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- /*=============================================================================
- Copyright (c) 2001-2014 Joel de Guzman
- Copyright (c) 2001-2011 Hartmut Kaiser
- 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_0.txt)
- =============================================================================*/
- #if !defined(BOOST_SPIRIT_X3_CAST_CHAR_NOVEMBER_10_2006_0907AM)
- #define BOOST_SPIRIT_X3_CAST_CHAR_NOVEMBER_10_2006_0907AM
- #include <boost/type_traits/is_signed.hpp>
- #include <boost/type_traits/make_unsigned.hpp>
- #include <boost/type_traits/make_signed.hpp>
- namespace boost { namespace spirit { namespace x3 { namespace detail
- {
- // Here's the thing... typical encodings (except ASCII) deal with unsigned
- // integers > 127 (ASCII uses only 127). Yet, most char and wchar_t are signed.
- // Thus, a char with value > 127 is negative (e.g. char 233 is -23). When you
- // cast this to an unsigned int with 32 bits, you get 4294967273!
- //
- // The trick is to cast to an unsigned version of the source char first
- // before casting to the target. {P.S. Don't worry about the code, the
- // optimizer will optimize the if-else branches}
- template <typename TargetChar, typename SourceChar>
- TargetChar cast_char(SourceChar ch)
- {
- #if defined(_MSC_VER)
- # pragma warning(push)
- # pragma warning(disable: 4127) // conditional expression is constant
- #endif
- if (is_signed<TargetChar>::value != is_signed<SourceChar>::value)
- {
- if (is_signed<SourceChar>::value)
- {
- // source is signed, target is unsigned
- typedef typename make_unsigned<SourceChar>::type USourceChar;
- return TargetChar(USourceChar(ch));
- }
- else
- {
- // source is unsigned, target is signed
- typedef typename make_signed<SourceChar>::type SSourceChar;
- return TargetChar(SSourceChar(ch));
- }
- }
- else
- {
- // source and target has same signedness
- return TargetChar(ch); // just cast
- }
- #if defined(_MSC_VER)
- # pragma warning(pop)
- #endif
- }
- }}}}
- #endif
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