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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
#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
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