From 534969d42ca5168d645678345cd21242fe41f389 Mon Sep 17 00:00:00 2001
From: Phil Burk <philburk@mobileer.com>
Date: Tue, 30 Dec 2014 16:53:03 -0800
Subject: Initial commit of code.

---
 src/com/jsyn/unitgen/PowerOfTwo.java | 99 ++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 src/com/jsyn/unitgen/PowerOfTwo.java

(limited to 'src/com/jsyn/unitgen/PowerOfTwo.java')

diff --git a/src/com/jsyn/unitgen/PowerOfTwo.java b/src/com/jsyn/unitgen/PowerOfTwo.java
new file mode 100644
index 0000000..5f1b4cd
--- /dev/null
+++ b/src/com/jsyn/unitgen/PowerOfTwo.java
@@ -0,0 +1,99 @@
+/*
+ * Copyright 2010 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;
+
+/**
+ * output = (2.0^input) This is useful for converting a pitch modulation value into a frequency
+ * scaler. An input value of +1.0 will output 2.0 for an octave increase. An input value of -1.0
+ * will output 0.5 for an octave decrease. This implementation uses a table lookup to optimize for
+ * speed. It is accurate enough for tuning. It also checks to see if the current input value is the
+ * same as the previous input value. If so then it reuses the previous computed value.
+ * 
+ * @author Phil Burk (C) 2010 Mobileer Inc
+ */
+public class PowerOfTwo extends UnitGenerator {
+    public UnitInputPort input;
+    public UnitOutputPort output;
+
+    private static double[] table;
+    private static final int NUM_VALUES = 1024;
+    // Cached computation.
+    private double lastInput = 0.0;
+    private double lastOutput = 1.0;
+
+    static {
+        // Add guard point for faster interpolation.
+        // Add another point to handle inputs like -1.5308084989341915E-17,
+        // which generate indices above range.
+        table = new double[NUM_VALUES + 2];
+        // Fill one octave of the table.
+        for (int i = 0; i < table.length; i++) {
+            double value = Math.pow(2.0, ((double) i) / NUM_VALUES);
+            table[i] = value;
+        }
+    }
+
+    public PowerOfTwo() {
+        addPort(input = new UnitInputPort("Input"));
+        input.setup(-8.0, 0.0, 8.0);
+        addPort(output = new UnitOutputPort("Output"));
+    }
+
+    @Override
+    public void generate(int start, int limit) {
+        double[] inputs = input.getValues();
+        double[] outputs = output.getValues();
+
+        if (true) {
+            for (int i = start; i < limit; i++) {
+                double in = inputs[i];
+                // Can we reuse a previously computed value?
+                if (in == lastInput) {
+                    outputs[i] = lastOutput;
+                } else {
+                    int octave = (int) Math.floor(in);
+                    double normal = in - octave;
+                    // Do table lookup.
+                    double findex = normal * NUM_VALUES;
+                    int index = (int) findex;
+                    double fraction = findex - index;
+                    double value = table[index] + (fraction * (table[index + 1] - table[index]));
+
+                    // Adjust for octave.
+                    while (octave > 0) {
+                        octave -= 1;
+                        value *= 2.0;
+                    }
+                    while (octave < 0) {
+                        octave += 1;
+                        value *= 0.5;
+                    }
+                    outputs[i] = value;
+                    lastInput = in;
+                    lastOutput = value;
+                }
+            }
+        } else {
+            for (int i = start; i < limit; i++) {
+                outputs[i] = Math.pow(2.0, inputs[i]);
+            }
+        }
+    }
+}
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