Class: Concurrent::MutexCountDownLatch

Inherits:
Object
  • Object
show all
Defined in:
lib/concurrent/atomic/count_down_latch.rb

Overview

A synchronization object that allows one thread to wait on multiple other threads. The thread that will wait creates a ‘CountDownLatch` and sets the initial value (normally equal to the number of other threads). The initiating thread passes the latch to the other threads then waits for the other threads by calling the `#wait` method. Each of the other threads calls `#count_down` when done with its work. When the latch counter reaches zero the waiting thread is unblocked and continues with its work. A `CountDownLatch` can be used only once. Its value cannot be reset.

Direct Known Subclasses

CountDownLatch

Instance Method Summary collapse

Constructor Details

#initialize(count) ⇒ MutexCountDownLatch

Create a new ‘CountDownLatch` with the initial `count`.

Parameters:

  • count (Fixnum) —

    the initial count

Raises:

  • (ArgumentError) —

    if ‘count` is not an integer or is less than zero



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# File 'lib/concurrent/atomic/count_down_latch.rb', line 23

def initialize(count)
  unless count.is_a?(Fixnum) && count >= 0
    raise ArgumentError.new('count must be in integer greater than or equal zero')
  end
  @mutex = Mutex.new
  @condition = Condition.new
  @count = count
end

Instance Method Details

#count ⇒ Fixnum

The current value of the counter.

Returns:

  • (Fixnum) —

    the current value of the counter



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# File 'lib/concurrent/atomic/count_down_latch.rb', line 67

def count
  @mutex.synchronize { @count }
end

#count_down ⇒ Object

Signal the latch to decrement the counter. Will signal all blocked threads when the ‘count` reaches zero.



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# File 'lib/concurrent/atomic/count_down_latch.rb', line 55

def count_down
  @mutex.synchronize do
    @count -= 1 if @count > 0
    @condition.broadcast if @count == 0
  end
end

#wait(timeout = nil) ⇒ Boolean

Block on the latch until the counter reaches zero or until ‘timeout` is reached.

Parameters:

  • timeout (Fixnum) (defaults to: nil) —

    the number of seconds to wait for the counter or ‘nil` to block indefinitely

Returns:

  • (Boolean) —

    ‘true` if the `count` reaches zero else false on `timeout`



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# File 'lib/concurrent/atomic/count_down_latch.rb', line 39

def wait(timeout = nil)
  @mutex.synchronize do

    remaining = Condition::Result.new(timeout)
    while @count > 0 && remaining.can_wait?
      remaining = @condition.wait(@mutex, remaining.remaining_time)
    end

    @count == 0
  end
end