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+
+// Copyright 2012 John Maddock. 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_
+
+#ifndef BOOST_MP_CPP_INT_CHECKED_HPP
+#define BOOST_MP_CPP_INT_CHECKED_HPP
+
+namespace boost{ namespace multiprecision{ namespace backends{ namespace detail{
+
+//
+// Simple routines for performing checked arithmetic with a builtin arithmetic type.
+// Note that this is not a complete header, it must be included as part of boost/multiprecision/cpp_int.hpp.
+//
+
+inline void raise_overflow(std::string op)
+{
+ BOOST_THROW_EXCEPTION(std::overflow_error("overflow in " + op));
+}
+inline void raise_add_overflow()
+{
+ raise_overflow("addition");
+}
+inline void raise_subtract_overflow()
+{
+ BOOST_THROW_EXCEPTION(std::range_error("Subtraction resulted in a negative value, but the type is unsigned"));
+}
+inline void raise_mul_overflow()
+{
+ raise_overflow("multiplication");
+}
+inline void raise_div_overflow()
+{
+ raise_overflow("division");
+}
+
+template <class A>
+inline A checked_add_imp(A a, A b, const mpl::true_&)
+{
+ if(a > 0)
+ {
+ if((b > 0) && ((integer_traits<A>::const_max - b) < a))
+ raise_add_overflow();
+ }
+ else
+ {
+ if((b < 0) && ((integer_traits<A>::const_min - b) > a))
+ raise_add_overflow();
+ }
+ return a + b;
+}
+template <class A>
+inline A checked_add_imp(A a, A b, const mpl::false_&)
+{
+ if((integer_traits<A>::const_max - b) < a)
+ raise_add_overflow();
+ return a + b;
+}
+template <class A>
+inline A checked_add(A a, A b, const mpl::int_<checked>&)
+{
+ return checked_add_imp(a, b, boost::is_signed<A>());
+}
+template <class A>
+inline A checked_add(A a, A b, const mpl::int_<unchecked>&)
+{
+ return a + b;
+}
+
+template <class A>
+inline A checked_subtract_imp(A a, A b, const mpl::true_&)
+{
+ if(a > 0)
+ {
+ if((b < 0) && ((integer_traits<A>::const_max + b) < a))
+ raise_subtract_overflow();
+ }
+ else
+ {
+ if((b > 0) && ((integer_traits<A>::const_min + b) > a))
+ raise_subtract_overflow();
+ }
+ return a - b;
+}
+template <class A>
+inline A checked_subtract_imp(A a, A b, const mpl::false_&)
+{
+ if(a < b)
+ raise_subtract_overflow();
+ return a - b;
+}
+template <class A>
+inline A checked_subtract(A a, A b, const mpl::int_<checked>&)
+{
+ return checked_subtract_imp(a, b, boost::is_signed<A>());
+}
+template <class A>
+inline A checked_subtract(A a, A b, const mpl::int_<unchecked>&)
+{
+ return a - b;
+}
+
+template <class A>
+inline A checked_multiply(A a, A b, const mpl::int_<checked>&)
+{
+ BOOST_MP_USING_ABS
+ if(a && (integer_traits<A>::const_max / abs(a) < abs(b)))
+ raise_mul_overflow();
+ return a * b;
+}
+template <class A>
+inline A checked_multiply(A a, A b, const mpl::int_<unchecked>&)
+{
+ return a * b;
+}
+
+template <class A>
+inline A checked_divide(A a, A b, const mpl::int_<checked>&)
+{
+ if(b == 0)
+ raise_div_overflow();
+ return a / b;
+}
+template <class A>
+inline A checked_divide(A a, A b, const mpl::int_<unchecked>&)
+{
+ return a / b;
+}
+
+template <class A>
+inline A checked_left_shift(A a, boost::ulong_long_type shift, const mpl::int_<checked>&)
+{
+ if(a && shift)
+ {
+ if((shift > sizeof(A) * CHAR_BIT) || (a >> (sizeof(A) * CHAR_BIT - shift)))
+ BOOST_THROW_EXCEPTION(std::overflow_error("Shift out of range"));
+ }
+ return a << shift;
+}
+template <class A>
+inline A checked_left_shift(A a, boost::ulong_long_type shift, const mpl::int_<unchecked>&)
+{
+ return (shift >= sizeof(A) * CHAR_BIT) ? 0 : a << shift;
+}
+
+}}}} // namespaces
+
+#endif
+