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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef vm_SharedMem_h
#define vm_SharedMem_h
#include "mozilla/TypeTraits.h"
template<typename T>
class SharedMem
{
static_assert(mozilla::IsPointer<T>::value,
"SharedMem encapsulates pointer types");
enum Sharedness {
IsUnshared,
IsShared
};
T ptr_;
#ifdef DEBUG
Sharedness sharedness_;
#endif
SharedMem(T ptr, Sharedness sharedness)
: ptr_(ptr)
#ifdef DEBUG
, sharedness_(sharedness)
#endif
{}
public:
// Create a SharedMem<T> that is an unshared nullptr.
SharedMem()
: ptr_(nullptr)
#ifdef DEBUG
, sharedness_(IsUnshared)
#endif
{}
// Create a SharedMem<T> that's shared/unshared in the same way as
// "forSharedness".
SharedMem(T ptr, const SharedMem& forSharedness)
: ptr_(ptr)
#ifdef DEBUG
, sharedness_(forSharedness.sharedness_)
#endif
{}
// Create a SharedMem<T> that's marked as shared.
static SharedMem shared(void* p) {
return SharedMem(static_cast<T>(p), IsShared);
}
// Create a SharedMem<T> that's marked as unshared.
static SharedMem unshared(void* p) {
return SharedMem(static_cast<T>(p), IsUnshared);
}
SharedMem& operator =(const SharedMem& that) {
ptr_ = that.ptr_;
#ifdef DEBUG
sharedness_ = that.sharedness_;
#endif
return *this;
}
// Reinterpret-cast the pointer to type U, preserving sharedness.
template<typename U>
inline SharedMem<U> cast() const {
#ifdef DEBUG
MOZ_ASSERT(asValue() % sizeof(mozilla::Conditional<mozilla::IsVoid<typename mozilla::RemovePointer<U>::Type>::value,
char,
typename mozilla::RemovePointer<U>::Type>) == 0);
if (sharedness_ == IsUnshared)
return SharedMem<U>::unshared(unwrap());
#endif
return SharedMem<U>::shared(unwrap());
}
explicit operator bool() { return ptr_ != nullptr; }
SharedMem operator +(size_t offset) {
return SharedMem(ptr_ + offset, *this);
}
SharedMem operator -(size_t offset) {
return SharedMem(ptr_ - offset, *this);
}
SharedMem operator ++() {
ptr_++;
return *this;
}
SharedMem operator ++(int) {
SharedMem<T> result(*this);
ptr_++;
return result;
}
SharedMem operator --() {
ptr_--;
return *this;
}
SharedMem operator --(int) {
SharedMem<T> result(*this);
ptr_--;
return result;
}
uintptr_t asValue() const {
return reinterpret_cast<uintptr_t>(ptr_);
}
// Cast to char*, add nbytes, and cast back to T. Simplifies code in a few places.
SharedMem addBytes(size_t nbytes) {
MOZ_ASSERT(nbytes % sizeof(mozilla::Conditional<mozilla::IsVoid<typename mozilla::RemovePointer<T>::Type>::value,
char,
typename mozilla::RemovePointer<T>::Type>) == 0);
return SharedMem(reinterpret_cast<T>(reinterpret_cast<char*>(ptr_) + nbytes), *this);
}
T unwrap() const {
return ptr_;
}
T unwrapUnshared() const {
MOZ_ASSERT(sharedness_ == IsUnshared);
return ptr_;
}
uintptr_t unwrapValue() const {
return reinterpret_cast<uintptr_t>(ptr_);
}
};
template<typename T>
inline bool
operator >=(const SharedMem<T>& a, const SharedMem<T>& b)
{
return a.unwrap() >= b.unwrap();
}
template<typename T>
inline bool
operator >=(const void* a, const SharedMem<T>& b)
{
return a >= b.unwrap();
}
template<typename T>
inline bool
operator ==(const void* a, const SharedMem<T>& b)
{
return a == b.unwrap();
}
template<typename T>
inline bool
operator ==(const SharedMem<T>& a, decltype(nullptr) b)
{
return a.unwrap() == b;
}
template<typename T>
inline bool
operator ==(const SharedMem<T>& a, const SharedMem<T>& b)
{
return a.unwrap() == b.unwrap();
}
template<typename T>
inline bool
operator !=(const SharedMem<T>& a, decltype(nullptr) b)
{
return a.unwrap() != b;
}
template<typename T>
inline bool
operator !=(const SharedMem<T>& a, const SharedMem<T>& b)
{
return a.unwrap() != b.unwrap();
}
template<typename T>
inline bool
operator >(const SharedMem<T>& a, const SharedMem<T>& b)
{
return a.unwrap() > b.unwrap();
}
template<typename T>
inline bool
operator >(const void* a, const SharedMem<T>& b)
{
return a > b.unwrap();
}
template<typename T>
inline bool
operator <=(const SharedMem<T>& a, const SharedMem<T>& b)
{
return a.unwrap() <= b.unwrap();
}
template<typename T>
inline bool
operator <=(const void* a, const SharedMem<T>& b)
{
return a <= b.unwrap();
}
template<typename T>
inline bool
operator <(const void* a, const SharedMem<T>& b)
{
return a < b.unwrap();
}
#endif // vm_SharedMem_h
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