# * George Moschovitis  <gm@navel.gr>
# (c) 2004-2005 Navel, all rights reserved.
# $Id: hash.rb 1 2005-04-11 11:04:30Z gmosx $

require 'sync'

module Glue 

# A thread-safe hash. We use a sync object instead of a mutex,
# because it is re-entrant. An exclusive lock is needed when 
# writing, a shared lock IS NEEDED when reading
# uses the delegator pattern to allow for multiple
# implementations!

class SafeHash < Hash
	attr :sync

	# gmosx: delegator is not used.
	#
	def initialize(delegator = nil)
		@sync = ::Sync.new
	end

	def [](key)
		@sync.synchronize(::Sync::SH) { super }
	end

	def []=(key, value)
		@sync.synchronize(::Sync::EX) { super }
	end

	def delete(key)
		@sync.synchronize(::Sync::EX) { super }
	end

	def clear
		@sync.synchronize(::Sync::EX) {	super }
	end

	def size
		@sync.synchronize(::Sync::SH) {	super }
	end

	def values
		@sync.synchronize(::Sync::SH) { super }
	end

	def keys
		@sync.synchronize(::Sync::SH) { super }
	end

end 

# A thread-safe hash. We use a sync object instead of a mutex,
# because it is re-entrant. An exclusive lock is needed when 
# writing, a shared lock IS NEEDED when reading.
#
# === Design
#
# This class uses the delegator pattern. However we dont use rubys
# delegation facilities, they are more general and powerfull than we
# need here (and slower). Instead a custom (but simple) solution is
# used.
#
# === Example
#
# hash = SafeHashDelegator.new(Hash.new)
# hash = SafeHashDelegator.new(Hash.new)

class SafeHashDelegator < Hash
	attr :delegate, :sync

	def initialize(delegate)
		@delegate = delegate
		@sync = ::Sync.new
	end

	def [](key)
		@sync.synchronize(::Sync::SH) {
			@delegate[key]
		}
  end

  def []=(key, value)
		@sync.synchronize(::Sync::EX) {
			@delegate[key] = value
		}
  end

	def delete(key)
		@sync.synchronize(::Sync::EX) {
			@delegate.delete(key)
		}
	end

	def clear
		@sync.synchronize(::Sync::EX) {
			@delegate.clear
		}
	end

	def size
		@sync.synchronize(::Sync::SH) {
			@delegate.size()
		}
	end

	def values
		@sync.synchronize(::Sync::SH) {
			@delegate.values()
		}
	end

	def keys
		@sync.synchronize(::Sync::SH) {
			@delegate.keys()
		}
	end

end

end