75 lines
2.2 KiB
C++
75 lines
2.2 KiB
C++
#ifndef __refcount_h__
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#define __refcount_h__
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#include "lispassert.h"
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#include "yacasbase.h"
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//------------------------------------------------------------------------------
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// RefPtr - Smart pointer for (intrusive) reference counting.
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// Simply, an object's reference count is the number of RefPtrs refering to it.
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// The RefPtr will delete the referenced object when the count reaches zero.
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/*TODO: this might be improved a little by having RefPtr wrap the object being
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pointed to so the user of RefPtr does not need to add ReferenceCount explicitly.
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One can use RefPtr on any arbitrary object from that moment on.
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*/
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typedef ReferenceType ReferenceCount;
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template<class T>
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class RefPtr : public YacasBase // derived, so we can 'NEW LispPtr[nnn]'
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{
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public:
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// Default constructor (not explicit, so it auto-initializes)
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inline RefPtr() : iPtr(NULL) {}
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// Construct from pointer to T
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explicit RefPtr(T *ptr) : iPtr(ptr) { if (ptr) { ptr->iReferenceCount++; } }
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// Copy constructor
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RefPtr(const RefPtr &refPtr) : iPtr(refPtr.ptr()) { if (iPtr) { iPtr->iReferenceCount++; } }
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// Destructor
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~RefPtr()
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{
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if (iPtr)
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{
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iPtr->iReferenceCount--;
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if (iPtr->iReferenceCount == 0)
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{
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delete iPtr;
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}
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}
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}
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// Assignment from pointer
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RefPtr &operator=(T *ptr)
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{
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if (ptr)
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{
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ptr->iReferenceCount++;
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}
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if (iPtr)
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{
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iPtr->iReferenceCount--;
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if (iPtr->iReferenceCount == 0)
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{
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delete iPtr;
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}
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}
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iPtr = ptr;
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return *this;
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}
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// Assignment from another
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RefPtr &operator=(const RefPtr &refPtr) { return this->operator=(refPtr.ptr()); }
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operator T*() const { return iPtr; } // implicit conversion to pointer to T
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T &operator*() const { return *iPtr; } // so (*refPtr) is a reference to T
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T *operator->() const { return iPtr; } // so (refPtr->member) accesses T's member
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T *ptr() const { return iPtr; } // so (refPtr.ptr()) returns the pointer to T (boost calls this method 'get')
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bool operator!() const { return !iPtr; } // is null pointer
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private:
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T *iPtr;
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};
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#endif
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