snippet.js

    p.FFT = function(_bufferSize) {
      var bufferSize = _bufferSize;

      var self = {
        initialize: function() {
          self.buildReverseTable();
          self.buildTrigTables();
          return self;
        }
        
        buildReverseTable: function() {
          self.reverseTable = new Array(bufferSize);
          self.reverseTable[0] = 0;

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

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

            limit = limit << 1;
            bit = bit >> 1;
          }
        },
        
        buildTrigTables: function() {
          for ( var i = 0; i < bufferSize; i++ ) {
            self.SinTable[i] = Math.sin(-Math.PI/i);
            self.CosTable[i] = Math.cos(-Math.PI/i);
          }
        }
      }

      return self.initialize();
    }