101 lines
2.3 KiB
Ruby
101 lines
2.3 KiB
Ruby
# frozen_string_literal: true
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module Rake
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# A Promise object represents a promise to do work (a chore) in the
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# future. The promise is created with a block and a list of
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# arguments for the block. Calling value will return the value of
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# the promised chore.
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#
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# Used by ThreadPool.
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#
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class Promise # :nodoc: all
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NOT_SET = Object.new.freeze # :nodoc:
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attr_accessor :recorder
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# Create a promise to do the chore specified by the block.
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def initialize(args, &block)
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@mutex = Mutex.new
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@result = NOT_SET
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@error = NOT_SET
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@args = args
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@block = block
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end
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# Return the value of this promise.
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#
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# If the promised chore is not yet complete, then do the work
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# synchronously. We will wait.
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def value
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unless complete?
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stat :sleeping_on, item_id: object_id
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@mutex.synchronize do
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stat :has_lock_on, item_id: object_id
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chore
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stat :releasing_lock_on, item_id: object_id
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end
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end
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error? ? raise(@error) : @result
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end
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# If no one else is working this promise, go ahead and do the chore.
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def work
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stat :attempting_lock_on, item_id: object_id
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if @mutex.try_lock
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stat :has_lock_on, item_id: object_id
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chore
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stat :releasing_lock_on, item_id: object_id
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@mutex.unlock
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else
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stat :bailed_on, item_id: object_id
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end
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end
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private
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# Perform the chore promised
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def chore
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if complete?
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stat :found_completed, item_id: object_id
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return
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end
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stat :will_execute, item_id: object_id
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begin
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@result = @block.call(*@args)
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rescue Exception => e
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@error = e
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end
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stat :did_execute, item_id: object_id
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discard
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end
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# Do we have a result for the promise
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def result?
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! @result.equal?(NOT_SET)
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end
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# Did the promise throw an error
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def error?
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! @error.equal?(NOT_SET)
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end
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# Are we done with the promise
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def complete?
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result? || error?
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end
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# free up these items for the GC
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def discard
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@args = nil
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@block = nil
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end
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# Record execution statistics if there is a recorder
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def stat(*args)
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@recorder.call(*args) if @recorder
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end
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end
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end
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