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final class TSemaphore extends Serializable

A TSemaphore is a semaphore that can be composed transactionally. Because of the extremely high performance of ZIO's implementation of software transactional memory TSemaphore can support both controlling access to some resource on a standalone basis as well as composing with other STM data structures to solve more advanced concurrency problems.

For basic use cases, the most idiomatic way to work with a semaphore is to use the withPermit operator, which acquires a permit before executing some ZIO effect and release the permit immediately afterward. The permit is guaranteed to be released immediately after the effect completes execution, whether by success, failure, or interruption. Attempting to acquire a permit when a sufficient number of permits are not available will semantically block until permits become available without blocking any underlying operating system threads. If you want to acquire more than one permit at a time you can use withPermits, which allows specifying a number of permits to acquire. You can also use withPermitScoped or withPermitsScoped to acquire and release permits within the context of a scoped effect for composing with other resources.

For more advanced concurrency problems you can use the acquire and release operators directly, or their variants acquireN and releaseN, all of which return STM transactions. Thus, they can be composed to form larger STM transactions, for example acquiring permits from two different semaphores transactionally and later releasing them transactionally to safely synchronize on access to two different mutable variables.

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  4. def acquire: USTM[Unit]

    Acquires a single permit in transactional context.

  5. def acquireBetween(min: Long, max: Long): USTM[Long]

    Acquire at least min permits and at most max permits in a transactional context.

  6. def acquireN(n: Long): USTM[Unit]

    Acquires the specified number of permits in a transactional context.

  7. def acquireUpTo(max: Long): USTM[Long]

    Acquire at most max permits in a transactional context.

  8. final def asInstanceOf[T0]: T0
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  9. def available: USTM[Long]

    Returns the number of available permits in a transactional context.

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  18. final def notifyAll(): Unit
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  19. val permits: TRef[Long]
  20. def release: USTM[Unit]

    Releases a single permit in a transactional context.

  21. def releaseN(n: Long): USTM[Unit]

    Releases the specified number of permits in a transactional context

  22. final def synchronized[T0](arg0: => T0): T0
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  26. final def wait(arg0: Long): Unit
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  27. def withPermit[R, E, A](zio: ZIO[R, E, A])(implicit trace: Trace): ZIO[R, E, A]

    Executes the specified effect, acquiring a permit immediately before the effect begins execution and releasing it immediately after the effect completes execution, whether by success, failure, or interruption.

  28. def withPermitScoped(implicit trace: Trace): ZIO[Scope, Nothing, Unit]

    Returns a scoped effect that describes acquiring a permit as the acquire action and releasing it as the release action.

  29. def withPermits[R, E, A](n: Long)(zio: ZIO[R, E, A])(implicit trace: Trace): ZIO[R, E, A]

    Executes the specified effect, acquiring the specified number of permits immediately before the effect begins execution and releasing them immediately after the effect completes execution, whether by success, failure, or interruption.

  30. def withPermitsBetween[R, E, A](min: Long, max: Long)(zio: (Long) => ZIO[R, E, A])(implicit trace: Trace): ZIO[R, E, A]

    Executes the specified effect, acquiring at least min and at most max permits immediately before the effect begins execution and releasing them immediately after the effect completes execution, whether by success, failure, or interruption.

  31. def withPermitsBetweenScoped(min: Long, max: Long)(implicit trace: Trace): ZIO[Scope, Nothing, Long]

    Returns a scoped effect that describes acquiring at least min and at most max permits and releasing them when the scope is closed.

  32. def withPermitsScoped(n: Long)(implicit trace: Trace): ZIO[Scope, Nothing, Unit]

    Returns a scoped effect that describes acquiring the specified number of permits and releasing them when the scope is closed.

  33. def withPermitsUpTo[R, E, A](max: Long)(zio: (Long) => ZIO[R, E, A])(implicit trace: Trace): ZIO[R, E, A]

    Executes the specified effect, acquiring at most the specified number of permits immediately before the effect begins execution and releasing them immediately after the effect completes execution, whether by success, failure, or interruption.

  34. def withPermitsUpToScoped(max: Long)(implicit trace: Trace): ZIO[Scope, Nothing, Long]

    Returns a scoped effect that describes acquiring at most max permits and releasing them when the scope is closed.

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    (Since version 9)

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