57 lines
1.6 KiB
Ruby
57 lines
1.6 KiB
Ruby
# frozen_string_literal: true
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# Released under the MIT License.
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# Copyright, 2022-2024, by Samuel Williams.
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# Copyright, 2024, by Patrik Wenger.
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module Async
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# 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}.
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class Waiter
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# Create a waiter instance.
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#
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# @parameter parent [Interface(:async) | Nil] The parent task to use for asynchronous operations.
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# @parameter finished [Async::Condition] The condition to signal when a task completes.
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def initialize(parent: nil, finished: Async::Condition.new)
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@finished = finished
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@done = []
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@parent = parent
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end
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# Execute a child task and add it to the waiter.
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# @asynchronous Executes the given block concurrently.
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def async(parent: (@parent or Task.current), **options, &block)
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parent.async(**options) do |task|
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yield(task)
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ensure
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@done << task
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@finished.signal
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end
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end
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# Wait for the first `count` tasks to complete.
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# @parameter count [Integer | Nil] The number of tasks to wait for.
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# @returns [Array(Async::Task)] If an integer is given, the tasks which have completed.
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# @returns [Async::Task] Otherwise, the first task to complete.
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def first(count = nil)
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minimum = count || 1
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while @done.size < minimum
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@finished.wait
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end
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return @done.shift(*count)
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end
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# Wait for the first `count` tasks to complete.
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# @parameter count [Integer | Nil] The number of tasks to wait for.
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def wait(count = nil)
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if count
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first(count).map(&:wait)
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else
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first.wait
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end
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end
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end
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end
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