gcc/m2/gm2-libs-iso/Processes.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 Processes;
  13
  14   (* This module allows concurrent algorithms to be expressed using
  15      processes. A process is a unit of a program that has the
  16      potential to run in parallel with other processes.
  17   *)
  18
  19 IMPORT SYSTEM;
  20
  21 TYPE
  22   ProcessId;                      (* Used to identify processes *)
  23   Parameter     = SYSTEM.ADDRESS; (* Used to pass data between processes *)
  24   Body          = PROC;           (* Used as the type of a process body *)
  25   Urgency       = INTEGER;        (* Used by the internal scheduler *)
  26   Sources       = CARDINAL;       (* Used to identify event sources *)
  27   ProcessesExceptions =           (* Exceptions raised by this module *)
  28     (passiveProgram, processError);
  29
  30 (* The following procedures create processes and switch control between
  31    them. *)
  32
  33 PROCEDURE Create (procBody: Body; extraSpace: CARDINAL; procUrg: Urgency;
  34                   procParams: Parameter; VAR procId: ProcessId);
  35   (* Creates a new process with procBody as its body, and with urgency
  36      and parameters given by procUrg and procParams.  At least as
  37      much workspace (in units of SYSTEM.LOC) as is specified by
  38      extraSpace is allocated to the process.
  39      An identity for the new process is returned in procId.
  40      The process is created in the passive state; it will not run
  41      until activated.
  42   *)
  43
  44 PROCEDURE Start (procBody: Body; extraSpace: CARDINAL; procUrg: Urgency;
  45                  procParams: Parameter; VAR procId: ProcessId);
  46   (* Creates a new process, with parameters as for Create.
  47      The process is created in the ready state; it is eligible to
  48      run immediately.
  49   *)
  50
  51 PROCEDURE StopMe ();
  52   (* Terminates the calling process.
  53      The process must not be associated with a source of events.
  54   *)
  55
  56 PROCEDURE SuspendMe ();
  57   (* Causes the calling process to enter the passive state.  The
  58      procedure only returns when the calling process is again
  59      activated by another process.
  60   *)
  61
  62 PROCEDURE Activate (procId: ProcessId);
  63   (* Causes the process identified by procId to enter the ready
  64      state, and thus to become eligible to run again.
  65   *)
  66
  67 PROCEDURE SuspendMeAndActivate (procId: ProcessId);
  68   (* Executes an atomic sequence of SuspendMe() and
  69      Activate(procId). *)
  70
  71 PROCEDURE Switch (procId: ProcessId; VAR info: Parameter);
  72   (* Causes the calling process to enter the passive state; the
  73      process identified by procId becomes the currently executing
  74      process.  info is used to pass parameter information from the
  75      calling to the activated process.  On return, info will
  76      contain information from the process that chooses to switch
  77      back to this one (or will be NIL if Activate or
  78      SuspendMeAndActivate are used instead of Switch).
  79   *)
  80
  81 PROCEDURE Wait ();
  82   (* Causes the calling process to enter the waiting state.
  83      The procedure will return when the calling process is
  84      activated by another process, or when one of its associated
  85      eventSources has generated an event.
  86   *)
  87
  88 (* The following procedures allow the association of processes
  89    with sources of external events.
  90 *)
  91
  92 PROCEDURE Attach (eventSource: Sources);
  93   (* Associates the specified eventSource with the calling
  94      process. *)
  95
  96 PROCEDURE Detach (eventSource: Sources);
  97   (* Dissociates the specified eventSource from the program. *)
  98
  99 PROCEDURE IsAttached (eventSource: Sources): BOOLEAN;
 100   (* Returns TRUE if and only if the specified eventSource is
 101      currently associated with one of the processes of the
 102      program.
 103   *)
 104
 105 PROCEDURE Handler (eventSource: Sources): ProcessId;
 106   (* Returns the identity of the process, if any, that is
 107      associated with the specified eventSource.
 108   *)
 109
 110 (* The following procedures allow processes to obtain their
 111    identity, parameters, and urgency.
 112 *)
 113
 114 PROCEDURE Me (): ProcessId;
 115   (* Returns the identity of the calling process (as assigned
 116      when the process was first created).
 117   *)
 118
 119 PROCEDURE MyParam (): Parameter;
 120   (* Returns the value specified as procParams when the calling
 121      process was created. *)
 122
 123 PROCEDURE UrgencyOf (procId: ProcessId): Urgency;
 124   (* Returns the urgency established when the process identified
 125      by procId was first created.
 126   *)
 127
 128 (* The following procedure provides facilities for exception
 129    handlers. *)
 130
 131 PROCEDURE ProcessesException (): ProcessesExceptions;
 132   (* If the current coroutine is in the exceptional execution state
 133      because of the raising of a language exception, returns the
 134      corresponding enumeration value, and otherwise raises an
 135      exception.
 136   *)
 137
 138 PROCEDURE IsProcessesException (): BOOLEAN;
 139   (* Returns TRUE if the current coroutine is in the exceptional
 140      execution state because of the raising of an exception in
 141      a routine from this module; otherwise returns FALSE.
 142   *)
 143
 144 (*
 145    Reschedule - rotates the ready queue and transfers to the process
 146                 with the highest run priority.
 147 *)
 148
 149 PROCEDURE Reschedule ;
 150
 151
 152 (*
 153    displayProcesses -
 154 *)
 155
 156 PROCEDURE displayProcesses (message: ARRAY OF CHAR) ;
 157
 158
 159 END Processes.