| /*============================================================================= |
| 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 |
| |
| #if defined(_MSC_VER) |
| #pragma once |
| #endif |
| |
| #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 (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 |
| } |
| } |
| }}}} |
| |
| #endif |
| |
| |
