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In actuality, prototyping is an iterative process with the design and implementation phases. By clarifying the most difficult aspects of the design, prototyping can actually result in avoiding costly mistakes and bringing the product in on time. 3 Our Image Framework Prototyping Strategy In Chapter 2, we showed our first attempt to design an image object to handle the simple problem of generating a thumbnail image. We presented this test application to show how easy it is to design an object that solves a simple problem.

The full base class definition is shown here. template class apAllocatorBase_ { public: apAllocatorBase_ (unsigned int n, unsigned int align) : pRaw_ (0), pData_ (0), ref_ (0), size_ (n), align_ (align) {} // Derived classes alloc memory; store details in base class virtual ~apAllocatorBase_ () {} // Derived classes will deallocate memory operator T* () { return pData_;} operator const T* () const { return pData_;} // Conversion to pointer of allocated memory type unsigned int size () const { return size_;} // Number of elements unsigned int ref () const { return ref_;} // Number of references unsigned int align () const { return align_;} // Alignment void addRef () { ref_++; } void subRef () { --ref_; if (ref_ == 0) delete this; } // Increment or decrement the reference count protected: virtual void allocate () = 0; virtual void deallocate () = 0; // Used to allocate/deallocate memory.

Many libraries require memory alignment to avoid the performance hit of copying images. We use the pRaw_ pointer (defined as a char*) for the allocation, and then align and coerce the pointer to be compatible with pData_: pRaw_ = new char [sizeof(T) * size_ + (align_ - 1)]; pData_ = alignPointer (pRaw_); Our base class provides a function, alignPointer(), to handle the alignment and conversion to type T*. We saw how this function can alter the memory address by up to (align_-1) bytes during alignment.