222 lines
7.1 KiB
Java
222 lines
7.1 KiB
Java
/* SequenceInputStream.java -- Reads multiple input streams in sequence
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Copyright (C) 1998, 1999, 2001 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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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.io;
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import java.util.Enumeration;
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/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
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* "The Java Language Specification", ISBN 0-201-63451-1
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* plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
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* Status: Believed complete and correct.
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*/
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/**
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* This class merges a sequence of multiple <code>InputStream</code>'s in
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* order to form a single logical stream that can be read by applications
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* that expect only one stream.
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* <p>
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* The streams passed to the constructor method are read in order until
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* they return -1 to indicate they are at end of stream. When a stream
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* reports end of stream, it is closed, then the next stream is read.
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* When the last stream is closed, the next attempt to read from this
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* stream will return a -1 to indicate it is at end of stream.
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* <p>
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* If this stream is closed prior to all subordinate streams being read
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* to completion, all subordinate streams are closed.
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*
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* @author Aaron M. Renn (arenn@urbanophile.com)
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* @author Warren Levy <warrenl@cygnus.com>
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*/
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public class SequenceInputStream extends InputStream
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{
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/** The handle for the current input stream. */
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private InputStream in;
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/** Secondary input stream; not used if constructed w/ enumeration. */
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private InputStream in2;
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/** The enum handle; not used if constructed w/ 2 explicit input streams. */
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private Enumeration enum;
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/**
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* This method creates a new <code>SequenceInputStream</code> that obtains
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* its list of subordinate <code>InputStream</code>s from the specified
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* <code>Enumeration</code>
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*
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* @param e An <code>Enumeration</code> that will return a list of
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* <code>InputStream</code>s to read in sequence
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*/
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public SequenceInputStream(Enumeration e)
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{
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enum = e;
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in = (InputStream) enum.nextElement();
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in2 = null;
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}
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/**
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* This method creates a new <code>SequenceInputStream</code> that will read
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* the two specified subordinate <code>InputStream</code>s in sequence.
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*
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* @param s1 The first <code>InputStream</code> to read
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* @param s2 The second <code>InputStream</code> to read
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*/
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public SequenceInputStream(InputStream s1, InputStream s2)
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{
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in = s1;
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in2 = s2;
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}
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/**
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* This method returns the number of bytes than can be read from the
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* currently being read subordinate stream before that stream could
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* block. Note that it is possible more bytes than this can actually
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* be read without the stream blocking. If a 0 is returned, then the
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* stream could block on the very next read.
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*
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* @return The number of bytes that can be read before blocking could occur
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*
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* @exception IOException If an error occurs
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*/
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public int available() throws IOException
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{
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if (in == null)
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return 0;
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return in.available();
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}
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/**
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* Closes this stream. This will cause any remaining unclosed subordinate
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* <code>InputStream</code>'s to be closed as well. Subsequent attempts to
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* read from this stream may cause an exception.
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*
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* @exception IOException If an error occurs
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*/
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public void close() throws IOException
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{
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while (in != null)
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{
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in.close();
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in = getNextStream ();
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}
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}
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/**
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* This method reads an unsigned byte from the input stream and returns it
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* as an int in the range of 0-255. This method also will return -1 if
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* the end of the stream has been reached. This will only happen when
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* all of the subordinate streams have been read.
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* <p>
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* This method will block until the byte can be read.
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*
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* @return The byte read, or -1 if end of stream
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*
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* @exception IOException If an error occurs
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*/
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public int read() throws IOException
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{
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int ch = -1;
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while (in != null && (ch = in.read()) < 0)
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{
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in.close();
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in = getNextStream();
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}
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return ch;
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}
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/**
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* This method reads bytes from a stream and stores them into a caller
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* supplied buffer. It starts storing the data at index <code>offset</code>
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* into the buffer and attempts to read <code>len</code> bytes. This method
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* can return before reading the number of bytes requested. The actual number
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* of bytes read is returned as an int. A -1 is returend to indicate the
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* end of the stream. This will only happen when all of the subordinate
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* streams have been read.
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* <p>
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* This method will block until at least one byte can be read.
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*
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* @param b The array into which bytes read should be stored
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* @param off The offset into the array to start storing bytes
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* @param len The requested number of bytes to read
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*
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* @return The actual number of bytes read, or -1 if end of stream
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*
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* @exception IOException If an error occurs
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*/
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public int read(byte[] b, int off, int len) throws IOException
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{
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int ch = -1;
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// The validity of the parameters will be checked by in.read so
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// don't bother doing it here.
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while (in != null && (ch = in.read(b, off, len)) < 0)
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{
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in.close();
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in = getNextStream();
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}
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return ch;
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}
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/**
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* This private method is used to get the next <code>InputStream</code> to
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* read from. Returns null when no more streams are available.
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*/
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private InputStream getNextStream()
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{
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InputStream nextIn = null;
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if (enum != null)
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{
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if (enum.hasMoreElements())
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nextIn = (InputStream) enum.nextElement();
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}
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else
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if (in2 != null)
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{
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nextIn = in2;
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in2 = null;
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}
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return nextIn;
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}
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}
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