C/C++ Users Group Library 1996 July/C-C++ Users Group Library July 1996.iso/listings/v_02_07/2n07024a

Text File | 1991-05-14 | 5KB | 214 lines

(*
    File:           TryEms.Pas;
    Description:    A Test Bed for a TEmsStream Object.
    Compiler:       Turbo Pascal V.6.0
    Date:           3/6/91;
    Author:         Michael Kelly;

    Comments:       A TEmsStream provides Stream I/O
                    for Expanded Memory Specification
                    3.2 and 4.0 type memory.

                    The TEmsStream interface eliminates
                    the book-keeping that would be
                    required if calls to Interrupt $67
                    ( the Ems Interrupt ) were made
                    directly.

                    This program was debugged using
                    the AboveDisk+ Expanded Memory
                    Manager on an XT Clone using
                    disk space to emulate expanded
                    memory.

    Copyright:      Put in the Public Domain by
                    the Author.

                    $$$   Warning  $$$

                    Error recovery should include calling
                    the TEmsStream destructor ( Done ) if
                    at all possible, otherwise the user
                    will have to reboot the machine to
                    reclaim any memory allocated from Ems.

*)


Program TryEms;
Uses Objects, Dos;

     (*
      *  minimum and maximum Ems Memory to
      *  allocate to the TEmsStream.
      *)
    Const
         MinEmsMem: LongInt = 64 * 1024;
         MaxEmsMem: LongInt = 256 * 1024;

    var
       MyStream : TEmsStream; { The Ems Stream }


(*
 *  Reads an open file of type "text" a line at
 *  a time, and writes each line to the Ems
 *  Stream "MyStream" using the WriteStr method
 *  inherited from TStream.
 *
 *  returns:  False on error, True otherwise.
 *)
function LoadFileInEms(var TextFile: text) : Boolean;
    var
       file_line: String;
       len      : Word;

begin
  while (not Eof(TextFile)) and
        (MyStream.GetSize < MaxEmsMem) do
  begin
    ReadLn(TextFile, file_line);
    if IOResult <> 0 then
    begin
      LoadFileInEms := False;
      close(TextFile);
      exit;
    end;
    len := Length(file_line) + 1;
    if (MyStream.GetSize + len) > MaxEmsMem then
    begin
      LoadFileInEms := False;
      close(TextFile);
      exit;
    end
    else
    begin
      MyStream.WriteStr(@file_line);
      if MyStream.Status <> stOk then
      begin
    LoadFileInEms := False;
    close(TextFile);
    exit;
      end;
    end;
  end;
  LoadFileInEms := True;
  close(TextFile);
end;
    (* LoadFileInEms *)

(*
 *  Opens text file entered on the command line
 *  and calls LoadFileInEms to read the file
 *  and write it on the TEmsStream.
 *
 *  returns:  False on error, True otherwise.
 *)
function ReadFile(file_name: String) : Boolean;
    var
       FileVar: Text;

begin

  {$I-}  Assign(FileVar, file_name);
  Reset(FileVar);            {$I+}
  if IOResult <> 0 then
  begin
    ReadFile := False;
    exit;
  end;
  {$I-}  ReadFile := LoadFileInEms(FileVar); {$I+}
end;
    (* ReadFile *)

(*
 *  Seeks to the start of the TEmsStream "MyStream"
 *  and alternately reads a string from the stream
 *  and writes it to the screen.  First a byte is
 *  read from the TEmsStream into the length byte
 *  of the string, then that number of bytes is
 *  read into the string at index 1, completing
 *  the string.  The string is then output to
 *  the screen using WriteLn.
 *)
procedure DisplayEms;
    var
       str : String;

begin
  MyStream.Seek(0);
  if MyStream.Status <> stOK then
    exit;
  WriteLn;
  WriteLn;
  WriteLn('File Contexts  ...');
  WriteLn;
  while MyStream.GetPos < MyStream.GetSize do
  begin
    MyStream.Read(str[0], 1);
    MyStream.Read(str[1], Word(Byte(str[0])));
    if MyStream.Status <> stOK then
      exit;
    WriteLn(str);
  end;
end;
    (* DisplayEms *)

(*
 *  When debugging, it's easy to reset the program
 *  and then realize EMS is allocated (that's why
 *  they call it oops!).  When this happens, put
 *  lines like the following at the start of the
 *  main program body: FreeEmsHandle(1);
 *                     FreeEmsHandle(2);
 *                     ....
 *                     ....
 *                     Halt;
 *
 *  re-compile and run.
 *
 *  call FreeEmsHandle as many times as needed
 *  to free EMS memory without rebooting, then
 *  delete the lines and re-compile.  Kinda Kludgy
 *  but better'n rebootin'.
 *)
procedure FreeEmsHandle(handle: Word);
var
   R:Registers;

begin
     R.AH := $45;
     R.DX := handle;
     Intr($67, R);
end;

        {  Main  }
begin
  if ParamCount < 1 then
  begin
    WriteLn('Usage: TryEms text_file');
    halt;
  end;
  MyStream.Init(MinEmsMem, MaxEmsMem);
  if MyStream.Status <> stOk then
  begin
    WriteLn('Could not open Ems Stream');
    Halt;
  end;
  if (not ReadFile(ParamStr(1))) then
  begin
    WriteLn;
    Write('Error Reading File ');
    WriteLn(ParamStr(1));
    if MyStream.Status <> stOK then
      MyStream.Reset;
    MyStream.Done;
    halt;
  end;
  DisplayEms;
  if MyStream.Status <> stOK then
    MyStream.Reset;
  MyStream.Done;
end.