Initial commit of code.

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diff --git a/src/com/jsyn/unitgen/PeakFollower.java b/src/com/jsyn/unitgen/PeakFollower.java
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+/*
+ * Copyright 1997 Phil Burk, Mobileer Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.jsyn.unitgen;
+
+import com.jsyn.ports.UnitInputPort;
+import com.jsyn.ports.UnitOutputPort;
+import com.jsyn.ports.UnitVariablePort;
+
+/**
+ * Tracks the peaks of an input signal. This can be used to monitor the overall amplitude of a
+ * signal. The output can be used to drive color organs, vocoders, VUmeters, etc. Output drops
+ * exponentially when the input drops below the current output level. The output approaches zero
+ * based on the value on the halfLife port.
+ * 
+ * @author (C) 1997-2009 Phil Burk, SoftSynth.com
+ */
+public class PeakFollower extends UnitGenerator {
+    public UnitInputPort input;
+    public UnitVariablePort current;
+    public UnitInputPort halfLife;
+    public UnitOutputPort output;
+
+    private double previousHalfLife = -1.0;
+    private double decayScalar = 0.99;
+
+    /* Define Unit Ports used by connect() and set(). */
+    public PeakFollower() {
+        addPort(input = new UnitInputPort("Input"));
+        addPort(halfLife = new UnitInputPort(1, "HalfLife", 0.1));
+        addPort(current = new UnitVariablePort("Current"));
+        addPort(output = new UnitOutputPort("Output"));
+    }
+
+    @Override
+    public void generate(int start, int limit) {
+        double[] inputs = input.getValues();
+        double[] outputs = output.getValues();
+        double currentHalfLife = halfLife.getValues()[0];
+        double currentValue = current.getValue();
+
+        if (currentHalfLife != previousHalfLife) {
+            decayScalar = this.convertHalfLifeToMultiplier(currentHalfLife);
+            previousHalfLife = currentHalfLife;
+        }
+
+        double scalar = 1.0 - decayScalar;
+
+        for (int i = start; i < limit; i++) {
+            double inputValue = inputs[i];
+            if (inputValue < 0.0) {
+                inputValue = -inputValue; // absolute value
+            }
+
+            if (inputValue >= currentValue) {
+                currentValue = inputValue;
+            } else {
+                currentValue = currentValue * scalar;
+            }
+
+            outputs[i] = currentValue;
+        }
+
+        /*
+         * When current gets close to zero, set current to zero to prevent FP underflow, which can
+         * cause a severe performance degradation in 'C'.
+         */
+        if (currentValue < VERY_SMALL_FLOAT) {
+            currentValue = 0.0;
+        }
+
+        current.setValue(currentValue);
+    }
+}