mirror of git://gcc.gnu.org/git/gcc.git
333 lines
10 KiB
Java
333 lines
10 KiB
Java
/* InputStreamReader.java -- Reader than transforms bytes to chars
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Copyright (C) 1998, 1999, 2001, 2003, 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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import gnu.gcj.convert.*;
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import java.nio.charset.Charset;
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import java.nio.charset.CharsetDecoder;
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/**
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* This class reads characters from a byte input stream. The characters
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* read are converted from bytes in the underlying stream by a
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* decoding layer. The decoding layer transforms bytes to chars according
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* to an encoding standard. There are many available encodings to choose
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* from. The desired encoding can either be specified by name, or if no
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* encoding is selected, the system default encoding will be used. The
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* system default encoding name is determined from the system property
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* <code>file.encoding</code>. The only encodings that are guaranteed to
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* be availalbe are "8859_1" (the Latin-1 character set) and "UTF8".
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* Unforunately, Java does not provide a mechanism for listing the
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* ecodings that are supported in a given implementation.
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* <p>
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* Here is a list of standard encoding names that may be available:
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* <p>
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* <ul>
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* <li>8859_1 (ISO-8859-1/Latin-1)</li>
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* <li>8859_2 (ISO-8859-2/Latin-2)</li>
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* <li>8859_3 (ISO-8859-3/Latin-3)</li>
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* <li>8859_4 (ISO-8859-4/Latin-4)</li>
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* <li>8859_5 (ISO-8859-5/Latin-5)</li>
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* <li>8859_6 (ISO-8859-6/Latin-6)</li>
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* <li>8859_7 (ISO-8859-7/Latin-7)</li>
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* <li>8859_8 (ISO-8859-8/Latin-8)</li>
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* <li>8859_9 (ISO-8859-9/Latin-9)</li>
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* <li>ASCII (7-bit ASCII)</li>
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* <li>UTF8 (UCS Transformation Format-8)</li>
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* <li>More later</li>
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* </ul>
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* <p>
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* It is recommended that applications do not use
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* <code>InputStreamReader</code>'s
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* directly. Rather, for efficiency purposes, an object of this class
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* should be wrapped by a <code>BufferedReader</code>.
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* <p>
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* Due to a deficiency the Java class library design, there is no standard
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* way for an application to install its own byte-character encoding.
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*
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* @see BufferedReader
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* @see InputStream
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*
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* @author Aaron M. Renn (arenn@urbanophile.com)
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* @author Per Bothner (bothner@cygnus.com)
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* @date April 22, 1998.
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*/
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public class InputStreamReader extends Reader
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{
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BufferedInputStream in;
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// Buffer of chars read from in and converted but not consumed.
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char[] work;
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// Next available character (in work buffer) to read.
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int wpos;
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// Last available character (in work buffer) to read.
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int wcount;
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/*
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* This is the byte-character decoder class that does the reading and
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* translation of bytes from the underlying stream.
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*/
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BytesToUnicode converter;
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/**
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* This method initializes a new instance of <code>InputStreamReader</code>
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* to read from the specified stream using the default encoding.
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*
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* @param in The <code>InputStream</code> to read from
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*/
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public InputStreamReader(InputStream in)
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{
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this(in, BytesToUnicode.getDefaultDecoder());
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}
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/**
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* This method initializes a new instance of <code>InputStreamReader</code>
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* to read from the specified stream using a caller supplied character
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* encoding scheme. Note that due to a deficiency in the Java language
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* design, there is no way to determine which encodings are supported.
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*
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* @param in The <code>InputStream</code> to read from
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* @param encoding_name The name of the encoding scheme to use
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*
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* @exception UnsupportedEncodingException If the encoding scheme
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* requested is not available.
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*/
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public InputStreamReader(InputStream in, String encoding_name)
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throws UnsupportedEncodingException
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{
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this(in, BytesToUnicode.getDecoder(encoding_name));
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}
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/**
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* Creates an InputStreamReader that uses a decoder of the given
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* charset to decode the bytes in the InputStream into
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* characters.
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*/
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public InputStreamReader(InputStream in, Charset charset)
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{
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this(in, new BytesToCharsetAdaptor(charset));
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}
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/**
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* Creates an InputStreamReader that uses the given charset decoder
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* to decode the bytes in the InputStream into characters.
