Chapter 7: Bitwise and Logical Functions | Cryptography in C and C++

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Overview

And sprinkled just a bit

Over each banana split.

—Tom Lehrer, "In My Home Town"

"Contrariwise," continued Tweedledee, "if it was so, it might be; and if it were so, it would be: but as it isn't, it ain't. That's logic."

—Lewis Carroll, Through the Looking-Glass

IN THIS CHAPTER WE SHALL present functions that carry out bitwise operations on CLINT objects, and we shall also introduce functions for determining the equality and size of CLINT objects, which we have already used quite a bit.

Among the bitwise functions are to be found the shift operations, which shift a CLINT argument in its binary representation by individual bit positions, and certain other functions taking two CLINT arguments that enable the direct manipulation of the binary representation of CLINT objects. How such operations can be applied to arithmetic purposes is most clearly seen in the shift operations described below, but we have also seen, in Section 4.3, how the bitwise AND operation can be used in reduction modulo a power of two.

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