Implemented CircularBuffer resizing (#224)

wpilibc/shared/include/CircularBuffer.h

@@ -23,6 +23,7 @@ class CircularBuffer {
   void PushBack(T value);
   T PopFront();
   T PopBack();
+  void Resize(size_t size);
   void Reset();
 
   T& operator[](size_t index);

wpilibc/shared/include/CircularBuffer.inc

@@ -81,6 +81,59 @@ T CircularBuffer<T>::PopBack() {
   return m_data[(m_front + m_length) % m_data.size()];
 }
 
+/**
+ * Resizes internal buffer to given size.
+ */
+template <class T>
+void CircularBuffer<T>::Resize(size_t size) {
+  if (size > m_data.size()) {
+    // Find end of buffer
+    size_t insertLocation = (m_front + m_length) % m_data.size();
+
+    // If insertion location precedes front of buffer, push front index back
+    if (insertLocation <= m_front) {
+      m_front += size - m_data.size();
+    }
+
+    // Add elements to end of buffer
+    m_data.insert(m_data.begin() + insertLocation, size - m_data.size(), 0);
+  } else if (size < m_data.size()) {
+    /* 1) Shift element block start at "front" left as many blocks as were
+     *    removed up to but not exceeding buffer[0]
+     * 2) Shrink buffer, which will remove even more elements automatically if
+     *    necessary
+     */
+    size_t elemsToRemove = m_data.size() - size;
+    auto frontIter = m_data.begin() + m_front;
+    if (m_front < elemsToRemove) {
+      /* Remove elements from end of buffer before shifting start of element
+       * block. Doing so saves a few copies.
+       */
+      m_data.erase(frontIter + size, m_data.end());
+
+      // Shift start of element block to left
+      m_data.erase(m_data.begin(), frontIter);
+
+      // Update metadata
+      m_front = 0;
+    } else {
+      // Shift start of element block to left
+      m_data.erase(frontIter - elemsToRemove, frontIter);
+
+      // Update metadata
+      m_front -= elemsToRemove;
+    }
+
+    /* Length only changes during a shrink if all unused spaces have been
+     * removed. Length decreases as used spaces are removed to meet the
+     * required size.
+     */
+    if (m_length > size) {
+      m_length = size;
+    }
+  }
+}
+
 /**
  * Sets internal buffer contents to zero.
  */

