1 files changed, 166 insertions, 0 deletions
diff --git a/graphs/cpp/smtptr/shared_pointer.hh b/graphs/cpp/smtptr/shared_pointer.hh
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+++ b/graphs/cpp/smtptr/shared_pointer.hh
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+#pragma once
+
+#include <cassert>
+#include <iostream>
+#include <string>
+
+template <typename T>
+class SharedPointer
+{
+public:
+    // The type pointed to.
+    using element_type = T;
+
+    /**
+    ** \brief Construct a counted reference to a newly allocated object.
+    */
+    SharedPointer(element_type* p = nullptr);
+
+    /**
+    ** \brief Destroy the SharedPointer.
+    ** The object pointed to is destroyed only if it is not referenced anymore.
+    ** Take care to free everything ...
+    */
+    ~SharedPointer();
+
+    /**
+    ** \brief Copy constructor.
+    ** \return A new SharedPointer, pointing
+    ** to the underlying data of \a other.
+    **
+    ** Although the implementation is subsumed by the previous, more
+    ** generic one, the C++ standard still mandates this specific
+    ** signature.  Otherwise, the compiler will provide a default
+    ** implementation, which is of course wrong.  Note that the
+    ** same applies for the assignment operator.
+    */
+    SharedPointer(const SharedPointer<element_type>& other);
+
+    /// \name Assignments.
+    /// \{
+
+    /**
+    ** \brief Replace the underlying data with \a p
+    ** A call to \c reset is strictly equivalent to:
+    ** \code
+    **     r = SharedPointer<element_type>(p);
+    ** \endcode
+    ** This line implicitly calls the destructor of \a r before assigning
+    ** it a new value.
+    ** \warning You can't reset your \c SharedPointer with the
+    ** same pointer as the current one. In this case, nothing should
+    ** be done.
+    ** \warning Be mindful of other \c SharedPointers
+    ** which could also be pointing to the same data.
+    */
+    void reset(element_type* p);
+
+    /**
+    ** \brief Reference assignment
+    ** Its behavior is similar to \c reset() but you
+    ** have to use the existing SharedPointer \a other
+    ** instead of creating a new instance.
+    */
+    SharedPointer<element_type>&
+    operator=(const SharedPointer<element_type>& other);
+    /// \}
+
+    /// \name Access to data.
+    /// \{
+
+    // Access via a reference.
+    element_type& operator*() const;
+    // Access via a pointer.
+    element_type* operator->() const;
+
+    // Returns the underlying data pointer.
+    element_type* get() const;
+
+    // Returns the number of SharedPointer objects referring to the same managed
+    // object
+    long use_count() const;
+    /// \}
+
+    /// \name Equality operators.
+    /// \{
+
+    /**
+    ** \brief Reference comparison.
+    ** Returns true if the two references point to the same object.
+    */
+    template <typename U>
+    bool operator==(const SharedPointer<U>& rhs) const;
+
+    /**
+    ** \brief Reference comparison.
+    ** Returns false if the two references point to the same object.
+    */
+    template <typename U>
+    bool operator!=(const SharedPointer<U>& rhs) const;
+
+    /**
+    ** \brief Reference comparison.
+    ** Returns true if this points to \a p.
+    */
+    bool operator==(const element_type* p) const;
+
+    /**
+    ** \brief Reference comparison.
+    ** Returns false if this points to \a p.
+    */
+    bool operator!=(const element_type* p) const;
+
+    /**
+     ** \brief Move assignment operator for SharedPointer.
+     **
+     ** This operator transfers ownership of the managed object from the
+     ** \a other to this SharePointer.
+     ** After the assignment, the \a other will be empty.
+     ** \warning Don't forget to update the reference counter.
+     **
+     ** Returns a reference to this SharedPointer.
+     */
+    SharedPointer<element_type>& operator=(SharedPointer&& other) noexcept;
+
+    /**
+     ** \brief Move constructor for SharedPointer.
+     **
+     ** This constructor transfers ownership of the managed object from \a other
+     ** SharedPointer to the newly created SharedPointer.
+     **
+     */
+    SharedPointer(SharedPointer&& other);
+
+    /// \}
+
+    /**
+    ** \brief Test for validity
+    ** Returns true if the reference is valid, i.e. it points to an object.
+    ** This conversion operator allows users to write:
+    **
+    ** \code
+    ** SharedPointer<int> p1;
+    ** if (p1) // Here false
+    **   ...
+    ** \endcode
+    */
+    operator bool() const;
+
+    /**
+    ** \brief Test fellowship.
+    ** Returns true if the SharedPointer points to an object which
+    ** is of the specified type.
+    ** Look at the given example file shared_pointer_is_a.cc
+    ** to better understand its purpose.
+    */
+    template <typename U>
+    bool is_a() const;
+
+private:
+    // Pointer to the underlying data.
+    element_type* data_;
+    // A counter shared between all ref pointers to \a data_.
+    long* count_;
+};
+
+#include "shared_pointer.hxx"