module Concurrent::AtomicDirectUpdate

def try_update
  old_value = get
  new_value = yield old_value
  return unless compare_and_set old_value, new_value
  new_value
end

def try_update!
  old_value = get
  new_value = yield old_value
  unless compare_and_set(old_value, new_value)
    if $VERBOSE
      raise ConcurrentUpdateError, "Update failed"
    else
      raise ConcurrentUpdateError, "Update failed", ConcurrentUpdateError::CONC_UP_ERR_BACKTRACE
    end
  end
  new_value
end

def update
  true until compare_and_set(old_value = get, new_value = yield(old_value))
  new_value
end