gcc/m2/gm2-libs-iso/Semaphores.def

   1 (* Library module defined by the International Standard
   2    Information technology - programming languages
   3    BS ISO/IEC 10514-1:1996E Part 1: Modula-2, Base Language.
   4
   5    Copyright ISO/IEC (International Organization for Standardization
   6    and International Electrotechnical Commission) 1996-2021.
   7
   8    It may be freely copied for the purpose of implementation (see page
   9    707 of the Information technology - Programming languages Part 1:
  10    Modula-2, Base Language.  BS ISO/IEC 10514-1:1996).  *)
  11
  12 DEFINITION MODULE Semaphores;
  13
  14   (* Provides mutual exclusion facilities for use by processes. *)
  15
  16 TYPE
  17   SEMAPHORE;
  18
  19 PROCEDURE Create (VAR s: SEMAPHORE; initialCount: CARDINAL );
  20   (* Creates and returns s as the identity of a new semaphore that
  21      has its associated count initialized to initialCount, and has
  22      no processes yet waiting on it.
  23   *)
  24
  25 PROCEDURE Destroy (VAR s: SEMAPHORE);
  26   (* Recovers the resources used to implement the semaphore s,
  27      provided that no process is waiting for s to become free.
  28   *)
  29
  30 PROCEDURE Claim (s: SEMAPHORE);
  31   (* If the count associated with the semaphore s is non-zero,
  32      decrements this count and allows the calling process to
  33      continue; otherwise suspends the calling process until
  34      s is released.
  35   *)
  36
  37 PROCEDURE Release (s: SEMAPHORE);
  38   (* If there are any processes waiting on the semaphore s,
  39      allows one of them to enter the ready state; otherwise
  40      increments the count associated with s.
  41   *)
  42
  43 PROCEDURE CondClaim (s: SEMAPHORE): BOOLEAN;
  44   (* Returns FALSE if the call Claim(s) would cause the calling
  45      process to be suspended; in this case the count associated
  46      with s is not changed. Otherwise returns TRUE and the
  47      associated count is decremented.
  48   *)
  49
  50 END Semaphores.
  51