Handle.h
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上传日期:2022-06-29
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书籍源码
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Visual C++
- /*
- * This file contains code from "C++ Primer, Fourth Edition", by Stanley B.
- * Lippman, Jose Lajoie, and Barbara E. Moo, and is covered under the
- * copyright and warranty notices given in that book:
- *
- * "Copyright (c) 2005 by Objectwrite, Inc., Jose Lajoie, and Barbara E. Moo."
- *
- *
- * "The authors and publisher have taken care in the preparation of this book,
- * but make no expressed or implied warranty of any kind and assume no
- * responsibility for errors or omissions. No liability is assumed for
- * incidental or consequential damages in connection with or arising out of the
- * use of the information or programs contained herein."
- *
- * Permission is granted for this code to be used for educational purposes in
- * association with the book, given proper citation if and when posted or
- * reproduced.Any commercial use of this code requires the explicit written
- * permission of the publisher, Addison-Wesley Professional, a division of
- * Pearson Education, Inc. Send your request for permission, stating clearly
- * what code you would like to use, and in what specific way, to the following
- * address:
- *
- * Pearson Education, Inc.
- * Rights and Contracts Department
- * 75 Arlington Street, Suite 300
- * Boston, MA 02216
- * Fax: (617) 848-7047
- */
- #include <stdexcept>
- template <class T> class Handle {
- public:
- // unbound handle
- Handle(T *p = 0): ptr(p), use(new size_t(1)) { }
- // overloaded operators to support pointer behavior
- T& operator*();
- T* operator->();
- const T& operator*() const;
- const T* operator->() const;
- // copy control: normal pointer behavior, but last Handle deletes the object
- Handle(const Handle& h): ptr(h.ptr), use(h.use)
- { ++*use; }
- Handle& operator=(const Handle&);
- ~Handle() { rem_ref(); }
- private:
- T* ptr; // shared object
- size_t *use; // count of how many Handles point to *ptr
- void rem_ref()
- { if (--*use == 0) { delete ptr; delete use; } }
- };
- template <class T>
- inline Handle<T>& Handle<T>::operator=(const Handle &rhs)
- {
- ++*rhs.use; // protect against self-assignment
- rem_ref(); // decrement use count and delete pointers if needed
- ptr = rhs.ptr;
- use = rhs.use;
- return *this;
- }
- template <class T> inline T& Handle<T>::operator*()
- {
- if (ptr) return *ptr;
- throw std::runtime_error
- ("dereference of unbound Handle");
- }
- template <class T> inline T* Handle<T>::operator->()
- {
- if (ptr) return ptr;
- throw std::runtime_error
- ("access through unbound Handle");
- }
- template <class T> inline
- const T& Handle<T>::operator*() const
- {
- if (ptr) return *ptr;
- throw std::runtime_error("dereference of unbound Handle");
- }
- template <class T> inline
- const T* Handle<T>::operator->() const
- {
- if (ptr) return ptr;
- throw std::runtime_error("access through unbound Handle");
- }