// -*- c-basic-offset: 4; tab-width: 8; indent-tabs-mode: t -*- // Copyright (c) 2001-2005 International Computer Science Institute // // Permission is hereby granted, free of charge, to any person obtaining a // copy of this software and associated documentation files (the "Software") // to deal in the Software without restriction, subject to the conditions // listed in the XORP LICENSE file. These conditions include: you must // preserve this copyright notice, and you cannot mention the copyright // holders in advertising related to the Software without their permission. // The Software is provided WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED. This // notice is a summary of the XORP LICENSE file; the license in that file is // legally binding. // $XORP: xorp/libxorp/ref_ptr.hh,v 1.17 2005/03/25 02:53:44 pavlin Exp $ #ifndef __LIBXORP_REF_PTR_HH__ #define __LIBXORP_REF_PTR_HH__ #include "config.h" #include "xorp.h" #include <vector> /** * @short class for maintaining the storage of counters used by ref_ptr. * * The ref_counter_pool is a singleton class that maintains the counters * for all ref_ptr objects. The counters are maintained in a vector. This * class is used by ref_ptr and not intended any other purpose. */ class ref_counter_pool { private: vector<int32_t> _counters; int32_t _free_index; int32_t _balance; static const int32_t LAST_FREE = -1; static ref_counter_pool _the_instance; /** * Expand counter storage. */ void grow(); public: /** * Create a new counter. * @return index associated with counter. */ int32_t new_counter(); /** * Increment the count associated with counter by 1. * @param index the counter to increment. */ int32_t incr_counter(int32_t index); /** * Decrement the count associated with counter by 1. * @param index the counter to decrement. */ int32_t decr_counter(int32_t index); /** * Get the count associated with counter. * @param index of the counter to query. * @return the counter value. */ int32_t count(int32_t index); /** * Recycle counter. Places counter on free-list. * @param index of the counter to recycle. */ void recycle(int32_t index); /** * Dumps counter info to stdout. Debugging function. */ void dump(); /** * Sanity check internal data structure. Debugging function. */ void check(); /** * Check index is on free list. */ bool on_free_list(int32_t index); /** * Return number of valid ref pointer entries in pool. */ inline int32_t balance() const { return _balance; } /** * @return singleton ref_counter_pool. */ static ref_counter_pool& instance(); ref_counter_pool(); }; /** * @short Reference Counted Pointer Class. * * The ref_ptr class is a strong reference class. It maintains a count of * how many references to an object exist and releases the memory associated * with the object when the reference count reaches zero. The reference * pointer can be dereferenced like an ordinary pointer to call methods * on the reference counted object. * * At the time of writing the only supported memory management is * through the new and delete operators. At a future date, this class * should support the STL allocator classes or an equivalent to * provide greater flexibility. */ template <class _Tp> class ref_ptr { public: typedef ref_ptr<const _Tp> const_ref_ptr; public: /** * Construct a reference pointer for object. * * @param p pointer to object to be reference counted. p must be * allocated using operator new as it will be destructed using delete * when the reference count reaches zero. */ ref_ptr(_Tp* __p = 0) : _M_ptr(__p), _M_index(0) { if (_M_ptr) _M_index = ref_counter_pool::instance().new_counter(); } /** * Copy Constructor * * Constructs a reference pointer for object. Raises reference count * associated with object by 1. */ ref_ptr(const ref_ptr& __r) : _M_ptr(0), _M_index(-1) { ref(&__r); } /** * Assignment Operator * * Assigns reference pointer to new object. */ ref_ptr& operator=(const ref_ptr& __r) { if (&__r != this) { unref(); ref(&__r); } return *this; } /** * Destruct reference pointer instance and lower reference count on * object being tracked. The object being tracked will be deleted if * the reference count falls to zero because of the destruction of the * reference pointer. */ ~ref_ptr() { unref(); } /** * Dereference reference counted object. * @return reference to object. */ inline _Tp& operator*() const { return *_M_ptr; } /** * Dereference pointer to reference counted object. * @return pointer to object. */ inline _Tp* operator->() const { return _M_ptr; } /** * Dereference pointer to reference counted object. * @return pointer to object. */ inline _Tp* get() const { return _M_ptr; } /** * Equality Operator * @return true if reference pointers refer to same object. */ inline bool operator==(const ref_ptr& rp) const { return _M_ptr == rp._M_ptr; } /** * Check if reference pointer refers to an object or whether it has * been assigned a null object. * @return true if reference pointer refers to a null object. */ inline bool is_empty() const { return _M_ptr == 0; } /** * @return true if reference pointer represents only reference to object. */ inline bool is_only() const { return ref_counter_pool::instance().count(_M_index) == 1; } /** * @param n minimum count. * @return true if there are at least n references to object. */ bool at_least(int32_t n) const { return ref_counter_pool::instance().count(_M_index) >= n; } /** * Release reference on object. The reference pointers underlying * object is set to null, and the former object is destructed if * necessary. */ inline void release() const { unref(); } inline operator const_ref_ptr() { const_ref_ptr crp(get(), _M_index); return crp; } ref_ptr(_Tp* data, int32_t index) : _M_ptr(data), _M_index(index) { ref_counter_pool::instance().incr_counter(_M_index); } protected: /** * Add reference. */ void ref(const ref_ptr* __r) const { _M_ptr = __r->_M_ptr; _M_index = __r->_M_index; if (_M_ptr) { ref_counter_pool::instance().incr_counter(_M_index); } } /** * Remove reference. */ void unref() const { if (_M_ptr && ref_counter_pool::instance().decr_counter(_M_index) == 0) { delete _M_ptr; } _M_ptr = 0; } mutable _Tp* _M_ptr; mutable int32_t _M_index; // index in ref_counter_pool }; #if 0 template <typename _Tp> ref_ptr<const _Tp>::ref_ptr(const ref_ptr<_Tp>& __r) : _M_ptr(0), _M_index(_r->_M_index) { ref_counter_pool::instance().incr_counter(_M_index); } #endif /** * @short class for maintaining the storage of counters used by cref_ptr. * * The cref_counter_pool is a singleton class that maintains the counters * for all cref_ptr objects. The counters are maintained in a vector. This * class is used by cref_ptr and not intended any other purpose. */ class cref_counter_pool { private: struct pool_item { int32_t count; void* data; }; vector<pool_item> _counters; int32_t _free_index; static const int32_t LAST_FREE = -1; static cref_counter_pool _the_instance; /** * Expand counter storage. */ void grow(); public: /** * Create a new counter. * @return index associated with counter. */ int32_t new_counter(void *data); /** * Increment the count associated with counter by 1. * @param index the counter to increment. */ int32_t incr_counter(int32_t index); /** * Decrement the count associated with counter by 1. * @param index the counter to decrement. */ int32_t decr_counter(int32_t index); /** * Get the count associated with counter. * @param index of the counter to query. * @return the counter value. */ int32_t count(int32_t index); void* data(int32_t index); /** * Recycle counter. Places counter on free-list. * @param index of the counter to recycle. */ void recycle(int32_t index); /** * Dumps counter info to stdout. Debugging function. */ void dump(); /** * Sanity check internal data structure. Debugging function. */ void check(); /** * @return singleton cref_counter_pool. */ static cref_counter_pool& instance(); cref_counter_pool(); }; /** * @short Compact Reference Counted Pointer Class. * * The cref_ptr class is a strong reference class. It maintains a count of * how many references to an object exist and releases the memory associated * with the object when the reference count reaches zero. The reference * pointer can be dereferenced like an ordinary pointer to call methods * on the reference counted object. * * In contrast to the ref_ptr class, accessing the pointer requires * two levels of indirection as the pointer is stored in the same * table as the counter. This is a performance hit, but means each * cref_ptr only consumes 4-bytes. * * At the time of writing the only supported memory management is * through the new and delete operators. At a future date, this class * should support the STL allocator classes or an equivalent to * provide greater flexibility. */ template <class _Tp> class cref_ptr { public: /** * Construct a compact reference pointer for object. * * @param p pointer to object to be reference counted. p must be * allocated using operator new as it will be destructed using delete * when the reference count reaches zero. */ cref_ptr(_Tp* __p = 0) : _M_index(cref_counter_pool::instance().new_counter(__p)) {} /** * Copy Constructor * * Constructs a reference pointer for object. Raises reference count * associated with object by 1. */ cref_ptr(const cref_ptr& __r) : _M_index(-1) { ref(&__r); } /** * Assignment Operator * * Assigns reference pointer to new object. */ cref_ptr& operator=(const cref_ptr& __r) { if (&__r != this) { unref(); ref(&__r); } return *this; } /** * Destruct reference pointer instance and lower reference count on * object being tracked. The object being tracked will be deleted if * the reference count falls to zero because of the destruction of the * reference pointer. */ ~cref_ptr() { unref(); } /** * Dereference pointer to reference counted object. * @return pointer to object. */ inline _Tp* get() const { return reinterpret_cast<_Tp*> (cref_counter_pool::instance().data(_M_index)); } /** * Dereference reference counted object. * @return reference to object. */ inline _Tp& operator*() const { return *(get()); } /** * Dereference pointer to reference counted object. * @return pointer to object. */ inline _Tp* operator->() const { return get(); } /** * Equality Operator * @return true if reference pointers refer to same object. */ inline bool operator==(const cref_ptr& rp) const { return get() == rp.get(); } /** * Check if reference pointer refers to an object or whether it has * been assigned a null object. * @return true if reference pointer refers to a null object. */ inline bool is_empty() const { return _M_index < 0 || 0 == get(); } /** * @return true if reference pointer represents only reference to object. */ inline bool is_only() const { return cref_counter_pool::instance().count(_M_index) == 1; } /** * @param n minimum count. * @return true if there are at least n references to object. */ bool at_least(int32_t n) const { return cref_counter_pool::instance().count(_M_index) >= n; } /** * Release reference on object. The reference pointers underlying * object is set to null, and the former object is destructed if * necessary. */ inline void release() const { unref(); } private: /** * Add reference. */ void ref(const cref_ptr* __r) const { _M_index = __r->_M_index; cref_counter_pool::instance().incr_counter(_M_index); } /** * Remove reference. */ void unref() const { if (_M_index >= 0 && cref_counter_pool::instance().decr_counter(_M_index) == 0) { delete get(); _M_index = -1; } } mutable int32_t _M_index; // index in cref_counter_pool }; #endif // __LIBXORP_REF_PTR_HH__