atomic_word_intrinsics.h

/*    Copyright 2012 10gen Inc.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

#pragma once

#include <boost/static_assert.hpp>

#include "mongo/base/disallow_copying.h"
#include "mongo/platform/atomic_intrinsics.h"
#include "mongo/platform/compiler.h"

namespace mongo {

template <typename _WordType>
class AtomicWord {
    MONGO_DISALLOW_COPYING(AtomicWord);

public:
    typedef _WordType WordType;

    explicit AtomicWord(WordType value = WordType(0)) : _value(value) {}

    WordType load() const {
        return AtomicIntrinsics<WordType>::load(&_value);
    }

    WordType loadRelaxed() const {
        return AtomicIntrinsics<WordType>::loadRelaxed(&_value);
    }

    void store(WordType newValue) {
        AtomicIntrinsics<WordType>::store(&_value, newValue);
    }

    WordType swap(WordType newValue) {
        return AtomicIntrinsics<WordType>::swap(&_value, newValue);
    }

    WordType compareAndSwap(WordType expected, WordType newValue) {
        return AtomicIntrinsics<WordType>::compareAndSwap(&_value, expected, newValue);
    }

    WordType fetchAndAdd(WordType increment) {
        return AtomicIntrinsics<WordType>::fetchAndAdd(&_value, increment);
    }

    WordType fetchAndSubtract(WordType decrement) {
        return fetchAndAdd(WordType(0) - decrement);
    }

    WordType addAndFetch(WordType increment) {
        return fetchAndAdd(increment) + increment;
    }

    WordType subtractAndFetch(WordType decrement) {
        return fetchAndSubtract(decrement) - decrement;
    }

private:
    volatile WordType _value;
};

#define _ATOMIC_WORD_DECLARE(NAME, WTYPE)               \
    typedef class AtomicWord<WTYPE> NAME;               \
    namespace {                                         \
    BOOST_STATIC_ASSERT(sizeof(NAME) == sizeof(WTYPE)); \
    }

_ATOMIC_WORD_DECLARE(AtomicUInt32, unsigned);
_ATOMIC_WORD_DECLARE(AtomicUInt64, unsigned long long);
_ATOMIC_WORD_DECLARE(AtomicInt32, int);
_ATOMIC_WORD_DECLARE(AtomicInt64, long long);
#undef _ATOMIC_WORD_DECLARE

}  // namespace mongo