391 lines
13 KiB
Java
391 lines
13 KiB
Java
/* BufferedInputStream.java -- An input stream that implements buffering
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Copyright (C) 1998, 1999, 2001, 2004, 2005 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.io;
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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 subclass of <code>FilterInputStream</code> buffers input from an
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* underlying implementation to provide a possibly more efficient read
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* mechanism. It maintains the buffer and buffer state in instance
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* variables that are available to subclasses. The default buffer size
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* of 2048 bytes can be overridden by the creator of the stream.
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* <p>
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* This class also implements mark/reset functionality. It is capable
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* of remembering any number of input bytes, to the limits of
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* system memory or the size of <code>Integer.MAX_VALUE</code>
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* <p>
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* Please note that this class does not properly handle character
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* encodings. Consider using the <code>BufferedReader</code> class which
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* does.
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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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* @author Jeroen Frijters (jeroen@frijters.net)
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*/
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public class BufferedInputStream extends FilterInputStream
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{
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/**
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* This is the default buffer size
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*/
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private static final int DEFAULT_BUFFER_SIZE = 2048;
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/**
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* The buffer used for storing data from the underlying stream.
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*/
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protected byte[] buf;
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/**
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* The number of valid bytes currently in the buffer. It is also the index
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* of the buffer position one byte past the end of the valid data.
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*/
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protected int count;
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/**
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* The index of the next character that will by read from the buffer.
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* When <code>pos == count</code>, the buffer is empty.
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*/
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protected int pos;
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/**
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* The value of <code>pos</code> when the <code>mark()</code> method was
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* called.
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* This is set to -1 if there is no mark set.
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*/
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protected int markpos = -1;
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/**
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* This is the maximum number of bytes than can be read after a
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* call to <code>mark()</code> before the mark can be discarded.
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* After this may bytes are read, the <code>reset()</code> method
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* may not be called successfully.
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*/
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protected int marklimit;
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/**
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* This is the initial buffer size. When the buffer is grown because
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* of marking requirements, it will be grown by bufferSize increments.
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* The underlying stream will be read in chunks of bufferSize.
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*/
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private final int bufferSize;
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/**
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* This method initializes a new <code>BufferedInputStream</code> that will
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* read from the specified subordinate stream with a default buffer size
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* of 2048 bytes
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*
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* @param in The subordinate stream to read from
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*/
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public BufferedInputStream(InputStream in)
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{
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this(in, DEFAULT_BUFFER_SIZE);
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}
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/**
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* This method initializes a new <code>BufferedInputStream</code> that will
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* read from the specified subordinate stream with a buffer size that
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* is specified by the caller.
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*
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* @param in The subordinate stream to read from
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* @param size The buffer size to use
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*
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* @exception IllegalArgumentException when size is smaller then 1
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*/
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public BufferedInputStream(InputStream in, int size)
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{
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super(in);
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if (size <= 0)
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throw new IllegalArgumentException();
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buf = new byte[size];
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// initialize pos & count to bufferSize, to prevent refill from
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// allocating a new buffer (if the caller starts out by calling mark()).
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pos = count = bufferSize = size;
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}
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/**
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* This method returns the number of bytes that can be read from this
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* stream before a read can block. A return of 0 indicates that blocking
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* might (or might not) occur on the very next read attempt.
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* <p>
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* The number of available bytes will be the number of read ahead bytes
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* stored in the internal buffer plus the number of available bytes in
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* the underlying stream.
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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 synchronized int available() throws IOException
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{
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return count - pos + in.available();
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}
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/**
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* This method closes the underlying input stream and frees any
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* resources associated with it. Sets <code>buf</code> to <code>null</code>.
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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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// Free up the array memory.
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buf = null;
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pos = count = 0;
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markpos = -1;
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in.close();
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}
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/**
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* This method marks a position in the input to which the stream can be
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* "reset" by calling the <code>reset()</code> method. The parameter
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* <code>readlimit</code> is the number of bytes that can be read from the
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* stream after setting the mark before the mark becomes invalid. For
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* example, if <code>mark()</code> is called with a read limit of 10, then
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* when 11 bytes of data are read from the stream before the
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* <code>reset()</code> method is called, then the mark is invalid and the
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* stream object instance is not required to remember the mark.
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* <p>
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* Note that the number of bytes that can be remembered by this method
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* can be greater than the size of the internal read buffer. It is also
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* not dependent on the subordinate stream supporting mark/reset
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* functionality.
