Generate random files

procedure GenerateRandomFile(FileName : String; FileSize : Int64; CompressibilityPercentage : Integer);
const
     BUFFER_LENGTH = 4;
     ARRAY_LENGTH  = 1 * 1024;

var
   TheTime : Integer;
   i, k    : Integer;

   BufArr  : Array [0..ARRAY_LENGTH - 1] of Integer;
   TheFile : TFileStream;
begin
     TheTime  := GetTickCount();

     Randomize;
     FileSize := Trunc(FileSize / BUFFER_LENGTH);    // Buf (Integer) uses 4 bytes, thus we divide by 4

     if (CompressibilityPercentage > 0) then
     begin
          CompressibilityPercentage := Trunc(100 / CompressibilityPercentage);
          FileSize                  := Trunc(FileSize / CompressibilityPercentage);
          if (CompressibilityPercentage > 1) then
             Dec(CompressibilityPercentage);
     end;


     // ============================================ //
     // Generate truly non-compressible, random file //
     // ============================================ //
     TheFile       := TFileStream.Create(FileName, fmCreate OR fmOpenReadWrite);
     with TheFile do
     begin
          for i := 0 to Trunc(FileSize / ARRAY_LENGTH) - 1 do    // Iterate
          begin
               for k := 0 to (ARRAY_LENGTH - 1) do
                   BufArr[k] := Random(9999999) * i;

               WriteBuffer(BufArr, BUFFER_LENGTH * ARRAY_LENGTH);
          end;    // for

          // ============================ //
          // Adjust compressibility level //
          // ============================ //
          for k := 1 to CompressibilityPercentage do
          begin
               for i := 0 to Trunc(FileSize / ARRAY_LENGTH) - 1 do    // Iterate
               begin
                    Position := (i * BUFFER_LENGTH * ARRAY_LENGTH);
                    Read(BufArr, BUFFER_LENGTH * ARRAY_LENGTH);

                    Position := Size;
                    WriteBuffer(BufArr, BUFFER_LENGTH * ARRAY_LENGTH);
               end;    // for
          end;    // for

          Free;
     end;    // with

     ShowMessage('Generated [' + FileName + '] in ' + IntToStr(GetTickCount() - TheTime) + ' milli-seconds');
end;