/*
* eXist Open Source Native XML Database
* Copyright (C) 2010 The eXist Project
* http://exist-db.org
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
* $Id$
*/
package org.exist.xquery.modules.file;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PushbackInputStream;
import java.io.Reader;
/**
* Generic unicode textreader, which will use BOM mark
* to identify the encoding to be used. If BOM is not found
* then use a given default or system encoding. This is a bug fix
* workaround for a known issue with InputStreamReader not detecting and
* ignoring the UTF-* BOM (EF BB BF).
*
* http://www.unicode.org/unicode/faq/utf_bom.html
* BOMs:
* 00 00 FE FF = UTF-32, big-endian
* FF FE 00 00 = UTF-32, little-endian
* EF BB BF = UTF-8,
* FE FF = UTF-16, big-endian
* FF FE = UTF-16, little-endian
*
* Win2k Notepad:
* Unicode format = UTF-16LE
*
* Based on code by Thomas Weidenfeller and Aki Nieminen
*
* @author Andrzej Taramina <andrzej@chaeron.com>
* @serial 2008-03-06
* @version 1.1
*/
public class UnicodeReader extends Reader
{
PushbackInputStream internalIn;
InputStreamReader internalIn2 = null;
String defaultEnc;
private static final int BOM_SIZE = 4;
/**
*
* @param in inputstream to be read
*/
public UnicodeReader( InputStream in )
{
internalIn = new PushbackInputStream( in, BOM_SIZE );
this.defaultEnc = null;
}
/**
*
* @param in inputstream to be read
* @param defaultEnc default encoding if stream does not have
* BOM marker. Give NULL to use system-level default.
*/
public UnicodeReader( InputStream in, String defaultEnc )
{
internalIn = new PushbackInputStream( in, BOM_SIZE );
this.defaultEnc = defaultEnc;
}
public String getDefaultEncoding()
{
return( defaultEnc );
}
/**
* Get stream encoding or NULL if stream is uninitialized.
* Call init() or read() method to initialize it.
*/
public String getEncoding()
{
String ret = null;
if( internalIn2 != null ) {
ret = internalIn2.getEncoding();
}
return( ret );
}
/**
* Read-ahead four bytes and check for BOM marks. Extra bytes are
* unread back to the stream, only BOM bytes are skipped.
*/
protected void init() throws IOException
{
if( internalIn2 == null ) {
String encoding;
byte bom[] = new byte[BOM_SIZE];
int n, unread;
n = internalIn.read( bom, 0, bom.length );
if( (bom[0] == (byte)0x00) && (bom[1] == (byte)0x00) && (bom[2] == (byte)0xFE) && (bom[3] == (byte)0xFF) ) {
encoding = "UTF-32BE";
unread = n - 4;
} else if( (bom[0] == (byte)0xFF) && (bom[1] == (byte)0xFE) && (bom[2] == (byte)0x00) && (bom[3] == (byte)0x00) ) {
encoding = "UTF-32LE";
unread = n - 4;
} else if( (bom[0] == (byte)0xEF) && (bom[1] == (byte)0xBB) && (bom[2] == (byte)0xBF) ) {
encoding = "UTF-8";
unread = n - 3;
} else if( (bom[0] == (byte)0xFE) && (bom[1] == (byte)0xFF) ) {
encoding = "UTF-16BE";
unread = n - 2;
} else if( (bom[0] == (byte)0xFF) && (bom[1] == (byte)0xFE) ) {
encoding = "UTF-16LE";
unread = n - 2;
} else {
// Unicode BOM mark not found, unread all bytes
encoding = defaultEnc;
unread = n;
}
//System.out.println("read=" + n + ", unread=" + unread);
if( unread > 0 ) {
internalIn.unread( bom, (n - unread), unread );
}
// Use given encoding
if( encoding == null ) {
internalIn2 = new InputStreamReader( internalIn );
} else {
internalIn2 = new InputStreamReader( internalIn, encoding );
}
}
}
public void close() throws IOException
{
init();
internalIn2.close();
}
public int read( char[] cbuf, int off, int len ) throws IOException
{
init();
return( internalIn2.read( cbuf, off, len ) );
}
}