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#pragma once
namespace WAVM {
// A smart pointer that uses an intrusive reference counter.
// Needs Pointee to define memory functions to manipulate the reference count:
// void addRef();
// void removeRef();
template<typename Pointee> struct IntrusiveSharedPtr
{
// Constructors/destructor
constexpr IntrusiveSharedPtr() : value(nullptr) {}
IntrusiveSharedPtr(Pointee* inValue)
{
value = inValue;
if(value) { value->addRef(); }
}
IntrusiveSharedPtr(const IntrusiveSharedPtr<Pointee>& inCopy)
{
value = inCopy.value;
if(value) { value->addRef(); }
}
IntrusiveSharedPtr(IntrusiveSharedPtr<Pointee>&& inMove) noexcept
{
value = inMove.value;
inMove.value = nullptr;
}
~IntrusiveSharedPtr()
{
if(value) { value->removeRef(); }
}
// Adopt a raw pointer: coerces the pointer to an IntrusiveSharedPtr without calling addRef
// or removeRef.
static IntrusiveSharedPtr<Pointee> adopt(Pointee*&& inValue)
{
IntrusiveSharedPtr<Pointee> result(adoptConstructorSelector, inValue);
inValue = nullptr;
return result;
}
// Assignment operators
void operator=(Pointee* inValue)
{
auto oldValue = value;
value = inValue;
if(value) { value->addRef(); }
if(oldValue) { oldValue->removeRef(); }
}
void operator=(const IntrusiveSharedPtr<Pointee>& inCopy)
{
auto oldValue = value;
value = inCopy.value;
if(value) { value->addRef(); }
if(oldValue) { oldValue->removeRef(); }
}
void operator=(IntrusiveSharedPtr<Pointee>&& inMove) noexcept
{
auto oldValue = value;
value = inMove.value;
inMove.value = nullptr;
if(oldValue) { oldValue->removeRef(); }
}
// Accessors
constexpr operator Pointee*() const { return value; }
constexpr Pointee& operator*() const { return *value; }
constexpr Pointee* operator->() const { return value; }
private:
Pointee* value;
enum AdoptConstructorSelector
{
adoptConstructorSelector
};
constexpr IntrusiveSharedPtr(AdoptConstructorSelector, Pointee* inValue) : value(inValue) {}
};
}
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