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A library to read and give access to Tiff files.
There is a newer version: 1.9.7
/**
 * PagedInputBuffer.java
  This program is free software: you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later version; or, at your
 * choice, under the terms of the Mozilla Public License, v. 2.0. SPDX GPL-3.0+ or MPL-2.0+. 
 *  This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License and the Mozilla Public License for more details. 
  You should
 * have received a copy of the GNU General Public License and the Mozilla Public License along with
 * this program. If not, see http://www.gnu.org/licenses/
 * and at http://mozilla.org/MPL/2.0 . 
  NB: for the
 * © statement, include Easy Innova SL or other company/Person contributing the code. 
  ©
 * 2015 Easy Innova, SL 
 *
 * @author Víctor Muñoz Solà
 * @version 1.0
 * @since 14/7/2015
 */
package com.easyinnova.tiff.io;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

/**
 * Paged Buffered Tiff File Stream.
 Incorporates a set of pages (set of buffers) for minimizing
 * the file reads all over the file.
 */
public class PagedInputBuffer {

  /**
   * The buffer pages.
   */
  private List pages;

  /**
   * The Max number of pages.
   */
  private int MaxPages = 5;

  /**
   * The current buffer.
   */
  private InputBuffer currentBuffer;

  /**
   * The input stream.
   */
  private TiffInputStream input;

  /**
   * Instantiates a new paged input buffer.
   *
   * @param input the input
   */
  public PagedInputBuffer(TiffInputStream input) {
    pages = new ArrayList();
    currentBuffer = null;
    this.input = input;
  }

  /**
   * Select buffer.
   *
   * @param offset the offset
   */
  private void selectPage(long offset) {
    currentBuffer = null;
    int i = 0;

    // Look if the given offset is already stored in a page
    while (i < pages.size() && currentBuffer == null) {
      if (pages.get(i).seekSuccessful(offset))
        currentBuffer = pages.get(i);
      i++;
    }

    if (currentBuffer == null) {
      // If the offset is not contained in any of the loaded pages, create a new one

      // FIFO
      if (pages.size() >= MaxPages)
        pages.remove(0);
      pages.add(new InputBuffer(input));

      currentBuffer = pages.get(pages.size() - 1);
    }
  }

  /**
   * Seek an offset.
   *
   * @param offset the offset
   * @throws IOException Signals that an I/O exception has occurred.
   */
  public void seek(long offset) throws IOException {
    selectPage(offset);
    currentBuffer.seek(offset);
  }

  /**
   * Reads a byte.
   *
   * @param offset the offset
   * @return the byte
   * @throws IOException Signals that an I/O exception has occurred.
   */
  public int read(long offset) throws IOException {
    selectPage(offset);
    return currentBuffer.read(offset);
  }
}