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New standard type ANYFILE - VOIDPTR renamed to ANYPTR

Compiler version: 05.2017

I am planning to rewrite parts of the Pascal runtime in Pascal and, as told before, I am working all the time doing extensions to the Pascal runtime, for example working with PDS members on MVS.

What makes things difficult:

the Pascal language defined files as typed files; the files differ by the types of their element. So for example it is not possible to write a function that works for a file of type TEXT (FILE OF CHAR) as well as for a file of type FILE OF INTEGER, even if the function doesn't do anything with respect to the content of the file - e.g. if the function does only ASSIGN file names or member names to the file.

The only solution to this problem until now was: the function had to be implemented by the compiler itself, and the compiler could be tolerant for all types of files.

But I wanted to be able to write such functions as ASSIGN in Pascal, in a library seperate from the compiler.

My solution is:

I added a new standard type ANYFILE to the compiler, much the same way as I added last year a new type VOIDPTR. The type ANYFILE is compatible to every other file type. But, because you cannot assign files using the assignment statement, the only thing you can do: you can call a procedure or function and pass a "normal" file argument to an ANYFILE var parameter. Inside the function, the (somehow) restricted actions on the ANYFILE variable may be executed - for example ASSIGN, or FILEFCB, which gives you access to the file's FCB.

This extension will be present in the next release of the Stanford Pascal compiler; and then the ASSIGN and ASSIGNMEM Procedures, which were limited to TEXT files until now, will be possible for all sorts of files.

BTW: ANYPTR is the new name for VOIDPTR; VOIDPTR will be kept for compatibility reasons. For both ANYPTR and ANYFILE, access to the elements (dereferencing) via the arrow operator is not allowed; this is now flagged by the compiler with two new error messages

187: DEREF NOT ALLOWED WITH ANYPTR TYPE;
188: ACCESS TO FILE BUFFER NOT ALLOWED WITH ANYFILE TYPE.

Here is a short example of a function using the new ANYFILE type: 



   procedure ASSIGNMEM ( var X : ANYFILE ;
                         MEMBNAME : CHARPTR ;
                         LEN : INTEGER ) ;

      var FCB : VOIDPTR ;
          CPT : -> CHAR ;

      begin (* ASSIGNMEM *)
        if PLATF = PLATF_UNKNOWN then
          CHECK_PLATFORM ;
        if PLATF = PLATF_INTEL then
          begin

          end (* then *)
        else
          begin
            FCB := FILEFCB ( X ) ;
            CPT := PTRADD ( FCB , 40 ) ;
            MEMSET ( CPT , ' ' , 8 ) ;
            if MEMBNAME <> NIL then
              if LEN > 8 then
                MEMCPY ( CPT , MEMBNAME , 8 )
              else
                MEMCPY ( CPT , MEMBNAME , LEN )
          end (* else *)
      end (* ASSIGNMEM *) ;

this way, ASSIGNMEM is usable for every type of file.

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