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implement Poco::SharedPtr using std::shared_ptr (#1993)
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@obiltschnig @aleks-f
obiltschnig authored and aleks-f committed Nov 13, 2017
1 parent 3ada2d9 commit e12458a
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Showing 2 changed files with 82 additions and 170 deletions.
218 changes: 62 additions & 156 deletions Foundation/include/Poco/SharedPtr.h
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Original file line number Diff line number Diff line change
Expand Up @@ -20,147 +20,67 @@

#include "Poco/Foundation.h"
#include "Poco/Exception.h"
#include "Poco/AtomicCounter.h"
#include <memory>
#include <algorithm>


namespace Poco {


class ReferenceCounter
/// Simple ReferenceCounter object, does not delete itself when count reaches 0.
{
public:
ReferenceCounter(): _cnt(1)
{
}

void duplicate()
{
++_cnt;
}

int release()
{
return --_cnt;
}

int referenceCount() const
{
return _cnt.value();
}

private:
AtomicCounter _cnt;
};


//@ deprecated
template <class C>
class ReleasePolicy
/// The default release policy for SharedPtr, which
/// simply uses the delete operator to delete an object.
{
public:
static void release(C* pObj)
/// Delete the object.
/// Note that pObj can be 0.
{
delete pObj;
}
};


template <class C>
class ReleaseArrayPolicy
/// The release policy for SharedPtr holding arrays.
class SharedPtr
/// As of POCO C++ Libraries Release 2.0, SharedPtr is a small wrapper around
/// std::shared_ptr, providing basic backwards compatibility to the 1.x SharedPtr
/// implementation.
///
/// Note: ReleasePolicy is no longer supported.
///
/// SharedPtr will be removed in a future release. New code should use
/// std::shared_ptr and existing code should be changed to use std::shared_ptr
/// instead of Poco::SharedPtr.
{
public:
static void release(C* pObj)
/// Delete the object.
/// Note that pObj can be 0.
SharedPtr()
{
delete [] pObj;
}
};


template <class C, class RC = ReferenceCounter, class RP = ReleasePolicy<C> >
class SharedPtr
/// SharedPtr is a "smart" pointer for classes implementing
/// reference counting based garbage collection.
/// SharedPtr is thus similar to AutoPtr. Unlike the
/// AutoPtr template, which can only be used with
/// classes that support reference counting, SharedPtr
/// can be used with any class. For this to work, a
/// SharedPtr manages a reference count for the object
/// it manages.
///
/// SharedPtr works in the following way:
/// If an SharedPtr is assigned an ordinary pointer to
/// an object (via the constructor or the assignment operator),
/// it takes ownership of the object and the object's reference
/// count is initialized to one.
/// If the SharedPtr is assigned another SharedPtr, the
/// object's reference count is incremented by one.
/// The destructor of SharedPtr decrements the object's
/// reference count by one and deletes the object if the
/// reference count reaches zero.
/// SharedPtr supports dereferencing with both the ->
/// and the * operator. An attempt to dereference a null
/// SharedPtr results in a NullPointerException being thrown.
/// SharedPtr also implements all relational operators and
/// a cast operator in case dynamic casting of the encapsulated data types
/// is required.
{
public:
SharedPtr(): _pCounter(new RC), _ptr(0)
SharedPtr(C* ptr):
_ptr(ptr)
{
}

SharedPtr(C* ptr)
try:
_pCounter(new RC),
SharedPtr(const std::shared_ptr<C>& ptr):
_ptr(ptr)
{
}
catch (...)

template <class Other>
SharedPtr(const SharedPtr<Other>& ptr):
_ptr(std::dynamic_pointer_cast<C>(ptr.shared_ptr()))
{
RP::release(ptr);
}

template <class Other, class OtherRP>
SharedPtr(const SharedPtr<Other, RC, OtherRP>& ptr): _pCounter(ptr._pCounter), _ptr(const_cast<Other*>(ptr.get()))
SharedPtr(const SharedPtr& ptr):
_ptr(ptr._ptr)
{
_pCounter->duplicate();
}

SharedPtr(const SharedPtr& ptr): _pCounter(ptr._pCounter), _ptr(ptr._ptr)
SharedPtr(SharedPtr&& ptr):
_ptr(std::move(ptr._ptr))
{
_pCounter->duplicate();
}

