Class: Async::Condition

Inherits:
Object
  • Object
show all
Defined in:
lib/async/condition.rb

Overview

A synchronization primative, which allows fibers to wait until a particular condition is triggered. Signalling the condition directly resumes the waiting fibers and thus blocks the caller.

Direct Known Subclasses

Notification

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Condition

Returns a new instance of Condition.



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# File 'lib/async/condition.rb', line 30

def initialize
  @waiting = []
end

Instance Method Details

#empty? ⇒ Boolean

Is any fiber waiting on this notification?

Returns:

  • (Boolean) 


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# File 'lib/async/condition.rb', line 51

def empty?
  @waiting.empty?
end

#signal(value = nil) ⇒ void

This method returns an undefined value.

Signal to a given task that it should resume operations.

Parameters:

  • value (defaults to: nil) —

    The value to return to the waiting fibers.

See Also:



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# File 'lib/async/condition.rb', line 59

def signal(value = nil)
  waiting = @waiting
  @waiting = []
  
  waiting.each do |fiber|
    fiber.resume(value) if fiber.alive?
  end
  
  return nil
end

#wait ⇒ Object

Queue up the current fiber and wait on yielding the task.

Returns:

  • (Object) 


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# File 'lib/async/condition.rb', line 36

def wait
  fiber = Fiber.current
  @waiting << fiber
  
  Task.yield
  
  # It would be nice if there was a better construct for this. We only need to invoke #delete if the task was not resumed normally. This can only occur with `raise` and `throw`. But there is no easy way to detect this.
# ensure when not return or ensure when raise, throw
rescue Exception
  @waiting.delete(fiber)
  raise
end