include/core/SkAtomics.h

#ifndef SkAtomics_DEFINED
#define SkAtomics_DEFINED

// This file is not part of the public Skia API.
#include "SkTypes.h"

enum sk_memory_order {
    sk_memory_order_relaxed,
    sk_memory_order_consume,
    sk_memory_order_acquire,
    sk_memory_order_release,
    sk_memory_order_acq_rel,
    sk_memory_order_seq_cst,
};

template <typename T>
T sk_atomic_load(const T*, sk_memory_order = sk_memory_order_seq_cst);

template <typename T>
void sk_atomic_store(T*, T, sk_memory_order = sk_memory_order_seq_cst);

template <typename T>
T sk_atomic_fetch_add(T*, T, sk_memory_order = sk_memory_order_seq_cst);

template <typename T>
bool sk_atomic_compare_exchange(T*, T* expected, T desired,
                                sk_memory_order success = sk_memory_order_seq_cst,
                                sk_memory_order failure = sk_memory_order_seq_cst);
#if defined(_MSC_VER)
    #include "../ports/SkAtomics_std.h"
#elif !defined(SK_BUILD_FOR_IOS) && defined(__ATOMIC_RELAXED)
    #include "../ports/SkAtomics_atomic.h"
#else
    #include "../ports/SkAtomics_sync.h"
#endif

// From here down we have shims for our old atomics API, to be weaned off of.
// We use the default sequentially-consistent memory order to make things simple
// and to match the practical reality of our old _sync and _win implementations.

inline int32_t sk_atomic_inc(int32_t* ptr)            { return sk_atomic_fetch_add(ptr, +1); }
inline int32_t sk_atomic_dec(int32_t* ptr)            { return sk_atomic_fetch_add(ptr, -1); }
inline int32_t sk_atomic_add(int32_t* ptr, int32_t v) { return sk_atomic_fetch_add(ptr,  v); }

inline int64_t sk_atomic_inc(int64_t* ptr) { return sk_atomic_fetch_add<int64_t>(ptr, +1); }

inline bool sk_atomic_cas(int32_t* ptr, int32_t expected, int32_t desired) {
    return sk_atomic_compare_exchange(ptr, &expected, desired);
}

inline void* sk_atomic_cas(void** ptr, void* expected, void* desired) {
    (void)sk_atomic_compare_exchange(ptr, &expected, desired);
    return expected;
}

inline int32_t sk_atomic_conditional_inc(int32_t* ptr) {
    int32_t prev = sk_atomic_load(ptr);
    do {
        if (0 == prev) {
            break;
        }
    } while(!sk_atomic_compare_exchange(ptr, &prev, prev+1));
    return prev;
}

template <typename T>
T sk_acquire_load(T* ptr) { return sk_atomic_load(ptr, sk_memory_order_acquire); }

template <typename T>
void sk_release_store(T* ptr, T val) { sk_atomic_store(ptr, val, sk_memory_order_release); }

inline void sk_membar_acquire__after_atomic_dec() {}
inline void sk_membar_acquire__after_atomic_conditional_inc() {}

#endif//SkAtomics_DEFINED