C++ Library - <atomic>

Introduction

It is an objects of atomic types contain a value of a particular type (T) and the main characteristic of atomic objects is that access to this contained value from different threads cannot cause data races (i.e., doing that is well-defined behavior, with accesses properly sequenced). Generally, for all other objects, the possibility of causing a data race for accessing the same object concurrently qualifies the operation as undefined behavior.

Declaration

Following is the declaration for std::atomic.

template <class T> struct atomic;

Parameters

T − It is a type of the contained value.

Member functions

Sr.No.	Member functions & Definition
1	(constructor) It is a constructs an atomic object
2	operator= It is stores a value into an atomic object
3	is_lock_free It checks if the atomic object is lock-free
4	store It atomically replaces the value of the atomic object with a non-atomic argument
5	load It atomically obtains the value of the atomic object
6	operator T It loads a value from an atomic object
7	exchange It atomically replaces the value of the atomic object and obtains the value held previously
8	compare_exchange_weak & compare_exchange_strong It atomically compares the value of the atomic object with non-atomic argument and performs atomic exchange if equal or atomic load if not

Operations supported by certain specializations

Sr.No.	Operations & Definition
1	fetch_add It atomically adds the argument to the value stored in the atomic object and obtains the value held previously
2	fetch_sub It atomically subtracts the argument from the value stored in the atomic object and obtains the value held previously
3	fetch_and It atomically performs bitwise AND between the argument and the value of the atomic object and obtains the value held previously
4	fetch_or It atomically performs bitwise OR between the argument and the value of the atomic object and obtains the value held previously
5	fetch_xor It atomically compares the value of the atomic object with non-atomic argument and performs atomic exchange if equal or atomic load if not
6	operator++ It increments the atomic value by one
7	operator-- It decrements the atomic value by one

atomic.htm