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require 'concurrent/synchronization'
require 'concurrent/utility/engine'
require 'concurrent/atomic_reference/numeric_cas_wrapper'
# Shim for TruffleRuby::AtomicReference
if Concurrent.on_truffleruby? && !defined?(TruffleRuby::AtomicReference)
# @!visibility private
module TruffleRuby
AtomicReference = Truffle::AtomicReference
end
end
module Concurrent
# Define update methods that use direct paths
#
# @!visibility private
# @!macro internal_implementation_note
module AtomicDirectUpdate
# @!macro atomic_reference_method_update
#
# Pass the current value to the given block, replacing it
# with the block's result. May retry if the value changes
# during the block's execution.
#
# @yield [Object] Calculate a new value for the atomic reference using
# given (old) value
# @yieldparam [Object] old_value the starting value of the atomic reference
# @return [Object] the new value
def update
true until compare_and_set(old_value = get, new_value = yield(old_value))
new_value
end
# @!macro atomic_reference_method_try_update
#
# Pass the current value to the given block, replacing it
# with the block's result. Return nil if the update fails.
#
# @yield [Object] Calculate a new value for the atomic reference using
# given (old) value
# @yieldparam [Object] old_value the starting value of the atomic reference
# @note This method was altered to avoid raising an exception by default.
# Instead, this method now returns `nil` in case of failure. For more info,
# please see: https://github.com/ruby-concurrency/concurrent-ruby/pull/336
# @return [Object] the new value, or nil if update failed
def try_update
old_value = get
new_value = yield old_value
return unless compare_and_set old_value, new_value
new_value
end
# @!macro atomic_reference_method_try_update!
#
# Pass the current value to the given block, replacing it
# with the block's result. Raise an exception if the update
# fails.
#
# @yield [Object] Calculate a new value for the atomic reference using
# given (old) value
# @yieldparam [Object] old_value the starting value of the atomic reference
# @note This behavior mimics the behavior of the original
# `AtomicReference#try_update` API. The reason this was changed was to
# avoid raising exceptions (which are inherently slow) by default. For more
# info: https://github.com/ruby-concurrency/concurrent-ruby/pull/336
# @return [Object] the new value
# @raise [Concurrent::ConcurrentUpdateError] if the update fails
def try_update!
old_value = get
new_value = yield old_value
unless compare_and_set(old_value, new_value)
if $VERBOSE
raise ConcurrentUpdateError, "Update failed"
else
raise ConcurrentUpdateError, "Update failed", ConcurrentUpdateError::CONC_UP_ERR_BACKTRACE
end
end
new_value
end
end
require 'concurrent/atomic_reference/mutex_atomic'
# @!macro atomic_reference
#
# An object reference that may be updated atomically. All read and write
# operations have java volatile semantic.
#
# @!macro thread_safe_variable_comparison
#
# @see http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/atomic/AtomicReference.html
# @see http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/atomic/package-summary.html
#
# @!method initialize(value = nil)
# @!macro atomic_reference_method_initialize
# @param [Object] value The initial value.
#
# @!method get
# @!macro atomic_reference_method_get
# Gets the current value.
# @return [Object] the current value
#
# @!method set(new_value)
# @!macro atomic_reference_method_set
# Sets to the given value.
# @param [Object] new_value the new value
# @return [Object] the new value
#
# @!method get_and_set(new_value)
# @!macro atomic_reference_method_get_and_set
# Atomically sets to the given value and returns the old value.
# @param [Object] new_value the new value
# @return [Object] the old value
#
# @!method compare_and_set(old_value, new_value)
# @!macro atomic_reference_method_compare_and_set
#
# Atomically sets the value to the given updated value if
# the current value == the expected value.
#
# @param [Object] old_value the expected value
# @param [Object] new_value the new value
#
# @return [Boolean] `true` if successful. A `false` return indicates
# that the actual value was not equal to the expected value.
#
# @!method update
# @!macro atomic_reference_method_update
#
# @!method try_update
# @!macro atomic_reference_method_try_update
#
# @!method try_update!
# @!macro atomic_reference_method_try_update!
# @!macro internal_implementation_note
class ConcurrentUpdateError < ThreadError
# frozen pre-allocated backtrace to speed ConcurrentUpdateError
CONC_UP_ERR_BACKTRACE = ['backtrace elided; set verbose to enable'].freeze
end
# @!macro internal_implementation_note
AtomicReferenceImplementation = case
when Concurrent.on_cruby? && Concurrent.c_extensions_loaded?
# @!visibility private
# @!macro internal_implementation_note
class CAtomicReference
include AtomicDirectUpdate
include AtomicNumericCompareAndSetWrapper
alias_method :compare_and_swap, :compare_and_set
end
CAtomicReference
when Concurrent.on_jruby?
# @!visibility private
# @!macro internal_implementation_note
class JavaAtomicReference
include AtomicDirectUpdate
end
JavaAtomicReference
when Concurrent.on_truffleruby?
class TruffleRubyAtomicReference < TruffleRuby::AtomicReference
include AtomicDirectUpdate
alias_method :value, :get
alias_method :value=, :set
alias_method :compare_and_swap, :compare_and_set
alias_method :swap, :get_and_set
end
when Concurrent.on_rbx?
# @note Extends `Rubinius::AtomicReference` version adding aliases
# and numeric logic.
#
# @!visibility private
# @!macro internal_implementation_note
class RbxAtomicReference < Rubinius::AtomicReference
alias_method :_compare_and_set, :compare_and_set
include AtomicDirectUpdate
include AtomicNumericCompareAndSetWrapper
alias_method :value, :get
alias_method :value=, :set
alias_method :swap, :get_and_set
alias_method :compare_and_swap, :compare_and_set
end
RbxAtomicReference
else
MutexAtomicReference
end
private_constant :AtomicReferenceImplementation
# @!macro atomic_reference
class AtomicReference < AtomicReferenceImplementation
# @return [String] Short string representation.
def to_s
format '%s value:%s>', super[0..-2], get
end
alias_method :inspect, :to_s
end
end
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