Stroustrup's Version
The original Device was made for copying to a (memory-mapped) register. To actually copy memory from one location to another, an auto-increment must be added to every reference to to, like so:
*to++ = *from++;This modified form of the Device appears as a "what does this code do?" exercise in Bjarne Stroustrup's book The C++ Programming Language, presumably because novice programmers cannot be expected to know about memory-mapped output registers. However, the standard C library provides the function memcpy for this purpose; it will not perform worse than this code, and may contain architecture specific optimizations that will make it significantly faster.
Read more about this topic: Duff's Device
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