using System.Threading; namespace System.Text { internal sealed class InternalDecoderBestFitFallbackBuffer : DecoderFallbackBuffer { internal char cBestFit; internal int iCount = -1; internal int iSize; private readonly InternalDecoderBestFitFallback _oFallback; private static object s_InternalSyncObject; private static object InternalSyncObject { get { if (s_InternalSyncObject == null) { object value = new object(); Interlocked.CompareExchange<object>(ref s_InternalSyncObject, value, (object)null); } return s_InternalSyncObject; } } public override int Remaining { get { if (iCount <= 0) return 0; return iCount; } } public InternalDecoderBestFitFallbackBuffer(InternalDecoderBestFitFallback fallback) { _oFallback = fallback; if (_oFallback.arrayBestFit == null) { lock (InternalSyncObject) { InternalDecoderBestFitFallback oFallback = _oFallback; if (oFallback.arrayBestFit == null) oFallback.arrayBestFit = fallback.encoding.GetBestFitBytesToUnicodeData(); } } } public override bool Fallback(byte[] bytesUnknown, int index) { cBestFit = TryBestFit(bytesUnknown); if (cBestFit == '') cBestFit = _oFallback.cReplacement; iCount = (iSize = 1); return true; } public override char GetNextChar() { iCount--; if (iCount < 0) return ''; if (iCount == 2147483647) { iCount = -1; return ''; } return cBestFit; } public override bool MovePrevious() { if (iCount >= 0) iCount++; if (iCount >= 0) return iCount <= iSize; return false; } public override void Reset() { iCount = -1; } private char TryBestFit(byte[] bytesCheck) { int num = 0; int num2 = _oFallback.arrayBestFit.Length; if (num2 == 0) return ''; if (bytesCheck.Length == 0 || bytesCheck.Length > 2) return ''; char c = (char)((bytesCheck.Length != 1) ? ((int)(char)((bytesCheck[0] << 8) + bytesCheck[1])) : ((int)bytesCheck[0])); if (c < _oFallback.arrayBestFit[0] || c > _oFallback.arrayBestFit[num2 - 2]) return ''; int num3; while ((num3 = num2 - num) > 6) { int num4 = (num3 / 2 + num) & 65534; char c2 = _oFallback.arrayBestFit[num4]; if (c2 == c) return _oFallback.arrayBestFit[num4 + 1]; if (c2 < c) num = num4; else num2 = num4; } for (int num4 = num; num4 < num2; num4 += 2) { if (_oFallback.arrayBestFit[num4] == c) return _oFallback.arrayBestFit[num4 + 1]; } return ''; } } }