wpilibcIntegrationTests/src/CircularBufferTest.cpp

@@ -87,3 +87,123 @@ TEST(CircularBufferTest, PushPopTest) {
   // Leaving only one element with value == 4
   EXPECT_EQ(4.0, queue[0]);
 }
+
+TEST(CircularBufferTest, ResetTest) {
+  CircularBuffer<double> queue(5);
+
+  for (size_t i = 1; i < 6; i++) {
+    queue.PushBack(i);
+  }
+
+  queue.Reset();
+
+  for (size_t i = 0; i < 5; i++) {
+    EXPECT_EQ(0.0, queue[i]);
+  }
+}
+
+TEST(CircularBufferTest, ResizeTest) {
+  CircularBuffer<double> queue(5);
+
+  /* Buffer contains {1, 2, 3, _, _}
+   *                  ^ front
+   */
+  queue.PushBack(1.0);
+  queue.PushBack(2.0);
+  queue.PushBack(3.0);
+
+  queue.Resize(2);
+  EXPECT_EQ(1.0, queue[0]);
+  EXPECT_EQ(2.0, queue[1]);
+
+  queue.Resize(5);
+  EXPECT_EQ(1.0, queue[0]);
+  EXPECT_EQ(2.0, queue[1]);
+
+  queue.Reset();
+
+  /* Buffer contains {_, 1, 2, 3, _}
+   *                     ^ front
+   */
+  queue.PushBack(0.0);
+  queue.PushBack(1.0);
+  queue.PushBack(2.0);
+  queue.PushBack(3.0);
+  queue.PopFront();
+
+  queue.Resize(2);
+  EXPECT_EQ(1.0, queue[0]);
+  EXPECT_EQ(2.0, queue[1]);
+
+  queue.Resize(5);
+  EXPECT_EQ(1.0, queue[0]);
+  EXPECT_EQ(2.0, queue[1]);
+
+  queue.Reset();
+
+  /* Buffer contains {_, _, 1, 2, 3}
+   *                        ^ front
+   */
+  queue.PushBack(0.0);
+  queue.PushBack(0.0);
+  queue.PushBack(1.0);
+  queue.PushBack(2.0);
+  queue.PushBack(3.0);
+  queue.PopFront();
+  queue.PopFront();
+
+  queue.Resize(2);
+  EXPECT_EQ(1.0, queue[0]);
+  EXPECT_EQ(2.0, queue[1]);
+
+  queue.Resize(5);
+  EXPECT_EQ(1.0, queue[0]);
+  EXPECT_EQ(2.0, queue[1]);
+
+  queue.Reset();
+
+  /* Buffer contains {3, _, _, 1, 2}
+   *                           ^ front
+   */
+  queue.PushBack(3.0);
+  queue.PushFront(2.0);
+  queue.PushFront(1.0);
+
+  queue.Resize(2);
+  EXPECT_EQ(1.0, queue[0]);
+  EXPECT_EQ(2.0, queue[1]);
+
+  queue.Resize(5);
+  EXPECT_EQ(1.0, queue[0]);
+  EXPECT_EQ(2.0, queue[1]);
+
+  queue.Reset();
+
+  /* Buffer contains {2, 3, _, _, 1}
+   *                              ^ front
+   */
+  queue.PushBack(2.0);
+  queue.PushBack(3.0);
+  queue.PushFront(1.0);
+
+  queue.Resize(2);
+  EXPECT_EQ(1.0, queue[0]);
+  EXPECT_EQ(2.0, queue[1]);
+
+  queue.Resize(5);
+  EXPECT_EQ(1.0, queue[0]);
+  EXPECT_EQ(2.0, queue[1]);
+
+  // Test PushBack() after resize
+  queue.PushBack(3.0);
+  EXPECT_EQ(1.0, queue[0]);
+  EXPECT_EQ(2.0, queue[1]);
+  EXPECT_EQ(3.0, queue[2]);
+
+  // Test PushFront() after resize
+  queue.PushFront(4.0);
+  EXPECT_EQ(4.0, queue[0]);
+  EXPECT_EQ(1.0, queue[1]);
+  EXPECT_EQ(2.0, queue[2]);
+  EXPECT_EQ(3.0, queue[3]);
+}

wpilibj/src/shared/java/edu/wpi/first/wpilibj/CircularBuffer.java

@@ -97,12 +97,27 @@ public class CircularBuffer {
     return m_data[(m_front + m_length) % m_data.length];
   }
 
+  /**
+   * Resizes internal buffer to given size.
+   *
+   * <p>A new buffer is allocated because arrays are not resizable.
+   */
+  void resize(int size) {
+    double[] newBuffer = new double[size];
+    m_length = Math.min(m_length, size);
+    for (int i = 0; i < m_length; i++) {
+      newBuffer[i] = m_data[(m_front + i) % m_data.length];
+    }
+    m_data = newBuffer;
+    m_front = 0;
+  }
+
   /**
    * Sets internal buffer contents to zero.
    */
   public void reset() {
-    for (double i : m_data) {
-      i = 0.0;
+    for (int i = 0; i < m_data.length; i++) {
+      m_data[i] = 0.0;
     }
     m_front = 0;
     m_length = 0;

