thread.rb

#--
# Be very careful about calling raise in here! Thread has its own
# raise which, if you're calling raise, you probably don't want. Use
# Kernel.raise to call the proper raise.
#++

class Thread
  MUTEX_FOR_THREAD_EXCLUSIVE = Mutex.new

  def self.exclusive
    MUTEX_FOR_THREAD_EXCLUSIVE.synchronize { yield }
  end

  attr_reader :recursive_objects

  # Implementation note: ideally, the recursive_objects
  # lookup table would be different per method call.
  # Currently it doesn't cause problems, but if ever
  # a method :foo calls a method :bar which could
  # recurse back to :foo, it could require making
  # the tables independant.

  def self.recursion_guard(obj)
    id = obj.object_id
    objects = current.recursive_objects
    objects[id] = true

    begin
      yield
    ensure
      objects.delete id
    end
  end

  def self.guarding?(obj)
    current.recursive_objects[obj.object_id]
  end

  # detect_recursion will return if there's a recursion
  # on obj (or the pair obj+paired_obj).
  # If there is one, it returns true.
  # Otherwise, it will yield once and return false.

  def self.detect_recursion(obj, paired_obj=undefined)
    id = obj.object_id
    pair_id = paired_obj.object_id
    objects = current.recursive_objects

    case objects[id]

      # Default case, we haven't seen +obj+ yet, so we add it and run the block.
    when nil
      objects[id] = pair_id
      begin
        yield
      ensure
        objects.delete id
      end

      # We've seen +obj+ before and it's got multiple paired objects associated
      # with it, so check the pair and yield if there is no recursion.
    when Rubinius::LookupTable
      return true if objects[id][pair_id]
      objects[id][pair_id] = true

      begin
        yield
      ensure
        objects[id].delete pair_id
      end

      # We've seen +obj+ with one paired object, so check the stored one for
      # recursion.
      #
      # This promotes the value to a LookupTable since there is another new paired
      # object.
    else
      previous = objects[id]
      return true if previous == pair_id

      objects[id] = Rubinius::LookupTable.new(previous => true, pair_id => true)

      begin
        yield
      ensure
        objects[id] = previous
      end
    end

    false
  end

  # Similar to detect_recursion, but will short circuit all inner recursion
  # levels (using a throw)

  class InnerRecursionDetected < Exception; end

  def self.detect_outermost_recursion(obj, paired_obj=undefined, &block)
    rec = current.recursive_objects

    if rec[:__detect_outermost_recursion__]
      if detect_recursion(obj, paired_obj, &block)
        raise InnerRecursionDetected
      end
      false
    else
      begin
        rec[:__detect_outermost_recursion__] = true

        begin
          detect_recursion(obj, paired_obj, &block)
        rescue InnerRecursionDetected
          return true
        end

        return nil
      ensure
        rec.delete :__detect_outermost_recursion__
      end
    end
  end

  def randomizer
    @randomizer ||= Rubinius::Randomizer.new
  end

  def backtrace
    mri_backtrace.map do |tup|
      code = tup[0]
      line = tup[1]
      is_block = tup[2]
      name = tup[3]

      "#{code.active_path}:#{line}:in `#{name}'"
    end
  end

  # This is a class in MRI, although you can't initialize it.
  class Backtrace
    # Stores location of a single call frame, available since Ruby 2.0.
    class Location
      attr_reader :label
      attr_reader :absolute_path
      attr_reader :lineno

      def initialize(label, absolute_path, lineno)
        @label         = label
        @absolute_path = absolute_path
        @lineno        = lineno
      end

      alias_method :base_label, :label

      ##
      # The MRI documentation states this method should return the file name. In
      # reality however this method just returns the full path.
      #
      # Rubinius here sticks to whatever the documentation specifies, thus we
      # return only the filename.
      #
      def path
        File.basename(absolute_path)
      end

      def to_s
        "#{absolute_path}:#{lineno}:in `#{label}'"
      end

      def inspect
        to_s
      end
    end
  end
end