164 lines
2.9 KiB
C++
164 lines
2.9 KiB
C++
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#ifndef INCLUDED_AI_BOOST_SHARED_PTR
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#define INCLUDED_AI_BOOST_SHARED_PTR
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#ifndef BOOST_SCOPED_PTR_HPP_INCLUDED
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#include <assert.h>
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// ------------------------------
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// Internal stub
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namespace boost {
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namespace detail {
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class controller {
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public:
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controller()
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: cnt(0)
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{}
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template <typename T>
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controller(T* ptr)
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: cnt(ptr?1:0)
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{}
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public:
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template <typename T>
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controller* decref(T* pt) {
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if (!pt) {
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return NULL;
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}
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if (--cnt <= 0) {
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delete this;
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delete pt;
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}
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return NULL;
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}
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controller* incref() {
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++cnt;
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return this;
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}
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private:
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long cnt;
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};
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struct empty {};
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template <typename DEST, typename SRC>
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struct is_convertible_stub {
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struct yes {char s[1];};
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struct no {char s[2];};
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static yes foo(DEST*);
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static no foo(...);
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enum {result = (sizeof(foo((SRC*)0)) == sizeof(yes) ? 1 : 0)};
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};
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template <bool> struct enable_if {};
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template <> struct enable_if<true> {
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typedef empty result;
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};
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template <typename DEST, typename SRC>
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struct is_convertible : public enable_if<is_convertible_stub<DEST,SRC>::result > {
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};
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}
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// ------------------------------
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// Small replacement for boost::shared_ptr, not threadsafe because no
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// atomic reference counter is in use.
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// ------------------------------
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template <class T>
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class shared_ptr
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{
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template <typename TT> friend class shared_ptr;
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public:
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// provide a default construtctor
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shared_ptr()
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: ptr()
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, ctr(new detail::controller())
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{
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}
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// construction from an existing object of type T
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explicit shared_ptr(T* _ptr)
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: ptr(_ptr)
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, ctr(new detail::controller(ptr))
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{
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}
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shared_ptr(const shared_ptr& o)
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: ptr(o.ptr)
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, ctr(o.ctr->incref())
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{
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}
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template <typename Y>
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shared_ptr(const shared_ptr<Y>& o,typename detail::is_convertible<T,Y>::result = detail::empty())
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: ptr(o.ptr)
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, ctr(o.ctr->incref())
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{
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}
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// automatic destruction of the wrapped object when all
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// references are freed.
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~shared_ptr() {
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ctr = ctr->decref(ptr);
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}
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// pointer access
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inline operator T*() {
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return ptr;
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}
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inline T* operator-> () {
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return ptr;
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}
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// standard semantics
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inline T* get() {
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return ptr;
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}
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inline void reset (T* t = 0) {
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ctr = ctr->decref(ptr);
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ptr = t;
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if(ptr) {
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ctr = new detail::controller(ptr);
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}
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}
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void swap(shared_ptr & b) {
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std::swap(ptr, b.ptr);
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std::swap(ctr, b.ctr);
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}
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private:
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// encapsulated object pointer
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T* ptr;
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// control block
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detail::controller* ctr;
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};
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template<class T>
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inline void swap(shared_ptr<T> & a, shared_ptr<T> & b)
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{
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a.swap(b);
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}
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} // end of namespace boost
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#else
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# error "shared_ptr.h was already included"
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#endif
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#endif // INCLUDED_AI_BOOST_SCOPED_PTR
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