asm.js with coffee-script wrapper

bits.coffee

asm = require('./bits_asm.js')


class Bits

  SIZE = 1024;
  bits: null
  asm: null

  constructor:(nbits=0) ->
    @bits = new ArrayBuffer(SIZE)
    @asm = asm({Uint32Array:Uint32Array, Math:Math}, {}, @bits)


  get:(index) -> @asm.get(index)

  set:(index) -> @asm.set(index)

  clear:(index) -> @asm.clear(index)

bits_asm.js

module.exports = function(stdlib, env, buffer) {
    "use asm";

    var LENGTH = 0;
    var BITS = 1;
    var MEM = new stdlib.Uint32Array(buffer);

    MEM[LENGTH] = 1;

    function bits_get(index) {
        index = index | 0;
        var word = index >>> 5;
        if (word >= MEM[LENGTH]) return;
        return (MEM[BITS+word] & (1 << (index & 0x1f))) != 0;
    }

    function bits_set(index) {
        index = index | 0;
        var word = index >>> 5;
        MEM[BITS+word] |= (1 << (index & 0x1f));
    }

    function bits_clear(index) {
        index = index | 0;
        var word = index >>> 5;
        MEM[BITS+word] &= ~(1 << (index & 0x1f));
    }

    return {
        get             : bits_get,
        set             : bits_set,
        clear           : bits_clear
    };


}

test_bits.coffee

describe 'Bits tests: ' , ->

  it "should set and clear bits independantly", ->

    b1 = new Bits()
    b2 = new Bits()

    b1.set(1)
    b2.set(2)

    b1.get(1).should.equal true
    b1.get(2).should.equal false
    b1.get(3).should.equal false

    b2.get(1).should.equal false
    b2.get(2).should.equal true
    b2.get(3).should.equal false

    b1.clear(1)
    b2.clear(2)

    b1.get(1).should.equal false
    b2.get(2).should.equal false