chickadee » srfi-18 » condition-variable-broadcast!

Unblocks all the threads blocked on the condition-variable. condition-variable-broadcast! returns an unspecified value.

    (define (make-semaphore n)
      (vector n (make-mutex) (make-condition-variable)))
 
    (define (semaphore-wait! sema)
      (mutex-lock! (vector-ref sema 1))
      (let ((n (vector-ref sema 0)))
        (if (> n 0)
            (begin
              (vector-set! sema 0 (- n 1))
              (mutex-unlock! (vector-ref sema 1)))
            (begin
              (mutex-unlock! (vector-ref sema 1) (vector-ref sema 2))
              (semaphore-wait! sema))))
 
    (define (semaphore-signal-by! sema increment)
      (mutex-lock! (vector-ref sema 1))
      (let ((n (+ (vector-ref sema 0) increment)))
        (vector-set! sema 0 n)
        (if (> n 0)
            (condition-variable-broadcast! (vector-ref sema 2)))
        (mutex-unlock! (vector-ref sema 1))))