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require 'drb/drb'
require 'thread'
##
# A module to implement the Linda distributed computing paradigm in Ruby.
#
# Rinda is part of DRb (dRuby).
#
# == Example(s)
#
# See the sample/drb/ directory in the Ruby distribution, from 1.8.2 onwards.
#
#--
# TODO
# == Introduction to Linda/rinda?
#
# == Why is this library separate from DRb?
module Rinda
##
# Rinda error base class
class RindaError < RuntimeError; end
##
# Raised when a hash-based tuple has an invalid key.
class InvalidHashTupleKey < RindaError; end
##
# Raised when trying to use a canceled tuple.
class RequestCanceledError < ThreadError; end
##
# Raised when trying to use an expired tuple.
class RequestExpiredError < ThreadError; end
##
# A tuple is the elementary object in Rinda programming.
# Tuples may be matched against templates if the tuple and
# the template are the same size.
class Tuple
##
# Creates a new Tuple from +ary_or_hash+ which must be an Array or Hash.
def initialize(ary_or_hash)
if hash?(ary_or_hash)
init_with_hash(ary_or_hash)
else
init_with_ary(ary_or_hash)
end
end
##
# The number of elements in the tuple.
def size
@tuple.size
end
##
# Accessor method for elements of the tuple.
def [](k)
@tuple[k]
end
##
# Fetches item +k+ from the tuple.
def fetch(k)
@tuple.fetch(k)
end
##
# Iterate through the tuple, yielding the index or key, and the
# value, thus ensuring arrays are iterated similarly to hashes.
def each # FIXME
if Hash === @tuple
@tuple.each { |k, v| yield(k, v) }
else
@tuple.each_with_index { |v, k| yield(k, v) }
end
end
##
# Return the tuple itself
def value
@tuple
end
private
def hash?(ary_or_hash)
ary_or_hash.respond_to?(:keys)
end
##
# Munges +ary+ into a valid Tuple.
def init_with_ary(ary)
@tuple = Array.new(ary.size)
@tuple.size.times do |i|
@tuple[i] = ary[i]
end
end
##
# Ensures +hash+ is a valid Tuple.
def init_with_hash(hash)
@tuple = Hash.new
hash.each do |k, v|
raise InvalidHashTupleKey unless String === k
@tuple[k] = v
end
end
end
##
# Templates are used to match tuples in Rinda.
class Template < Tuple
##
# Matches this template against +tuple+. The +tuple+ must be the same
# size as the template. An element with a +nil+ value in a template acts
# as a wildcard, matching any value in the corresponding position in the
# tuple. Elements of the template match the +tuple+ if the are #== or
# #===.
#
# Template.new([:foo, 5]).match Tuple.new([:foo, 5]) # => true
# Template.new([:foo, nil]).match Tuple.new([:foo, 5]) # => true
# Template.new([String]).match Tuple.new(['hello']) # => true
#
# Template.new([:foo]).match Tuple.new([:foo, 5]) # => false
# Template.new([:foo, 6]).match Tuple.new([:foo, 5]) # => false
# Template.new([:foo, nil]).match Tuple.new([:foo]) # => false
# Template.new([:foo, 6]).match Tuple.new([:foo]) # => false
def match(tuple)
return false unless tuple.respond_to?(:size)
return false unless tuple.respond_to?(:fetch)
return false unless self.size == tuple.size
each do |k, v|
begin
it = tuple.fetch(k)
rescue
return false
end
next if v.nil?
next if v == it
next if v === it
return false
end
return true
end
##
# Alias for #match.
def ===(tuple)
match(tuple)
end
end
##
# <i>Documentation?</i>
class DRbObjectTemplate
##
# Creates a new DRbObjectTemplate that will match against +uri+ and +ref+.
def initialize(uri=nil, ref=nil)
@drb_uri = uri
@drb_ref = ref
end
##
# This DRbObjectTemplate matches +ro+ if the remote object's drburi and
# drbref are the same. +nil+ is used as a wildcard.
def ===(ro)
return true if super(ro)
unless @drb_uri.nil?
return false unless (@drb_uri === ro.__drburi rescue false)
end
unless @drb_ref.nil?
return false unless (@drb_ref === ro.__drbref rescue false)
end
true
end
end
##
# TupleSpaceProxy allows a remote Tuplespace to appear as local.
class TupleSpaceProxy
##
# Creates a new TupleSpaceProxy to wrap +ts+.
def initialize(ts)
@ts = ts
end
##
# Adds +tuple+ to the proxied TupleSpace. See TupleSpace#write.
def write(tuple, sec=nil)
@ts.write(tuple, sec)
end
##
# Takes +tuple+ from the proxied TupleSpace. See TupleSpace#take.
def take(tuple, sec=nil, &block)
port = []
@ts.move(DRbObject.new(port), tuple, sec, &block)
port[0]
end
##
# Reads +tuple+ from the proxied TupleSpace. See TupleSpace#read.
def read(tuple, sec=nil, &block)
@ts.read(tuple, sec, &block)
end
##
# Reads all tuples matching +tuple+ from the proxied TupleSpace. See
# TupleSpace#read_all.
def read_all(tuple)
@ts.read_all(tuple)
end
##
# Registers for notifications of event +ev+ on the proxied TupleSpace.
# See TupleSpace#notify
def notify(ev, tuple, sec=nil)
@ts.notify(ev, tuple, sec)
end
end
##
# An SimpleRenewer allows a TupleSpace to check if a TupleEntry is still
# alive.
class SimpleRenewer
include DRbUndumped
##
# Creates a new SimpleRenewer that keeps an object alive for another +sec+
# seconds.
def initialize(sec=180)
@sec = sec
end
##
# Called by the TupleSpace to check if the object is still alive.
def renew
@sec
end
end
end
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