/*=============================================================================
    Boost.Wave: A Standard compliant C++ preprocessor library

    Grammar for universal character validation (see C++ standard: Annex E)
    
    http://www.boost.org/

    Copyright (c) 2001-2007 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(CONVERT_TRIGRAPHS_HK050403_INCLUDED)
#define CONVERT_TRIGRAPHS_HK050403_INCLUDED

#include <boost/wave/wave_config.hpp>
#include <boost/wave/cpplexer/cpplexer_exceptions.hpp>

// this must occur after all of the includes and before any code appears
#ifdef BOOST_HAS_ABI_HEADERS
#include BOOST_ABI_PREFIX
#endif

///////////////////////////////////////////////////////////////////////////////
namespace boost {
namespace wave {
namespace cpplexer {
namespace impl {

///////////////////////////////////////////////////////////////////////////////
//
//  Test, whether the given string represents a valid trigraph sequence
//
///////////////////////////////////////////////////////////////////////////////
template <typename StringT>
inline bool 
is_trigraph(StringT const& trigraph)
{
    if (trigraph.size() < 3 || '?' != trigraph[0] || '?' != trigraph[1])
        return false;
        
    switch (trigraph[2]) {
    case '\'': case '=': case '/': case '(':
    case ')':  case '<': case '>': case '!':
    case '-':
        break;

    default:
        return false;
    }

    return true;
}

///////////////////////////////////////////////////////////////////////////////
//
//  convert_trigraph
//
//    The function convert_trigraph() converts a single trigraph character 
//    sequence into the corresponding character.
//
//    If the given character sequence doesn't form a valid trigraph sequence
//    no conversion is performed. 
//
///////////////////////////////////////////////////////////////////////////////
template <typename StringT>
inline StringT
convert_trigraph(StringT const &trigraph)
{
StringT result (trigraph);

    if (is_trigraph(trigraph)) {
        switch (trigraph[2]) {
        case '\'':  result = "^"; break;
        case '=':   result = "#"; break;
        case '/':   result = "\\"; break;
        case '(':   result = "["; break;
        case ')':   result = "]"; break;
        case '<':   result = "{"; break;
        case '>':   result = "}"; break;
        case '!':   result = "|"; break;
        case '-':   result = "~"; break;
        }
    }
    return result;
}

///////////////////////////////////////////////////////////////////////////////
//
//  convert_trigraphs
//
//    The function convert_trigraph() converts all trigraphs in the given 
//    string into the corresponding characters.
//
//    If one of the given character sequences doesn't form a valid trigraph 
//    sequence no conversion is performed. 
//
///////////////////////////////////////////////////////////////////////////////
template <typename StringT>
inline StringT
convert_trigraphs(StringT const &value)
{
    StringT result;
    typename StringT::size_type pos = 0;
    typename StringT::size_type pos1 = value.find_first_of ("?", 0);
    if (StringT::npos != pos1) {
        do {
            result += value.substr(pos, pos1-pos);
            StringT trigraph (value.substr(pos1)); 
            if (is_trigraph(trigraph)) {
                result += convert_trigraph(trigraph);
                pos1 = value.find_first_of ("?", pos = pos1+3);
            }
            else {
                result += value[pos1];
                pos1 = value.find_first_of ("?", pos = pos1+1);
            }
        } while (StringT::npos != pos1);
        result += value.substr(pos);
    }
    else {
        result = value;
    }
    return result;
}

///////////////////////////////////////////////////////////////////////////////
}   // namespace impl           
}   // namespace cpplexer
}   // namespace wave
}   // namespace boost

// the suffix header occurs after all of the code
#ifdef BOOST_HAS_ABI_HEADERS
#include BOOST_ABI_SUFFIX
#endif

#endif // !defined(CONVERT_TRIGRAPHS_HK050403_INCLUDED)


