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/* 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.
*/
/**
* Implementation of the AtomicIntrinsics<T>::* operations for Windows systems.
*/
#pragma once
#include <boost/utility.hpp>
#include "mongo/platform/windows_basic.h"
#include <intrin.h>
#pragma intrinsic(_InterlockedCompareExchange64)
namespace mongo {
/**
* Default instantiation of AtomicIntrinsics<>, for unsupported types.
*/
template <typename T, typename _IsTSupported=void>
class AtomicIntrinsics {
private:
AtomicIntrinsics();
~AtomicIntrinsics();
};
/**
* Instantiation of AtomicIntrinsics<> for 32-bit word sizes (i.e., unsigned).
*/
template <typename T>
class AtomicIntrinsics<T, typename boost::enable_if_c<sizeof(T) == sizeof(LONG)>::type> {
public:
static T compareAndSwap(volatile T* dest, T expected, T newValue) {
return InterlockedCompareExchange(reinterpret_cast<volatile LONG*>(dest),
LONG(newValue),
LONG(expected));
}
static T swap(volatile T* dest, T newValue) {
return InterlockedExchange(reinterpret_cast<volatile LONG*>(dest), LONG(newValue));
}
static T load(volatile const T* value) {
MemoryBarrier();
T result = *value;
MemoryBarrier();
return result;
}
static T loadRelaxed(volatile const T* value) {
return *value;
}
static void store(volatile T* dest, T newValue) {
MemoryBarrier();
*dest = newValue;
MemoryBarrier();
}
static T fetchAndAdd(volatile T* dest, T increment) {
return InterlockedExchangeAdd(reinterpret_cast<volatile LONG*>(dest), LONG(increment));
}
private:
AtomicIntrinsics();
~AtomicIntrinsics();
};
namespace details {
template <typename T, bool HaveInterlocked64Ops>
struct InterlockedImpl64;
// Implementation of 64-bit Interlocked operations via Windows API calls.
template<typename T>
struct InterlockedImpl64<T, true> {
static T compareAndSwap(volatile T* dest, T expected, T newValue) {
return InterlockedCompareExchange64(
reinterpret_cast<volatile LONGLONG*>(dest),
LONGLONG(newValue),
LONGLONG(expected));
}
static T swap(volatile T* dest, T newValue) {
return InterlockedExchange64(
reinterpret_cast<volatile LONGLONG*>(dest),
LONGLONG(newValue));
}
static T fetchAndAdd(volatile T* dest, T increment) {
return InterlockedExchangeAdd64(
reinterpret_cast<volatile LONGLONG*>(dest),
LONGLONG(increment));
}
};
// Implementation of 64-bit Interlocked operations for systems where the API does not
// yet provide the Interlocked...64 operations.
template<typename T>
struct InterlockedImpl64<T, false> {
static T compareAndSwap(volatile T* dest, T expected, T newValue) {
// NOTE: We must use the compiler intrinsic here: WinXP does not offer
// InterlockedCompareExchange64 as an API call.
return _InterlockedCompareExchange64(
reinterpret_cast<volatile LONGLONG*>(dest),
LONGLONG(newValue),
LONGLONG(expected));
}
static T swap(volatile T* dest, T newValue) {
// NOTE: You may be tempted to replace this with
// 'InterlockedExchange64'. Resist! It will compile just fine despite not being
// listed in the docs as available on XP, but the compiler may replace it with
// calls to the non-intrinsic 'InterlockedCompareExchange64', which does not
// exist on XP. We work around this by rolling our own synthetic in terms of
// compareAndSwap which we have explicitly formulated in terms of the compiler
// provided _InterlockedCompareExchange64 intrinsic.
T currentValue = *dest;
while (true) {
const T result = compareAndSwap(dest, currentValue, newValue);
if (result == currentValue)
return result;
currentValue = result;
}
}
static T fetchAndAdd(volatile T* dest, T increment) {
// NOTE: See note for 'swap' on why we roll this ourselves.
T currentValue = *dest;
while (true) {
const T incremented = currentValue + increment;
const T result = compareAndSwap(dest, currentValue, incremented);
if (result == currentValue)
return result;
currentValue = result;
}
}
};
// On 32-bit IA-32 systems, 64-bit load and store must be implemented in terms of
// Interlocked operations, but on 64-bit systems they support a simpler, native
// implementation. The LoadStoreImpl type represents the abstract implementation of
// loading and storing 64-bit values.
template <typename U, typename _IsTTooBig=void>
struct LoadStoreImpl;
// Implementation on 64-bit systems.
template <typename U>
struct LoadStoreImpl<U, typename boost::enable_if_c<sizeof(U) <= sizeof(void*)>::type> {
static U load(volatile const U* value) {
MemoryBarrier();
U result = *value;
MemoryBarrier();
return result;
}
static void store(volatile U* dest, U newValue) {
MemoryBarrier();
*dest = newValue;
MemoryBarrier();
}
};
// Implementation on 32-bit systems.
template <typename U>
struct LoadStoreImpl<U, typename boost::disable_if_c<sizeof(U) <= sizeof(void*)>::type> {
// NOTE: Implemented out-of-line below since the implementation relies on
// AtomicIntrinsics.
static U load(volatile const U* value);
static void store(volatile U* dest, U newValue);
};
} // namespace details
/**
* Instantiation of AtomicIntrinsics<> for 64-bit word sizes.
*/
template <typename T>
class AtomicIntrinsics<T, typename boost::enable_if_c<sizeof(T) == sizeof(LONGLONG)>::type> {
public:
#if defined(NTDDI_VERSION) && defined(NTDDI_WS03SP2) && (NTDDI_VERSION >= NTDDI_WS03SP2)
static const bool kHaveInterlocked64 = true;
#else
static const bool kHaveInterlocked64 = false;
#endif
typedef details::InterlockedImpl64<T, kHaveInterlocked64> InterlockedImpl;
typedef details::LoadStoreImpl<T> LoadStoreImpl;
static T compareAndSwap(volatile T* dest, T expected, T newValue) {
return InterlockedImpl::compareAndSwap(dest, expected, newValue);
}
static T swap(volatile T* dest, T newValue) {
return InterlockedImpl::swap(dest, newValue);
}
static T load(volatile const T* value) {
return LoadStoreImpl::load(value);
}
static void store(volatile T* dest, T newValue) {
LoadStoreImpl::store(dest, newValue);
}
static T fetchAndAdd(volatile T* dest, T increment) {
return InterlockedImpl::fetchAndAdd(dest, increment);
}
private:
AtomicIntrinsics();
~AtomicIntrinsics();
};
namespace details {
template <typename U>
U LoadStoreImpl<U, typename boost::disable_if_c<sizeof(U) <= sizeof(void*)>::type>
::load(volatile const U* value) {
return AtomicIntrinsics<U>::compareAndSwap(const_cast<volatile U*>(value),
U(0),
U(0));
}
template<typename U>
void LoadStoreImpl<U, typename boost::disable_if_c<sizeof(U) <= sizeof(void*)>::type>
::store(volatile U* dest, U newValue) {
AtomicIntrinsics<U>::swap(dest, newValue);
}
} // namespace details
} // namespace mongo
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