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// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_BASE_ATOMIC_UTILS_H_
#define V8_BASE_ATOMIC_UTILS_H_
#include <limits.h>
#include <type_traits>
#include "src/base/atomicops.h"
#include "src/base/macros.h"
namespace v8 {
namespace base {
// Deprecated. Use std::atomic<T> for new code.
// Flag using T atomically. Also accepts void* as T.
template <typename T>
class AtomicValue {
public:
AtomicValue() : value_(0) {}
explicit AtomicValue(T initial)
: value_(cast_helper<T>::to_storage_type(initial)) {}
V8_INLINE T Value() const {
return cast_helper<T>::to_return_type(base::Acquire_Load(&value_));
}
V8_INLINE bool TrySetValue(T old_value, T new_value) {
return base::Release_CompareAndSwap(
&value_, cast_helper<T>::to_storage_type(old_value),
cast_helper<T>::to_storage_type(new_value)) ==
cast_helper<T>::to_storage_type(old_value);
}
V8_INLINE void SetBits(T bits, T mask) {
DCHECK_EQ(bits & ~mask, static_cast<T>(0));
T old_value;
T new_value;
do {
old_value = Value();
new_value = (old_value & ~mask) | bits;
} while (!TrySetValue(old_value, new_value));
}
V8_INLINE void SetBit(int bit) {
SetBits(static_cast<T>(1) << bit, static_cast<T>(1) << bit);
}
V8_INLINE void ClearBit(int bit) { SetBits(0, 1 << bit); }
V8_INLINE void SetValue(T new_value) {
base::Release_Store(&value_, cast_helper<T>::to_storage_type(new_value));
}
private:
STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
template <typename S>
struct cast_helper {
static base::AtomicWord to_storage_type(S value) {
return static_cast<base::AtomicWord>(value);
}
static S to_return_type(base::AtomicWord value) {
return static_cast<S>(value);
}
};
template <typename S>
struct cast_helper<S*> {
static base::AtomicWord to_storage_type(S* value) {
return reinterpret_cast<base::AtomicWord>(value);
}
static S* to_return_type(base::AtomicWord value) {
return reinterpret_cast<S*>(value);
}
};
base::AtomicWord value_;
};
class AsAtomic32 {
public:
template <typename T>
static T Acquire_Load(T* addr) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::Atomic32));
return to_return_type<T>(base::Acquire_Load(to_storage_addr(addr)));
}
template <typename T>
static T Relaxed_Load(T* addr) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::Atomic32));
return to_return_type<T>(base::Relaxed_Load(to_storage_addr(addr)));
}
template <typename T>
static void Release_Store(T* addr,
typename std::remove_reference<T>::type new_value) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::Atomic32));
base::Release_Store(to_storage_addr(addr), to_storage_type(new_value));
}
template <typename T>
static void Relaxed_Store(T* addr,
typename std::remove_reference<T>::type new_value) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::Atomic32));
base::Relaxed_Store(to_storage_addr(addr), to_storage_type(new_value));
}
template <typename T>
static T Release_CompareAndSwap(
T* addr, typename std::remove_reference<T>::type old_value,
typename std::remove_reference<T>::type new_value) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::Atomic32));
return to_return_type<T>(base::Release_CompareAndSwap(
to_storage_addr(addr), to_storage_type(old_value),
to_storage_type(new_value)));
}
// Atomically sets bits selected by the mask to the given value.
// Returns false if the bits are already set as needed.
template <typename T>
static bool SetBits(T* addr, T bits, T mask) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::Atomic32));
DCHECK_EQ(bits & ~mask, static_cast<T>(0));
T old_value;
T new_value;
do {
old_value = Relaxed_Load(addr);
if ((old_value & mask) == bits) return false;
new_value = (old_value & ~mask) | bits;
} while (Release_CompareAndSwap(addr, old_value, new_value) != old_value);
return true;
}
private:
template <typename T>
static base::Atomic32 to_storage_type(T value) {
return static_cast<base::Atomic32>(value);
}
template <typename T>
static T to_return_type(base::Atomic32 value) {
return static_cast<T>(value);
}
template <typename T>
static base::Atomic32* to_storage_addr(T* value) {
return reinterpret_cast<base::Atomic32*>(value);
}
template <typename T>
static const base::Atomic32* to_storage_addr(const T* value) {
return reinterpret_cast<const base::Atomic32*>(value);
}
};
class AsAtomicWord {
public:
template <typename T>
static T Acquire_Load(T* addr) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
return to_return_type<T>(base::Acquire_Load(to_storage_addr(addr)));
}
template <typename T>
static T Relaxed_Load(T* addr) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
return to_return_type<T>(base::Relaxed_Load(to_storage_addr(addr)));
}
template <typename T>
static void Release_Store(T* addr,
typename std::remove_reference<T>::type new_value) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
base::Release_Store(to_storage_addr(addr), to_storage_type(new_value));
}
template <typename T>
static void Relaxed_Store(T* addr,
typename std::remove_reference<T>::type new_value) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
base::Relaxed_Store(to_storage_addr(addr), to_storage_type(new_value));
}
template <typename T>
static T Release_CompareAndSwap(
T* addr, typename std::remove_reference<T>::type old_value,
typename std::remove_reference<T>::type new_value) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
return to_return_type<T>(base::Release_CompareAndSwap(
to_storage_addr(addr), to_storage_type(old_value),
to_storage_type(new_value)));
}
// Atomically sets bits selected by the mask to the given value.
// Returns false if the bits are already set as needed.
template <typename T>
static bool SetBits(T* addr, T bits, T mask) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
DCHECK_EQ(bits & ~mask, static_cast<T>(0));
T old_value;
T new_value;
do {
old_value = Relaxed_Load(addr);
if ((old_value & mask) == bits) return false;
new_value = (old_value & ~mask) | bits;
} while (Release_CompareAndSwap(addr, old_value, new_value) != old_value);
return true;
}
private:
template <typename T>
static base::AtomicWord to_storage_type(T value) {
return static_cast<base::AtomicWord>(value);
}
template <typename T>
static T to_return_type(base::AtomicWord value) {
return static_cast<T>(value);
}
template <typename T>
static base::AtomicWord* to_storage_addr(T* value) {
return reinterpret_cast<base::AtomicWord*>(value);
}
template <typename T>
static const base::AtomicWord* to_storage_addr(const T* value) {
return reinterpret_cast<const base::AtomicWord*>(value);
}
};
class AsAtomic8 {
public:
template <typename T>
static T Acquire_Load(T* addr) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::Atomic8));
return to_return_type<T>(base::Acquire_Load(to_storage_addr(addr)));
}
template <typename T>
static T Relaxed_Load(T* addr) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::Atomic8));
return to_return_type<T>(base::Relaxed_Load(to_storage_addr(addr)));
}
template <typename T>
static void Release_Store(T* addr,
typename std::remove_reference<T>::type new_value) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::Atomic8));
base::Release_Store(to_storage_addr(addr), to_storage_type(new_value));
}
template <typename T>
static void Relaxed_Store(T* addr,
typename std::remove_reference<T>::type new_value) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::Atomic8));
base::Relaxed_Store(to_storage_addr(addr), to_storage_type(new_value));
}
template <typename T>
static T Release_CompareAndSwap(
T* addr, typename std::remove_reference<T>::type old_value,
typename std::remove_reference<T>::type new_value) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::Atomic8));
return to_return_type<T>(base::Release_CompareAndSwap(
to_storage_addr(addr), to_storage_type(old_value),
to_storage_type(new_value)));
}
private:
template <typename T>
static base::Atomic8 to_storage_type(T value) {
return static_cast<base::Atomic8>(value);
}
template <typename T>
static T to_return_type(base::Atomic8 value) {
return static_cast<T>(value);
}
template <typename T>
static base::Atomic8* to_storage_addr(T* value) {
return reinterpret_cast<base::Atomic8*>(value);
}
template <typename T>
static const base::Atomic8* to_storage_addr(const T* value) {
return reinterpret_cast<const base::Atomic8*>(value);
}
};
class AsAtomicPointer {
public:
template <typename T>
static T Acquire_Load(T* addr) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
return to_return_type<T>(base::Acquire_Load(to_storage_addr(addr)));
}
template <typename T>
static T Relaxed_Load(T* addr) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
return to_return_type<T>(base::Relaxed_Load(to_storage_addr(addr)));
}
template <typename T>
static void Release_Store(T* addr,
typename std::remove_reference<T>::type new_value) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
base::Release_Store(to_storage_addr(addr), to_storage_type(new_value));
}
template <typename T>
static void Relaxed_Store(T* addr,
typename std::remove_reference<T>::type new_value) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
base::Relaxed_Store(to_storage_addr(addr), to_storage_type(new_value));
}
template <typename T>
static T Release_CompareAndSwap(
T* addr, typename std::remove_reference<T>::type old_value,
typename std::remove_reference<T>::type new_value) {
STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
return to_return_type<T>(base::Release_CompareAndSwap(
to_storage_addr(addr), to_storage_type(old_value),
to_storage_type(new_value)));
}
private:
template <typename T>
static base::AtomicWord to_storage_type(T value) {
return reinterpret_cast<base::AtomicWord>(value);
}
template <typename T>
static T to_return_type(base::AtomicWord value) {
return reinterpret_cast<T>(value);
}
template <typename T>
static base::AtomicWord* to_storage_addr(T* value) {
return reinterpret_cast<base::AtomicWord*>(value);
}
template <typename T>
static const base::AtomicWord* to_storage_addr(const T* value) {
return reinterpret_cast<const base::AtomicWord*>(value);
}
};
// This class is intended to be used as a wrapper for elements of an array
// that is passed in to STL functions such as std::sort. It ensures that
// elements accesses are atomic.
// Usage example:
// Object** given_array;
// AtomicElement<Object*>* wrapped =
// reinterpret_cast<AtomicElement<Object*>(given_array);
// std::sort(wrapped, wrapped + given_length, cmp);
// where the cmp function uses the value() accessor to compare the elements.
template <typename T>
class AtomicElement {
public:
AtomicElement(const AtomicElement<T>& other) {
AsAtomicPointer::Relaxed_Store(
&value_, AsAtomicPointer::Relaxed_Load(&other.value_));
}
void operator=(const AtomicElement<T>& other) {
AsAtomicPointer::Relaxed_Store(
&value_, AsAtomicPointer::Relaxed_Load(&other.value_));
}
T value() const { return AsAtomicPointer::Relaxed_Load(&value_); }
bool operator<(const AtomicElement<T>& other) const {
return value() < other.value();
}
bool operator==(const AtomicElement<T>& other) const {
return value() == other.value();
}
private:
T value_;
};
} // namespace base
} // namespace v8
#endif // V8_BASE_ATOMIC_UTILS_H_
|
