Reading and Writing

What is translated > Reading and Writing

Delphi has Stream classes to read and write files similar to those in C#. But there are also an classic, non-object oriented Pascal routines for this purpose. For this classic approach there are three file types, which have no counterpart in C#

Delphi2C# tries to convert this classic approach to the C# object-oriented approach. For all three file types in C# a Stream is created at first. In a second step in dependence of the different Delphi file types different kinds of Streams are created from the first basic stream. For example a StreamWriter will be created, if ASCII data shall be written to a Text file:

var

  myFile : Text;

begin

  AssignFile(myFile, 'Test.txt');

  Rewrite(myFile);

->

  Stream myFile_stream;

  myFile_stream = new FileStream("Test.txt", FileMode.Create);

  using (StreamWriter myFile = new StreamWriter(myFile_stream)) {

  ...

  }

In Delphi the access mode of these file types are specified by the FileMode variable. In C# there also exists a FileMode, but this variable specifies how to open a file, eg. create a new file or append to an existing file. Therefore the Delphi FileMode variable cannot be defined in the C# code. In translated code the Delphi FileMode is passed as explicit parameter to the file opening commands, "FileMode.Create" in the example above. "FileMode.CreateOrOpen" is the FileMode for readers.The kind of opening a file  in Delphi is determined by the command which is used to open the file. The ReWrite command and the Reset command are truncating an existing file or creating a new file, whereas the Append command opens a file to add output to the existing content of a file.

The default FileMode in Delphi is fmOpenReadWrite (=2). but in C# a stream cannot have read and write access at the same time. Delphi2C# therefore looks at the subsequent use of the stream. If writing operations are following a Writer is created else a Reader is created. If the Delphi code really reads and writes to the file without resetting it, the translation will fail.

If a Write function is called with a file as first parameter, the output will be written into that file. Otherwise the Output is written to the console:

WriteLn(myFile, 'Hello');

WriteLn('Hello');

->

myFile.WriteLine("Hello");

Console.WriteLine("Hello");

The same for Read-functions:

Read(myFile, Letter); 

Read(Letter); 

->

Letter = (char) myFile.Read();

Letter = (char) Console.Read(); 

For Files and Files of a type Delphi2C# creates BinaryReader and BinaryWriter. Delphi2C# only converts uses of File of [builtin type]  An automatic treatment of files of records might partly be possible, but hasn't be done so far.

var

  myWord : WORD;

  myFile : File of WORD;

begin

  AssignFile(myFile, 'Test.cus');

  Rewrite(myFile);

  While not Eof(myFile) do

  begin

    Read(myFile, myWord);

  end;

  CloseFile(myFile); 

->

ushort myWord = 0;

Stream myFile_stream;

myFile_stream = new FileStream("Test.cus", FileMode.OpenOrCreate);

using (BinaryReader myFile = new BinaryReader(myFile_stream, System.Text.Encoding.ASCII)) {

while(!(myFile.PeekChar() < 0))

{

  myWord = (ushort) myFile.ReadInt16();

}

myFile.Close();

} // using 

Delphi2C# also converts Rename commands.

The width and precision arguments in write operations aren't converted correctly yet.

This page belongs to the Delphi2C# Documentation