/* boost random/tausworthe.hpp header file

  *

  * Copyright Jens Maurer 2002

  * Distributed under the Boost Software License, Version 1.0. (See

  * accompanying file LICENSE_1_0.txt or copy at

  * http://www.boost.org/LICENSE_1_0.txt)

  *

  * See http://www.boost.org for most recent version including documentation.

  *

  * $Id: linear_feedback_shift.hpp,v 1.12 2005/05/21 15:57:00 dgregor Exp $

  *

  */

 #ifndef BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP

 #define BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP

 #include <iostream>

 #include <cassert>

 #include <stdexcept>

 #include <boost/config.hpp>

 #include <boost/static_assert.hpp>

 #include <boost/limits.hpp>

 namespace boost {

 namespace random {

 // Tausworte 1965

 template<class UIntType, int w, int k, int q, int s, UIntType val>

 class linear_feedback_shift

 {

 public:

   typedef UIntType result_type;

   // avoid the warning trouble when using (1<<w) on 32 bit machines

   BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);

   BOOST_STATIC_CONSTANT(int, word_size = w);

   BOOST_STATIC_CONSTANT(int, exponent1 = k);

   BOOST_STATIC_CONSTANT(int, exponent2 = q);

   BOOST_STATIC_CONSTANT(int, step_size = s);

   result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return 0; }

   result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return wordmask; }

   // MSVC 6 and possibly others crash when encountering complicated integral

   // constant expressions.  Avoid the checks for now.

   // BOOST_STATIC_ASSERT(w > 0);

   // BOOST_STATIC_ASSERT(q > 0);

   // BOOST_STATIC_ASSERT(k < w);

   // BOOST_STATIC_ASSERT(0 < 2*q && 2*q < k);

   // BOOST_STATIC_ASSERT(0 < s && s <= k-q);

   explicit linear_feedback_shift(UIntType s0 = 341) : wordmask(0)

   {

     // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope

 #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS

     BOOST_STATIC_ASSERT(std::numeric_limits<UIntType>::is_integer);

     BOOST_STATIC_ASSERT(!std::numeric_limits<UIntType>::is_signed);

 #endif

     // avoid "left shift count >= with of type" warning

     for(int i = 0; i < w; ++i)

       wordmask |= (1u << i);

     seed(s0);

   }

   template<class It> linear_feedback_shift(It& first, It last) : wordmask(0)

   {

     // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope

 #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS

     BOOST_STATIC_ASSERT(std::numeric_limits<UIntType>::is_integer);

     BOOST_STATIC_ASSERT(!std::numeric_limits<UIntType>::is_signed);

 #endif

     // avoid "left shift count >= with of type" warning

     for(int i = 0; i < w; ++i)

       wordmask |= (1u << i);

     seed(first, last);

   }

   void seed(UIntType s0 = 341) { assert(s0 >= (1 << (w-k))); value = s0; }

   template<class It> void seed(It& first, It last)

   {

     if(first == last)

       throw std::invalid_argument("linear_feedback_shift::seed");

     value = *first++;

     assert(value >= (1 << (w-k)));

   }

   result_type operator()()

   {

     const UIntType b = (((value << q) ^ value) & wordmask) >> (k-s);

     const UIntType mask = ( (~static_cast<UIntType>(0)) << (w-k) ) & wordmask;

     value = ((value & mask) << s) ^ b;

     return value;

   }

   bool validation(result_type x) const { return val == x; }

 #ifndef BOOST_NO_OPERATORS_IN_NAMESPACE

 #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS

   template<class CharT, class Traits>

   friend std::basic_ostream<CharT,Traits>&

   operator<<(std::basic_ostream<CharT,Traits>& os, linear_feedback_shift x)

   { os << x.value; return os; }

   template<class CharT, class Traits>

   friend std::basic_istream<CharT,Traits>&

   operator>>(std::basic_istream<CharT,Traits>& is, linear_feedback_shift& x)

   { is >> x.value; return is; }

 #endif

   friend bool operator==(linear_feedback_shift x, linear_feedback_shift y)

   { return x.value == y.value; }

   friend bool operator!=(linear_feedback_shift x, linear_feedback_shift y)

   { return !(x == y); }

 #else

   // Use a member function; Streamable concept not supported.

   bool operator==(linear_feedback_shift rhs) const

   { return value == rhs.value; }

   bool operator!=(linear_feedback_shift rhs) const

   { return !(*this == rhs); }

 #endif

 private:

   UIntType wordmask; // avoid "left shift count >= width of type" warnings

   UIntType value;

 };

 #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION

 //  A definition is required even for integral static constants

 template<class UIntType, int w, int k, int q, int s, UIntType val>

 const bool linear_feedback_shift<UIntType, w, k, q, s, val>::has_fixed_range;

 template<class UIntType, int w, int k, int q, int s, UIntType val>

 const int linear_feedback_shift<UIntType, w, k, q, s, val>::word_size;

 template<class UIntType, int w, int k, int q, int s, UIntType val>

 const int linear_feedback_shift<UIntType, w, k, q, s, val>::exponent1;

 template<class UIntType, int w, int k, int q, int s, UIntType val>

 const int linear_feedback_shift<UIntType, w, k, q, s, val>::exponent2;

 template<class UIntType, int w, int k, int q, int s, UIntType val>

 const int linear_feedback_shift<UIntType, w, k, q, s, val>::step_size;

 #endif

 } // namespace random

 } // namespace boost

 #endif // BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP