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Added monitor.rb from 1.9.2p290.

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commit 413ebbf2b23483af7eb5a4090273d97d84923a25 1 parent f5d6493
@brixen brixen authored
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  1. +277 −0 lib/19/monitor.rb
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277 lib/19/monitor.rb
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+=begin
+
+= monitor.rb
+
+Copyright (C) 2001 Shugo Maeda <shugo@ruby-lang.org>
+
+This library is distributed under the terms of the Ruby license.
+You can freely distribute/modify this library.
+
+== example
+
+This is a simple example.
+
+ require 'monitor.rb'
+
+ buf = []
+ buf.extend(MonitorMixin)
+ empty_cond = buf.new_cond
+
+ # consumer
+ Thread.start do
+ loop do
+ buf.synchronize do
+ empty_cond.wait_while { buf.empty? }
+ print buf.shift
+ end
+ end
+ end
+
+ # producer
+ while line = ARGF.gets
+ buf.synchronize do
+ buf.push(line)
+ empty_cond.signal
+ end
+ end
+
+The consumer thread waits for the producer thread to push a line
+to buf while buf.empty?, and the producer thread (main thread)
+reads a line from ARGF and push it to buf, then call
+empty_cond.signal.
+
+=end
+
+require 'thread'
+
+#
+# Adds monitor functionality to an arbitrary object by mixing the module with
+# +include+. For example:
+#
+# require 'monitor'
+#
+# buf = []
+# buf.extend(MonitorMixin)
+# empty_cond = buf.new_cond
+#
+# # consumer
+# Thread.start do
+# loop do
+# buf.synchronize do
+# empty_cond.wait_while { buf.empty? }
+# print buf.shift
+# end
+# end
+# end
+#
+# # producer
+# while line = ARGF.gets
+# buf.synchronize do
+# buf.push(line)
+# empty_cond.signal
+# end
+# end
+#
+# The consumer thread waits for the producer thread to push a line
+# to buf while buf.empty?, and the producer thread (main thread)
+# reads a line from ARGF and push it to buf, then call
+# empty_cond.signal.
+#
+module MonitorMixin
+ #
+ # FIXME: This isn't documented in Nutshell.
+ #
+ # Since MonitorMixin.new_cond returns a ConditionVariable, and the example
+ # above calls while_wait and signal, this class should be documented.
+ #
+ class ConditionVariable
+ class Timeout < Exception; end
+
+ #
+ # Releases the lock held in the associated monitor and waits; reacquires the lock on wakeup.
+ #
+ # If +timeout+ is given, this method returns after +timeout+ seconds passed,
+ # even if no other thread doesn't signal.
+ #
+ def wait(timeout = nil)
+ @monitor.__send__(:mon_check_owner)
+ count = @monitor.__send__(:mon_exit_for_cond)
+ begin
+ @cond.wait(@monitor.instance_variable_get("@mon_mutex"), timeout)
+ return true
+ ensure
+ @monitor.__send__(:mon_enter_for_cond, count)
+ end
+ end
+
+ #
+ # Calls wait repeatedly while the given block yields a truthy value.
+ #
+ def wait_while
+ while yield
+ wait
+ end
+ end
+
+ #
+ # Calls wait repeatedly until the given block yields a truthy value.
+ #
+ def wait_until
+ until yield
+ wait
+ end
+ end
+
+ #
+ # Wakes up the first thread in line waiting for this lock.
+ #
+ def signal
+ @monitor.__send__(:mon_check_owner)
+ @cond.signal
+ end
+
+ #
+ # Wakes up all threads waiting for this lock.
+ #
+ def broadcast
+ @monitor.__send__(:mon_check_owner)
+ @cond.broadcast
+ end
+
+ private
+
+ def initialize(monitor)
+ @monitor = monitor
+ @cond = ::ConditionVariable.new
+ end
+ end
+
+ def self.extend_object(obj)
+ super(obj)
+ obj.__send__(:mon_initialize)
+ end
+
+ #
+ # Attempts to enter exclusive section. Returns +false+ if lock fails.
+ #
+ def mon_try_enter
+ if @mon_owner != Thread.current
+ unless @mon_mutex.try_lock
+ return false
+ end
+ @mon_owner = Thread.current
+ end
+ @mon_count += 1
+ return true
+ end
+ # For backward compatibility
+ alias try_mon_enter mon_try_enter
+
+ #
+ # Enters exclusive section.
+ #
+ def mon_enter
+ if @mon_owner != Thread.current
+ @mon_mutex.lock
+ @mon_owner = Thread.current
+ end
+ @mon_count += 1
+ end
+
+ #
+ # Leaves exclusive section.
+ #
+ def mon_exit
+ mon_check_owner
+ @mon_count -=1
+ if @mon_count == 0
+ @mon_owner = nil
+ @mon_mutex.unlock
+ end
+ end
+
+ #
+ # Enters exclusive section and executes the block. Leaves the exclusive
+ # section automatically when the block exits. See example under
+ # +MonitorMixin+.
+ #
+ def mon_synchronize
+ mon_enter
+ begin
+ yield
+ ensure
+ mon_exit
+ end
+ end
+ alias synchronize mon_synchronize
+
+ #
+ # Creates a new MonitorMixin::ConditionVariable associated with the
+ # receiver.
+ #
+ def new_cond
+ return ConditionVariable.new(self)
+ end
+
+ private
+
+ def initialize(*args)
+ super
+ mon_initialize
+ end
+
+ def mon_initialize
+ @mon_owner = nil
+ @mon_count = 0
+ @mon_mutex = Mutex.new
+ end
+
+ def mon_check_owner
+ if @mon_owner != Thread.current
+ raise ThreadError, "current thread not owner"
+ end
+ end
+
+ def mon_enter_for_cond(count)
+ @mon_owner = Thread.current
+ @mon_count = count
+ end
+
+ def mon_exit_for_cond
+ count = @mon_count
+ @mon_owner = nil
+ @mon_count = 0
+ return count
+ end
+end
+
+class Monitor
+ include MonitorMixin
+ alias try_enter try_mon_enter
+ alias enter mon_enter
+ alias exit mon_exit
+end
+
+
+# Documentation comments:
+# - All documentation comes from Nutshell.
+# - MonitorMixin.new_cond appears in the example, but is not documented in
+# Nutshell.
+# - All the internals (internal modules Accessible and Initializable, class
+# ConditionVariable) appear in RDoc. It might be good to hide them, by
+# making them private, or marking them :nodoc:, etc.
+# - The entire example from the RD section at the top is replicated in the RDoc
+# comment for MonitorMixin. Does the RD section need to remain?
+# - RDoc doesn't recognise aliases, so we have mon_synchronize documented, but
+# not synchronize.
+# - mon_owner is in Nutshell, but appears as an accessor in a separate module
+# here, so is hard/impossible to RDoc. Some other useful accessors
+# (mon_count and some queue stuff) are also in this module, and don't appear
+# directly in the RDoc output.
+# - in short, it may be worth changing the code layout in this file to make the
+# documentation easier
+
+# Local variables:
+# mode: Ruby
+# tab-width: 8
+# End:
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