How read the content of file to a string in delphi XE

Question

I'm migrating my application from delphi 2007 to delphi xe, but i having problems with a procedure which read a file (ascii) and store the content in a string

this is the code which work ok in delphi 2007

function LoadFileToStr(const FileName: TFileName): String;
var
  FileStream : TFileStream;
begin
  FileStream:= TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);
    try
     if FileStream.Size>0 then
     begin
      SetLength(Result, FileStream.Size);
      FileStream.Read(Pointer(Result)^, FileStream.Size);
     end;
    finally
     FileStream.Free;
    end;
end;

but when execute this code in delphi XE the result are just symbols like '????????', i know which delphi xe is unicode so i change these lines

      SetLength(Result, FileStream.Size);
      FileStream.Read(Pointer(Result)^, FileStream.Size);

to

      SetLength(Result, FileStream.Size*2);
      FileStream.Read(Pointer(Result)^, FileStream.Size);

to store the content of the file in the unicode string but the result is the same.

how i can fix this procedure to read the content of this file?

Be careful with TStringList, because if the 'text' file somehow contains ASCII NUL (0x00) characters, the parser stops and you end up with less lines than actually in the file. — E. van Putten, Nov 23 '12 at 16:15

score 31 · Accepted Answer · answered May 23 '11 at 23:49

you code does not work because you are reading the content of the file using a unicode string as buffer, so you are just moving bytes from the internal buffer of the TFileStream to the unicode string ignoring the encoding.

you can fix easily your procedure , just changing the result type to AnsiString

function LoadFileToStr(const FileName: TFileName): AnsiString;

but i will recommend you which you use the TFile.ReadAllText function instead which in a single line of code read the content of a file a also handle the encoding of the file.

Note that TFile.ReadAllText puts a lock on the file. – Jan Doggen Jul 23 '19 at 09:04 — Jan Doggen, Jul 23 '19 at 09:04

Gabriel · Answer 2 · 2021-08-12T15:39:19.253

23

You can achieve this with one line of code using ReadAllText function. Like this:

Uses IOUtils;

TFile.ReadAllText(FileName);

or

TFile.ReadAllText(FileName, s, TEncoding.ASCII) // if you want to force ASCII (other) encoding

It will correctly detect ANSI, Unicode and binary files.

edited Aug 12 '21 at 15:39

answered Feb 27 '14 at 14:58

Gabriel

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score 12 · Answer 3 · answered May 24 '11 at 00:05

You should take encoding into account, for example:

function LoadFileToStr(const FileName: TFileName): String;
var
  FileStream : TFileStream;
  Bytes: TBytes;

begin
  Result:= '';
  FileStream:= TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);
  try
    if FileStream.Size>0 then begin
      SetLength(Bytes, FileStream.Size);
      FileStream.Read(Bytes[0], FileStream.Size);
    end;
    Result:= TEncoding.ASCII.GetString(Bytes);
  finally
    FileStream.Free;
  end;
end;


//test
procedure TForm2.Button1Click(Sender: TObject);
begin
  ShowMessage(LoadFileToStr('C:\autoexec.bat'));
end;

score 6 · Answer 4 · answered May 24 '11 at 00:10

I recommend using a TStringList to load the content of the file and then set the result to variable.Text, for example:

function LoadFileToStr(const FileName: TFileName): String;  
var LStrings: TStringList;  
begin  
    LStrings := TStringList.Create;
    try  
      LStrings.Loadfromfile(FileName);  
      Result := LStrings.text;  
    finally  
      FreeAndNil(LStrings);  
    end;  
end;

In this way you don't have to worry about anything, it will be backwards and future compatible IMHO.

EDIT: If you need to load from a TStream descendant, then replace LoadFromFile with LoadFromStream.

How read the content of file to a string in delphi XE

4 Answers4