Paginated file viewer

README.md

View

A paginated file viewer similar to Unix more(1) developed in Turbo Pascal under CP/M-86.

The code is currently just a stub and it's still being written.

Usage

To run the program:

A>view filename.txt

view.pas

{ Paginated file viewer similar to Unix more(1) }

program View;

type
   String12  = string[12];
   String255 = string[255];

var
   FileName : String12;
   Infile   : text;
   Line     : String255;

   function GetFilename: String12;

      begin
         if paramcount <> 1 then
            writeln('INVALID ARGUMENT')
         else
            GetFilename := paramstr(1)
      end;

   procedure Open(var Stream: text; Name: String12);

      begin
         assign(Stream, Name);
         reset(Stream)
      end;

   procedure PrintStatusLine(Filename: String12);

      begin
         write(Filename);
         write(' - Press Q to exit, any other key for next screen.')
      end;

   procedure Wait4Keypress;

      begin
      end;

   procedure ViewFile(var Stream: text);

      const
         ScreenWidth  = 80;
         ScreenHeight = 24;

      type
         Height   = 1..ScreenHeight;
         StrIndex = 0..255;

      var
         Line          : String255;
         LineLength    : StrIndex; { Length of current line. }
         LeftoverText  : String255;
         LeftoverLines : integer;
         LineNo        : 1..ScreenHeight;
         LinesLeft     : 1..ScreenHeight; { Number of lines left until last
                                            line on screen. }
         ScreenLines   : 1..ScreenHeight; { How many screen lines the current
                                            line spans. }

      begin
{
while not eof
  if text left over from long line
    print leftover_text
  read line
  screen_lines = how many lines line take when printed on screen
  lines_left=screen_height - lineno - 1 (1 accounts for status line)
  if len(line) <= screenwidth & lineno < screenheight - 1
    print line(stream, line)
    lineno = lineno + 1
  else
    (* print long line *)
    if screen_lines > lines_left
       string_to_print = substr(line, 1, lines_left * screen_width)
       print string_to_print
       lineno = lineno + lines_left
       leftover_text = substr(line, lines_left * screen_width, len(line))
  if lineno = screen height - 1
    print status line
    wait for key press
}
         LineNo := 1;
         LeftoverText := '';
         LeftoverLines := 0;
         ScreenLines := 1;
         while not eof(Stream) do
            begin
               if length(LeftoverText) > 0 then
                  begin
                     writeln(LeftoverText);
                     LineNo := LineNo + LeftoverLines;
                     LeftoverText := '';
                     LeftoverLines := 0
                  end;
               readln(Stream, Line);
               LineLength := length(Line);
               ScreenLines := LineLength div ScreenWidth;
               if (LineLength mod ScreenWidth) > 0 then
                  ScreenLines := ScreenLines + 1;
               if (LineLength <= ScreenWidth) and
                  (LineNo < ScreenHeight - 1) then
                     begin
                        writeln(Line);
                        LineNo := LineNo + 1;
                     end;
               { -1 accounts for status line that spans 1 screen line. }
               LinesLeft := ScreenHeight - LineNo - 1;
               { Current Line is longer than blank lines left on screen. }
               if ScreenLines > LinesLeft then
                  begin
                     writeln(copy(Line, 1, LinesLeft * ScreenWidth));
                     LeftoverText := copy(Line, LinesLeft * ScreenWidth,
                                          length(Line) - (LinesLeft * ScreenWidth));
                     LeftoverLines := ScreenLines - LinesLeft;
                     LineNo := LineNo + LinesLeft
                  end
            end
      end;

BEGIN
    FileName := GetFilename;
    Open(Infile, FileName);
    ViewFile(Infile);
    close(Infile);
END.