/**
 * 
 */
package at.gv.egiz.pdfas.impl.input;

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

/**
 * An input stream that has a delimited length.
 * 
 * @author wprinz
 */
public class DelimitedInputStream extends InputStream
{
  /**
   * The underlying InputStream.
   */
  protected InputStream is = null;

  /**
   * The number of bytes that can be read from the stream.
   */
  protected int bytes_to_read = -1;

  /**
   * Constructs the DelimitedInputStream from which a maximum of length bytes
   * can be read.
   */
  public DelimitedInputStream(InputStream is, int length)
  {
    this.is = is;
    this.bytes_to_read = length;
  }

  /**
   * @see java.io.InputStream#read()
   */
  public int read() throws IOException
  {
    if (this.bytes_to_read <= 0)
    {
      return -1;
    }
    int read = this.is.read();
    if (read > 0)
    {
      this.bytes_to_read--;
    }
    return read;
  }

  /**
   * @see java.io.InputStream#read(byte[], int, int)
   */
  public int read(byte[] b, int off, int len) throws IOException
  {
    int btr = Math.min(len, this.bytes_to_read);
    int read = this.is.read(b, off, btr);
    if (read > 0)
    {
      this.bytes_to_read -= read;
    }
    return read;
  }

  /**
   * @see java.io.InputStream#read(byte[])
   */
  public int read(byte[] b) throws IOException
  {
    return read(b, 0, b.length);
  }

  /**
   * @see java.io.InputStream#skip(long)
   */
  public long skip(long n) throws IOException
  {
    long bts = Math.min(n, this.bytes_to_read);
    long skipped = this.is.skip(bts);
    if (skipped > 0)
    {
      this.bytes_to_read -= skipped;
    }
    return skipped;
  }

  /**
   * @see java.io.InputStream#close()
   */
  public void close() throws IOException
  {
    this.is.close();
  }

  /**
   * @see java.io.InputStream#available()
   */
  public int available() throws IOException
  {
    int avail = this.is.available();
    return Math.min(this.bytes_to_read, avail);
  }
}