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
raise_overflow(std::string op)16 inline void raise_overflow(std::string op)
17 {
18 BOOST_THROW_EXCEPTION(std::overflow_error("overflow in " + op));
19 }
raise_add_overflow()20 inline void raise_add_overflow()
21 {
22 raise_overflow("addition");
23 }
raise_subtract_overflow()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 }
raise_mul_overflow()28 inline void raise_mul_overflow()
29 {
30 raise_overflow("multiplication");
31 }
raise_div_overflow()32 inline void raise_div_overflow()
33 {
34 raise_overflow("division");
35 }
36
37 template <class A>
checked_add_imp(A a,A b,const mpl::true_ &)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>
checked_add_imp(A a,A b,const mpl::false_ &)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>
checked_add(A a,A b,const mpl::int_<checked> &)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>
checked_add(A a,A b,const mpl::int_<unchecked> &)65 inline A checked_add(A a, A b, const mpl::int_<unchecked>&)
66 {
67 return a + b;
68 }
69
70 template <class A>
checked_subtract_imp(A a,A b,const mpl::true_ &)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>
checked_subtract_imp(A a,A b,const mpl::false_ &)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>
checked_subtract(A a,A b,const mpl::int_<checked> &)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>
checked_subtract(A a,A b,const mpl::int_<unchecked> &)98 inline A checked_subtract(A a, A b, const mpl::int_<unchecked>&)
99 {
100 return a - b;
101 }
102
103 template <class A>
checked_multiply(A a,A b,const mpl::int_<checked> &)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>
checked_multiply(A a,A b,const mpl::int_<unchecked> &)112 inline A checked_multiply(A a, A b, const mpl::int_<unchecked>&)
113 {
114 return a * b;
115 }
116
117 template <class A>
checked_divide(A a,A b,const mpl::int_<checked> &)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>
checked_divide(A a,A b,const mpl::int_<unchecked> &)125 inline A checked_divide(A a, A b, const mpl::int_<unchecked>&)
126 {
127 return a / b;
128 }
129
130 template <class A>
checked_left_shift(A a,boost::ulong_long_type shift,const mpl::int_<checked> &)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>
checked_left_shift(A a,boost::ulong_long_type shift,const mpl::int_<unchecked> &)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
150