510 lines
15 KiB
Java
510 lines
15 KiB
Java
/* InputStreamReader.java -- Reader than transforms bytes to chars
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Copyright (C) 1998, 1999, 2001, 2003, 2004, 2005, 2006
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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.classpath.SystemProperties;
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import gnu.java.nio.charset.EncodingHelper;
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import java.nio.ByteBuffer;
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import java.nio.CharBuffer;
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import java.nio.charset.Charset;
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import java.nio.charset.CharsetDecoder;
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import java.nio.charset.CoderResult;
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import java.nio.charset.CodingErrorAction;
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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 Robert Schuster
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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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/**
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* The input stream.
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*/
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private InputStream in;
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/**
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* The charset decoder.
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*/
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private CharsetDecoder decoder;
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/**
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* End of stream reached.
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*/
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private boolean isDone = false;
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/**
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* Need this.
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*/
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private float maxBytesPerChar;
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/**
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* Buffer holding surplus loaded bytes (if any)
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*/
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private ByteBuffer byteBuffer;
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/**
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* java.io canonical name of the encoding.
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*/
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private String encoding;
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/**
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* We might decode to a 2-char UTF-16 surrogate, which won't fit in the
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* output buffer. In this case we need to save the surrogate char.
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*/
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private char savedSurrogate;
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private boolean hasSavedSurrogate = false;
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/**
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* A byte array to be reused in read(byte[], int, int).
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*/
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private byte[] bytesCache;
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/**
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* Locks the bytesCache above in read(byte[], int, int).
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*/
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private Object cacheLock = new Object();
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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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if (in == null)
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throw new NullPointerException();
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this.in = in;
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try
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{
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encoding = SystemProperties.getProperty("file.encoding");
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// Don't use NIO if avoidable
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if(EncodingHelper.isISOLatin1(encoding))
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{
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encoding = "ISO8859_1";
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maxBytesPerChar = 1f;
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decoder = null;
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return;
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}
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Charset cs = EncodingHelper.getCharset(encoding);
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decoder = cs.newDecoder();
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encoding = EncodingHelper.getOldCanonical(cs.name());
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try {
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maxBytesPerChar = cs.newEncoder().maxBytesPerChar();
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} catch(UnsupportedOperationException _){
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maxBytesPerChar = 1f;
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}
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decoder.onMalformedInput(CodingErrorAction.REPLACE);
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decoder.onUnmappableCharacter(CodingErrorAction.REPLACE);
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decoder.reset();
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} catch(RuntimeException e) {
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encoding = "ISO8859_1";
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maxBytesPerChar = 1f;
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decoder = null;
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} catch(UnsupportedEncodingException e) {
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encoding = "ISO8859_1";
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maxBytesPerChar = 1f;
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decoder = null;
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}
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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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if (in == null
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|| encoding_name == null)
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throw new NullPointerException();
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this.in = in;
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// Don't use NIO if avoidable
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if(EncodingHelper.isISOLatin1(encoding_name))
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{
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encoding = "ISO8859_1";
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maxBytesPerChar = 1f;
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decoder = null;
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return;
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}
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try {
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Charset cs = EncodingHelper.getCharset(encoding_name);
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try {
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maxBytesPerChar = cs.newEncoder().maxBytesPerChar();
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} catch(UnsupportedOperationException _){
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maxBytesPerChar = 1f;
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}
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decoder = cs.newDecoder();
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decoder.onMalformedInput(CodingErrorAction.REPLACE);
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decoder.onUnmappableCharacter(CodingErrorAction.REPLACE);
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decoder.reset();
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// The encoding should be the old name, if such exists.
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encoding = EncodingHelper.getOldCanonical(cs.name());
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} catch(RuntimeException e) {
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encoding = "ISO8859_1";
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maxBytesPerChar = 1f;
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decoder = null;
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}
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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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* @since 1.4
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*/
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public InputStreamReader(InputStream in, Charset charset) {
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if (in == null)
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throw new NullPointerException();
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this.in = in;
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decoder = charset.newDecoder();
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try {
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maxBytesPerChar = charset.newEncoder().maxBytesPerChar();
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} catch(UnsupportedOperationException _){
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maxBytesPerChar = 1f;
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}
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decoder.onMalformedInput(CodingErrorAction.REPLACE);
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decoder.onUnmappableCharacter(CodingErrorAction.REPLACE);
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decoder.reset();
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encoding = EncodingHelper.getOldCanonical(charset.name());
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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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* @since 1.4
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*/
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public InputStreamReader(InputStream in, CharsetDecoder decoder) {
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if (in == null)
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throw new NullPointerException();
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this.in = in;
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this.decoder = decoder;
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Charset charset = decoder.charset();
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try {
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if (charset == null)
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maxBytesPerChar = 1f;
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else
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maxBytesPerChar = charset.newEncoder().maxBytesPerChar();
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} catch(UnsupportedOperationException _){
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maxBytesPerChar = 1f;
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}
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decoder.onMalformedInput(CodingErrorAction.REPLACE);
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decoder.onUnmappableCharacter(CodingErrorAction.REPLACE);
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decoder.reset();
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if (charset == null)
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encoding = "US-ASCII";
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else
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encoding = EncodingHelper.getOldCanonical(decoder.charset().name());
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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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// Makes sure all intermediate data is released by the decoder.
