All of reactor spec passing using Fiber#transfer only.

examples/reactor.rb

@@ -0,0 +1,64 @@
+#!/usr/bin/env ruby
+
+require 'fiber'
+
+module Async
+	class Reactor
+		def initialize
+			@fiber = nil
+			@waiting = []
+		end
+
+		def yield
+			@fiber.transfer
+		end
+
+		def resume(fiber)
+			previous = @fiber
+
+			@fiber = Fiber.current
+			fiber.transfer
+
+			@fiber = previous
+		end
+
+		def async(&block)
+			fiber = Fiber.new do
+				block.call
+				self.yield
+			end
+
+			resume(fiber)
+		end
+
+		# Wait for some event...
+		def wait
+			@waiting << Fiber.current
+			self.yield
+		end
+
+		def run
+			while @waiting.any?
+				fiber = @waiting.pop
+				resume(fiber)
+			end
+		end
+	end
+end
+
+reactor = Async::Reactor.new
+
+reactor.async do
+	puts "Hello World"
+	reactor.async do
+		puts "Goodbye World"
+		reactor.wait
+		puts "I'm back!"
+	end
+	puts "Foo Bar"
+end
+
+puts "Running"
+reactor.run
+puts "Finished"
+

lib/async/condition.rb

@@ -48,11 +48,13 @@ def empty?
 		# @see Task.yield which is responsible for handling value.
 		# @return [void]
 		def signal(value = nil)
+			reactor = Task.current.reactor
+
 			waiting = @waiting
 			@waiting = []
 
 			waiting.each do |fiber|
-				fiber.resume(value) if fiber.alive?
+				reactor.resume(fiber, value) if fiber.alive?
 			end
 
 			return nil

lib/async/reactor.rb

@@ -66,9 +66,28 @@ def initialize(parent = nil, selector: NIO::Selector.new)
 
 			@ready = []
 
+			# This is where we come back to when calling `#yield`.
+			@fiber = nil
+
 			@stopped = true
 		end
 
+		# Yield the current fiber and resume it on the next iteration of the event loop.
+		def yield(fiber = Fiber.current)
+			@ready << fiber if fiber
+
+			@fiber.transfer
+		end
+
+		def resume(fiber, *args)
+			previous = @fiber
+
+			@fiber = Fiber.current
+			fiber.transfer(*args)
+
+			@fiber = previous
+		end
+
 		def to_s
 			"<#{self.description} stopped=#{@stopped}>"
 		end
@@ -127,13 +146,6 @@ def << fiber
 			@ready << fiber
 		end
 
-		# Yield the current fiber and resume it on the next iteration of the event loop.
-		def yield(fiber = Fiber.current)
-			@ready << fiber
-
-			Fiber.yield
-		end
-
 		def finished?
 			super && @ready.empty?
 		end
@@ -151,7 +163,7 @@ def run(*args, &block)
 			@timers.wait do |interval|
 				if @ready.any?
 					@ready.each do |fiber|
-						fiber.resume if fiber.alive?
+						resume(fiber) if fiber.alive?
 					end
 
 					@ready.clear
@@ -179,7 +191,7 @@ def run(*args, &block)
 				# Async.logger.debug(self) {"Selecting with #{@children.count} fibers interval = #{interval.inspect}..."}
 				if monitors = @selector.select(interval)
 					monitors.each do |monitor|
-						monitor.value.resume
+						monitor.value.transfer
 					end
 				end
 			end until @stopped
@@ -215,11 +227,13 @@ def sleep(duration)
 
 			timer = self.after(duration) do
 				if fiber.alive?
-					fiber.resume
+					resume(fiber)
 				end
 			end
 
-			Task.yield
+			Task.yield do
+				self.yield(nil)
+			end
 		ensure
 			timer.cancel if timer
 		end
@@ -236,7 +250,7 @@ def timeout(duration)
 				if fiber.alive?
 					error = TimeoutError.new("execution expired")
 					error.set_backtrace backtrace
-					fiber.resume error
+					resume(fiber, error)
 				end
 			end
 

lib/async/task.rb

@@ -34,7 +34,7 @@ class Stop < Exception
 	class Task < Node
 		extend Forwardable
 
-		# Yield the unerlying `result` for the task. If the result
+		# Yield the underlying `result` for the task. If the result
 		# is an Exception, then that result will be raised an its
 		# exception.
 		# @return [Object] result of the task
@@ -44,7 +44,7 @@ def self.yield
 			if block_given?
 				result = yield
 			else
-				result = Fiber.yield
+				result = Task.current.reactor.yield
 			end
 
 			if result.is_a? Exception
@@ -86,6 +86,8 @@ def initialize(reactor, parent = Task.current?)
 					# Async.logger.debug("Task #{self} closing: #{$!}")
 					finish!
 				end
+
+				@reactor.yield(nil)
 			end
 		end
 
@@ -113,7 +115,7 @@ def yield
 		def run(*args)
 			if @status == :initialized
 				@status = :running
-				@fiber.resume(*args)
+				@reactor.resume(fiber, *args)
 			else
 				raise RuntimeError, "Task already running!"
 			end
@@ -149,7 +151,7 @@ def stop
 			@children.each(&:stop)
 
 			if @fiber.alive?
-				@fiber.resume(Stop.new)
+				@reactor.resume(@fiber, Stop.new)
 			end
 		end