{$ifndef VER2_4}
type
  EEncodingError = class(Exception);

  { TEncoding }

  TEncoding = class
  strict private
    type
      TStandardEncoding = (
        seAnsi,
        seAscii,
        seUnicode,
        seBigEndianUnicode,
        seUTF7,
        seUTF8);
    var
      FStandardEncodings: array[TStandardEncoding] of TEncoding; static;

    class function GetANSI: TEncoding; static;
    class function GetASCII: TEncoding; static;
    class function GetBigEndianUnicode: TEncoding; static;
    class function GetDefault: TEncoding; static;
    class function GetUnicode: TEncoding; static;
    class function GetUTF7: TEncoding; static;
    class function GetUTF8: TEncoding; static;

    class constructor Create;
    class destructor Destroy;
  strict protected
    FIsSingleByte: Boolean;
    FMaxCharSize: Integer;
    function GetByteCount(Chars: PUnicodeChar; CharCount: Integer): Integer; overload; virtual; abstract;
    function GetBytes(Chars: PUnicodeChar; CharCount: Integer; Bytes: PByte; ByteCount: Integer): Integer; overload; virtual; abstract;
    function GetCharCount(Bytes: PByte; ByteCount: Integer): Integer; overload; virtual; abstract;
    function GetChars(Bytes: PByte; ByteCount: Integer; Chars: PUnicodeChar; CharCount: Integer): Integer; overload; virtual; abstract;
    function GetCodePage: Cardinal; virtual; abstract;
    function GetEncodingName: UnicodeString; virtual; abstract;
  public
    class procedure FreeEncodings;
    function Clone: TEncoding; virtual;
    class function Convert(Source, Destination: TEncoding; const Bytes: TBytes): TBytes; overload;
    class function Convert(Source, Destination: TEncoding; const Bytes: TBytes; StartIndex, Count: Integer): TBytes; overload;
    class function IsStandardEncoding(AEncoding: TEncoding): Boolean; static;
    class function GetBufferEncoding(const Buffer: TBytes; var AEncoding: TEncoding): Integer; overload; static;
    class function GetBufferEncoding(const Buffer: TBytes; var AEncoding: TEncoding;
      ADefaultEncoding: TEncoding): Integer; overload; static;
    function GetByteCount(const Chars: TUnicodeCharArray): Integer; overload;
    function GetByteCount(const Chars: TUnicodeCharArray; CharIndex, CharCount: Integer): Integer; overload;
    function GetByteCount(const S: UnicodeString): Integer; overload;
    function GetByteCount(const S: UnicodeString; CharIndex, CharCount: Integer): Integer; overload;
    function GetBytes(const Chars: TUnicodeCharArray): TBytes; overload;
    function GetBytes(const Chars: TUnicodeCharArray; CharIndex, CharCount: Integer): TBytes; overload;
    function GetBytes(const Chars: TUnicodeCharArray; CharIndex, CharCount: Integer;
      const Bytes: TBytes; ByteIndex: Integer): Integer; overload;
    function GetBytes(const S: UnicodeString): TBytes; overload;
    function GetBytes(const S: UnicodeString; CharIndex, CharCount: Integer;
      const Bytes: TBytes; ByteIndex: Integer): Integer; overload;
    function GetCharCount(const Bytes: TBytes): Integer; overload;
    function GetCharCount(const Bytes: TBytes; ByteIndex, ByteCount: Integer): Integer; overload;
    function GetChars(const Bytes: TBytes): TUnicodeCharArray; overload;
    function GetChars(const Bytes: TBytes; ByteIndex, ByteCount: Integer): TUnicodeCharArray; overload;
    function GetChars(const Bytes: TBytes; ByteIndex, ByteCount: Integer;
      const Chars: TUnicodeCharArray; CharIndex: Integer): Integer; overload;
    class function GetEncoding(CodePage: Integer): TEncoding; overload; static;
    class function GetEncoding(const EncodingName: UnicodeString): TEncoding; overload; static;
    function GetMaxByteCount(CharCount: Integer): Integer; virtual; abstract;
    function GetMaxCharCount(ByteCount: Integer): Integer; virtual; abstract;
    function GetPreamble: TBytes; virtual; abstract;
    function GetString(const Bytes: TBytes): UnicodeString; overload;
    function GetString(const Bytes: TBytes; ByteIndex, ByteCount: Integer): UnicodeString; overload;

