Promise

Define the result value of future.

Waits for an item to arrive from the source. Suspends until an item returns.

This is an utility method for direct waiting with Async, instead of going through listeners.

Link this cancellable to the cancellable group of the current async context.

Add this cancellable to the given group after removing it from the previous group in which it was.

Once data is available, pass it to the listener k. onComplete is always non-blocking.

Note that k's methods will be executed on the same thread as the Source, usually in sequence. It is hence important that the listener itself does not perform expensive operations.

Similar to poll, but instead of passing in a listener, directly return the value T if it is available.

Unlink this cancellable from its group.

Add k to the listener set of this source.

Issue a cancel request

Signal that listener k is dead (i.e. will always fail to acquire locks from now on), and should be removed from onComplete queues.

This permits original, (i.e. non-derived) sources like futures or channels to drop the listener from their waiting sets.

Checks whether data is available at present and pass it to k if so. Calls to poll are always synchronous and non-blocking.

The process is as follows:

• If no data is immediately available, return false immediately.
• If there is data available, attempt to lock k.
  • If k is no longer available, true is returned to signal this source's general availability.
  • If locking k succeeds:
    • If data is still available, complete k and return true.
    • Otherwise, unlock k and return false.

Note that in all cases, a return value of false indicates that k should be put into onComplete to receive data in a later point in time.