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require 'concurrent/thread_safe/util'
module Concurrent
# @!visibility private
module ThreadSafe
# @!visibility private
module Util
# @!visibility private
module Volatile
# Provides +volatile+ (in the JVM's sense) attribute accessors implemented
# atop of +Concurrent::AtomicReference+.
#
# Usage:
# class Foo
# extend Concurrent::ThreadSafe::Util::Volatile
# attr_volatile :foo, :bar
#
# def initialize(bar)
# super() # must super() into parent initializers before using the volatile attribute accessors
# self.bar = bar
# end
#
# def hello
# my_foo = foo # volatile read
# self.foo = 1 # volatile write
# cas_foo(1, 2) # => true | a strong CAS
# end
# end
def attr_volatile(*attr_names)
return if attr_names.empty?
include(Module.new do
atomic_ref_setup = attr_names.map {|attr_name| "@__#{attr_name} = Concurrent::AtomicReference.new"}
initialize_copy_setup = attr_names.zip(atomic_ref_setup).map do |attr_name, ref_setup|
"#{ref_setup}(other.instance_variable_get(:@__#{attr_name}).get)"
end
class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
def initialize(*)
super
#{atomic_ref_setup.join('; ')}
end
def initialize_copy(other)
super
#{initialize_copy_setup.join('; ')}
end
RUBY_EVAL
attr_names.each do |attr_name|
class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
def #{attr_name}
@__#{attr_name}.get
end
def #{attr_name}=(value)
@__#{attr_name}.set(value)
end
def compare_and_set_#{attr_name}(old_value, new_value)
@__#{attr_name}.compare_and_set(old_value, new_value)
end
RUBY_EVAL
alias_method :"cas_#{attr_name}", :"compare_and_set_#{attr_name}"
alias_method :"lazy_set_#{attr_name}", :"#{attr_name}="
end
end)
end
end
end
end
end
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