Module: Functor::Method

Defined in:
lib/functor.rb

Class Method Summary collapse

Class Method Details

.included(k) ⇒ Object 



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# File 'lib/functor.rb', line 11

def self.included( k )
        
  def k.functor_cache
    @functor_cache ||= Hash.new { |hash, key| hash[key] = [ {},{},{},{} ] }
  end
  
  def k.functor_cache_config(options={})
    @functor_cache_config = ( @functor_cache_config || Functor.cache_config ).merge(options)
  end
  
  def k.functor( name, *pattern, &action )
    _functor( name, false, *pattern, &action)
  end
  
  def k.functor_with_self( name, *pattern, &action )
    _functor( name, true, *pattern, &action)
  end
  
  # undefined methods beginning with '_' can be used as wildcards in Functor patterns
  def k.method_missing(name, *args)
    args.empty? && name.to_s =~ /^_/  ?  lambda { |args| true }  :  super
  end
  
  private
  
  def k._functor( name, with_self=false, *pattern, &action)
    name = name.to_s
    mc = functor_cache[name]  # grab the cache tiers for The Method
    cache_size, cache_base = functor_cache_config[:size], functor_cache_config[:base]
    c0_size, c1_size, c2_size, c3_size = cache_size * 4, cache_size * 3, cache_size * 2, cache_size
    c1_thresh,c2_thresh,c3_thresh = cache_base.to_i, (cache_base ** 2).to_i, (cache_base ** 3).to_i
    old_method = instance_method(name) if method_defined?( name ) # grab The Method's current incarnation        
    define_method( name, action ) # redefine The Method
    newest = instance_method(name) # grab newly redefined The Method
    
    # Recursively redefine The Method using the newest and previous incarnations
    define_method( name ) do | *args |
      match_args = with_self ? [self] + args : args
      sig = match_args.hash
      if meth = mc[3][sig]  # check caches from top down
        meth[0].bind(self).call(*args)
      elsif meth = mc[2][sig]
        meth[1] += 1  # increment hit count
        mc[3][sig] = mc[2].delete(sig) if meth[1] > c3_thresh # promote sig if it has enough hits
        (mc[0], mc[1], mc[2], mc[3] = mc[1], mc[2], mc[3], {}) if mc[3].size >= c3_size # cascade if c3 is full
        meth[0].bind(self).call(*args)
      elsif meth = mc[1][sig]
        meth[1] += 1
        mc[2][sig] = mc[1].delete(sig) if meth[1] > c2_thresh
        mc[0], mc[1], mc[2] = mc[1], mc[2], {} if mc[2].size >= c2_size
        meth[0].bind(self).call(*args)
      elsif meth = mc[0][sig]
        meth[1] += 1
        mc[1][sig] = mc[0].delete(sig) if meth[1] > c1_thresh 
        mc[0], mc[1] = mc[1], {} if mc[1].size >= c1_size
        meth[0].bind(self).call(*args)
      elsif Functor.match?(match_args, pattern) # not cached?  Try newest meth/pat.
        (mc[0], mc[1], mc[2], mc[3] = mc[1], mc[2], mc[3], {})  if mc[3].size >= c3_size
        mc[3][sig] = [newest, 0]  # methods are cached as [ method, counter ]
        newest.bind(self).call(*args)
      elsif old_method  # or call the previous incarnation of The Method
        old_method.bind(self).call(*args)
      else  # and if there are no older incarnations, whine about it
        raise NoMatch.new( "No functor matches the given arguments for method :#{name}." )
      end
    end 
  end
  
end