= 16;
const BITBLOCK_SIZEF	: f32	= 16.0;
type BitBlock = u16;

fn calc_block_size( n: f32 ) -> usize { ( n / BITBLOCK_SIZEF ).ceil() as usize }
fn calc_block( n: f32 ) -> usize { ( n / BITBLOCK_SIZEF ).floor() as usize }


#[derive(Debug)]
struct BitSet{
	data: Vec< BitBlock >,
}


impl BitSet{
	//////////////////////////////////////////////////////////////////
	// Constructors
	//////////////////////////////////////////////////////////////////
		pub fn new() -> Self{ BitSet::with_size( BITBLOCK_SIZE ) }

		pub fn with_size( size: usize ) -> Self {
			let b_size	= calc_block_size( size as f32 );
			let mut bs	= BitSet{ data: Vec::with_capacity( b_size ) };

			for i in 0..b_size{ bs.data.push( 0 ); }

			bs
		}

	//////////////////////////////////////////////////////////////////
	// Methods
	//////////////////////////////////////////////////////////////////
		pub fn on( &mut self, bit: usize ) -> &mut Self{
			let b_idx = calc_block( bit as f32 );
			if b_idx >= self.data.len() { self.expand( b_idx ); }

			self.data[ b_idx ] |= 1 << (bit % BITBLOCK_SIZE);
			self
		}

		pub fn off( &mut self, bit: usize )-> &mut Self{
			let b_idx = calc_block( bit as f32 );
			if b_idx >= self.data.len() { self.expand( b_idx ); }

			self.data[ b_idx ] &= !(1 << (bit % BITBLOCK_SIZE)); //Flip it to make a Masks 1011
			self
		}

		pub fn clear( &mut self ) -> &mut Self {
			for i in 0..self.data.len(){ self.data[i] = 0; }
			self 
		}

		pub fn is_mask( &self, b: &BitSet ) -> bool {
			let imax = b.data.len();
			if self.data.len() < imax { return false; }	// If the bitset has less data then a mask, automatic false
			for i in 0..imax{ if self.data[i] & b.data[i] != b.data[i] { return false; } }
			true
		}
	
	//////////////////////////////////////////////////////////////////
	// Private Helper Functions
	//////////////////////////////////////////////////////////////////
		fn expand( &mut self, idx: usize ){
			let cap		= self.data.capacity();
			let resize	= idx - (cap - 1);
			self.data.reserve_exact( resize );

			for i in 0..resize{ self.data.push( 0 ); }
		}
}