snippet.js

    p.FFT = function(bufferSize) {
      this.bufferSize = bufferSize;

      this.ReverseTable = this.buildReverseTable();

      this.prototype.buildReverseTable = function() {
        var reverseTable = new Array(this.bufferSize);
        reverseTable[0] = 0;

        var limit = 1;
        var bit = this.bufferSize >> 1;

        while ( limit < this.bufferSize ) {
          for ( var i = 0; i < limit; i++ ) {
            reverseTable[i + limit] = reverseTable[i] + bit;
          }

          limit = limit << 1;
          bit = bit >> 1;
        }
        return reverseTable
      }