snippet.js

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

      this.SinTable = new Array(bufferSize);
      this.CosTable = new Array(bufferSize);
      this.ReverseTable = new Array(bufferSize);


      this.prototype.FFT(bufferSize) {
        this.buildTrigTables();
        this.buildReverseTable();
      }


      this.prototype.buildTrigTables = function() {
        for ( var i = 0; i < this.bufferSize; i++ ) {
          this.SinTable[i] = Math.sin(-Math.PI/i);
          this.CosTable[i] = Math.cos(-Math.PI/i);
        }
      }

      this.prototype.buildReverseTable = function() {
        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;
        }
      }
    }