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*
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* @param readlimit The number of bytes that can be read before the mark
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* becomes invalid
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*/
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public synchronized void mark(int readlimit)
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{
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marklimit = readlimit;
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markpos = pos;
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}
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/**
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* This method returns <code>true</code> to indicate that this class
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* supports mark/reset functionality.
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*
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* @return <code>true</code> to indicate that mark/reset functionality is
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* supported
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*
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*/
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public boolean markSupported()
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{
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return true;
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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.
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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 synchronized int read() throws IOException
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{
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if (pos >= count && !refill())
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return -1; // EOF
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return buf[pos++] & 0xFF;
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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>off</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, but it will try
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* to read the requested number of bytes by repeatedly calling the underlying
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* stream as long as available() for this stream continues to return a
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* non-zero value (or until the requested number of bytes have been read).
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* The actual number of bytes read is returned as an int. A -1 is returned
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* to indicate the end of the stream.
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* <p>
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* This method will block until some data can be read.
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*
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* @param b The array into which the 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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* @exception IndexOutOfBoundsException when <code>off</code> or
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* <code>len</code> are negative, or when <code>off + len</code>
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* is larger then the size of <code>b</code>,
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*/
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public synchronized int read(byte[] b, int off, int len) throws IOException
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{
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if (off < 0 || len < 0 || b.length - off < len)
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throw new IndexOutOfBoundsException();
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if (len == 0)
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return 0;
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if (pos >= count && !refill())
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return -1; // No bytes were read before EOF.
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int totalBytesRead = Math.min(count - pos, len);
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System.arraycopy(buf, pos, b, off, totalBytesRead);
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pos += totalBytesRead;
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off += totalBytesRead;
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len -= totalBytesRead;
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while (len > 0 && in.available() > 0 && refill())
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{
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int remain = Math.min(count - pos, len);
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System.arraycopy(buf, pos, b, off, remain);
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pos += remain;
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off += remain;
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len -= remain;
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totalBytesRead += remain;
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}
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return totalBytesRead;
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}
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/**
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* This method resets a stream to the point where the <code>mark()</code>
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* method was called. Any bytes that were read after the mark point was
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* set will be re-read during subsequent reads.
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* <p>
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* This method will throw an IOException if the number of bytes read from
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* the stream since the call to <code>mark()</code> exceeds the mark limit
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* passed when establishing the mark.
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*
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* @exception IOException If <code>mark()</code> was never called or more
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* then <code>marklimit</code> bytes were read since the last
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* call to <code>mark()</code>
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*/
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public synchronized void reset() throws IOException
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{
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if (markpos == -1)
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throw new IOException(buf == null ? "Stream closed." : "Invalid mark.");
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pos = markpos;
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}
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/**
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* This method skips the specified number of bytes in the stream. It
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* returns the actual number of bytes skipped, which may be less than the
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* requested amount.
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*
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* @param n The requested number of bytes to skip
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*
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* @return The actual number of bytes skipped.
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*
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* @exception IOException If an error occurs
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*/
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public synchronized long skip(long n) throws IOException
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{
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if (buf == null)
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throw new IOException("Stream closed.");
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final long origN = n;
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while (n > 0L)
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{
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if (pos >= count)
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{
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if (markpos == -1)
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{
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// Buffer is empty and no mark is set, skip on the
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// underlying stream.
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n -= in.skip(n);
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break;
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}
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else if (!refill())
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break;
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}
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int numread = (int) Math.min((long) (count - pos), n);
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pos += numread;
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n -= numread;
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}
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return origN - n;
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}
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// GCJ LOCAL: package-private for use by InputStreamReader
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/**
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* Called to refill the buffer (when count is equal to pos).
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*
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* @return <code>true</code> when at least one additional byte was read
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* into <code>buf</code>, <code>false</code> otherwise (at EOF).
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*/
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boolean refill() throws IOException
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{
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if (buf == null)
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throw new IOException("Stream closed.");
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if (markpos == -1 || count - markpos >= marklimit)
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{
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markpos = -1;
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pos = count = 0;
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}
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else
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{
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byte[] newbuf = buf;
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if (markpos < bufferSize)
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{
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newbuf = new byte[count - markpos + bufferSize];
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}
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System.arraycopy(buf, markpos, newbuf, 0, count - markpos);
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buf = newbuf;
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count -= markpos;
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pos -= markpos;
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markpos = 0;
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}
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int numread = in.read(buf, count, bufferSize);
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if (numread <= 0) // EOF
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return false;
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count += numread;
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return true;
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}
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}
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