TEncoding Class

TEncoding is a class that defines a specific encoding for a character or string.

Pascal

TEncoding = class;

C++

class TEncoding;

File

SysUtils

Description

Use the TEncoding class to define a specific encoding desired for a given string. For instance, the TStringStream class now includes an overloaded constructor that enables the developer to define encoding for strings that will be added to an instance of TStringStream.

To simplify cross platform developement, there are similarities between this interface and System.Text.Encoding. For that reason, links are provided to MSDN counterparts in Encoding (MSDN) class.

C++ Examples:

Copy Code

/*
This example reads any file and converts the encoding to UTF8.
This example uses the TBytesStream to read the files into a TBytes'
and also uses the auto_ptr construction to clean up created class
instances.

*/
#include <tchar.h>
#include <memory>       //for STL auto_ptr class
//---------------------------------------------------------------------------

#pragma argsused
int _tmain(int argc, _TCHAR* argv[])
{
  // Sample to convert a file of any encoding to UTF8.
  TEncoding *LEncoding = NULL;
  std::auto_ptr<TFileStream> LFileStream(new TFileStream("..\\Sample.txt", fmOpenRead));

  // Read file into buffer
  TBytes myBytes;
  std::auto_ptr<TBytesStream> myBytesStream(new TBytesStream(myBytes));
  myBytesStream->CopyFrom(LFileStream.get(), LFileStream->Size);

  // Identify encoding and convert buffer to UTF8
  int LOffset = TEncoding::GetBufferEncoding(myBytesStream->Bytes, LEncoding);
  if (LOffset == 0)
    return 1; // Unknown encoding, don't convert.
  myBytes = TEncoding::Convert(LEncoding, TEncoding::UTF8,
                               myBytesStream->Bytes,
                               LOffset, myBytesStream->Size-LOffset);
  // Create output file
  std::auto_ptr<TFileStream> DestFileStream(new TFileStream("..\\SampleUTF8.txt", fmCreate));

  // Write UTF8 byte order mark and buffer to output file
  TBytes LByteOrderMark;
  LByteOrderMark = TEncoding::UTF8->GetPreamble();

  // Grab preamble and write to destination
  DestFileStream->Write(&LByteOrderMark[0], LByteOrderMark.Length);

  // Write converted buffer
  DestFileStream->Write(&myBytes[0], myBytes.Length);
  return 0;
}

Delphi Examples:

Copy Code

{
This example determines the encoding of a source file and then
writes the file in any encoding chosen.  Use this project to
create files of any encoding.  This example requires two text edits
and a combobox.
}
procedure TForm1.Button1Click(Sender: TObject);
var
  LBuffer: TBytes;
  LByteOrderMark: TBytes;
  LOffset: Integer;
  LEncoding, DestEncoding: TEncoding;
  LFileStream: TFileStream;
  EncodingArray: array[0..5] of TEncoding;
begin
  LEncoding:= nil;
  EncodingArray[0]:= TEncoding.UTF8;
  EncodingArray[1]:= TEncoding.UTF7;
  EncodingArray[2]:= TEncoding.Unicode;
  EncodingArray[3]:= TEncoding.Default;
  EncodingArray[4]:= TEncoding.BigEndianUnicode;
  EncodingArray[5]:= TEncoding.ASCII;
  DestEncoding := EncodingArray[ComboBox1.ItemIndex];
  LFileStream := TFileStream.Create(Edit1.Text, fmOpenRead);
  try
    // Read file into buffer
    SetLength(LBuffer, LFileStream.Size);
//    LFileStream.Read(LBuffer[0], Length(LBuffer));
    LFileStream.ReadBuffer(Pointer(LBuffer)^, Length(LBuffer));

    // Identify encoding and convert buffer to UTF8
    LOffset := TEncoding.GetBufferEncoding(LBuffer, LEncoding);
//    for I := 0 to Length(LBuffer) - 1 do
//      Memo1.Lines.Add((LBuffer[I]));
    LBuffer := LEncoding.Convert(LEncoding, DestEncoding, LBuffer,
      LOffset, Length(LBuffer) - LOffset);
  finally
    LFileStream.Free;
  end;

  LFileStream := TFileStream.Create(Edit2.Text, fmCreate);
  try
    // Write an encoding byte order mark and buffer to output file
    LByteOrderMark := DestEncoding.GetPreamble;
    LFileStream.Write(LByteOrderMark[0], Length(LByteOrderMark));
    LFileStream.Write(LBuffer[0], Length(LBuffer));
  finally
    LFileStream.Free;
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  StringList: TStrings;
begin
  StringList := TStringList.Create;
  try
    with StringList do begin
      Add('TEncoding.UTF8');
      Add('TEncoding.UTF7');
      Add('TEncoding.Unicode');
      Add('TEncoding.Default');
      Add('TEncoding.BigEndianUnicode');
      Add('TEncoding.ASCII');
    end;
    with ComboBox1 do begin
      Items.Assign(StringList);
      ItemIndex := 0;
    end;
  finally
    StringList.free;
  end;
end;