Tom Duff | The Binary Auditor™

Duff’s device

Posted Jul 28 2009 by Dr. Thorsten Schneider in The Binary Auditor™ Labs with Comments Off

The famous “Duff’s device” in C makes use of the fact that a case statement is still legal within a sub-block of its matching switch statement. Tom Duff used this for an optimised output loop. Duff’s device is an optimized implementation of a serial copy that uses a technique widely applied in assembly language for loop unwinding. It is perhaps the most dramatic use of case label fall-through in the C programming language to date.

And the solutions?

The Binary Auditor™ Modules do not include solutions at the moment. You should work on the free exercises and try to analyze and solve them on your own. At some day we might start to add the solutions either as single PDF or as a growing body (book) of knowledge. You should check from time to time the The Binary Auditor™ Modules. Goal of this project is to motivate people to think on their own and not to feed them with a ready made meal! Take it as a challenge to learn for your knowledge.

Duff’s device

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