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# core.sync.semaphore

The `semaphore` module provides a general use `semaphore` for synchronization.
License:
Boost License 1.0
Authors:
Sean Kelly

Source core/sync/semaphore.d

class `Semaphore`;
  This class represents a general counting semaphore as concieved by Edsger Dijkstra. As per Mesa type monitors however, "signal" has been replaced with "notify" to indicate that control is not transferred to the waiter when a notification is sent.
  this(uint `count` = 0);
    Initializes a semaphore object with the specified initial `count`.
    Parameters:

    uint `count` | The initial `count` for the semaphore.

    Throws:
    SyncError on error.
  void `wait`();
    Wait until the current count is above zero, then atomically decrement the count by one and return.
    Throws:
    SyncError on error.
  bool `wait`(Duration `period`);
    Suspends the calling thread until the current count moves above zero or until the supplied time `period` has elapsed. If the count moves above zero in this interval, then atomically decrement the count by one and return `true`. Otherwise, return `false`.
    Parameters:

    Duration `period` | The time to `wait`.

    In `period` must be non-negative.

    Throws:
    SyncError on error.
    Returns:
    `true` if notified before the timeout and `false` if not.
  void `notify`();
    Atomically increment the current count by one. This will `notify` one waiter, if there are any in the queue.
    Throws:
    SyncError on error.
  bool `tryWait`();
    If the current count is equal to zero, return. Otherwise, atomically decrement the count by one and return `true`.
    Throws:
    SyncError on error.
    Returns:
    `true` if the count was above zero and `false` if not.

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