/*
 *                 Sun Public License Notice
 * 
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 * 
 * The Original Code is NetBeans. The Initial Developer of the Original
 * Code is Sun Microsystems, Inc. Portions Copyright 1997-2003 Sun
 * Microsystems, Inc. All Rights Reserved.
 */
package org.netbeans.modules.tasklist.providers;

import org.openide.ErrorManager;

import java.io.*;

/**
 * XML uses inband encoding detection - this class obtains it.
 * 
 * @author  Petr Kuzel
 * @version 1.0
 */
final class XMLEncodingHelper extends Object {

    //
    // taken from XML module xml.core.lib.EncodingHelper
    //

    // heuristic constant guessing max prolog length
    private static final int EXPECTED_PROLOG_LENGTH = 1000;

    /** Detect input stream encoding.
    * The stream stays intact.
    * @return iana encoding names or Java hisrotical ("UTF8", "ASCII", etc.) or null
    * if the stream is not markable or enoding cannot be detected.
    */
    public static String detectEncoding(InputStream in) throws IOException {

        if (! in.markSupported()) {
            ErrorManager.getDefault().log("XMLEncodingHelper got unmarkable stream: " + in.getClass()); // NOI18N
            return null;
        }

        try {
            in.mark(EXPECTED_PROLOG_LENGTH);

            byte[] bytes = new byte[EXPECTED_PROLOG_LENGTH];
            for (int i = 0; inull for unrecognized
     */
    static String autoDetectEncoding(byte[] buf) throws IOException {
        

        if (buf.length >= 4) {
            switch (buf[0]) {
                case 0:  
                    // byte order mark of (1234-big endian) or (2143) USC-4
                    // or '<' encoded as UCS-4 (1234, 2143, 3412) or UTF-16BE 
                    if (buf[1] == (byte)0x3c && buf[2] == (byte)0x00 && buf[3] == (byte)0x3f) {
                        return "UnicodeBigUnmarked"; // NOI18N
                    }
                    // else it's probably UCS-4
                    break;

                case 0x3c:
                    switch (buf[1]) {
                        // First character is '<'; could be XML without
                        // an XML directive such as "", "