Delphi-如何在保存之前删除非 ANSI（不可打印）字符？

Question

Can somebody guide me to extend this procedure in a way so it removes all Non Printable characters or replaces with SPACE before it saves the stream to file? String is read from Binary and could be maximum of 1 MB size. My Procedure:

var
  i : Word;
  FileName : TFileName;
  SizeofFiles,posi : Integer;
  fs, sStream: TFileStream;
  SplitFileName: String;
begin
  ProgressBar1.Position := 0;
  FileName:= lblFilePath.Caption;
  SizeofFiles := StrToInt(edt2.Text)  ;
  posi := StrToInt(edt1.text) ;
  fs := TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);
  try
             fs.Position := Posi ;
    begin
      SplitFileName := ChangeFileExt(FileName, '.'+ FormatFloat('000', i));
      sStream := TFileStream.Create(SplitFileName, fmCreate or fmShareExclusive);
      try
        if fs.Size - fs.Position < SizeofFiles then
          SizeofFiles := fs.Size - fs.Position;
        sStream.CopyFrom(fs, SizeofFiles);
        ProgressBar1.Position := Round((fs.Position / fs.Size) * 100);
      finally
        sStream.Free;
      end;
    end;
  finally
    fs.Free;
  end;
end;

Answer 1

You won't be able to use TStream.CopyFrom() anymore. You would have to Read(Buffer)() from the source TStream into a local byte array, strip off whatever you don't want from that array, and then Write(Buffer)() the remaining bytes to the destination TStream .

Answer 2

Here is a simple demo that should do what you want:

const
    SrcFileName   : String = 'Test.txt';
    DstFileName   : String = 'TestResult.txt';
    StartPosition : Int64  = 50;

procedure TForm1.Button1Click(Sender: TObject);
var
    FS  : TFileStream;
    Buf : TBytes;
    I   : Integer;
begin
    // Read the source file from starting position
    FS := TFileStream.Create(SrcFileName, fmOpenRead or fmShareDenyWrite);
    try
        FS.Position := StartPosition;
        SetLength(Buf, FS.Size - FS.Position);
        FS.Read(Buf[0], Length(Buf));
    finally
        FreeAndNil(FS);
    end;

    // Replace all non printable character by a space
    // Assume file content is ASCII characters
    for I := 0 to Length(Buf) - 1 do begin
        // You may want to make a more complex test for printable of not
        if (Ord(Buf[I]) < Ord(' ')) or (Ord(Buf[I]) > 126) then
            Buf[I] := Ord(' ');
    end;

    // Write destination file
    FS := TFileStream.Create(DstFileName, fmCreate);
    try
        FS.Write(Buf[0], Length(Buf));
    finally
        FreeAndNil(FS);
    end;
end;

This code assume the file is pure ASCII text and that every character whose ASCII code is below 32 (space) or above 126 is not printable. This may not be the case for European languages. You'll easily adapt the test to fit your needs.

The source file could also be Unicode (16 bits characters). You should use a buffer made of Unicode characters or 16 bit integers (Word). And adapt the test for printable.

Could also be UTF8...