CircularStringBuffer.java

/*
Copyright 2011-2016 Google Inc. All Rights Reserved.

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.google.security.zynamics.zylib.strings;

import java.util.LinkedList;
import java.util.Queue;
import java.util.stream.Collectors;

/**
 * Manages a string which behaves like a circular buffer with a fixed number of lines.
 */
public class CircularStringBuffer {
  /**
   * FIFO string container.
   */
  private final Queue<String> m_buffer = new LinkedList<>();

  /**
   * Maximum number of lines to be held in the buffer.
   */
  private final int m_maxSize;

  /**
   * Creates a new instance of the circular string buffer.
   * 
   * @param maxLines The maximum number of lines which are held by the string buffer.
   */
  public CircularStringBuffer(final int maxLines) {
    m_maxSize = maxLines;
  }

  private void addToBuffer(final String[] lines) {
    final int index = 0;

    for (int i = 0; i < lines.length; ++i) {
      while ((m_maxSize - m_buffer.size()) <= 0) {
        m_buffer.remove();
      }
      m_buffer.add(lines[index]);
    }
  }

  /**
   * Adds the given text to the circular buffer.
   * 
   * @param text The text to be added to the buffer.
   */
  public void add(final String text) {
    final String[] lines = text.split("\n");
    if (lines.length > 0) {
      addToBuffer(lines);
    } else {
      addToBuffer(new String[] {text});
    }
  }

  /**
   * Return the number of lines in the buffer.
   * 
   * @return The number of lines in the buffer.
   */
  public int getSize() {
    return m_buffer.size();
  }

  /**
   * Returns the circular buffer in one string object.
   * 
   * @return The whole buffer represented as one string.
   */
  public String getText() {
    return m_buffer.stream().collect(Collectors.joining("\n", "", "\n"));
  }
}