/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package com.sun.xml.internal.messaging.saaj.util;

// Cut&paste from sun.net.www.ParseUtil: decode, unescape

public class ParseUtil {

    /**

     * Un-escape and return the character at position i in string s.

     */

    private static char unescape(String s, int i) {

        return (char) Integer.parseInt(s.substring(i+1,i+3),16);

    }

    /**

     * Returns a new String constructed from the specified String by replacing

     * the URL escape sequences and UTF8 encoding with the characters they

     * represent.

     */

    public static String decode(String s) {

        StringBuilder sb = new StringBuilder();

        int i=0;

        while (i<s.length()) {

            char c = s.charAt(i);

            char c2, c3;

            if (c != '%') {

                i++;

            } else {

                try {

                    c = unescape(s, i);

                    i += 3;

                    if ((c & 0x80) != 0) {

                        switch (c >> 4) {

                            case 0xC: case 0xD:

                                c2 = unescape(s, i);

                                i += 3;

                                c = (char)(((c & 0x1f) << 6) | (c2 & 0x3f));

                                break;

                            case 0xE:

                                c2 = unescape(s, i);

                                i += 3;

                                c3 = unescape(s, i);

                                i += 3;

                                c = (char)(((c & 0x0f) << 12) |

                                           ((c2 & 0x3f) << 6) |

                                            (c3 & 0x3f));

                                break;

                            default:

                                throw new IllegalArgumentException();

                        }

                    }

                } catch (NumberFormatException e) {

                    throw new IllegalArgumentException();

                }

            }

            sb.append(c);

        }

        return sb.toString();

    }

}