136 lines
3.8 KiB
Java
136 lines
3.8 KiB
Java
/* CheckedInputStream.java - Compute checksum of data being read
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Copyright (C) 1999, 2000, 2004 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.util.zip;
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import java.io.FilterInputStream;
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import java.io.IOException;
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import java.io.InputStream;
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/* Written using on-line Java Platform 1.2 API Specification
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* and JCL book.
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* Believed complete and correct.
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*/
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/**
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* InputStream that computes a checksum of the data being read using a
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* supplied Checksum object.
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*
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* @see Checksum
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*
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* @author Tom Tromey
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* @date May 17, 1999
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*/
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public class CheckedInputStream extends FilterInputStream
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{
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/**
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* Creates a new CheckInputStream on top of the supplied OutputStream
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* using the supplied Checksum.
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*/
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public CheckedInputStream (InputStream in, Checksum sum)
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{
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super (in);
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this.sum = sum;
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}
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/**
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* Returns the Checksum object used. To get the data checksum computed so
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* far call <code>getChecksum.getValue()</code>.
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*/
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public Checksum getChecksum ()
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{
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return sum;
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}
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/**
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* Reads one byte, updates the checksum and returns the read byte
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* (or -1 when the end of file was reached).
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*/
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public int read () throws IOException
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{
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int x = in.read();
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if (x != -1)
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sum.update(x);
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return x;
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}
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/**
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* Reads at most len bytes in the supplied buffer and updates the checksum
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* with it. Returns the number of bytes actually read or -1 when the end
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* of file was reached.
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*/
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public int read (byte[] buf, int off, int len) throws IOException
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{
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int r = in.read(buf, off, len);
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if (r != -1)
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sum.update(buf, off, r);
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return r;
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}
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/**
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* Skips n bytes by reading them in a temporary buffer and updating the
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* the checksum with that buffer. Returns the actual number of bytes skiped
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* which can be less then requested when the end of file is reached.
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*/
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public long skip (long n) throws IOException
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{
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if (n == 0)
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return 0;
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int min = (int) Math.min(n, 1024);
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byte[] buf = new byte[min];
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long s = 0;
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while (n > 0)
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{
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int r = in.read(buf, 0, min);
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if (r == -1)
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break;
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n -= r;
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s += r;
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min = (int) Math.min(n, 1024);
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sum.update(buf, 0, r);
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}
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return s;
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}
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/** The checksum object. */
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private Checksum sum;
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}
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