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if (decoder != null)
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decoder.reset();
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if (in != null)
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in.close();
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in = null;
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isDone = true;
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decoder = null;
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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 ? encoding : null;
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}
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/**
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* This method checks to see if the stream is ready 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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if (in == null)
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throw new IOException("Reader has been closed");
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return in.available() != 0;
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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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if (in == null)
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throw new IOException("Reader has been closed");
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if (isDone)
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return -1;
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if(decoder != null)
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{
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int totalBytes = (int)((double) length * maxBytesPerChar);
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if (byteBuffer != null)
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totalBytes = Math.max(totalBytes, byteBuffer.remaining());
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byte[] bytes;
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// Fetch cached bytes array if available and big enough.
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synchronized(cacheLock)
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{
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bytes = bytesCache;
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if (bytes == null || bytes.length < totalBytes)
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bytes = new byte[totalBytes];
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else
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bytesCache = null;
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}
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int remaining = 0;
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if(byteBuffer != null)
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{
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remaining = byteBuffer.remaining();
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byteBuffer.get(bytes, 0, remaining);
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}
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int read;
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if(totalBytes - remaining > 0)
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{
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read = in.read(bytes, remaining, totalBytes - remaining);
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if(read == -1){
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read = remaining;
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isDone = true;
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} else
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read += remaining;
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} else
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read = remaining;
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byteBuffer = ByteBuffer.wrap(bytes, 0, read);
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CharBuffer cb = CharBuffer.wrap(buf, offset, length);
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int startPos = cb.position();
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if(hasSavedSurrogate){
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hasSavedSurrogate = false;
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cb.put(savedSurrogate);
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read++;
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}
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CoderResult cr = decoder.decode(byteBuffer, cb, isDone);
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decoder.reset();
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// 1 char remains which is the first half of a surrogate pair.
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if(cr.isOverflow() && cb.hasRemaining()){
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CharBuffer overflowbuf = CharBuffer.allocate(2);
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cr = decoder.decode(byteBuffer, overflowbuf, isDone);
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overflowbuf.flip();
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if(overflowbuf.hasRemaining())
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{
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cb.put(overflowbuf.get());
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savedSurrogate = overflowbuf.get();
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hasSavedSurrogate = true;
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isDone = false;
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}
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}
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if(byteBuffer.hasRemaining()) {
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byteBuffer.compact();
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byteBuffer.flip();
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isDone = false;
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} else
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byteBuffer = null;
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read = cb.position() - startPos;
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// Put cached bytes array back if we are finished and the cache
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// is null or smaller than the used bytes array.
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synchronized (cacheLock)
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{
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if (byteBuffer == null
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&& (bytesCache == null || bytesCache.length < bytes.length))
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bytesCache = bytes;
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}
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return (read <= 0) ? -1 : read;
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}
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else
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{
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byte[] bytes;
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// Fetch cached bytes array if available and big enough.
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synchronized (cacheLock)
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{
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bytes = bytesCache;
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if (bytes == null || length < bytes.length)
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bytes = new byte[length];
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else
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bytesCache = null;
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}
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int read = in.read(bytes);
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for(int i=0;i<read;i++)
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buf[offset+i] = (char)(bytes[i]&0xFF);
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// Put back byte array into cache if appropriate.
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synchronized (cacheLock)
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{
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if (bytesCache == null || bytesCache.length < bytes.length)
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bytesCache = bytes;
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}
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return read;
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}
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}
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/**
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* Reads an char from the input stream and returns it
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* as an int in the range of 0-65535. 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 char can be read.
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*
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* @return The char 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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char[] buf = new char[1];
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int count = read(buf, 0, 1);
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return count > 0 ? buf[0] : -1;
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}
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/**
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* Skips the specified number of chars in the stream. It
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* returns the actual number of chars skipped, which may be less than the
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* requested amount.
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*
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* @param count The requested number of chars to skip
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*
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* @return The actual number of chars skipped.
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*
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* @exception IOException If an error occurs
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*/
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public long skip(long count) throws IOException
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{
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if (in == null)
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throw new IOException("Reader has been closed");
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return super.skip(count);
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}
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}
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