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The Apache PDFBox library is an open source Java tool for working with PDF documents.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.pdfbox.encoding;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CoderResult;
/**
* {@link Charset} implementation for the single-byte encodings.
* @version $Revision$
*/
public class SingleByteCharset extends Charset
{
/** Unicode replacement character 0xFFFD. */
protected static final char REPLACEMENT_CHARACTER = '\uFFFD';
private final char[] toUnicodeMap;
private byte[][] toByteMap;
/**
* Creates a new single-byte charset using an array of unicode characters.
* @param canonicalName the canonical name
* @param aliases An array of this charset's aliases, or null if it has no aliases
* @param toUnicodeMap the array of unicode characters (may have a maximum of 256 characters,
* first character must be 0x0000)
*/
protected SingleByteCharset(String canonicalName, String[] aliases, char[] toUnicodeMap)
{
super(canonicalName, aliases);
if (toUnicodeMap.length > 256)
{
throw new IllegalArgumentException("Single-byte encodings may have at most 256 characters.");
}
//Copy array so it cannot be changed accidentally from the outside
this.toUnicodeMap = new char[256];
System.arraycopy(toUnicodeMap, 0, this.toUnicodeMap, 0, toUnicodeMap.length);
//build the inverse lookup table
initInverseMap();
}
private void initInverseMap()
{
toByteMap = new byte[256][];
if (toUnicodeMap[0] != '\u0000')
{
throw new IllegalArgumentException("First character in map must be a NUL (0x0000) character.");
//because we're using 0x00 for encoding otherwise unmapped characters
}
//we're building a kind of sparse lookup table in which not all subranges are covered.
for (int i = 1, len = toUnicodeMap.length; i < len; i++)
{
char ch = toUnicodeMap[i];
if (ch == REPLACEMENT_CHARACTER)
{
continue; //skip
}
int upper = ch >> 8;
int lower = ch & 0xFF;
if (upper > 0xFF)
{
throw new IllegalArgumentException("Not a compatible character: "
+ ch + " (" + Integer.toHexString(ch) + ")");
}
byte[] map = toByteMap[upper];
if (map == null)
{
map = new byte[256];
toByteMap[upper] = map;
}
map[lower] = (byte)(i & 0xFF);
}
}
/** {@inheritDoc} */
@Override
public boolean contains(Charset cs)
{
return (cs.getClass() == getClass());
}
/** {@inheritDoc} */
@Override
public CharsetDecoder newDecoder()
{
return new Decoder();
}
/** {@inheritDoc} */
@Override
public CharsetEncoder newEncoder()
{
return new Encoder();
}
/** The decoder. */
private class Decoder extends CharsetDecoder
{
protected Decoder()
{
super(SingleByteCharset.this, 1, 1);
}
@Override
protected CoderResult decodeLoop(ByteBuffer in, CharBuffer out)
{
while (in.hasRemaining())
{
byte b = in.get();
char ch;
if (!out.hasRemaining())
{
in.position(in.position() - 1);
return CoderResult.OVERFLOW;
}
ch = toUnicodeMap[b & 0xFF];
if (ch == REPLACEMENT_CHARACTER)
{
in.position(in.position() - 1);
return CoderResult.unmappableForLength(1);
}
out.put(ch);
}
return CoderResult.UNDERFLOW;
}
}
/** The encoder. */
private class Encoder extends CharsetEncoder
{
protected Encoder()
{
super(SingleByteCharset.this, 1, 1);
}
@Override
protected CoderResult encodeLoop(CharBuffer in, ByteBuffer out)
{
while (in.hasRemaining())
{
int ch = in.get();
if (!out.hasRemaining())
{
in.position(in.position() - 1);
return CoderResult.OVERFLOW;
}
int upper = ch >> 8;
int lower = ch & 0xFF;
if (upper > 0xFF)
{
in.position(in.position() - 1);
return CoderResult.unmappableForLength(1);
}
byte[] map = toByteMap[upper];
if (map == null)
{
in.position(in.position() - 1);
return CoderResult.unmappableForLength(1);
}
byte b = map[lower];
if (b == 0x00)
{
in.position(in.position() - 1);
return CoderResult.unmappableForLength(1);
}
out.put(b);
}
return CoderResult.UNDERFLOW;
}
}
}