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# frozen_string_literal: false
require 'monitor'
require 'drb/drb'
require_relative 'rinda'
require 'forwardable'
module Rinda
##
# A TupleEntry is a Tuple (i.e. a possible entry in some Tuplespace)
# together with expiry and cancellation data.
class TupleEntry
include DRbUndumped
attr_accessor :expires
##
# Creates a TupleEntry based on +ary+ with an optional renewer or expiry
# time +sec+.
#
# A renewer must implement the +renew+ method which returns a Numeric,
# nil, or true to indicate when the tuple has expired.
def initialize(ary, sec=nil)
@cancel = false
@expires = nil
@tuple = make_tuple(ary)
@renewer = nil
renew(sec)
end
##
# Marks this TupleEntry as canceled.
def cancel
@cancel = true
end
##
# A TupleEntry is dead when it is canceled or expired.
def alive?
!canceled? && !expired?
end
##
# Return the object which makes up the tuple itself: the Array
# or Hash.
def value; @tuple.value; end
##
# Returns the canceled status.
def canceled?; @cancel; end
##
# Has this tuple expired? (true/false).
#
# A tuple has expired when its expiry timer based on the +sec+ argument to
# #initialize runs out.
def expired?
return true unless @expires
return false if @expires > Time.now
return true if @renewer.nil?
renew(@renewer)
return true unless @expires
return @expires < Time.now
end
##
# Reset the expiry time according to +sec_or_renewer+.
#
# +nil+:: it is set to expire in the far future.
# +true+:: it has expired.
# Numeric:: it will expire in that many seconds.
#
# Otherwise the argument refers to some kind of renewer object
# which will reset its expiry time.
def renew(sec_or_renewer)
sec, @renewer = get_renewer(sec_or_renewer)
@expires = make_expires(sec)
end
##
# Returns an expiry Time based on +sec+ which can be one of:
# Numeric:: +sec+ seconds into the future
# +true+:: the expiry time is the start of 1970 (i.e. expired)
# +nil+:: it is Tue Jan 19 03:14:07 GMT Standard Time 2038 (i.e. when
# UNIX clocks will die)
def make_expires(sec=nil)
case sec
when Numeric
Time.now + sec
when true
Time.at(1)
when nil
Time.at(2**31-1)
end
end
##
# Retrieves +key+ from the tuple.
def [](key)
@tuple[key]
end
##
# Fetches +key+ from the tuple.
def fetch(key)
@tuple.fetch(key)
end
##
# The size of the tuple.
def size
@tuple.size
end
##
# Creates a Rinda::Tuple for +ary+.
def make_tuple(ary)
Rinda::Tuple.new(ary)
end
private
##
# Returns a valid argument to make_expires and the renewer or nil.
#
# Given +true+, +nil+, or Numeric, returns that value and +nil+ (no actual
# renewer). Otherwise it returns an expiry value from calling +it.renew+
# and the renewer.
def get_renewer(it)
case it
when Numeric, true, nil
return it, nil
else
begin
return it.renew, it
rescue Exception
return it, nil
end
end
end
end
##
# A TemplateEntry is a Template together with expiry and cancellation data.
class TemplateEntry < TupleEntry
##
# Matches this TemplateEntry against +tuple+. See Template#match for
# details on how a Template matches a Tuple.
def match(tuple)
@tuple.match(tuple)
end
alias === match
def make_tuple(ary) # :nodoc:
Rinda::Template.new(ary)
end
end
##
# <i>Documentation?</i>
class WaitTemplateEntry < TemplateEntry
attr_reader :found
def initialize(place, ary, expires=nil)
super(ary, expires)
@place = place
@cond = place.new_cond
@found = nil
end
def cancel
super
signal
end
def wait
@cond.wait
end
def read(tuple)
