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# Copyright 2022 Google LLC
#
# Licensed 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
#
# https://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.
module Gapic
module Rest
##
# @private
# A class to provide the Enumerable interface to an incoming stream of data.
#
# ThreadedEnumerator provides the enumerations over the individual chunks of data received from the server.
#
# @example normal iteration over resources.
# chunk = threaded_enumerator.next
#
# @attribute [r] in_q
# @return [Queue] Input queue.
# @attribute [r] out_q
# @return [Queue] Output queue.
class ThreadedEnumerator
attr_reader :in_q
attr_reader :out_q
# Spawns a new thread and does appropriate clean-up
# in case thread fails. Propagates exception back
# to main thread.
#
# @yieldparam in_q[Queue] input queue
# @yieldparam out_q[Queue] output queue
def initialize
@in_q = Queue.new
@out_q = Queue.new
Thread.new do
yield @in_q, @out_q
@out_q.enq nil
rescue StandardError => e
@out_q.push e
end
end
def next
@in_q.enq :next
chunk = @out_q.deq
if chunk.is_a? StandardError
@out_q.close
@in_q.close
raise chunk
end
if chunk.nil?
@out_q.close
@in_q.close
raise StopIteration
end
chunk
end
end
end
end
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