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Diffstat (limited to 'libjava/java/io/InputStreamReader.java')
| -rw-r--r-- | libjava/java/io/InputStreamReader.java | 332 |
1 files changed, 332 insertions, 0 deletions
diff --git a/libjava/java/io/InputStreamReader.java b/libjava/java/io/InputStreamReader.java new file mode 100644 index 000000000..91568c5cc --- /dev/null +++ b/libjava/java/io/InputStreamReader.java @@ -0,0 +1,332 @@ +/* InputStreamReader.java -- Reader than transforms bytes to chars + Copyright (C) 1998, 1999, 2001, 2003, 2004, 2005 Free Software Foundation, Inc. + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + + +package java.io; + +import gnu.gcj.convert.*; +import java.nio.charset.Charset; +import java.nio.charset.CharsetDecoder; + +/** + * This class reads characters from a byte input stream. The characters + * read are converted from bytes in the underlying stream by a + * decoding layer. The decoding layer transforms bytes to chars according + * to an encoding standard. There are many available encodings to choose + * from. The desired encoding can either be specified by name, or if no + * encoding is selected, the system default encoding will be used. The + * system default encoding name is determined from the system property + * <code>file.encoding</code>. The only encodings that are guaranteed to + * be availalbe are "8859_1" (the Latin-1 character set) and "UTF8". + * Unforunately, Java does not provide a mechanism for listing the + * ecodings that are supported in a given implementation. + * <p> + * Here is a list of standard encoding names that may be available: + * <p> + * <ul> + * <li>8859_1 (ISO-8859-1/Latin-1)</li> + * <li>8859_2 (ISO-8859-2/Latin-2)</li> + * <li>8859_3 (ISO-8859-3/Latin-3)</li> + * <li>8859_4 (ISO-8859-4/Latin-4)</li> + * <li>8859_5 (ISO-8859-5/Latin-5)</li> + * <li>8859_6 (ISO-8859-6/Latin-6)</li> + * <li>8859_7 (ISO-8859-7/Latin-7)</li> + * <li>8859_8 (ISO-8859-8/Latin-8)</li> + * <li>8859_9 (ISO-8859-9/Latin-9)</li> + * <li>ASCII (7-bit ASCII)</li> + * <li>UTF8 (UCS Transformation Format-8)</li> + * <li>More later</li> + * </ul> + * <p> + * It is recommended that applications do not use + * <code>InputStreamReader</code>'s + * directly. Rather, for efficiency purposes, an object of this class + * should be wrapped by a <code>BufferedReader</code>. + * <p> + * Due to a deficiency the Java class library design, there is no standard + * way for an application to install its own byte-character encoding. + * + * @see BufferedReader + * @see InputStream + * + * @author Aaron M. Renn (arenn@urbanophile.com) + * @author Per Bothner (bothner@cygnus.com) + * @date April 22, 1998. + */ +public class InputStreamReader extends Reader +{ + BufferedInputStream in; + + // Buffer of chars read from in and converted but not consumed. + char[] work; + // Next available character (in work buffer) to read. + int wpos; + // Last available character (in work buffer) to read. + int wcount; + + /* + * This is the byte-character decoder class that does the reading and + * translation of bytes from the underlying stream. + */ + BytesToUnicode converter; + + /** + * This method initializes a new instance of <code>InputStreamReader</code> + * to read from the specified stream using the default encoding. + * + * @param in The <code>InputStream</code> to read from + */ + public InputStreamReader(InputStream in) + { + this(in, BytesToUnicode.getDefaultDecoder()); + } + + /** + * This method initializes a new instance of <code>InputStreamReader</code> + * to read from the specified stream using a caller supplied character + * encoding scheme. Note that due to a deficiency in the Java language + * design, there is no way to determine which encodings are supported. + * + * @param in The <code>InputStream</code> to read from + * @param encoding_name The name of the encoding scheme to use + * + * @exception UnsupportedEncodingException If the encoding scheme + * requested is not available. + */ + public InputStreamReader(InputStream in, String encoding_name) + throws UnsupportedEncodingException + { + this(in, BytesToUnicode.getDecoder(encoding_name)); + } + + /** + * Creates an InputStreamReader that uses a decoder of the given + * charset to decode the bytes in the InputStream into + * characters. + */ + public InputStreamReader(InputStream in, Charset charset) + { + this(in, new BytesToCharsetAdaptor(charset)); + } + + /** + * Creates an InputStreamReader that uses the given charset decoder + * to decode the bytes in the InputStream into characters. + */ + public InputStreamReader(InputStream in, CharsetDecoder decoder) + { + this(in, new