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[wpimath] Add generic circular buffer class to Java
The original is now called DoubleCircularBuffer.
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191
wpiutil/src/main/java/edu/wpi/first/util/DoubleCircularBuffer.java
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| Original file line number | Diff line number | Diff line change |
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| // Copyright (c) FIRST and other WPILib contributors. | ||
| // Open Source Software; you can modify and/or share it under the terms of | ||
| // the WPILib BSD license file in the root directory of this project. | ||
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| package edu.wpi.first.util; | ||
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| import java.util.Arrays; | ||
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| /** This is a simple circular buffer so we don't need to "bucket brigade" copy old values. */ | ||
| public class DoubleCircularBuffer { | ||
| private double[] m_data; | ||
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| // Index of element at front of buffer | ||
| private int m_front; | ||
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| // Number of elements used in buffer | ||
| private int m_length; | ||
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| /** | ||
| * Create a CircularBuffer with the provided size. | ||
| * | ||
| * @param size The size of the circular buffer. | ||
| */ | ||
| public DoubleCircularBuffer(int size) { | ||
| m_data = new double[size]; | ||
| Arrays.fill(m_data, 0.0); | ||
| } | ||
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| /** | ||
| * Returns number of elements in buffer. | ||
| * | ||
| * @return number of elements in buffer | ||
| */ | ||
| public int size() { | ||
| return m_length; | ||
| } | ||
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| /** | ||
| * Get value at front of buffer. | ||
| * | ||
| * @return value at front of buffer | ||
| */ | ||
| public double getFirst() { | ||
| return m_data[m_front]; | ||
| } | ||
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| /** | ||
| * Get value at back of buffer. | ||
| * | ||
| * @return value at back of buffer | ||
| */ | ||
| public double getLast() { | ||
| // If there are no elements in the buffer, do nothing | ||
| if (m_length == 0) { | ||
| return 0.0; | ||
| } | ||
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| return m_data[(m_front + m_length - 1) % m_data.length]; | ||
| } | ||
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| /** | ||
| * Push new value onto front of the buffer. The value at the back is overwritten if the buffer is | ||
| * full. | ||
| * | ||
| * @param value The value to push. | ||
| */ | ||
| public void addFirst(double value) { | ||
| if (m_data.length == 0) { | ||
| return; | ||
| } | ||
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| m_front = moduloDec(m_front); | ||
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| m_data[m_front] = value; | ||
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| if (m_length < m_data.length) { | ||
| m_length++; | ||
| } | ||
| } | ||
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| /** | ||
| * Push new value onto back of the buffer. The value at the front is overwritten if the buffer is | ||
| * full. | ||
| * | ||
| * @param value The value to push. | ||
| */ | ||
| public void addLast(double value) { | ||
| if (m_data.length == 0) { | ||
| return; | ||
| } | ||
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| m_data[(m_front + m_length) % m_data.length] = value; | ||
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| if (m_length < m_data.length) { | ||
| m_length++; | ||
| } else { | ||
| // Increment front if buffer is full to maintain size | ||
| m_front = moduloInc(m_front); | ||
| } | ||
| } | ||
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| /** | ||
| * Pop value at front of buffer. | ||
| * | ||
| * @return value at front of buffer | ||
| */ | ||
| public double removeFirst() { | ||
| // If there are no elements in the buffer, do nothing | ||
| if (m_length == 0) { | ||
| return 0.0; | ||
| } | ||
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| double temp = m_data[m_front]; | ||
| m_front = moduloInc(m_front); | ||
| m_length--; | ||
| return temp; | ||
| } | ||
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| /** | ||
| * Pop value at back of buffer. | ||
| * | ||
| * @return value at back of buffer | ||
| */ | ||
| public double removeLast() { | ||
| // If there are no elements in the buffer, do nothing | ||
| if (m_length == 0) { | ||
| return 0.0; | ||
| } | ||
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| m_length--; | ||
| return m_data[(m_front + m_length) % m_data.length]; | ||
| } | ||
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| /** | ||
| * Resizes internal buffer to given size. | ||
| * | ||
| * <p>A new buffer is allocated because arrays are not resizable. | ||
| * | ||
| * @param size New buffer size. | ||
| */ | ||
| public 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; | ||
| } | ||
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| /** Sets internal buffer contents to zero. */ | ||
| public void clear() { | ||
| Arrays.fill(m_data, 0.0); | ||
| m_front = 0; | ||
| m_length = 0; | ||
| } | ||
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| /** | ||
| * Get the element at the provided index relative to the start of the buffer. | ||
| * | ||
| * @param index Index into the buffer. | ||
| * @return Element at index starting from front of buffer. | ||
| */ | ||
| public double get(int index) { | ||
| return m_data[(m_front + index) % m_data.length]; | ||
| } | ||
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| /** | ||
| * Increment an index modulo the length of the buffer. | ||
| * | ||
| * @param index Index into the buffer. | ||
| * @return The incremented index. | ||
| */ | ||
| private int moduloInc(int index) { | ||
| return (index + 1) % m_data.length; | ||
| } | ||
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| /** | ||
| * Decrement an index modulo the length of the buffer. | ||
| * | ||
| * @param index Index into the buffer. | ||
| * @return The decremented index. | ||
| */ | ||
| private int moduloDec(int index) { | ||
| if (index == 0) { | ||
| return m_data.length - 1; | ||
| } else { | ||
| return index - 1; | ||
| } | ||
| } | ||
| } |
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