/* ====================================================================
* Copyright (c) 2006 J.T. Beetstra
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
* ====================================================================
*/
package com.beetstra.jutf7;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.util.Arrays;
import java.util.List;
/**
* <p>
* Abstract base class for UTF-7 style encoding and decoding.
* </p>
*
* @author Jaap Beetstra
*/
abstract class UTF7StyleCharset extends Charset {
private static final List CONTAINED = Arrays.asList(new String[] {
"US-ASCII", "ISO-8859-1", "UTF-8", "UTF-16", "UTF-16LE", "UTF-16BE"
});
final boolean strict;
Base64Util base64;
/**
* <p>
* Besides the name and aliases, two additional parameters are required.
* First the base 64 alphabet used; in modified UTF-7 a slightly different
* alphabet is used. Additionally, it should be specified if encoders and
* decoders should be strict about the interpretation of malformed encoded
* sequences. This is used since modified UTF-7 specifically disallows some
* constructs which are allowed (or not specifically disallowed) in UTF-7
* (RFC 2152).
* </p>
*
* @param canonicalName The name as defined in java.nio.charset.Charset
* @param aliases The aliases as defined in java.nio.charset.Charset
* @param alphabet The base 64 alphabet used
* @param strict True if strict handling of sequences is requested
*/
protected UTF7StyleCharset(String canonicalName, String[] aliases, String alphabet,
boolean strict) {
super(canonicalName, aliases);
this.base64 = new Base64Util(alphabet);
this.strict = strict;
}
/*
* (non-Javadoc)
* @see java.nio.charset.Charset#contains(java.nio.charset.Charset)
*/
public boolean contains(final Charset cs) {
return CONTAINED.contains(cs.name());
}
/*
* (non-Javadoc)
* @see java.nio.charset.Charset#newDecoder()
*/
public CharsetDecoder newDecoder() {
return new UTF7StyleCharsetDecoder(this, base64, strict);
}
/*
* (non-Javadoc)
* @see java.nio.charset.Charset#newEncoder()
*/
public CharsetEncoder newEncoder() {
return new UTF7StyleCharsetEncoder(this, base64, strict);
}
/**
* Tells if a character can be encoded using simple (US-ASCII) encoding or
* requires base 64 encoding.
*
* @param ch The character
* @return True if the character can be encoded directly, false otherwise
*/
abstract boolean canEncodeDirectly(char ch);
/**
* Returns character used to switch to base 64 encoding.
*
* @return The shift character
*/
abstract byte shift();
/**
* Returns character used to switch from base 64 encoding to simple
* encoding.
*
* @return The unshift character
*/
abstract byte unshift();
}