More C++ Idioms/Fast Pimpl

Intent
Increase performance of Handle Body idiom.

Motivation
Regular PIMPL idiom achieves "Compilation Firewall" by sacrificing performance. Fast PIMPL attempts to reduce the overhead of heap allocation and non-local memory access by composing the implementation object within the original interface object.

Solution and Sample Code
Note that handle to instance of Wrapped class is not required. To reduce memory footprint Wrapped class can be accessed by a helper function instead.

Known Uses
This pattern is frequently used in high performance or memory constrained environments when implementation is desired to be unseen or decoupled.

Related Idioms

 * Handle Body (aka pimpl)