BoolChannel: Don't spawn fiber

src/lavinmq/bool_channel.cr

@@ -1,46 +1,69 @@
 # A class which has two channels, one for which a state is true
 # and the other for when the state if false
 class BoolChannel
-  getter when_true = Channel(Nil).new
-  getter when_false = Channel(Nil).new
-  @value = Channel(Bool).new
+  class StateChannel < Channel(Nil)
+    class EndlessQueue < Deque(Nil)
+      property? empty : Bool = true
+
+      def shift(&)
+        yield if empty?
+      end
+
+      def push(value : T)
+        raise "Can't push to an EndlessQueue"
+      end
+    end
+
+    @queue = EndlessQueue.new
+
+    def activate
+      @lock.sync do
+        @queue.as(EndlessQueue).empty = false
+        while receiver_ptr = dequeue_receiver
+          receiver_ptr.value.data = nil
+          receiver_ptr.value.state = DeliveryState::Delivered
+          receiver_ptr.value.fiber.enqueue
+        end
+      end
+    end
+
+    def deactivate
+      @lock.sync do
+        @queue.as(EndlessQueue).empty = true
+      end
+    end
+  end
+
+  getter when_true = StateChannel.new
+  getter when_false = StateChannel.new
+  @value : Atomic(Bool)
 
   def initialize(value : Bool)
-    spawn(name: "BoolChannel#send_loop") do
-      send_loop(value)
+    @value = Atomic.new(value)
+    if value
+      @when_true.activate
+    else
+      @when_false.activate
     end
   end
 
-  def set(value : Bool)
-    @value.send value
-  rescue ::Channel::ClosedError
-    Log.debug { "BoolChannel closed, could not set value" }
+  def value
+    @value.get
   end
 
-  def value : Bool
-    select
-    when when_true.receive
-      true
-    when when_false.receive
-      false
+  def set(value : Bool)
+    return if @value.swap(value) == value
+    if value
+      @when_false.deactivate
+      @when_true.activate
+    else
+      @when_true.deactivate
+      @when_false.activate
     end
   end
 
   def close
     @when_true.close
     @when_false.close
-    @value.close
-  end
-
-  private def send_loop(value)
-    loop do
-      channel = value ? @when_true : @when_false
-      select
-      when value = @value.receive
-      when channel.send nil
-        Fiber.yield # Improves fairness by allowing the receiving fiber to run instead of notifying all waiting fibers
-      end
-    end
-  rescue ::Channel::ClosedError
   end
 end