Scrambler

Introduction

A Scrambler reduces the current State to a single output word, which in our case will always be a 32-bit or 64-bit unsigned integer.

Our xso::generator class takes a State and a Scrambler template parameter.
The requirements for the former are discussed on the State page.

The requirements for the Scrambler are rather simple:

Required Methods

Item	Description
xso_name()	Class method that should return a name for the output function.
operator()(const auto& state)	Instance method that reduces the passed state to a single output word.

Our Scrambler Classes

We provide four scrambler classes in the xso namespace:

1template<auto S, std::size_t w>
struct xso::star;

2template<auto S, auto R, auto T, std::size_t w>
struct xso::star_star;

3template<std::size_t w0, std::size_t w1>
struct xso::plus;

4template<auto R, std::size_t w0, std::size_t w1>
struct xso::plus_plus;

1

Functor: state[w] * S

2

Functor: std::rotl(state[w] * S, R) * T

3

Functor: state[w0] + state[w1]

4

Functor: std::rotl(state[w0] + state[w1], R) + state[w0]

Template Parameters

Parameter	Description
w, w0, w1	Indices for specific words of state to work on/scramble.
S, T	Scaling parameters.
R	Rotation parameter.

Methods

Item	Description
operator()(const auto& state)	Returns the values given above.
xso_name()	Class method that returns a name for the output function, which incorporates all the template parameters.
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Notes:

1. The name returned by the xso_name() class method might look like star_star<5,7,9,1>.
2. The names for the output functions match the ones used in this original paper.

See Also

State
xso::generator