jellyfin/Emby.Server.Implementations/TextEncoding/UniversalDetector/Core/GB18030Prober.cs

/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla Universal charset detector code.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 2001
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *          Shy Shalom <shooshX@gmail.com>
 *          Rudi Pettazzi <rudi.pettazzi@gmail.com> (C# port)
 * 
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 * either the GNU General Public License Version 2 or later (the "GPL"), or
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namespace UniversalDetector.Core
{
    // We use gb18030 to replace gb2312, because 18030 is a superset. 
    public class GB18030Prober : CharsetProber
    {
        private CodingStateMachine codingSM;
        private GB18030DistributionAnalyser analyser;
        private byte[] lastChar;

        public GB18030Prober()
        {
            lastChar = new byte[2];
            codingSM = new CodingStateMachine(new GB18030SMModel());
            analyser = new GB18030DistributionAnalyser();
            Reset();
        }
        
        public override string GetCharsetName()
        {
            return "gb18030";        
        }
        

        public override ProbingState HandleData(byte[] buf, int offset, int len)
        {
            int codingState = SMModel.START;
            int max = offset + len;
            
            for (int i = offset; i < max; i++) {
                codingState = codingSM.NextState(buf[i]);
                if (codingState == SMModel.ERROR) {
                    state = ProbingState.NotMe;
                    break;
                }
                if (codingState == SMModel.ITSME) {
                    state = ProbingState.FoundIt;
                    break;
                }
                if (codingState == SMModel.START) {
                    int charLen = codingSM.CurrentCharLen;
                    if (i == offset) {
                        lastChar[1] = buf[offset];
                        analyser.HandleOneChar(lastChar, 0, charLen);
                    } else {
                        analyser.HandleOneChar(buf, i-1, charLen);
                    }
                }
            }

            lastChar[0] = buf[max-1];

            if (state == ProbingState.Detecting) {
                if (analyser.GotEnoughData() && GetConfidence() > SHORTCUT_THRESHOLD)
                    state = ProbingState.FoundIt;
            }
            
            return state;
        }
        
        public override float GetConfidence()
        {
            return analyser.GetConfidence();
        }
        
        public override void Reset()
        {
            codingSM.Reset(); 
            state = ProbingState.Detecting;
            analyser.Reset();
        }

    }
}