epoc32/include/stdapis/boost/random/linear_feedback_shift.hpp
author William Roberts <williamr@symbian.org>
Tue, 16 Mar 2010 16:12:26 +0000
branchSymbian2
changeset 2 2fe1408b6811
permissions -rw-r--r--
Final list of Symbian^2 public API header files
     1 /* boost random/tausworthe.hpp header file
     2  *
     3  * Copyright Jens Maurer 2002
     4  * Distributed under the Boost Software License, Version 1.0. (See
     5  * accompanying file LICENSE_1_0.txt or copy at
     6  * http://www.boost.org/LICENSE_1_0.txt)
     7  *
     8  * See http://www.boost.org for most recent version including documentation.
     9  *
    10  * $Id: linear_feedback_shift.hpp,v 1.12 2005/05/21 15:57:00 dgregor Exp $
    11  *
    12  */
    13 
    14 #ifndef BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP
    15 #define BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP
    16 
    17 #include <iostream>
    18 #include <cassert>
    19 #include <stdexcept>
    20 #include <boost/config.hpp>
    21 #include <boost/static_assert.hpp>
    22 #include <boost/limits.hpp>
    23 
    24 namespace boost {
    25 namespace random {
    26 
    27 // Tausworte 1965
    28 template<class UIntType, int w, int k, int q, int s, UIntType val>
    29 class linear_feedback_shift
    30 {
    31 public:
    32   typedef UIntType result_type;
    33   // avoid the warning trouble when using (1<<w) on 32 bit machines
    34   BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
    35   BOOST_STATIC_CONSTANT(int, word_size = w);
    36   BOOST_STATIC_CONSTANT(int, exponent1 = k);
    37   BOOST_STATIC_CONSTANT(int, exponent2 = q);
    38   BOOST_STATIC_CONSTANT(int, step_size = s);
    39 
    40   result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return 0; }
    41   result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return wordmask; }
    42 
    43   // MSVC 6 and possibly others crash when encountering complicated integral
    44   // constant expressions.  Avoid the checks for now.
    45   // BOOST_STATIC_ASSERT(w > 0);
    46   // BOOST_STATIC_ASSERT(q > 0);
    47   // BOOST_STATIC_ASSERT(k < w);
    48   // BOOST_STATIC_ASSERT(0 < 2*q && 2*q < k);
    49   // BOOST_STATIC_ASSERT(0 < s && s <= k-q);
    50 
    51   explicit linear_feedback_shift(UIntType s0 = 341) : wordmask(0)
    52   {
    53     // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
    54 #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
    55     BOOST_STATIC_ASSERT(std::numeric_limits<UIntType>::is_integer);
    56     BOOST_STATIC_ASSERT(!std::numeric_limits<UIntType>::is_signed);
    57 #endif
    58 
    59     // avoid "left shift count >= with of type" warning
    60     for(int i = 0; i < w; ++i)
    61       wordmask |= (1u << i);
    62     seed(s0);
    63   }
    64 
    65   template<class It> linear_feedback_shift(It& first, It last) : wordmask(0)
    66   {
    67     // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
    68 #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
    69     BOOST_STATIC_ASSERT(std::numeric_limits<UIntType>::is_integer);
    70     BOOST_STATIC_ASSERT(!std::numeric_limits<UIntType>::is_signed);
    71 #endif
    72 
    73     // avoid "left shift count >= with of type" warning
    74     for(int i = 0; i < w; ++i)
    75       wordmask |= (1u << i);
    76     seed(first, last);
    77   }
    78 
    79   void seed(UIntType s0 = 341) { assert(s0 >= (1 << (w-k))); value = s0; }
    80   template<class It> void seed(It& first, It last)
    81   {
    82     if(first == last)
    83       throw std::invalid_argument("linear_feedback_shift::seed");
    84     value = *first++;
    85     assert(value >= (1 << (w-k)));
    86   }
    87 
    88   result_type operator()()
    89   {
    90     const UIntType b = (((value << q) ^ value) & wordmask) >> (k-s);
    91     const UIntType mask = ( (~static_cast<UIntType>(0)) << (w-k) ) & wordmask;
    92     value = ((value & mask) << s) ^ b;
    93     return value;
    94   }
    95   bool validation(result_type x) const { return val == x; }
    96 
    97 #ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
    98 
    99 #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
   100   template<class CharT, class Traits>
   101   friend std::basic_ostream<CharT,Traits>&
   102   operator<<(std::basic_ostream<CharT,Traits>& os, linear_feedback_shift x)
   103   { os << x.value; return os; }
   104 
   105   template<class CharT, class Traits>
   106   friend std::basic_istream<CharT,Traits>&
   107   operator>>(std::basic_istream<CharT,Traits>& is, linear_feedback_shift& x)
   108   { is >> x.value; return is; }
   109 #endif
   110 
   111   friend bool operator==(linear_feedback_shift x, linear_feedback_shift y)
   112   { return x.value == y.value; }
   113   friend bool operator!=(linear_feedback_shift x, linear_feedback_shift y)
   114   { return !(x == y); }
   115 #else
   116   // Use a member function; Streamable concept not supported.
   117   bool operator==(linear_feedback_shift rhs) const
   118   { return value == rhs.value; }
   119   bool operator!=(linear_feedback_shift rhs) const
   120   { return !(*this == rhs); }
   121 #endif
   122 
   123 private:
   124   UIntType wordmask; // avoid "left shift count >= width of type" warnings
   125   UIntType value;
   126 };
   127 
   128 #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
   129 //  A definition is required even for integral static constants
   130 template<class UIntType, int w, int k, int q, int s, UIntType val>
   131 const bool linear_feedback_shift<UIntType, w, k, q, s, val>::has_fixed_range;
   132 template<class UIntType, int w, int k, int q, int s, UIntType val>
   133 const int linear_feedback_shift<UIntType, w, k, q, s, val>::word_size;
   134 template<class UIntType, int w, int k, int q, int s, UIntType val>
   135 const int linear_feedback_shift<UIntType, w, k, q, s, val>::exponent1;
   136 template<class UIntType, int w, int k, int q, int s, UIntType val>
   137 const int linear_feedback_shift<UIntType, w, k, q, s, val>::exponent2;
   138 template<class UIntType, int w, int k, int q, int s, UIntType val>
   139 const int linear_feedback_shift<UIntType, w, k, q, s, val>::step_size;
   140 #endif
   141 
   142 } // namespace random
   143 } // namespace boost
   144 
   145 #endif // BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP