content: /*
   * Copyright (c) 1996, 2006, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code 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
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package java.util.zip;
  
  import java.io.FilterInputStream;
  import java.io.InputStream;
  import java.io.IOException;
  
  /**
   * An input stream that also maintains a checksum of the data being read.
   * The checksum can then be used to verify the integrity of the input data.
   *
   * @see         Checksum
   * @author      David Connelly
   */
  public
  class CheckedInputStream extends FilterInputStream {
      private Checksum cksum;
  
      /**
       * Creates an input stream using the specified Checksum.
       * @param in the input stream
       * @param cksum the Checksum
       */
      public CheckedInputStream(InputStream in, Checksum cksum) {
          super(in);
          this.cksum = cksum;
      }
  
      /**
       * Reads a byte. Will block if no input is available.
       * @return the byte read, or -1 if the end of the stream is reached.
       * @exception IOException if an I/O error has occurred
       */
      public int read() throws IOException {
          int b = in.read();
          if (b != -1) {
              cksum.update(b);
          }
          return b;
      }
  
      /**
       * Reads into an array of bytes. If <code>len</code> is not zero, the method
       * blocks until some input is available; otherwise, no
       * bytes are read and <code>0</code> is returned.
       * @param buf the buffer into which the data is read
       * @param off the start offset in the destination array <code>b</code>
       * @param len the maximum number of bytes read
       * @return    the actual number of bytes read, or -1 if the end
       *            of the stream is reached.
       * @exception  NullPointerException If <code>buf</code> is <code>null</code>.
       * @exception  IndexOutOfBoundsException If <code>off</code> is negative,
       * <code>len</code> is negative, or <code>len</code> is greater than
       * <code>buf.length - off</code>
       * @exception IOException if an I/O error has occurred
       */
      public int read(byte[] buf, int off, int len) throws IOException {
          len = in.read(buf, off, len);
          if (len != -1) {
              cksum.update(buf, off, len);
          }
          return len;
      }
  
      /**
       * Skips specified number of bytes of input.
       * @param n the number of bytes to skip
       * @return the actual number of bytes skipped
       * @exception IOException if an I/O error has occurred
       */
      public long skip(long n) throws IOException {
          byte[] buf = new byte[512];
          long total = 0;
          while (total < n) {
              long len = n - total;
              len = read(buf, 0, len < buf.length ? (int)len : buf.length);
              if (len == -1) {
                  return total;
              }
              total += len;
          }
          return total;
      }
  
      /**
       * Returns the Checksum for this input stream.
       * @return the Checksum value
       */
      public Checksum getChecksum() {
          return cksum;
      }
  }
  