smartptr.h

和modern c++ design 这本书配套的程序库。可以从作者的网站上免费下载。

////////////////////////////////////////////////////////////////////////////////
// The Loki Library
// Copyright (c) 2001 by Andrei Alexandrescu
// This code accompanies the book:
// Alexandrescu, Andrei. "Modern C++ Design: Generic Programming and Design 
//     Patterns Applied". Copyright (c) 2001. Addison-Wesley.
// Permission to use, copy, modify, distribute and sell this software for any 
//     purpose is hereby granted without fee, provided that the above copyright 
//     notice appear in all copies and that both that copyright notice and this 
//     permission notice appear in supporting documentation.
// The author or Addison-Welsey Longman make no representations about the 
//     suitability of this software for any purpose. It is provided "as is" 
//     without express or implied warranty.
////////////////////////////////////////////////////////////////////////////////

// Last update: June 20, 2001

#ifndef SMARTPTR_INC_
#define SMARTPTR_INC_

////////////////////////////////////////////////////////////////////////////////
// IMPORTANT NOTE
// Due to threading issues, the OwnershipPolicy has been changed as follows:
//     Release() returns a boolean saying if that was the last release
//        so the pointer can be deleted by the StoragePolicy
//     IsUnique() was removed
////////////////////////////////////////////////////////////////////////////////


#include "SmallObj.h"
#include "TypeManip.h"
#include "static_check.h"
#include <functional>
#include <stdexcept>

namespace Loki
{

////////////////////////////////////////////////////////////////////////////////
// class template DefaultSPStorage
// Implementation of the StoragePolicy used by SmartPtr
////////////////////////////////////////////////////////////////////////////////

    template <class T>
    class DefaultSPStorage
    {
    protected:
        typedef T* StoredType;    // the type of the pointee_ object
        typedef T* PointerType;   // type returned by operator->
        typedef T& ReferenceType; // type returned by operator*
        
    public:
        DefaultSPStorage() : pointee_(Default()) 
        {}

        // The storage policy doesn't initialize the stored pointer 
        //     which will be initialized by the OwnershipPolicy's Clone fn
        DefaultSPStorage(const DefaultSPStorage&)
        {}

        template <class U>
        DefaultSPStorage(const DefaultSPStorage<U>&) 
        {}
        
        DefaultSPStorage(const StoredType& p) : pointee_(p) {}
        
        PointerType operator->() const { return pointee_; }
        
        ReferenceType operator*() const { return *pointee_; }
        
        void Swap(DefaultSPStorage& rhs)
        { std::swap(pointee_, rhs.pointee_); }
    
        // Accessors
        friend inline PointerType GetImpl(const DefaultSPStorage& sp)
        { return sp.pointee_; }
        
    	friend inline const StoredType& GetImplRef(const DefaultSPStorage& sp)
    	{ return sp.pointee_; }

    	friend inline StoredType& GetImplRef(DefaultSPStorage& sp)
    	{ return sp.pointee_; }

    protected:
        // Destroys the data stored
        // (Destruction might be taken over by the OwnershipPolicy)
        void Destroy()
        { delete pointee_; }
        
        // Default value to initialize the pointer
        static StoredType Default()
        { return 0; }
    
    private:
        // Data
        StoredType pointee_;
    };

////////////////////////////////////////////////////////////////////////////////
// class template RefCounted
// Implementation of the OwnershipPolicy used by SmartPtr
// Provides a classic external reference counting implementation
////////////////////////////////////////////////////////////////////////////////

    template <class P>
    class RefCounted
    {
    public:
        RefCounted() 
        {
            pCount_ = static_cast<unsigned int*>(
                SmallObject<>::operator new(sizeof(unsigned int)));
            assert(pCount_);
            *pCount_ = 1;
        }
        
        RefCounted(const RefCounted& rhs) 
        : pCount_(rhs.pCount_)
        {}
        
        // MWCW lacks template friends, hence the following kludge
        template <typename P1>
        RefCounted(const RefCounted<P1>& rhs) 
        : pCount_(reinterpret_cast<const RefCounted&>(rhs).pCount_)
        {}
        
        P Clone(const P& val)
        {
            ++*pCount_;
            return val;
        }
        
        bool Release(const P&)
        {
            if (!--*pCount_)
            {
                SmallObject<>::operator delete(pCount_, sizeof(unsigned int));
                return true;
            }
            return false;
        }
        
        void Swap(RefCounted& rhs)
        { std::swap(pCount_, rhs.pCount_); }
    
        enum { destructiveCopy = false };

    private:
        // Data
        unsigned int* pCount_;
    };
    
////////////////////////////////////////////////////////////////////////////////
// class template RefCountedMT
// Implementation of the OwnershipPolicy used by SmartPtr
// Implements external reference counting for multithreaded programs
////////////////////////////////////////////////////////////////////////////////
    template <class P,
        template <class> class ThreadingModel>
    class RefCountedMT : public ThreadingModel< RefCountedMT<P, ThreadingModel> >
    {
    public:
        RefCountedMT() 
        {
            pCount_ = static_cast<unsigned int*>(
                SmallObject<ThreadingModel>::operator new(
                    sizeof(unsigned int)));
            assert(pCount_);
            *pCount_ = 1;
        }
        