    property CodePage: Cardinal read GetCodePage;
    property EncodingName: UnicodeString read GetEncodingName;
    property IsSingleByte: Boolean read FIsSingleByte;

    class property ANSI: TEncoding read GetANSI;
    class property ASCII: TEncoding read GetASCII;
    class property BigEndianUnicode: TEncoding read GetBigEndianUnicode;
    class property Default: TEncoding read GetDefault;
    class property Unicode: TEncoding read GetUnicode;
    class property UTF7: TEncoding read GetUTF7;
    class property UTF8: TEncoding read GetUTF8;
  end;

  { TMBCSEncoding }

  TMBCSEncoding = class(TEncoding)
  strict private
    FCodePage: Integer;
    FMBToWCharFlags: Integer;
    FWCharToMBFlags: Integer;
  strict protected
    function GetByteCount(Chars: PUnicodeChar; CharCount: Integer): Integer; overload; override;
    function GetBytes(Chars: PUnicodeChar; CharCount: Integer; Bytes: PByte; ByteCount: Integer): Integer; overload; override;
    function GetCharCount(Bytes: PByte; ByteCount: Integer): Integer; overload; override;
    function GetChars(Bytes: PByte; ByteCount: Integer; Chars: PUnicodeChar; CharCount: Integer): Integer; overload; override;
    function GetCodePage: Cardinal; override;
    function GetEncodingName: UnicodeString; override;
  public
    constructor Create; overload; virtual;
    constructor Create(ACodePage: Integer); overload; virtual;
    constructor Create(ACodePage, MBToWCharFlags, WCharToMBFlags: Integer); overload; virtual;
    function Clone: TEncoding; override;
    function GetMaxByteCount(CharCount: Integer): Integer; override;
    function GetMaxCharCount(ByteCount: Integer): Integer; override;
    function GetPreamble: TBytes; override;
  end;

  { TUTF7Encoding }

  TUTF7Encoding = class(TMBCSEncoding)
  public
    constructor Create; override;
    function Clone: TEncoding; override;
    function GetMaxByteCount(CharCount: Integer): Integer; override;
    function GetMaxCharCount(ByteCount: Integer): Integer; override;
  end;

  { TUTF8Encoding }

  TUTF8Encoding = class(TUTF7Encoding)
  public
    constructor Create; override;
    function Clone: TEncoding; override;
    function GetMaxByteCount(CharCount: Integer): Integer; override;
    function GetMaxCharCount(ByteCount: Integer): Integer; override;
    function GetPreamble: TBytes; override;
  end;

  { TUnicodeEncoding }

  TUnicodeEncoding = class(TEncoding)
  strict protected
    function GetByteCount(Chars: PUnicodeChar; CharCount: Integer): Integer; overload; override;
    function GetBytes(Chars: PUnicodeChar; CharCount: Integer; Bytes: PByte; ByteCount: Integer): Integer; overload; override;
    function GetCharCount(Bytes: PByte; ByteCount: Integer): Integer; overload; override;
    function GetChars(Bytes: PByte; ByteCount: Integer; Chars: PUnicodeChar; CharCount: Integer): Integer; overload; override;
    function GetCodePage: Cardinal; override;
    function GetEncodingName: UnicodeString; override;
  public
    constructor Create; virtual;
    function Clone: TEncoding; override;
    function GetMaxByteCount(CharCount: Integer): Integer; override;
    function GetMaxCharCount(ByteCount: Integer): Integer; override;
    function GetPreamble: TBytes; override;
  end;

  { TBigEndianUnicodeEncoding }

  TBigEndianUnicodeEncoding = class(TUnicodeEncoding)
  strict protected
    function GetBytes(Chars: PUnicodeChar; CharCount: Integer; Bytes: PByte; ByteCount: Integer): Integer; overload; override;
    function GetChars(Bytes: PByte; ByteCount: Integer; Chars: PUnicodeChar; CharCount: Integer): Integer; overload; override;
    function GetCodePage: Cardinal; override;
    function GetEncodingName: UnicodeString; override;
  public
    function Clone: TEncoding; override;
    function GetPreamble: TBytes; override;
  end;
{$endif VER2_4}