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#
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements. See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership. The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied. See the License for the
# specific language governing permissions and limitations
# under the License.
#
# Augment the standard python multithreaded Queue implementation to add a
# close() method so that threads blocking on the content of a queue can be
# notified if the queue is no longer in use.
require 'thread'
# Python nominally uses a bounded queue, but the code never establishes
# a maximum size; we therefore use Ruby's unbounded queue
class Qpid::Queue < ::Queue
DONE = Object.new
STOP = Object.new
def initialize
super
@error = nil
@listener = nil
@exc_listener = nil
@exc_listener_lock = Monitor.new
@thread = nil
end
def close(error = nil)
@error = error
put(DONE)
unless @thread.nil?
@thread.join()
@thread = nil
end
end
def get(block = true, timeout = nil)
unless timeout.nil?
raise NotImplementedError
end
result = pop(! block)
if result == DONE
# this guarantees that any other waiting threads or any future
# calls to get will also result in a Qpid::Closed exception
put(DONE)
raise Qpid::Closed.new(@error)
else
return result
end
end
alias :put :push
def exc_listen(&block)
@exc_listener_lock.synchronize do
@exc_listener = block
end
end
def listen(&block)
if ! block_given? && @thread
put(STOP)
@thread.join()
@thread = nil
end
# FIXME: There is a potential race since we could be changing one
# non-nil listener to another
@listener = block
if block_given? && @thread.nil?
@thread = Thread.new do
loop do
begin
o = get()
break if o == STOP
@listener.call(o)
rescue Qpid::Closed => e
@exc_listener.call(e) if @exc_listener
break
end
end
end
end
end
end
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