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A pure virtual function or pure virtual method is a virtual function that is required to be implemented by a derived class if the derived class is not abstract. Classes containing pure virtual methods are termed "abstract" and they cannot be instantiated directly.
A virtual call requires at least an extra indexed dereference and sometimes a "fixup" addition, compared to a non-virtual call, which is simply a jump to a compiled-in pointer. Therefore, calling virtual functions is inherently slower than calling non-virtual functions.
Physical functions have the ability to move data in and out of the device while virtual functions are lightweight PCIe functions that support data flowing but also have a restricted set of configuration resources. The virtual or physical functions available to the hypervisor or guest operating system depend on the PCIe device. [3]
A virtualized network function, or VNF, is implemented within one or more virtual machines or containers running different software and processes, on top of commercial off the shelf (COTS) high-volume servers, switches and storage devices, or even cloud computing infrastructure, instead of having custom hardware appliances for each network ...
In essence, the visitor allows adding new virtual functions to a family of classes, without modifying the classes. Instead, a visitor class is created that implements all of the appropriate specializations of the virtual function. The visitor takes the instance reference as input, and implements the goal through double dispatch.
The default form of dispatch is static. To get dynamic dispatch the programmer must declare a method as virtual. C++ compilers typically implement dynamic dispatch with a data structure called a virtual function table (vtable) that defines the name-to-implementation mapping for a given class as a set of member function pointers. This is purely ...
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Like virtual functions, virtual classes follow the same rules of definition, overriding, and reference. [2] When a derived class inherits from a base class, it must define or override the virtual inner classes it inherited from the base class. An object of the child class may be referred to by a reference or pointer of the parent class type or ...