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*/
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public InputStreamReader(InputStream in, CharsetDecoder decoder)
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{
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this(in, new BytesToCharsetAdaptor(decoder));
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}
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private InputStreamReader(InputStream in, BytesToUnicode decoder)
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{
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// FIXME: someone could pass in a BufferedInputStream whose buffer
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// is smaller than the longest encoded character for this
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// encoding. We will probably go into an infinite loop in this
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// case. We probably ought to just have our own byte buffering
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// here.
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this.in = in instanceof BufferedInputStream
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? (BufferedInputStream) in
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: new BufferedInputStream(in);
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/* Don't need to call super(in) here as long as the lock gets set. */
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this.lock = in;
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converter = decoder;
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converter.setInput(this.in.buf, 0, 0);
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}
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/**
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* This method closes this stream, as well as the underlying
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* <code>InputStream</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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synchronized (lock)
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{
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if (in != null)
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in.close();
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in = null;
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work = null;
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wpos = wcount = 0;
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}
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}
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/**
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* This method returns the name of the encoding that is currently in use
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* by this object. If the stream has been closed, this method is allowed
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* to return <code>null</code>.
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*
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* @return The current encoding name
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*/
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public String getEncoding()
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{
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return in != null ? converter.getName() : null;
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}
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/**
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* This method checks to see if the stream is read to be read. It
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* will return <code>true</code> if is, or <code>false</code> if it is not.
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* If the stream is not ready to be read, it could (although is not required
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* to) block on the next read attempt.
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*
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* @return <code>true</code> if the stream is ready to be read,
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* <code>false</code> otherwise
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*
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* @exception IOException If an error occurs
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*/
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public boolean ready() throws IOException
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{
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synchronized (lock)
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{
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if (in == null)
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throw new IOException("Stream closed");
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if (wpos < wcount)
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return true;
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// According to the spec, an InputStreamReader is ready if its
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// input buffer is not empty (above), or if bytes are
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// available on the underlying byte stream.
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return in.available () > 0;
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}
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}
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/**
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* This method reads up to <code>length</code> characters from the stream into
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* the specified array starting at index <code>offset</code> into the
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* array.
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*
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* @param buf The character array to recieve the data read
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* @param offset The offset into the array to start storing characters
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* @param length The requested number of characters to read.
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*
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* @return The actual number of characters 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 (char[] buf, int offset, int length) throws IOException
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{
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synchronized (lock)
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{
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if (in == null)
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throw new IOException("Stream closed");
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if (length == 0)
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return 0;
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int wavail = wcount - wpos;
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if (wavail <= 0)
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{
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// Nothing waiting, so refill their buffer.
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return refill(buf, offset, length);
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}
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if (length > wavail)
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length = wavail;
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System.arraycopy(work, wpos, buf, offset, length);
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wpos += length;
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return length;
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}
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}
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/**
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* This method reads a single character of data from the stream.
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*
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* @return The char read, as an int, 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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synchronized (lock)
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{
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if (in == null)
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throw new IOException("Stream closed");
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int wavail = wcount - wpos;
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if (wavail <= 0)
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{
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// Nothing waiting, so refill our internal buffer.
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wpos = wcount = 0;
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if (work == null)
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work = new char[100];
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int count = refill(work, 0, work.length);
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if (count == -1)
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return -1;
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wcount += count;
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}
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return work[wpos++];
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}
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}
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// Read more bytes and convert them into the specified buffer.
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// Returns the number of converted characters or -1 on EOF.
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private int refill(char[] buf, int offset, int length) throws IOException
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{
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for (;;)
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{
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// We have knowledge of the internals of BufferedInputStream
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// here. Eww.
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// BufferedInputStream.refill() can only be called when
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// `pos>=count'.
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boolean r = in.pos < in.count || in.refill ();
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if (! r)
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return -1;
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converter.setInput(in.buf, in.pos, in.count);
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int count = converter.read(buf, offset, length);
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// We might have bytes but not have made any progress. In
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// this case we try to refill. If refilling fails, we assume
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// we have a malformed character at the end of the stream.
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if (count == 0 && converter.inpos == in.pos)
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{
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in.mark(in.count);
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if (! in.refill ())
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throw new CharConversionException ();
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in.reset();
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}
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else
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{
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in.skip(converter.inpos - in.pos);
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if (count > 0)
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return count;
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}
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}
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}
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}
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