@found = tuple
signal
end
def signal
@place.synchronize do
@cond.signal
end
end
end
##
# A NotifyTemplateEntry is returned by TupleSpace#notify and is notified of
# TupleSpace changes. You may receive either your subscribed event or the
# 'close' event when iterating over notifications.
#
# See TupleSpace#notify_event for valid notification types.
#
# == Example
#
# ts = Rinda::TupleSpace.new
# observer = ts.notify 'write', [nil]
#
# Thread.start do
# observer.each { |t| p t }
# end
#
# 3.times { |i| ts.write [i] }
#
# Outputs:
#
# ['write', [0]]
# ['write', [1]]
# ['write', [2]]
class NotifyTemplateEntry < TemplateEntry
##
# Creates a new NotifyTemplateEntry that watches +place+ for +event+s that
# match +tuple+.
def initialize(place, event, tuple, expires=nil)
ary = [event, Rinda::Template.new(tuple)]
super(ary, expires)
@queue = Thread::Queue.new
@done = false
end
##
# Called by TupleSpace to notify this NotifyTemplateEntry of a new event.
def notify(ev)
@queue.push(ev)
end
##
# Retrieves a notification. Raises RequestExpiredError when this
# NotifyTemplateEntry expires.
def pop
raise RequestExpiredError if @done
it = @queue.pop
@done = true if it[0] == 'close'
return it
end
##
# Yields event/tuple pairs until this NotifyTemplateEntry expires.
def each # :yields: event, tuple
while !@done
it = pop
yield(it)
end
rescue
ensure
cancel
end
end
##
# TupleBag is an unordered collection of tuples. It is the basis
# of Tuplespace.
class TupleBag
class TupleBin
extend Forwardable
def_delegators '@bin', :find_all, :delete_if, :each, :empty?
def initialize
@bin = []
end
def add(tuple)
@bin.push(tuple)
end
def delete(tuple)
idx = @bin.rindex(tuple)
@bin.delete_at(idx) if idx
end
def find
@bin.reverse_each do |x|
return x if yield(x)
end
nil
end
end
def initialize # :nodoc:
@hash = {}
@enum = enum_for(:each_entry)
end
##
# +true+ if the TupleBag to see if it has any expired entries.
def has_expires?
@enum.find do |tuple|
tuple.expires
end
end
##
# Add +tuple+ to the TupleBag.
def push(tuple)
key = bin_key(tuple)
@hash[key] ||= TupleBin.new
@hash[key].add(tuple)
end
##
# Removes +tuple+ from the TupleBag.
def delete(tuple)
key = bin_key(tuple)
bin = @hash[key]
return nil unless bin
bin.delete(tuple)
@hash.delete(key) if bin.empty?
tuple
end
##
# Finds all live tuples that match +template+.
def find_all(template)
bin_for_find(template).find_all do |tuple|
tuple.alive? && template.match(tuple)
end
end
##
# Finds a live tuple that matches +template+.
def find(template)
bin_for_find(template).find do |tuple|
tuple.alive? && template.match(tuple)
end
end
##
# Finds all tuples in the TupleBag which when treated as templates, match
# +tuple+ and are alive.
def find_all_template(tuple)
@enum.find_all do |template|
template.alive? && template.match(tuple)
end
end
##
# Delete tuples which dead tuples from the TupleBag, returning the deleted
# tuples.
def delete_unless_alive
deleted = []
@hash.each do |key, bin|
bin.delete_if do |tuple|
if tuple.alive?
false
else
deleted.push(tuple)
true
end
end
end
deleted
end
private
def each_entry(&blk)
@hash.each do |k, v|
v.each(&blk)
end
end
def bin_key(tuple)
head = tuple[0]
if head.class == Symbol
return head
else
false
end
end
def bin_for_find(template)
key = bin_key(template)
key ? @hash.fetch(key, []) : @enum
end
end
##
# The Tuplespace manages access to the tuples it contains,
# ensuring mutual exclusion requirements are met.
#
# The +sec+ option for the write, take, move, read and notify methods may
# either be a number of seconds or a Renewer object.
class TupleSpace
include DRbUndumped
include MonitorMixin
##
# Creates a new TupleSpace. +period+ is used to control how often to look
# for dead tuples after modifications to the TupleSpace.
#
# If no dead tuples are found +period+ seconds after the last
# modification, the TupleSpace will stop looking for dead tuples.
def initialize(period=60)
super()
@bag = TupleBag.new
@read_waiter = TupleBag.new
@take_waiter = TupleBag.new
@notify_waiter = TupleBag.new
@period = period
@keeper = nil
end
##
# Adds +tuple+
def write(tuple, sec=nil)
entry = create_entry(tuple, sec)
synchronize do
if entry.expired?
