semtx9.pll

来自「一个嵌入式系统的C代码」· PLL 代码 · 共 45 行

PROGRAM Semtx9 (INPUT, OUTPUT);

{-----------------------------------------------------------}
{ PURPOSE: Test of counting semaphores and initialisation.  }
{          Create (or open) two semaphores, one binary and  }
{          the other "counting" with an initial count set   }
{          at ZERO. The version of the program that runs    }
{          first (and so creates the semaphores) then waits }
{          on the one with the zero count - causing a block }
{          while the second instance, when started, SIGNALS }
{          on this semaphore, releasing the first instance. }
{          They then run in lock-step.                      }
{                                                           }
{ AUTHOR:  Ron Chernich                                     }
{ DATE:    13-APR-94                                        }
{-----------------------------------------------------------}

VAR
  s1, s2, count, dummy : INTEGER;

BEGIN {main}
  s1 := SYSTEM(SEM_OPEN, 'binary_one');
  IF (s1 > 0) THEN BEGIN
    count := 2;
    s2 := SYSTEM(SEM_OPEN, 'binary_zero');
    dummy := SYSTEM(SEM_SIGNAL, s2)
  END ELSE BEGIN
    count := 1;
    s1 := SYSTEM(SEM_CREATE, 'binary_one');
    s2 := SYSTEM(SEM_CREATE, 'binary_zero', 0);
    dummy := SYSTEM(SEM_WAIT, s2)
  END;
  REPEAT
    dummy := SYSTEM(SEM_WAIT, s1);
    FOR dummy := 1 TO 8 DO
      Write('~~');
    WriteLn;
    WriteLn(count#);
    count := count + 2;
    dummy := SYSTEM(SEM_SIGNAL, s1)
  UNTIL count > 200;
  s1 := SYSTEM(SEM_CLOSE, s1);
  s2 := SYSTEM(SEM_CLOSE, s2)
END.