The GNU Modula-2 front end to GCC

gm2-libs-coroutines/SYSTEM

DEFINITION MODULE SYSTEM ;

(*
   Description: Implements the SYSTEM dependent module
                in the Modula-2 compiler. This module is designed
                to be used on a native operating system rather than
                an embedded system as it implements the coroutine
                primitives TRANSFER, IOTRANSFER and
                NEWPROCESS through the GNU Pthread library.
*)

FROM COROUTINES IMPORT PROTECTION ;

EXPORT QUALIFIED (* the following are built into the compiler: *)
                 LOC, WORD, BYTE, ADDRESS, INTEGER8,
                 INTEGER16, INTEGER32, INTEGER64, CARDINAL8,
                 CARDINAL16, CARDINAL32, CARDINAL64, WORD16,
                 WORD32, WORD64, BITSET8, BITSET16,
                 BITSET32, REAL32, REAL64, REAL96,
                 REAL128, COMPLEX32, COMPLEX64, COMPLEX96,
                 COMPLEX128, CSIZE_T, CSSIZE_T,
                 ADR, TSIZE, ROTATE, SHIFT, THROW, TBITSIZE,
                 (* SIZE is exported depending upon -fpim2 and
                    -fpedantic *)
                 (* and the rest are implemented in SYSTEM.mod *)
                 PROCESS, TRANSFER, NEWPROCESS, IOTRANSFER,
                 LISTEN,
                 ListenLoop, TurnInterrupts,
                 (* Internal GM2 compiler functions *)
                 ShiftVal, ShiftLeft, ShiftRight,
                 RotateVal, RotateLeft, RotateRight ;


TYPE

   PROCESS  = RECORD
                 context: ADDRESS ;
                 ints   : PROTECTION ;

              END ;
(* all the following types are declared internally to gm2
   LOC ;
   WORD ;
   BYTE ;
   ADDRESS ;
   INTEGER8 ;
   INTEGER16 ;
   INTEGER32 ;
   INTEGER64 ;
   CARDINAL8 ;
   CARDINAL16 ;
   CARDINAL32 ;
   CARDINAL64 ;
   WORD16 ;
   WORD32 ;
   WORD64 ;
   BITSET8 ;
   BITSET16 ;
   BITSET32 ;
   REAL32 ;
   REAL64 ;
   REAL96 ;
   REAL128 ;
   COMPLEX32 ;
   COMPLEX64 ;
   COMPLEX96 ;
   COMPLEX128 ;
   CSIZE_T ;
   CSSIZE_T ;
*)


(*
   TRANSFER - save the current volatile environment into, p1.
              Restore the volatile environment from, p2.
*)


PROCEDURE TRANSFER (VAR p1: PROCESS; p2: PROCESS) ;


(*
   NEWPROCESS - p is a parameterless procedure, a, is the origin of
                the workspace used for the process stack and containing
                the volatile environment of the process. n, is the amount
                in bytes of this workspace. new, is the new process.
*)


PROCEDURE NEWPROCESS (p: PROC; a: ADDRESS; n: CARDINAL; VAR new: PROCESS) ;


(*
   IOTRANSFER - saves the current volatile environment into, First,
                and restores volatile environment, Second.
                When an interrupt, InterruptNo, is encountered then
                the reverse takes place. (The then current volatile
                environment is shelved onto Second and First is resumed).

                NOTE: that upon interrupt the Second might not be the
                      same process as that before the original call to
                      IOTRANSFER.
*)


PROCEDURE IOTRANSFER (VAR First, Second: PROCESS; InterruptNo: CARDINAL) ;


(*
   LISTEN - briefly listen for any interrupts.
*)


PROCEDURE LISTEN ;


(*
   ListenLoop - should be called instead of users writing:

                LOOP
                   LISTEN
                END

                It performs the same function but yields
                control back to the underlying operating system
                via a call to pth_select.
                It also checks for deadlock.
                This function returns when an interrupt occurs ie
                a file descriptor becomes ready or a time event expires.
                See the module RTint.
*)


PROCEDURE ListenLoop ;


(*
   TurnInterrupts - switches processor interrupts to the protection
                    level, to.  It returns the old value.
*)


PROCEDURE TurnInterrupts (to: PROTECTION) : PROTECTION ;


(*
   all the functions below are declared internally to gm2
   ====================================================


PROCEDURE ADR (VAR v: <anytype>): ADDRESS;
  (* Returns the address of variable v. *)