BytesToCharsetAdaptor(decoder)); + } + + private InputStreamReader(InputStream in, BytesToUnicode decoder) + { + // FIXME: someone could pass in a BufferedInputStream whose buffer + // is smaller than the longest encoded character for this + // encoding. We will probably go into an infinite loop in this + // case. We probably ought to just have our own byte buffering + // here. + this.in = in instanceof BufferedInputStream + ? (BufferedInputStream) in + : new BufferedInputStream(in); + /* Don't need to call super(in) here as long as the lock gets set. */ + this.lock = in; + converter = decoder; + converter.setInput(this.in.buf, 0, 0); + } + + /** + * This method closes this stream, as well as the underlying + * <code>InputStream</code>. + * + * @exception IOException If an error occurs + */ + public void close() throws IOException + { + synchronized (lock) + { + if (in != null) + in.close(); + in = null; + work = null; + wpos = wcount = 0; + } + } + + /** + * This method returns the name of the encoding that is currently in use + * by this object. If the stream has been closed, this method is allowed + * to return <code>null</code>. + * + * @return The current encoding name + */ + public String getEncoding() + { + return in != null ? converter.getName() : null; + } + + /** + * This method checks to see if the stream is read to be read. It + * will return <code>true</code> if is, or <code>false</code> if it is not. + * If the stream is not ready to be read, it could (although is not required + * to) block on the next read attempt. + * + * @return <code>true</code> if the stream is ready to be read, + * <code>false</code> otherwise + * + * @exception IOException If an error occurs + */ + public boolean ready() throws IOException + { + synchronized (lock) + { + if (in == null) + throw new IOException("Stream closed"); + + if (wpos < wcount) + return true; + + // According to the spec, an InputStreamReader is ready if its + // input buffer is not empty (above), or if bytes are + // available on the underlying byte stream. + return in.available () > 0; + } + } + + /** + * This method reads up to <code>length</code> characters from the stream into + * the specified array starting at index <code>offset</code> into the + * array. + * + * @param buf The character array to recieve the data read + * @param offset The offset into the array to start storing characters + * @param length The requested number of characters to read. + * + * @return The actual number of characters read, or -1 if end of stream. + * + * @exception IOException If an error occurs + */ + public int read (char[] buf, int offset, int length) throws IOException + { + synchronized (lock) + { + if (in == null) + throw new IOException("Stream closed"); + + if (length == 0) + return 0; + + int wavail = wcount - wpos; + if (wavail <= 0) + { + // Nothing waiting, so refill their buffer. + return refill(buf, offset, length); + } + + if (length > wavail) + length = wavail; + System.arraycopy(work, wpos, buf, offset, length); + wpos += length; + return length; + } + } + + /** + * This method reads a single character of data from the stream. + * + * @return The char read, as an int, or -1 if end of stream. + * + * @exception IOException If an error occurs + */ + public int read() throws IOException + { + synchronized (lock) + { + if (in == null) + throw new IOException("Stream closed"); + + int wavail = wcount - wpos; + if (wavail <= 0) + { + // Nothing waiting, so refill our internal buffer. + wpos = wcount = 0; + if (work == null) + work = new char[100]; + int count = refill(work, 0, work.length); + if (count == -1) + return -1; + wcount += count; + } + + return work[wpos++]; + } + } + + // Read more bytes and convert them into the specified buffer. + // Returns the number of converted characters or -1 on EOF. + private int refill(char[] buf, int offset, int length) throws IOException + { + for (;;) + { + // We have knowledge of the internals of BufferedInputStream + // here. Eww. + // BufferedInputStream.refill() can only be called when + // `pos>=count'. + boolean r = in.pos < in.count || in.refill (); + if (! r) + return -1; + converter.setInput(in.buf, in.pos, in.count); + int count = converter.read(buf, offset, length); + + // We might have bytes but not have made any progress. In + // this case we try to refill. If refilling fails, we assume + // we have a malformed character at the end of the stream. + if (count == 0 && converter.inpos == in.pos) + { + in.mark(in.count); + if (! in.refill ()) + throw new CharConversionException (); + in.reset(); + } + else + { + in.skip(converter.inpos - in.pos); + if (count > 0) + return count; + } + } + } +} |