#头文件
#include "co/atomic.h"
API 在 co 命名空间。
#内存序
using memorder_t = std::memory_order;
constexpr memorder_t mo_relaxed = std::memory_order_relaxed;
constexpr memorder_t mo_consume = std::memory_order_consume;
constexpr memorder_t mo_acquire = std::memory_order_acquire;
constexpr memorder_t mo_release = std::memory_order_release;
constexpr memorder_t mo_acq_rel = std::memory_order_acq_rel;
constexpr memorder_t mo_seq_cst = std::memory_order_seq_cst;
#加载与存储
template<typename T>
T atomic_load(const T* p, memorder_t mo = mo_seq_cst);
template<typename T, typename V>
void atomic_store(T* p, V v, memorder_t mo = mo_seq_cst);
atomic_load支持：mo_relaxed、mo_consume、mo_acquire、mo_seq_cst。atomic_store支持：mo_relaxed、mo_release、mo_seq_cst。
示例:
int i = 0;
co::atomic_store(&i, 3); // i -> 3
int x = co::atomic_load(&i); // x -> 3
#交换
template<typename T, typename V>
T atomic_swap(T* p, V v, memorder_t mo = mo_seq_cst);
template<typename T, typename O, typename V>
T atomic_compare_swap(
T* p, O o, V v,
memorder_t smo = mo_seq_cst, memorder_t fmo = mo_seq_cst
);
template<typename T, typename O, typename V>
T atomic_cas(
T* p, O o, V v,
memorder_t smo = mo_seq_cst, memorder_t fmo = mo_seq_cst
);
template<typename T, typename O, typename V>
bool atomic_bool_cas(
T* p, O o, V v,
memorder_t smo = mo_seq_cst, memorder_t fmo = mo_seq_cst
);
atomic_swap返回旧值，支持所有内存序。atomic_cas与atomic_compare_swap等价，*p == o时才执行交换操作，返回旧值。atomic_bool_cas与atomic_cas类似，成功返回 true，失败返回 false。- CAS 操作中，
smo是成功时内存序，支持所有，fmo是失败时内存序，不能是mo_release、mo_acq_rel，且不能强于smo。
示例:
bool b = false;
bool o = co::atomic_swap(&b, true); // b -> true, o -> false
int i = 0;
int r = co::atomic_cas(&i, 1, 2); // i 不变, r -> 0
r = co::atomic_cas(&i, 0, 2); // i -> 2, r -> 0
void* p = 0;
bool x = co::atomic_bool_cas(&p, 0, (void*)8); // p -> 8, x -> true
#加减
template<typename T, typename V>
T atomic_add(T* p, V v, memorder_t mo = mo_seq_cst);
template<typename T, typename V>
T atomic_sub(T* p, V v, memorder_t mo = mo_seq_cst);
template<typename T>
T atomic_inc(T* p, memorder_t mo = mo_seq_cst);
template<typename T>
T atomic_dec(T* p, memorder_t mo = mo_seq_cst);
template<typename T, typename V>
T atomic_fetch_add(T* p, V v, memorder_t mo = mo_seq_cst);
template<typename T, typename V>
T atomic_fetch_sub(T* p, V v, memorder_t mo = mo_seq_cst);
template<typename T>
T atomic_fetch_inc(T* p, memorder_t mo = mo_seq_cst);
template<typename T>
T atomic_fetch_dec(T* p, memorder_t mo = mo_seq_cst);
inc加 1，dec减 1。- 带 fetch 版本返回旧值，不带 fetch 版本返回新值。
- 支持所有内存序。
#位运算
template<typename T, typename V>
T atomic_or(T* p, V v, memorder_t mo = mo_seq_cst);
template<typename T, typename V>
T atomic_and(T* p, V v, memorder_t mo = mo_seq_cst);
template<typename T, typename V>
T atomic_xor(T* p, V v, memorder_t mo = mo_seq_cst);
template<typename T, typename V>
T atomic_fetch_or(T* p, V v, memorder_t mo = mo_seq_cst);
template<typename T, typename V>
T atomic_fetch_and(T* p, V v, memorder_t mo = mo_seq_cst);
template<typename T, typename V>
T atomic_fetch_xor(T* p, V v, memorder_t mo = mo_seq_cst);
- 带 fetch 版本返回旧值，不带 fetch 版本返回新值。
- 支持所有内存序。