Thread safe counter

tsc.rb

class ThreadsafeCounter
  include Comparable

  def initialize(initial = 0)
    @mutex = Mutex.new
    @count = initial + 0
  end

  def incr
    @mutex.synchronize { @count += 1 }
    self
  end

  def decr
    @mutex.synchronize { @count -= 1 }
    self
  end

  def value
    # N.B. The + 0 here is because you cannot #dup BigNums, but they are real
    # objects. Real objects can be subject to race conditions otherwise avoided
    # with immediates. This appears to be the most portable API to use to ensure
    # you get a "safe" object back.
    @mutex.synchronize { @count + 0 }
  end
  alias to_i value

  def <=>(other)
    to_i <=> other.to_i
  end
end