Add bin and edit workflow

bin/gems/eventmachine-1.2.7/lib/em/deferrable.rb

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+#--
+#
+# Author:: Francis Cianfrocca (gmail: blackhedd)
+# Homepage::  http://rubyeventmachine.com
+# Date:: 16 Jul 2006
+# 
+# See EventMachine and EventMachine::Connection for documentation and
+# usage examples.
+#
+#----------------------------------------------------------------------------
+#
+# Copyright (C) 2006-07 by Francis Cianfrocca. All Rights Reserved.
+# Gmail: blackhedd
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of either: 1) the GNU General Public License
+# as published by the Free Software Foundation; either version 2 of the
+# License, or (at your option) any later version; or 2) Ruby's License.
+# 
+# See the file COPYING for complete licensing information.
+#
+#---------------------------------------------------------------------------
+#
+# 
+
+module EventMachine
+  module Deferrable
+    autoload :Pool, 'em/deferrable/pool'
+
+    # Specify a block to be executed if and when the Deferrable object receives
+    # a status of :succeeded. See #set_deferred_status for more information.
+    #
+    # Calling this method on a Deferrable object whose status is not yet known
+    # will cause the callback block to be stored on an internal list.
+    # If you call this method on a Deferrable whose status is :succeeded, the
+    # block will be executed immediately, receiving the parameters given to the
+    # prior #set_deferred_status call.
+    #
+    #--
+    # If there is no status, add a callback to an internal list.
+    # If status is succeeded, execute the callback immediately.
+    # If status is failed, do nothing.
+    #
+    def callback &block
+      return unless block
+      @deferred_status ||= :unknown
+      if @deferred_status == :succeeded
+        block.call(*@deferred_args)
+      elsif @deferred_status != :failed
+        @callbacks ||= []
+        @callbacks.unshift block # << block
+      end
+      self
+    end
+
+    # Cancels an outstanding callback to &block if any. Undoes the action of #callback.
+    #
+    def cancel_callback block
+      @callbacks ||= []
+      @callbacks.delete block
+    end
+
+    # Specify a block to be executed if and when the Deferrable object receives
+    # a status of :failed. See #set_deferred_status for more information.
+    #--
+    # If there is no status, add an errback to an internal list.
+    # If status is failed, execute the errback immediately.
+    # If status is succeeded, do nothing.
+    #
+    def errback &block
+      return unless block
+      @deferred_status ||= :unknown
+      if @deferred_status == :failed
+        block.call(*@deferred_args)
+      elsif @deferred_status != :succeeded
+        @errbacks ||= []
+        @errbacks.unshift block # << block
+      end
+      self
+    end
+
+    # Cancels an outstanding errback to &block if any. Undoes the action of #errback.
+    #
+    def cancel_errback block
+      @errbacks ||= []
+      @errbacks.delete block
+    end
+
+    # Sets the "disposition" (status) of the Deferrable object. See also the large set of
+    # sugarings for this method.
+    # Note that if you call this method without arguments,
+    # no arguments will be passed to the callback/errback.
+    # If the user has coded these with arguments, then the
+    # user code will throw an argument exception.
+    # Implementors of deferrable classes <b>must</b>
+    # document the arguments they will supply to user callbacks.
+    #
+    # OBSERVE SOMETHING VERY SPECIAL here: you may call this method even
+    # on the INSIDE of a callback. This is very useful when a previously-registered
+    # callback wants to change the parameters that will be passed to subsequently-registered
+    # ones.
+    #
+    # You may give either :succeeded or :failed as the status argument.
+    #
+    # If you pass :succeeded, then all of the blocks passed to the object using the #callback
+    # method (if any) will be executed BEFORE the #set_deferred_status method returns. All of the blocks
+    # passed to the object using #errback will be discarded.
+    #
+    # If you pass :failed, then all of the blocks passed to the object using the #errback
+    # method (if any) will be executed BEFORE the #set_deferred_status method returns. All of the blocks
+    # passed to the object using # callback will be discarded.
+    #
+    # If you pass any arguments to #set_deferred_status in addition to the status argument,
+    # they will be passed as arguments to any callbacks or errbacks that are executed.
+    # It's your responsibility to ensure that the argument lists specified in your callbacks and
+    # errbacks match the arguments given in calls to #set_deferred_status, otherwise Ruby will raise
+    # an ArgumentError.
+    #
+    #--
+    # We're shifting callbacks off and discarding them as we execute them.
+    # This is valid because by definition callbacks are executed no more than
+    # once. It also has the magic effect of permitting recursive calls, which
+    # means that a callback can call #set_deferred_status and change the parameters
+    # that will be sent to subsequent callbacks down the chain.
+    #
+    # Changed @callbacks and @errbacks from push/shift to unshift/pop, per suggestion
+    # by Kirk Haines, to work around the memory leak bug that still exists in many Ruby
+    # versions.
+    #
+    # Changed 15Sep07: after processing callbacks or errbacks, CLEAR the other set of
+    # handlers. This gets us a little closer to the behavior of Twisted's "deferred,"
+    # which only allows status to be set once. Prior to making this change, it was possible
+    # to "succeed" a Deferrable (triggering its callbacks), and then immediately "fail" it,
+    # triggering its errbacks! That is clearly undesirable, but it's just as undesirable
+    # to raise an exception is status is set more than once on a Deferrable. The latter
+    # behavior would invalidate the idiom of resetting arguments by setting status from
+    # within a callback or errback, but more seriously it would cause spurious errors
+    # if a Deferrable was timed out and then an attempt was made to succeed it. See the
+    # comments under the new method #timeout.
+    #
+    def set_deferred_status status, *args
+      cancel_timeout
+      @errbacks ||= nil
+      @callbacks ||= nil
+      @deferred_status = status
+      @deferred_args = args
+      case @deferred_status
+      when :succeeded
+        if @callbacks
+          while cb = @callbacks.pop
+            cb.call(*@deferred_args)
+          end
+        end
+        @errbacks.clear if @errbacks
+      when :failed
+        if @errbacks
+          while eb = @errbacks.pop
+            eb.call(*@deferred_args)
+          end
+        end
+        @callbacks.clear if @callbacks
+      end
+    end
+
+
+    # Setting a timeout on a Deferrable causes it to go into the failed state after
+    # the Timeout expires (passing no arguments to the object's errbacks).
+    # Setting the status at any time prior to a call to the expiration of the timeout
+    # will cause the timer to be cancelled.
+    def timeout seconds, *args
+      cancel_timeout
+      me = self
+      @deferred_timeout = EventMachine::Timer.new(seconds) {me.fail(*args)}
+      self
+    end
+
+    # Cancels an outstanding timeout if any. Undoes the action of #timeout.
+    #
+    def cancel_timeout
+      @deferred_timeout ||= nil
+      if @deferred_timeout
+        @deferred_timeout.cancel
+        @deferred_timeout = nil
+      end
+    end
+
+
+    # Sugar for set_deferred_status(:succeeded, ...)
+    #
+    def succeed *args
+      set_deferred_status :succeeded, *args
+    end
+    alias set_deferred_success succeed
+
+    # Sugar for set_deferred_status(:failed, ...)
+    #
+    def fail *args
+      set_deferred_status :failed, *args
+    end
+    alias set_deferred_failure fail
+  end
+
+
+  # DefaultDeferrable is an otherwise empty class that includes Deferrable.
+  # This is very useful when you just need to return a Deferrable object
+  # as a way of communicating deferred status to some other part of a program.
+  class DefaultDeferrable
+    include Deferrable
+  end
+end