src/ports/SkAtomics_win.h

/*
 * Copyright 2013 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkAtomics_win_DEFINED
#define SkAtomics_win_DEFINED

/** Windows Interlocked atomics. */

#include <intrin.h>
#include <stdint.h>

//MSDN says in order to declare an interlocked function for use as an
//intrinsic, include intrin.h and put the function in a #pragma intrinsic
//directive.
//The pragma appears to be unnecessary, but doesn't hurt.
#pragma intrinsic(_InterlockedIncrement, _InterlockedExchangeAdd, _InterlockedDecrement)
#pragma intrinsic(_InterlockedCompareExchange)

static inline int32_t sk_atomic_inc(int32_t* addr) {
    // InterlockedIncrement returns the new value, we want to return the old.
    return _InterlockedIncrement(reinterpret_cast<long*>(addr)) - 1;
}

static inline int32_t sk_atomic_add(int32_t* addr, int32_t inc) {
    return _InterlockedExchangeAdd(reinterpret_cast<long*>(addr), static_cast<long>(inc));
}

static inline int32_t sk_atomic_dec(int32_t* addr) {
    // InterlockedDecrement returns the new value, we want to return the old.
    return _InterlockedDecrement(reinterpret_cast<long*>(addr)) + 1;
}

static inline void sk_membar_acquire__after_atomic_dec() { }

static inline int32_t sk_atomic_conditional_inc(int32_t* addr) {
    long value = *addr;
    while (true) {
        if (value == 0) {
            return 0;
        }

        long before = _InterlockedCompareExchange(reinterpret_cast<long*>(addr), value + 1, value);

        if (before == value) {
            return value;
        } else {
            value = before;
        }
    }
}

static inline void sk_membar_acquire__after_atomic_conditional_inc() { }

#endif