ceph/src/boost/libs/multiprecision/include/boost/multiprecision/cpp_int/checked.hpp

   1
   2 //  Copyright 2012 John Maddock. Distributed under the Boost
   3 //  Software License, Version 1.0. (See accompanying file
   4 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_
   5
   6 #ifndef BOOST_MP_CPP_INT_CHECKED_HPP
   7 #define BOOST_MP_CPP_INT_CHECKED_HPP
   8
   9 namespace boost{ namespace multiprecision{ namespace backends{ namespace detail{
  10
  11 //
  12 // Simple routines for performing checked arithmetic with a builtin arithmetic type.
  13 // Note that this is not a complete header, it must be included as part of boost/multiprecision/cpp_int.hpp.
  14 //
  15
  16 inline void raise_overflow(std::string op)
  17 {
  18    BOOST_THROW_EXCEPTION(std::overflow_error("overflow in " + op));
  19 }
  20 inline void raise_add_overflow()
  21 {
  22    raise_overflow("addition");
  23 }
  24 inline void raise_subtract_overflow()
  25 {
  26    BOOST_THROW_EXCEPTION(std::range_error("Subtraction resulted in a negative value, but the type is unsigned"));
  27 }
  28 inline void raise_mul_overflow()
  29 {
  30    raise_overflow("multiplication");
  31 }
  32 inline void raise_div_overflow()
  33 {
  34    raise_overflow("division");
  35 }
  36
  37 template <class A>
  38 inline A checked_add_imp(A a, A b, const mpl::true_&)
  39 {
  40    if(a > 0)
  41    {
  42       if((b > 0) && ((integer_traits<A>::const_max - b) < a))
  43          raise_add_overflow();
  44    }
  45    else
  46    {
  47       if((b < 0) && ((integer_traits<A>::const_min - b) > a))
  48          raise_add_overflow();
  49    }
  50    return a + b;
  51 }
  52 template <class A>
  53 inline A checked_add_imp(A a, A b, const mpl::false_&)
  54 {
  55    if((integer_traits<A>::const_max - b) < a)
  56       raise_add_overflow();
  57    return a + b;
  58 }
  59 template <class A>
  60 inline A checked_add(A a, A b, const mpl::int_<checked>&)
  61 {
  62    return checked_add_imp(a, b, boost::is_signed<A>());
  63 }
  64 template <class A>
  65 inline A checked_add(A a, A b, const mpl::int_<unchecked>&)
  66 {
  67    return a + b;
  68 }
  69
  70 template <class A>
  71 inline A checked_subtract_imp(A a, A b, const mpl::true_&)
  72 {
  73    if(a > 0)
  74    {
  75       if((b < 0) && ((integer_traits<A>::const_max + b) < a))
  76          raise_subtract_overflow();
  77    }
  78    else
  79    {
  80       if((b > 0) && ((integer_traits<A>::const_min + b) > a))
  81          raise_subtract_overflow();
  82    }
  83    return a - b;
  84 }
  85 template <class A>
  86 inline A checked_subtract_imp(A a, A b, const mpl::false_&)
  87 {
  88    if(a < b)
  89       raise_subtract_overflow();
  90    return a - b;
  91 }
  92 template <class A>
  93 inline A checked_subtract(A a, A b, const mpl::int_<checked>&)
  94 {
  95    return checked_subtract_imp(a, b, boost::is_signed<A>());
  96 }
  97 template <class A>
  98 inline A checked_subtract(A a, A b, const mpl::int_<unchecked>&)
  99 {
 100    return a - b;
 101 }
 102
 103 template <class A>
 104 inline A checked_multiply(A a, A b, const mpl::int_<checked>&)
 105 {
 106    BOOST_MP_USING_ABS
 107    if(a && (integer_traits<A>::const_max / abs(a) < abs(b)))
 108       raise_mul_overflow();
 109    return a * b;
 110 }
 111 template <class A>
 112 inline A checked_multiply(A a, A b, const mpl::int_<unchecked>&)
 113 {
 114    return a * b;
 115 }
 116
 117 template <class A>
 118 inline A checked_divide(A a, A b, const mpl::int_<checked>&)
 119 {
 120    if(b == 0)
 121       raise_div_overflow();
 122    return a / b;
 123 }
 124 template <class A>
 125 inline A checked_divide(A a, A b, const mpl::int_<unchecked>&)
 126 {
 127    return a / b;
 128 }
 129
 130 template <class A>
 131 inline A checked_left_shift(A a, boost::ulong_long_type shift, const mpl::int_<checked>&)
 132 {
 133    if(a && shift)
 134    {
 135       if((shift > sizeof(A) * CHAR_BIT) || (a >> (sizeof(A) * CHAR_BIT - shift)))
 136          BOOST_THROW_EXCEPTION(std::overflow_error("Shift out of range"));
 137    }
 138    return a << shift;
 139 }
 140 template <class A>
 141 inline A checked_left_shift(A a, boost::ulong_long_type shift, const mpl::int_<unchecked>&)
 142 {
 143    return (shift >= sizeof(A) * CHAR_BIT) ? 0 : a << shift;
 144 }
 145
 146 }}}} // namespaces
 147
 148 #endif
 149