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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 |