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