        RefCountedMT(const RefCountedMT& rhs) 
        : pCount_(rhs.pCount_)
        {}
        
        // MWCW lacks template friends, hence the following kludge
        template <typename P1>
        RefCountedMT(const RefCountedMT<P1, ThreadingModel>& rhs) 
        : pCount_(reinterpret_cast<const RefCounted<P>&>(rhs).pCount_)
        {}
        
        P Clone(const P& val)
        {
            ThreadingModel<RefCountedMT>::AtomicIncrement(*pCount_);
            return val;
        }
        
        bool Release(const P&)
        {
            if (!ThreadingModel<RefCountedMT>::AtomicDecrement(*pCount_))
            {
                SmallObject<ThreadingModel>::operator delete(pCount_, 
                    sizeof(unsigned int));
                return true;
            }
            return false;
        }
        
        void Swap(RefCountedMT& rhs)
        { std::swap(pCount_, rhs.pCount_); }
    
        enum { destructiveCopy = false };

    private:
        // Data
        volatile unsigned int* pCount_;
    };

////////////////////////////////////////////////////////////////////////////////
// class template COMRefCounted
// Implementation of the OwnershipPolicy used by SmartPtr
// Adapts COM intrusive reference counting to OwnershipPolicy-specific syntax
////////////////////////////////////////////////////////////////////////////////

    template <class P>
    class COMRefCounted
    {
    public:
        COMRefCounted()
        {}
        
        template <class U>
        COMRefCounted(const COMRefCounted<U>&)
        {}
        
        static P Clone(const P& val)
        {
            val->AddRef();
            return val;
        }
        
        static bool Release(const P& val)
        { val->Release(); return false; }
        
        enum { destructiveCopy = false };
        
        static void Swap(COMRefCounted&)
        {}
    };

////////////////////////////////////////////////////////////////////////////////
// class template DeepCopy
// Implementation of the OwnershipPolicy used by SmartPtr
// Implements deep copy semantics, assumes existence of a Clone() member 
//     function of the pointee type
////////////////////////////////////////////////////////////////////////////////

    template <class P>
    struct DeepCopy
    {
        DeepCopy()
        {}
        
        template <class P1>
        DeepCopy(const DeepCopy<P1>&)
        {}
        
        static P Clone(const P& val)
        { return val->Clone(); }
        
        static bool Release(const P& val)
        { return true; }
        
        static void Swap(DeepCopy&)
        {}
        
        enum { destructiveCopy = false };
    };
    
////////////////////////////////////////////////////////////////////////////////
// class template RefLinked
// Implementation of the OwnershipPolicy used by SmartPtr
// Implements reference linking
////////////////////////////////////////////////////////////////////////////////

    namespace Private
    {
        class RefLinkedBase
        {
        public:
            RefLinkedBase() 
            { prev_ = next_ = this; }
            
            RefLinkedBase(const RefLinkedBase& rhs) 
            {
                prev_ = &rhs;
                next_ = rhs.next_;
                prev_->next_ = this;
                next_->prev_ = this;
            }
            
            bool Release()
            {
                if (next_ == this)
                {   
                    assert(prev_ == this);
                    return true;
                }
                prev_->next_ = next_;
                next_->prev_ = prev_;
                return false;
            }
            
            void Swap(RefLinkedBase& rhs)
            {
                if (next_ == this)
                {
                    assert(prev_ == this);
                    if (rhs.next_ == &rhs)
                    {
                        assert(rhs.prev_ == &rhs);
                        // both lists are empty, nothing 2 do
                        return;
                    }
                    prev_ = rhs.prev_;
                    next_ = rhs.next_;
                    prev_->next_ = next_->prev_ = this;
                    rhs.next_ = rhs.prev_ = &rhs;
                    return;
                }
                if (rhs.next_ == &rhs)
                {
                    rhs.Swap(*this);
                    return;
                }
                std::swap(prev_, rhs.prev_);
                std::swap(next_, rhs.next_);
                std::swap(prev_->next_, rhs.prev_->next_);
                std::swap(next_->prev_, rhs.next_->prev_);
            }
                
            enum { destructiveCopy = false };

        private:
            mutable const RefLinkedBase* prev_;
            mutable const RefLinkedBase* next_;
        };
    }
    
    template <class P>
    class RefLinked : public Private::RefLinkedBase
    {
    public:
        RefLinked()
        {}
        
        template <class P1>
        RefLinked(const RefLinked<P1>& rhs) 
        : Private::RefLinkedBase(rhs)
        {}

        static P Clone(const P& val)
        { return val; }

        bool Release(const P&)
        { return Private::RefLinkedBase::Release(); }
    };
    
////////////////////////////////////////////////////////////////////////////////
// class template DestructiveCopy
// Implementation of the OwnershipPolicy used by SmartPtr
// Implements destructive copy semantics (a la std::auto_ptr)
////////////////////////////////////////////////////////////////////////////////

    template <class P>
    class DestructiveCopy
    {
    public:
        DestructiveCopy()
        {}
        
        template <class P1>
        DestructiveCopy(const DestructiveCopy<P1>&)
        {}
        
        template <class P1>
        static P Clone(P1& val)
        {
            P result(val);
            val = P1();
            return result;
        }
        
        static bool Release(const P&)
        { return true; }
        
        static void Swap(DestructiveCopy&)
        {}
        
        enum { destructiveCopy = true };
    };
    
////////////////////////////////////////////////////////////////////////////////
// class template NoCopy
// Implementation of the OwnershipPolicy used by SmartPtr
// Implements a policy that doesn't allow copying objects
////////////////////////////////////////////////////////////////////////////////