wpilibj/src/test/java/edu/wpi/first/wpilibj/CircularBufferTest.java

@@ -1,5 +1,5 @@
 /*----------------------------------------------------------------------------*/
-/* Copyright (c) FIRST 2008-2016. All Rights Reserved.                        */
+/* Copyright (c) FIRST 2015-2016. All Rights Reserved.                        */
 /* Open Source Software - may be modified and shared by FRC teams. The code   */
 /* must be accompanied by the FIRST BSD license file in the root directory of */
 /* the project.                                                               */
@@ -94,4 +94,126 @@ public class CircularBufferTest {
     // Leaving only one element with value == 4
     assertEquals(4.0, queue.get(0), 0.00005);
   }
+
+  @Test
+  public void resetTest() {
+    CircularBuffer queue = new CircularBuffer(5);
+
+    for (int i = 0; i < 6; i++) {
+      queue.pushBack(i);
+    }
+
+    queue.reset();
+
+    for (int i = 0; i < 5; i++) {
+      assertEquals(0.0, queue.get(i), 0.00005);
+    }
+  }
+
+  @Test
+  public void resizeTest() {
+    CircularBuffer queue = new CircularBuffer(5);
+
+    /* Buffer contains {1, 2, 3, _, _}
+     *                  ^ front
+     */
+    queue.pushBack(1.0);
+    queue.pushBack(2.0);
+    queue.pushBack(3.0);
+
+    queue.resize(2);
+    assertEquals(1.0, queue.get(0), 0.00005);
+    assertEquals(2.0, queue.get(1), 0.00005);
+
+    queue.resize(5);
+    assertEquals(1.0, queue.get(0), 0.00005);
+    assertEquals(2.0, queue.get(1), 0.00005);
+
+    queue.reset();
+
+    /* Buffer contains {_, 1, 2, 3, _}
+     *                     ^ front
+     */
+    queue.pushBack(0.0);
+    queue.pushBack(1.0);
+    queue.pushBack(2.0);
+    queue.pushBack(3.0);
+    queue.popFront();
+
+    queue.resize(2);
+    assertEquals(1.0, queue.get(0), 0.00005);
+    assertEquals(2.0, queue.get(1), 0.00005);
+
+    queue.resize(5);
+    assertEquals(1.0, queue.get(0), 0.00005);
+    assertEquals(2.0, queue.get(1), 0.00005);
+
+    queue.reset();
+
+    /* Buffer contains {_, _, 1, 2, 3}
+     *                        ^ front
+     */
+    queue.pushBack(0.0);
+    queue.pushBack(0.0);
+    queue.pushBack(1.0);
+    queue.pushBack(2.0);
+    queue.pushBack(3.0);
+    queue.popFront();
+    queue.popFront();
+
+    queue.resize(2);
+    assertEquals(1.0, queue.get(0), 0.00005);
+    assertEquals(2.0, queue.get(1), 0.00005);
+
+    queue.resize(5);
+    assertEquals(1.0, queue.get(0), 0.00005);
+    assertEquals(2.0, queue.get(1), 0.00005);
+
+    queue.reset();
+
+    /* Buffer contains {3, _, _, 1, 2}
+     *                           ^ front
+     */
+    queue.pushBack(3.0);
+    queue.pushFront(2.0);
+    queue.pushFront(1.0);
+
+    queue.resize(2);
+    assertEquals(1.0, queue.get(0), 0.00005);
+    assertEquals(2.0, queue.get(1), 0.00005);
+
+    queue.resize(5);
+    assertEquals(1.0, queue.get(0), 0.00005);
+    assertEquals(2.0, queue.get(1), 0.00005);
+
+    queue.reset();
+
+    /* Buffer contains {2, 3, _, _, 1}
+     *                              ^ front
+     */
+    queue.pushBack(2.0);
+    queue.pushBack(3.0);
+    queue.pushFront(1.0);
+
+    queue.resize(2);
+    assertEquals(1.0, queue.get(0), 0.00005);
+    assertEquals(2.0, queue.get(1), 0.00005);
+
+    queue.resize(5);
+    assertEquals(1.0, queue.get(0), 0.00005);
+    assertEquals(2.0, queue.get(1), 0.00005);
+
+    // Test pushBack() after resize
+    queue.pushBack(3.0);
+    assertEquals(1.0, queue.get(0), 0.00005);
+    assertEquals(2.0, queue.get(1), 0.00005);
+    assertEquals(3.0, queue.get(2), 0.00005);
+
+    // Test pushFront() after resize
+    queue.pushFront(4.0);
+    assertEquals(4.0, queue.get(0), 0.00005);
+    assertEquals(1.0, queue.get(1), 0.00005);
+    assertEquals(2.0, queue.get(2), 0.00005);
+    assertEquals(3.0, queue.get(3), 0.00005);
+  }
 }