@read_waiter.find_all_template(entry).each do |template|
template.read(tuple)
end
notify_event('write', entry.value)
notify_event('delete', entry.value)
else
@bag.push(entry)
start_keeper if entry.expires
@read_waiter.find_all_template(entry).each do |template|
template.read(tuple)
end
@take_waiter.find_all_template(entry).each do |template|
template.signal
end
notify_event('write', entry.value)
end
end
entry
end
##
# Removes +tuple+
def take(tuple, sec=nil, &block)
move(nil, tuple, sec, &block)
end
##
# Moves +tuple+ to +port+.
def move(port, tuple, sec=nil)
template = WaitTemplateEntry.new(self, tuple, sec)
yield(template) if block_given?
synchronize do
entry = @bag.find(template)
if entry
port.push(entry.value) if port
@bag.delete(entry)
notify_event('take', entry.value)
return port ? nil : entry.value
end
raise RequestExpiredError if template.expired?
begin
@take_waiter.push(template)
start_keeper if template.expires
while true
raise RequestCanceledError if template.canceled?
raise RequestExpiredError if template.expired?
entry = @bag.find(template)
if entry
port.push(entry.value) if port
@bag.delete(entry)
notify_event('take', entry.value)
return port ? nil : entry.value
end
template.wait
end
ensure
@take_waiter.delete(template)
end
end
end
##
# Reads +tuple+, but does not remove it.
def read(tuple, sec=nil)
template = WaitTemplateEntry.new(self, tuple, sec)
yield(template) if block_given?
synchronize do
entry = @bag.find(template)
return entry.value if entry
raise RequestExpiredError if template.expired?
begin
@read_waiter.push(template)
start_keeper if template.expires
template.wait
raise RequestCanceledError if template.canceled?
raise RequestExpiredError if template.expired?
return template.found
ensure
@read_waiter.delete(template)
end
end
end
##
# Returns all tuples matching +tuple+. Does not remove the found tuples.
def read_all(tuple)
template = WaitTemplateEntry.new(self, tuple, nil)
synchronize do
entry = @bag.find_all(template)
entry.collect do |e|
e.value
end
end
end
##
# Registers for notifications of +event+. Returns a NotifyTemplateEntry.
# See NotifyTemplateEntry for examples of how to listen for notifications.
#
# +event+ can be:
# 'write':: A tuple was added
# 'take':: A tuple was taken or moved
# 'delete':: A tuple was lost after being overwritten or expiring
#
# The TupleSpace will also notify you of the 'close' event when the
# NotifyTemplateEntry has expired.
def notify(event, tuple, sec=nil)
template = NotifyTemplateEntry.new(self, event, tuple, sec)
synchronize do
@notify_waiter.push(template)
end
template
end
private
def create_entry(tuple, sec)
TupleEntry.new(tuple, sec)
end
##
# Removes dead tuples.
def keep_clean
synchronize do
@read_waiter.delete_unless_alive.each do |e|
e.signal
end
@take_waiter.delete_unless_alive.each do |e|
e.signal
end
@notify_waiter.delete_unless_alive.each do |e|
e.notify(['close'])
end
@bag.delete_unless_alive.each do |e|
notify_event('delete', e.value)
end
end
end
##
# Notifies all registered listeners for +event+ of a status change of
# +tuple+.
def notify_event(event, tuple)
ev = [event, tuple]
@notify_waiter.find_all_template(ev).each do |template|
template.notify(ev)
end
end
##
# Creates a thread that scans the tuplespace for expired tuples.
def start_keeper
return if @keeper && @keeper.alive?
@keeper = Thread.new do
while true
sleep(@period)
synchronize do
break unless need_keeper?
keep_clean
end
end
end
end
##
# Checks the tuplespace to see if it needs cleaning.
def need_keeper?
return true if @bag.has_expires?
return true if @read_waiter.has_expires?
return true if @take_waiter.has_expires?
return true if @notify_waiter.has_expires?
end
end
end