PROCEDURE SIZE (v: <type>) : ZType;
  (* Returns the number of BYTES used to store a v of
     any specified <type>.  Only available if -fpim2 is used.
  *)


PROCEDURE TSIZE (<type>) : CARDINAL;
  (* Returns the number of BYTES used to store a value of the
     specified <type>.
  *)


PROCEDURE ROTATE (val: <a set type>;
                  num: INTEGER): <type of first parameter>;
  (* Returns a bit sequence obtained from val by rotating up or down
     (left or right) by the absolute value of num.  The direction is
     down if the sign of num is negative, otherwise the direction is up.
  *)


PROCEDURE SHIFT (val: <a set type>;
                 num: INTEGER): <type of first parameter>;
  (* Returns a bit sequence obtained from val by shifting up or down
     (left or right) by the absolute value of num, introducing
     zeros as necessary.  The direction is down if the sign of
     num is negative, otherwise the direction is up.
  *)


PROCEDURE THROW (i: INTEGER) ;
  (*
     THROW is a GNU extension and was not part of the PIM or ISO
     standards.  It throws an exception which will be caught by the EXCEPT
     block (assuming it exists).  This is a compiler builtin function which
     interfaces to the GCC exception handling runtime system.
     GCC uses the term throw, hence the naming distinction between
     the GCC builtin and the Modula-2 runtime library procedure Raise.
     The later library procedure Raise will call SYSTEM.THROW after
     performing various housekeeping activities.
  *)


PROCEDURE TBITSIZE (<type>) : CARDINAL ;
  (* Returns the minimum number of bits necessary to represent
     <type>.  This procedure function is only useful for determining
     the number of bits used for any type field within a packed RECORD.
     It is not particularly useful elsewhere since <type> might be
     optimized for speed, for example a BOOLEAN could occupy a WORD.
  *)
*)

(* The following procedures are invoked by GNU Modula-2 to
   shift non word sized set types. They are not strictly part
   of the core PIM Modula-2, however they are used by
   GNU Modula-2 to implement the SHIFT procedure defined above,
   which are in turn used by the Logitech compatible libraries.

   Users will access these procedures by using the procedure
   SHIFT above and GNU Modula-2 will map SHIFT onto one of
   the following procedures.
*)

(*
   ShiftVal - is a runtime procedure whose job is to implement
              the SHIFT procedure of ISO SYSTEM. GNU Modula-2 will
              inline a SHIFT of a single WORD sized set and will only
              call this routine for larger sets.
*)


PROCEDURE ShiftVal (VAR s, d: ARRAY OF BITSET;
                    SetSizeInBits: CARDINAL;
                    ShiftCount: INTEGER) ;


(*
   ShiftLeft - performs the shift left for a multi word set.
               This procedure might be called by the back end of
               GNU Modula-2 depending whether amount is known at compile
               time.
*)


PROCEDURE ShiftLeft (VAR s, d: ARRAY OF BITSET;
                     SetSizeInBits: CARDINAL;
                     ShiftCount: CARDINAL) ;

(*
   ShiftRight - performs the shift left for a multi word set.
                This procedure might be called by the back end of
                GNU Modula-2 depending whether amount is known at compile
                time.
*)


PROCEDURE ShiftRight (VAR s, d: ARRAY OF BITSET;
                     SetSizeInBits: CARDINAL;
                     ShiftCount: CARDINAL) ;


(*
   RotateVal - is a runtime procedure whose job is to implement
               the ROTATE procedure of ISO SYSTEM. GNU Modula-2 will
               inline a ROTATE of a single WORD (or less)
               sized set and will only call this routine for larger sets.
*)


PROCEDURE RotateVal (VAR s, d: ARRAY OF BITSET;
                     SetSizeInBits: CARDINAL;
                     RotateCount: INTEGER) ;


(*
   RotateLeft - performs the rotate left for a multi word set.
                This procedure might be called by the back end of
                GNU Modula-2 depending whether amount is known at compile
                time.
*)


PROCEDURE RotateLeft (VAR s, d: ARRAY OF BITSET;
                      SetSizeInBits: CARDINAL;
                      RotateCount: CARDINAL) ;


(*
   RotateRight - performs the rotate right for a multi word set.
                 This procedure might be called by the back end of
                 GNU Modula-2 depending whether amount is known at compile
                 time.
*)


PROCEDURE RotateRight (VAR s, d: ARRAY OF BITSET;
                       SetSizeInBits: CARDINAL;
                       RotateCount: CARDINAL) ;


END SYSTEM.