CountDownLatch implementation

In JDK we have CountDownLatch. It’d be useful to have a CountDownLatch which is aware of coroutines. It could have the following interface:

interface CountDownLatch {
    fun countDown()
    fun getCount(): Long
    suspend fun await()
    suspend fun await(time: Long, unit: TimeUnit = TimeUnit.MILLISECONDS): Boolean
}

I created two different implementations:

• First which uses a list of Continuations which are resumed when the counter goes down to 0,
• Second which uses ConflatedBroadcastChaneel holding current state of latch. Note that the countDown function in this version is suspending.

I’m sure a better(faster!) implementation could be made.

Looking for an opinion on this.

[elizarov]

I’m curious as to how I should go about implementing sendMessageAndWaitUntilProcessed without a CountDownLatch (or equivalent) in this gist: https://gist.github.com/Mahoney/52fa3184f5af6b00a380cb778cc551ca

@Mahoney You can use a locked mutex (that you unlock to signal event), or a semaphore (that you release to signal an event), or a channel (that you offer an event to) for this particular snippet. Any of those primitives would work.

[Mahoney]

I’m curious as to how I should go about implementing sendMessageAndWaitUntilProcessed without a CountDownLatch (or equivalent) in this gist: https://gist.github.com/Mahoney/52fa3184f5af6b00a380cb778cc551ca