struct Atomic(T)

Overview

A value that may be updated atomically.

If T is a non-union primitive integer type or enum type, all operations are supported. If T is a reference type, or a union type containing only reference types or Nil, then only #compare_and_set, #swap, #set, #lazy_set, #get, and #lazy_get are available.

Defined in:

atomic.cr

Constructors

Macro Summary

Instance Method Summary

Instance methods inherited from struct Struct

==(other) : Bool ==, hash(hasher) hash, inspect(io : IO) : Nil inspect, pretty_print(pp) : Nil pretty_print, to_s(io : IO) : Nil to_s

Instance methods inherited from struct Value

==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup

Instance methods inherited from class Object

! : Bool !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?, inspect(io : IO) : Nil
inspect : String inspect, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil!(message)
not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json, to_s(io : IO) : Nil
to_s : String to_s, to_yaml(io : IO) : Nil
to_yaml : String to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

Class methods inherited from class Object

from_json(string_or_io, root : String)
from_json(string_or_io) from_json, from_yaml(string_or_io : String | IO) from_yaml

Macros inherited from class Object

class_getter(*names, &block) class_getter, class_getter!(*names) class_getter!, class_getter?(*names, &block) class_getter?, class_property(*names, &block) class_property, class_property!(*names) class_property!, class_property?(*names, &block) class_property?, class_setter(*names) class_setter, def_clone def_clone, def_equals(*fields) def_equals, def_equals_and_hash(*fields) def_equals_and_hash, def_hash(*fields) def_hash, delegate(*methods, to object) delegate, forward_missing_to(delegate) forward_missing_to, getter(*names, &block) getter, getter!(*names) getter!, getter?(*names, &block) getter?, property(*names, &block) property, property!(*names) property!, property?(*names, &block) property?, setter(*names) setter

Constructor Detail

def self.new(value : T) #

Creates an Atomic with the given initial value.


[View source]

Macro Detail

macro fence(ordering = :sequentially_consistent) #

Adds an explicit memory barrier with the specified memory order guarantee.

Atomics on weakly-ordered CPUs (e.g. ARM32) may not guarantee memory order of other memory accesses, and an explicit memory barrier is thus required.

Notes:

  • X86 is strongly-ordered and trying to add a fence should be a NOOP;
  • AArch64 guarantees memory order and doesn't need explicit fences in addition to the atomics (but may need barriers in other cases).

[View source]

Instance Method Detail

def add(value : T, ordering : Ordering = :sequentially_consistent) : T #

Performs atomic_value &+= value. Returns the old value.

T cannot contain any reference types.

atomic = Atomic.new(1)
atomic.add(2) # => 1
atomic.get    # => 3

[View source]
def and(value : T, ordering : Ordering = :sequentially_consistent) : T #

Performs atomic_value &= value. Returns the old value.

T cannot contain any reference types.

atomic = Atomic.new(5)
atomic.and(3) # => 5
atomic.get    # => 1

[View source]
def compare_and_set(cmp : T, new : T, success_ordering : Ordering, failure_ordering : Ordering) : Tuple(T, Bool) #

Compares this atomic's value with cmp using explicit memory orderings:

  • if they are equal, sets the value to new, and returns {old_value, true}
  • if they are not equal the value remains the same, and returns {old_value, false}

Reference types are compared by #same?, not #==.

atomic = Atomic.new(0_u32)

value = atomic.get(:acquire)
loop do
  value, success = atomic.compare_and_set(value, value &+ 1, :acquire_release, :acquire)
  break if success
end

[View source]
def compare_and_set(cmp : T, new : T) : Tuple(T, Bool) #

Compares this atomic's value with cmp:

  • if they are equal, sets the value to new, and returns {old_value, true}
  • if they are not equal the value remains the same, and returns {old_value, false}

Reference types are compared by #same?, not #==.

atomic = Atomic.new(1)

atomic.compare_and_set(2, 3) # => {1, false}
atomic.get                   # => 1

atomic.compare_and_set(1, 3) # => {1, true}
atomic.get                   # => 3

[View source]
def get(ordering : Ordering = :sequentially_consistent) : T #

Atomically returns this atomic's value.


[View source]
def lazy_get #

Non-atomically returns this atomic's value.

NOTE use with caution, this may break atomic guarantees.


[View source]
def lazy_set(value : T) : T #

Non-atomically sets this atomic's value to value. Returns the new value.

atomic = Atomic.new(5)
atomic.lazy_set(10) # => 10
atomic.get          # => 10

NOTE use with caution, this may break atomic guarantees.


[View source]
def max(value : T, ordering : Ordering = :sequentially_consistent) #

Performs atomic_value = {atomic_value, value}.max. Returns the old value.

T cannot contain any reference types.

atomic = Atomic.new(5)

atomic.max(3) # => 5
atomic.get    # => 5

atomic.max(10) # => 5
atomic.get     # => 10

[View source]
def min(value : T, ordering : Ordering = :sequentially_consistent) #

Performs atomic_value = {atomic_value, value}.min. Returns the old value.

T cannot contain any reference types.

atomic = Atomic.new(5)

atomic.min(10) # => 5
atomic.get     # => 5

atomic.min(3) # => 5
atomic.get    # => 3

[View source]
def nand(value : T, ordering : Ordering = :sequentially_consistent) : T #

Performs atomic_value = ~(atomic_value & value). Returns the old value.

T cannot contain any reference types.

atomic = Atomic.new(5)
atomic.nand(3) # => 5
atomic.get     # => -2

[View source]
def or(value : T, ordering : Ordering = :sequentially_consistent) : T #

Performs atomic_value |= value. Returns the old value.

T cannot contain any reference types.

atomic = Atomic.new(5)
atomic.or(2) # => 5
atomic.get   # => 7

[View source]
def set(value : T, ordering : Ordering = :sequentially_consistent) : T #

Atomically sets this atomic's value to value. Returns the new value.

atomic = Atomic.new(5)
atomic.set(10) # => 10
atomic.get     # => 10

[View source]
def sub(value : T, ordering : Ordering = :sequentially_consistent) : T #

Performs atomic_value &-= value. Returns the old value.

T cannot contain any reference types.

atomic = Atomic.new(9)
atomic.sub(2) # => 9
atomic.get    # => 7

[View source]
def swap(value : T, ordering : Ordering = :sequentially_consistent) #

Atomically sets this atomic's value to value. Returns the old value.

atomic = Atomic.new(5)
atomic.swap(10) # => 5
atomic.get      # => 10

[View source]
def xor(value : T, ordering : Ordering = :sequentially_consistent) : T #

Performs atomic_value ^= value. Returns the old value.

T cannot contain any reference types.

atomic = Atomic.new(5)
atomic.xor(3) # => 5
atomic.get    # => 6

[View source]