override fun tryReceive()

in kotlinx-coroutines-core/common/src/channels/BufferedChannel.kt [785:821]
19 lines of code
3 McCabe index (conditional complexity)

    override fun tryReceive(): ChannelResult<E> {
        // Read the `receivers` counter first.
        val r = receivers.value
        val sendersAndCloseStatusCur = sendersAndCloseStatus.value
        // Is this channel closed for receive?
        if (sendersAndCloseStatusCur.isClosedForReceive0) {
            return closed(closeCause)
        }
        // Do not try to receive an element if the plain `receive()` operation would suspend.
        val s = sendersAndCloseStatusCur.sendersCounter
        if (r >= s) return failure()
        // Let's try to retrieve an element!
        // The logic is similar to the plain `receive()` operation, with
        // the only difference that we store `INTERRUPTED_RCV` in case
        // the operation decides to suspend. This way, we can leverage
        // the unconditional `Fetch-and-Add` instruction.
        // One may consider storing `INTERRUPTED_RCV` instead of an actual waiter
        // on suspension (a.k.a. "no elements to retrieve") as a short-cut of
        // "suspending and cancelling immediately".
        return receiveImpl( // <-- this is an inline function
            // Store an already interrupted receiver in case of suspension.
            waiter = INTERRUPTED_RCV,
            // Finish when an element is successfully retrieved.
            onElementRetrieved = { element -> success(unwrapTyped(element)) },
            // On suspension, the `INTERRUPTED_RCV` token has been
            // installed, and this `tryReceive()` must fail.
            onSuspend = { segm, _, globalIndex ->
                // Emulate "cancelled" receive, thus invoking 'waitExpandBufferCompletion' manually,
                // because effectively there were no cancellation
                waitExpandBufferCompletion(globalIndex)
                segm.onSlotCleaned()
                failure()
            },
            // If the channel is closed, return the corresponding result.
            onClosed = { closed(closeCause) }
        )
    }