org.jmrtd.io.SplittableInputStream Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of jmrtd Show documentation
Java Machine Readable Travel Documents API.
The newest version!
/*
 * JMRTD - A Java API for accessing machine readable travel documents.
 *
 * Copyright (C) 2006 - 2018  The JMRTD team
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * $Id: SplittableInputStream.java 1808 2019-03-07 21:32:19Z martijno $
 */

package org.jmrtd.io;

import java.io.IOException;
import java.io.InputStream;

/**
 * An input stream which will wrap another input stream (and yield the same bytes) and which can
 * spawn new fresh input stream copies (using {@link #getInputStream(int)})
 * (that also yield the same bytes).
 *
 * @author The JMRTD team ([email protected])
 *
 * @version $Revision: 1808 $
 */
public class SplittableInputStream extends InputStream {

  private InputStreamBuffer inputStreamBuffer;
  private InputStreamBuffer.SubInputStream carrier;

  /**
   * Wraps an input stream so that copy streams can be split off.
   *
   * @param inputStream the original input stream
   * @param length the precise length of bytes that the original input stream provides
   */
  public SplittableInputStream(InputStream inputStream, int length) {
    this.inputStreamBuffer = new InputStreamBuffer(inputStream, length);
    this.carrier = inputStreamBuffer.getInputStream();
  }

  /**
   * Updates this stream's buffer based on some other stream's buffer.
   *
   * @param other the other stream
   */
  public void updateFrom(SplittableInputStream other) {
    inputStreamBuffer.updateFrom(other.inputStreamBuffer);
  }

  /**
   * Returns a copy of the inputstream positioned at position.
   *
   * @param position a position between 0 and {@link #getPosition()}
   *
   * @return a fresh input stream
   */
  public InputStream getInputStream(int position) {
    try {
      InputStream inputStream = inputStreamBuffer.getInputStream();
      long skippedBytes = 0L;
      while (skippedBytes < position) {
        skippedBytes += inputStream.skip(position - skippedBytes);
      }
      return inputStream;
    } catch (IOException ioe) {
      throw new IllegalStateException(ioe);
    }
  }

  /**
   * Returns the position within the input stream (the number of bytes read since this input stream was constructed).
   *
   * @return the position within this input stream
   */
  public int getPosition() {
    return carrier.getPosition();
  }

  /**
   * Reads the next byte of data from the input stream. The value byte is
   * returned as an int in the range 0 to
   * 255. If no byte is available because the end of the stream
   * has been reached, the value -1 is returned. This method
   * blocks until input data is available, the end of the stream is detected,
   * or an exception is thrown.
   *
   * @return     the next byte of data, or -1 if the end of the
   *             stream is reached
   *
   * @throws IOException if an I/O error occurs
   */
  @Override
  public int read() throws IOException {
    return carrier.read();
  }

  /**
   * Skips over and discards n bytes of data from this input
   * stream. The skip method may, for a variety of reasons, end
   * up skipping over some smaller number of bytes, possibly 0.
   * This may result from any of a number of conditions; reaching end of file
   * before n bytes have been skipped is only one possibility.
   * The actual number of bytes skipped is returned.  If n is
   * negative, no bytes are skipped.
   *
   * @param n the number of bytes to be skipped
   *
   * @return the actual number of bytes skipped
   *
   * @throws IOException if the stream does not support seek, or if some other I/O error occurs
   */
  @Override
  public long skip(long n) throws IOException {
    return carrier.skip(n);
  }

  /**
   * Returns an estimate of the number of bytes that can be read (or
   * skipped over) from this input stream without blocking by the next
   * invocation of a method for this input stream. The next invocation
   * might be the same thread or another thread.  A single read or skip of this
   * many bytes will not block, but may read or skip fewer bytes.
   *
   * @return an estimate of the number of bytes that can be read (or skipped
   *         over) from this input stream without blocking or 0 when
   *         it reaches the end of the input stream
   *
   * @throws IOException on error
   */
  @Override
  public int available() throws IOException {
    return carrier.available();
  }

  /**
   * Closes this input stream and releases any system resources associated
   * with the stream.
   *
   * @throws IOException on error
   */
  @Override
  public void close() throws IOException {
    carrier.close();
  }

  /**
   * Marks the current position in this input stream. A subsequent call to
   * the reset method repositions this stream at the last marked
   * position so that subsequent reads re-read the same bytes.
   *
   * The readlimit arguments tells this input stream to
   * allow that many bytes to be read before the mark position gets
   * invalidated.
   *
   * The general contract of mark is that, if the method
   * markSupported returns true, the stream somehow
   * remembers all the bytes read after the call to mark and
   * stands ready to supply those same bytes again if and whenever the method
   * reset is called.  However, the stream is not required to
   * remember any data at all if more than readlimit bytes are
   * read from the stream before reset is called.
   *
   * @param readlimit the maximum limit of bytes that can be read before the mark position becomes invalid
   *
   * @see java.io.InputStream#reset()
   */
  @Override
  public synchronized void mark(int readlimit) {
    carrier.mark(readlimit);
  }

  /**
   * Repositions this stream to the position at the time the
   * mark method was last called on this input stream.
   *
   * The general contract of reset is:
   *
   * 
   *
   *  If the method markSupported returns
   * true, then:
   *
   *      If the method mark has not been called since
   *     the stream was created, or the number of bytes read from the stream
   *     since mark was last called is larger than the argument
   *     to mark at that last call, then an
   *     IOException might be thrown.
   *
   *     
 If such an IOException is not thrown, then the
   *     stream is reset to a state such that all the bytes read since the
   *     most recent call to mark (or since the start of the
   *     file, if mark has not been called) will be resupplied
   *     to subsequent callers of the read method, followed by
   *     any bytes that otherwise would have been the next input data as of
   *     the time of the call to reset. 
   *
   * 
 If the method markSupported returns
   * false, then:
   *
   *      The call to reset may throw an
   *     IOException.
   *
   *     
 If an IOException is not thrown, then the stream
   *     is reset to a fixed state that depends on the particular type of the
   *     input stream and how it was created. The bytes that will be supplied
   *     to subsequent callers of the read method depend on the
   *     particular type of the input stream. 
   *
   * @throws IOException if this stream has not been marked or if the mark has been invalidated
   *
   * @see java.io.InputStream#mark(int)
   * @see java.io.IOException
   *
   * @throws IOException on error
   */
  @Override
  public synchronized void reset() throws IOException {
    carrier.reset();
  }

  /**
   * Tests if this input stream supports the mark and
   * reset methods. Whether or not mark and
   * reset are supported is an invariant property of a
   * particular input stream instance. The markSupported method
   * of InputStream returns false.
   *
   * @return true if this stream instance supports the mark
   *          and reset methods and false otherwise
   *
   * @see java.io.InputStream#mark(int)
   * @see java.io.InputStream#reset()
   */
  @Override
  public boolean markSupported() {
    return carrier.markSupported();
  }

  /**
   * Returns the length of the underlying buffer.
   *
   * @return the length of the underlying buffer
   */
  public int getLength() {
    return inputStreamBuffer.getLength();
  }

  /**
   * Returns the number of buffered bytes in the underlying buffer.
   *
   * @return the number of buffered bytes in the underlying buffer
   */
  public int getBytesBuffered() {
    return inputStreamBuffer.getBytesBuffered();
  }
}