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# frozen_string_literal: true
# Released under the MIT License.
# Copyright, 2022-2025, by Samuel Williams.
# Copyright, 2024, by Patrik Wenger.
# Copyright, 2025, by Shopify Inc.
module Async
# A composable synchronization primitive, which allows one task to wait for a number of other tasks to complete. It can be used in conjunction with {Semaphore} and/or {Barrier}.
#
# @deprecated `Async::Waiter` is deprecated, use `Async::Barrier` instead.
class Waiter
# Create a waiter instance.
#
# @parameter parent [Interface(:async) | Nil] The parent task to use for asynchronous operations.
# @parameter finished [Async::Condition] The condition to signal when a task completes.
def initialize(parent: nil, finished: Async::Condition.new)
warn("`Async::Waiter` is deprecated, use `Async::Barrier` instead.", uplevel: 1, category: :deprecated) if $VERBOSE
@finished = finished
@done = []
@parent = parent
end
# Execute a child task and add it to the waiter.
# @asynchronous Executes the given block concurrently.
def async(parent: (@parent or Task.current), **options, &block)
parent.async(**options) do |task|
yield(task)
ensure
@done << task
@finished.signal
end
end
# Wait for the first `count` tasks to complete.
# @parameter count [Integer | Nil] The number of tasks to wait for.
# @returns [Array(Async::Task)] If an integer is given, the tasks which have completed.
# @returns [Async::Task] Otherwise, the first task to complete.
def first(count = nil)
minimum = count || 1
while @done.size < minimum
@finished.wait
end
return @done.shift(*count)
end
# Wait for the first `count` tasks to complete.
# @parameter count [Integer | Nil] The number of tasks to wait for.
def wait(count = nil)
if count
first(count).map(&:wait)
else
first.wait
end
end
end
end
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