~SharedPtr()
{
try
{
release();
}
catch (...)
{
poco_unexpected();
}
}

SharedPtr& assign(C* ptr)
{
if (get() != ptr)
{
SharedPtr tmp(ptr);
swap(tmp);
}
_ptr.reset(ptr);
return *this;
}

SharedPtr& assign(const SharedPtr& ptr)
{
if (&ptr != this)
Expand All @@ -170,9 +90,9 @@ class SharedPtr
}
return *this;
}
template <class Other, class OtherRP>
SharedPtr& assign(const SharedPtr<Other, RC, OtherRP>& ptr)

template <class Other>
SharedPtr& assign(const SharedPtr<Other>& ptr)
{
if (ptr.get() != _ptr)
{
Expand All @@ -192,43 +112,53 @@ class SharedPtr
return assign(ptr);
}

template <class Other, class OtherRP>
SharedPtr& operator = (const SharedPtr<Other, RC, OtherRP>& ptr)
template <class Other>
SharedPtr& operator = (const SharedPtr<Other>& ptr)
{
return assign<Other>(ptr);
}

void swap(SharedPtr& ptr)
{
std::swap(_ptr, ptr._ptr);
std::swap(_pCounter, ptr._pCounter);
}

template <class Other>
SharedPtr<Other, RC, RP> cast() const
SharedPtr<Other> cast() const
/// Casts the SharedPtr via a dynamic cast to the given type.
/// Returns an SharedPtr containing NULL if the cast fails.
/// Example: (assume class Sub: public Super)
/// SharedPtr<Super> super(new Sub());
/// SharedPtr<Sub> sub = super.cast<Sub>();
/// poco_assert (sub.get());
{
Other* pOther = dynamic_cast<Other*>(_ptr);
if (pOther)
return SharedPtr<Other, RC, RP>(_pCounter, pOther);
return SharedPtr<Other, RC, RP>();
return SharedPtr(std::dynamic_pointer_cast<Other>(_ptr));
}

template <class Other>
SharedPtr<Other, RC, RP> unsafeCast() const
SharedPtr<Other> unsafeCast() const
/// Casts the SharedPtr via a static cast to the given type.
/// Example: (assume class Sub: public Super)
/// SharedPtr<Super> super(new Sub());
/// SharedPtr<Sub> sub = super.unsafeCast<Sub>();
/// poco_assert (sub.get());
{
Other* pOther = static_cast<Other*>(_ptr);
return SharedPtr<Other, RC, RP>(_pCounter, pOther);
return SharedPtr(std::static_pointer_cast<Other>(_ptr));
}

operator std::shared_ptr<C>()
{
return _ptr;
}

const std::shared_ptr<C>& shared_ptr() const
{
return _ptr;
}

std::shared_ptr<C>& shared_ptr()
{
return _ptr;
}

C* operator -> ()
Expand All @@ -253,22 +183,22 @@ class SharedPtr

C* get()
{
return _ptr;
return _ptr.get();
}

const C* get() const
{
return _ptr;
return _ptr.get();
}

operator C* ()
{
return _ptr;
return _ptr.get();
}

operator const C* () const
{
return _ptr;
return _ptr.get();
}

bool operator ! () const
Expand Down Expand Up @@ -370,10 +300,10 @@ class SharedPtr
{
return get() >= ptr;
}
int referenceCount() const

long referenceCount() const
{
return _pCounter->referenceCount();
return _ptr.use_count();
}

protected:
Expand All @@ -382,40 +312,16 @@ class SharedPtr
if (!_ptr)
throw NullPointerException();

return _ptr;
}

void release()
{
poco_assert_dbg (_pCounter);
int i = _pCounter->release();
if (i == 0)
{
RP::release(_ptr);
_ptr = 0;

delete _pCounter;
_pCounter = 0;
}
}

SharedPtr(RC* pCounter, C* ptr): _pCounter(pCounter), _ptr(ptr)
/// for cast operation
{
poco_assert_dbg (_pCounter);
_pCounter->duplicate();
return _ptr.get();
}

protected:
RC* _pCounter;
C* _ptr;

template <class OtherC, class OtherRC, class OtherRP> friend class SharedPtr;
std::shared_ptr<C> _ptr;
};


template <class C, class RC, class RP>
inline void swap(SharedPtr<C, RC, RP>& p1, SharedPtr<C, RC, RP>& p2)
template <class C>
inline void swap(SharedPtr<C>& p1, SharedPtr<C>& p2)
{
p1.swap(p2);
}
Expand Down
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