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/* InputStreamReader.java -- Reader than transforms bytes to chars
Copyright (C) 1998 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., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.
As a special exception, if you link this library with other files to
produce an executable, this library does not by itself cause the
resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why the
executable file might be covered by the GNU General Public License. */
package java.io;
import gnu.java.io.EncodingManager;
import gnu.java.io.decode.Decoder;
/**
* 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>8859_2 (ISO-8859-2/Latin-2)
* <li>8859_3 (ISO-8859-3/Latin-3)
* <li>8859_4 (ISO-8859-4/Latin-4)
* <li>8859_5 (ISO-8859-5/Latin-5)
* <li>8859_6 (ISO-8859-6/Latin-6)
* <li>8859_7 (ISO-8859-7/Latin-7)
* <li>8859_8 (ISO-8859-8/Latin-8)
* <li>8859_9 (ISO-8859-9/Latin-9)
* <li>ASCII (7-bit ASCII)
* <li>UTF8 (UCS Transformation Format-8)
* <li>More later
* </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
*
* @version 0.0
*
* @author Aaron M. Renn (arenn@urbanophile.com)
*/
public class InputStreamReader extends Reader
{
/*************************************************************************/
/*
* Instance Variables
*/
/*
* This is the byte-character decoder class that does the reading and
* translation of bytes from the underlying stream.
*/
private Decoder in;
/*************************************************************************/
/**
* 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 = EncodingManager.getDecoder(in);
}
/*************************************************************************/
/**
* 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 = EncodingManager.getDecoder(in, encoding_name);
}
/*************************************************************************/
/*
* Instance Methods
*/
/**
* 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>.
*
* @param The current encoding name
*/
public String
getEncoding()
{
return(in.getSchemeName());
}
/*************************************************************************/
/**
* This method closes this stream, as well as the underlying
* <code>InputStream</code>.
*
* @exception IOException If an error occurs
*/
public void
close() throws IOException
{
in.close();
}
/*************************************************************************/
/**
* 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
{
return(in.ready());
}
/*************************************************************************/
/**
* 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
{
return(in.read());
}
/*************************************************************************/
/**
* This method reads up to <code>len</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 len 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 len) throws IOException
{
return(in.read(buf, offset, len));
}
} // class InputStreamReader
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