Class: Concurrent::Event

Inherits:
Synchronization::LockableObject
  • Object
show all
Defined in:
lib/concurrent/atomic/event.rb

Overview

Old school kernel-style event reminiscent of Win32 programming in C++.

When an Event is created it is in the unset state. Threads can choose to #wait on the event, blocking until released by another thread. When one thread wants to alert all blocking threads it calls the #set method which will then wake up all listeners. Once an Event has been set it remains set. New threads calling #wait will return immediately. An Event may be #reset at any time once it has been set.

Examples:

event = Concurrent::Event.new

t1 = Thread.new do
  puts "t1 is waiting"
  event.wait(1)
  puts "event ocurred"
end

t2 = Thread.new do
  puts "t2 calling set"
  event.set
end

[t1, t2].each(&:join)

# prints:
# t2 calling set
# t1 is waiting
# event ocurred

See Also:

Instance Method Summary (collapse)

Constructor Details

- (Event) initialize

Creates a new Event in the unset state. Threads calling #wait on the Event will block.



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# File 'lib/concurrent/atomic/event.rb', line 40

def initialize
  super
  synchronize { ns_initialize }
end

Instance Method Details

- (Boolean) reset

Reset a previously set event back to the unset state. Has no effect if the Event has not yet been set.

Returns:

  • (Boolean) —

    should always return true



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# File 'lib/concurrent/atomic/event.rb', line 68

def reset
  synchronize do
    if @set
      @set       = false
      @iteration +=1
    end
    true
  end
end

- (Boolean) set

Trigger the event, setting the state to set and releasing all threads waiting on the event. Has no effect if the Event has already been set.

Returns:

  • (Boolean) —

    should always return true



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# File 'lib/concurrent/atomic/event.rb', line 56

def set
  synchronize { ns_set }
end

- (Boolean) set?

Is the object in the set state?

Returns:

  • (Boolean) —

    indicating whether or not the Event has been set



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# File 'lib/concurrent/atomic/event.rb', line 48

def set?
  synchronize { @set }
end

- (Boolean) try?

Returns:

  • (Boolean) 


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# File 'lib/concurrent/atomic/event.rb', line 60

def try?
  synchronize { @set ? false : ns_set }
end

- (Boolean) wait(timeout = nil)

Wait a given number of seconds for the Event to be set by another thread. Will wait forever when no timeout value is given. Returns immediately if the Event has already been set.

Returns:

  • (Boolean) —

    true if the Event was set before timeout else false



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# File 'lib/concurrent/atomic/event.rb', line 83

def wait(timeout = nil)
  synchronize do
    unless @set
      iteration = @iteration
      ns_wait_until(timeout) { iteration < @iteration || @set }
    else
      true
    end
  end
end