michael@0: /*
michael@0:  * $HeadURL$
michael@0:  * $Revision$
michael@0:  * $Date$
michael@0:  *
michael@0:  * ====================================================================
michael@0:  *
michael@0:  *  Licensed to the Apache Software Foundation (ASF) under one or more
michael@0:  *  contributor license agreements.  See the NOTICE file distributed with
michael@0:  *  this work for additional information regarding copyright ownership.
michael@0:  *  The ASF licenses this file to You under the Apache License, Version 2.0
michael@0:  *  (the "License"); you may not use this file except in compliance with
michael@0:  *  the License.  You may obtain a copy of the License at
michael@0:  *
michael@0:  *      http://www.apache.org/licenses/LICENSE-2.0
michael@0:  *
michael@0:  *  Unless required by applicable law or agreed to in writing, software
michael@0:  *  distributed under the License is distributed on an "AS IS" BASIS,
michael@0:  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
michael@0:  *  See the License for the specific language governing permissions and
michael@0:  *  limitations under the License.
michael@0:  * ====================================================================
michael@0:  *
michael@0:  * This software consists of voluntary contributions made by many
michael@0:  * individuals on behalf of the Apache Software Foundation.  For more
michael@0:  * information on the Apache Software Foundation, please see
michael@0:  * <http://www.apache.org/>.
michael@0:  *
michael@0:  */
michael@0: 
michael@0: package ch.boye.httpclientandroidlib.client.utils;
michael@0: 
michael@0: import java.util.StringTokenizer;
michael@0: 
michael@0: import ch.boye.httpclientandroidlib.annotation.Immutable;
michael@0: 
michael@0: /**
michael@0:  * Implementation from pseudo code in RFC 3492.
michael@0:  *
michael@0:  * @since 4.0
michael@0:  */
michael@0: @Immutable
michael@0: public class Rfc3492Idn implements Idn {
michael@0:     private static final int base = 36;
michael@0:     private static final int tmin = 1;
michael@0:     private static final int tmax = 26;
michael@0:     private static final int skew = 38;
michael@0:     private static final int damp = 700;
michael@0:     private static final int initial_bias = 72;
michael@0:     private static final int initial_n = 128;
michael@0:     private static final char delimiter = '-';
michael@0:     private static final String ACE_PREFIX = "xn--";
michael@0: 
michael@0:     private int adapt(int delta, int numpoints, boolean firsttime) {
michael@0:         if (firsttime) delta = delta / damp;
michael@0:         else delta = delta / 2;
michael@0:         delta = delta + (delta / numpoints);
michael@0:         int k = 0;
michael@0:         while (delta > ((base - tmin) * tmax) / 2) {
michael@0:           delta = delta / (base - tmin);
michael@0:           k = k + base;
michael@0:         }
michael@0:         return k + (((base - tmin + 1) * delta) / (delta + skew));
michael@0:     }
michael@0: 
michael@0:     private int digit(char c) {
michael@0:         if ((c >= 'A') && (c <= 'Z')) return (c - 'A');
michael@0:         if ((c >= 'a') && (c <= 'z')) return (c - 'a');
michael@0:         if ((c >= '0') && (c <= '9')) return (c - '0') + 26;
michael@0:         throw new IllegalArgumentException("illegal digit: "+ c);
michael@0:     }
michael@0: 
michael@0:     public String toUnicode(String punycode) {
michael@0:         StringBuilder unicode = new StringBuilder(punycode.length());
michael@0:         StringTokenizer tok = new StringTokenizer(punycode, ".");
michael@0:         while (tok.hasMoreTokens()) {
michael@0:             String t = tok.nextToken();
michael@0:             if (unicode.length() > 0) unicode.append('.');
michael@0:             if (t.startsWith(ACE_PREFIX)) t = decode(t.substring(4));
michael@0:             unicode.append(t);
michael@0:         }
michael@0:         return unicode.toString();
michael@0:     }
michael@0: 
michael@0:     protected String decode(String input) {
michael@0:         int n = initial_n;
michael@0:         int i = 0;
michael@0:         int bias = initial_bias;
michael@0:         StringBuilder output = new StringBuilder(input.length());
michael@0:         int lastdelim = input.lastIndexOf(delimiter);
michael@0:         if (lastdelim != -1) {
michael@0:             output.append(input.subSequence(0, lastdelim));
michael@0:             input = input.substring(lastdelim + 1);
michael@0:         }
michael@0: 
michael@0:         while (input.length() > 0) {
michael@0:             int oldi = i;
michael@0:             int w = 1;
michael@0:             for (int k = base;; k += base) {
michael@0:                 if (input.length() == 0) break;
michael@0:                 char c = input.charAt(0);
michael@0:                 input = input.substring(1);
michael@0:                 int digit = digit(c);
michael@0:                 i = i + digit * w; // FIXME fail on overflow
michael@0:                 int t;
michael@0:                 if (k <= bias + tmin) {
michael@0:                     t = tmin;
michael@0:                 } else if (k >= bias + tmax) {
michael@0:                     t = tmax;
michael@0:                 } else {
michael@0:                     t = k - bias;
michael@0:                 }
michael@0:                 if (digit < t) break;
michael@0:                 w = w * (base - t); // FIXME fail on overflow
michael@0:             }
michael@0:             bias = adapt(i - oldi, output.length() + 1, (oldi == 0));
michael@0:             n = n + i / (output.length() + 1); // FIXME fail on overflow
michael@0:             i = i % (output.length() + 1);
michael@0:             // {if n is a basic code point then fail}
michael@0:             output.insert(i, (char) n);
michael@0:             i++;
michael@0:         }
michael@0:         return output.toString();
michael@0:     }
michael@0: 
michael@0: }