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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
// ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
// PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
// SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
// ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
// ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
// OR OTHER DEALINGS IN THE SOFTWARE.
//
// This software was developed from code available in the public domain
// and has no copyright.
// About Shared_Ptr:
// Shared_Ptr wraps a reference-counted smart pointer around a dynamically
// allocated object. Unlike auto_ptr, the Shared_Ptr can be used as a smart
// pointer for objects stored in containers like std::vector. Do not use
// Shared_Ptr (or shared_ptr or auto_ptr) for dynamically allocated arrays.
// See below for advice on how to wrap dynamically allocated arrays in a
// vector.
//
// The next standard of C++ will also contain a shared_ptr. Some modern
// compilers already have a shared_ptr available as std::tr1::shared_ptr. If
// your compiler already provides a shared_ptr, or if you have Boost, you
// should use that smart pointer instead. This class has been provided for
// those users who don't have easy access to an "official" shared_ptr.
// Note that this class is "Shared_Ptr", a slightly different name to the
// future "shared_ptr" to avoid naming conflicts.
// Advantages of Shared_Ptr (or shared_ptr where available):
// - Shared_Ptr can be safely copied. This makes then suitable for containers.
// - Shared_Ptr automatically calls delete for the wrapped pointer when
// its last copy goes out of scope.
// - Shared_Ptr simplifies exception safety.
//
// Without smart pointers, it can be quite challenging to ensure that every
// dynamically allocated pointer (i.e. use of new) is deleted in the event of
// all possible exceptions. In addition to the exceptions we throw ourselves,
// "new" itself will throw an exception it it fails, as does the STL (Standard
// Template Library which includes vector and string). Without smart pointers
// we often need to resort to additional try/catch blocks simply to avoid
// memory leaks when exceptions occur.
// Examples:
// Shared_Ptr<CWnd> w1(new CWnd);
// or
// Shared_Ptr<CWnd> w1 = new CWnd;
// or
// typedef Shared_Ptr<CWnd> CWndPtr;
// CWndPtr w1 = new CWnd;
// or
// typedef Shared_Ptr<CWnd> CWndPtr;
// CWndPtr w1(new CWnd);
//
// And with a vector
// typedef Shared_Ptr<CWnd> CWndPtr;
// std::vector<CWndPtr> MyVector;
// MyVector.push_back(new CWnd);
// or
// typedef Shared_Ptr<CWnd> CWndPtr;
// CWnd* pWnd = new CWnd;
// std::vector<CWndPtr> MyVector;
// MyVector.push_back(pWnd);
//
// How to handle dynamically allocated arrays:
// While we could create a smart pointer for arrays, we don't need to because
// std::vector already handles this for us. Consider the following example:
// int nLength = ::GetWindowTextLength(m_hWnd);
// pTChar = new TCHAR[nLength+1];
// memset(pTChar, 0, (nLength+1)*sizeof(TCHAR));
// ::GetWindowText(m_hWnd, m_pTChar, nLength+1);
// ....
// delete[] pTChar;
//
// This can be improved by using a vector instead of an array
// int nLength = ::GetWindowTextLength(m_hWnd);
// std::vector<TCHAR> vTChar( nLength+1, _T('\0') );
// TCHAR* pTCharArray = &vTChar.front();
// ::GetWindowText(m_hWnd, pTCharArray, nLength+1);
//
// This works because the memory in a vector is always contiguous. Note that
// this is NOT always true of std::string.
// Summing up:
// In my opinion, "naked" pointers for dynamically created objects should be
// avoided in modern C++ code. That's to say that calls to "new" should be
// wrapped in some sort of smart pointer wherever possible. This eliminates
// the possibility of memory leaks (particularly in the event of exceptions).
// It also elminiates the need for delete in user's code.
#ifndef _WIN32XX_SHARED_PTR_
#define _WIN32XX_SHARED_PTR_
namespace Win32xx
{
template <class T1>
class Shared_Ptr
{
public:
Shared_Ptr() : m_ptr(NULL), m_count(NULL) { }
Shared_Ptr(T1 * p) : m_ptr(p), m_count(NULL)
{
try
{
if (m_ptr) m_count = new long(0);
inc_ref();
}
// catch the unlikely event of 'new long(0)' throwing an exception
catch (const std::bad_alloc&)
{
delete m_ptr;
throw;
}
}
Shared_Ptr(const Shared_Ptr& rhs) : m_ptr(rhs.m_ptr), m_count(rhs.m_count) { inc_ref(); }
~Shared_Ptr()
{
if(m_count && 0 == dec_ref())
{
// Note: This code doesn't handle a pointer to an array.
// We would need delete[] m_ptr to handle that.
delete m_ptr;
delete m_count;
}
}
T1* get() const { return m_ptr; }
long use_count() const { return m_count? *m_count : 0; }
bool unique() const { return (m_count && (*m_count == 1)); }
void swap(Shared_Ptr& rhs)
{
std::swap(m_ptr, rhs.m_ptr);
std::swap(m_count, rhs.m_count);
}
Shared_Ptr& operator=(const Shared_Ptr& rhs)
{
Shared_Ptr tmp(rhs);
this->swap(tmp);
return *this;
}
T1* operator->() const
{
assert(m_ptr);
return m_ptr;
}
T1& operator*() const
{
assert (m_ptr);
return *m_ptr;
}
bool operator== (const Shared_Ptr& rhs) const
{
return ( *m_ptr == *rhs.m_ptr);
}
bool operator!= (const Shared_Ptr& rhs) const
{
return ( *m_ptr != *rhs.m_ptr);
}
bool operator< (const Shared_Ptr& rhs) const
{
return ( *m_ptr < *rhs.m_ptr );
}
bool operator> (const Shared_Ptr& rhs) const
{
return ( *m_ptr > *rhs.m_ptr );
}
private:
void inc_ref()
{
if(m_count)
InterlockedIncrement(m_count);
}
int dec_ref()
{
assert (m_count);
return InterlockedDecrement(m_count);
}
T1* m_ptr;
long* m_count;
};
}
#endif // _WIN32XX_SHARED_PTR_
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