124 lines
3.3 KiB
Java
124 lines
3.3 KiB
Java
/* CheckedInputStream.java - Compute checksum of data being read
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Copyright (C) 1999, 2000 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., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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As a special exception, if you link this library with other files to
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produce an executable, this library does not by itself cause the
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resulting executable to be covered by the GNU General Public License.
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This exception does not however invalidate any other reasons why the
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executable file might be covered by the GNU General Public License. */
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package java.util.zip;
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import java.io.FilterInputStream;
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import java.io.InputStream;
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import java.io.IOException;
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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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