STEllAR-GROUP / hpx / #882

// Copyright (c) 2001 Ronald Garcia, Indiana University (garcia@osl.iu.edu)

// Andrew Lumsdaine, Indiana University (lums@osl.iu.edu).

//

// SPDX-License-Identifier: BSL-1.0

// Distributed under the Boost Software License, Version 1.0. (See accompany-

// ing file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#pragma once

/////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8

// utf8_codecvt_facet.hpp

// This header defines class utf8_codecvt_facet, derived from

// std::codecvt<wchar_t, char>, which can be used to convert utf8 data in

// files into wchar_t strings in the application.

//

// The header is NOT STANDALONE, and is not to be included by the USER.

// There are at least two libraries which want to use this functionality, and

// we want to avoid code duplication. It would be possible to create utf8

// library, but:

// - this requires review process first

// - in the case, when linking the a library which uses utf8

//   (say 'program_options'), user should also link to the utf8 library.

//   This seems inconvenient, and asking a user to link to an unreviewed

//   library is strange.

// Until the above points are fixed, a library which wants to use utf8 must:

// - include this header in one of it's headers or sources

// - include the corresponding boost/detail/utf8_codecvt_facet.ipp file in one

//   of its sources

// - before including either file, the library must define

//   - BOOST_UTF8_BEGIN_NAMESPACE to the namespace declaration that must be used

//   - BOOST_UTF8_END_NAMESPACE to the code to close the previous namespace

//     declaration.

//   - BOOST_UTF8_DECL -- to the code which must be used for all 'exportable'

//     symbols.

//

// For example, program_options library might contain:

//    #define BOOST_UTF8_BEGIN_NAMESPACE <backslash character>

//             namespace boost { namespace program_options {

//    #define BOOST_UTF8_END_NAMESPACE }}

//    #define BOOST_UTF8_DECL BOOST_PROGRAM_OPTIONS_DECL

//    #include <boost/detail/utf8_codecvt_facet.ipp>

//

// Essentially, each library will have its own copy of utf8 code, in

// different namespaces.

// Note:(Robert Ramey).  I have made the following alterations in the original

// code.

// a) Rendered utf8_codecvt<wchar_t, char>  with using templates

// b) Move longer functions outside class definition to prevent inlining

// and make code smaller

// c) added on a derived class to permit translation to/from current

// locale to utf8

//  See http://www.boost.org for updates, documentation, and revision history.

// archives stored as text - note these ar templated on the basic

// stream templates to accommodate wide (and other?) kind of characters

//

// note the fact that on libraries without wide characters, ostream is

// is not a specialization of basic_ostream which in fact is not defined

// in such cases.   So we can't use basic_ostream<OStream::char_type> but rather

// use two template parameters

//

// utf8_codecvt_facet

//   This is an implementation of a std::codecvt facet for translating

//   from UTF-8 externally to UCS-4.  Note that this is not tied to

//   any specific types in order to allow customization on platforms

//   where wchar_t is not big enough.

//

// NOTES:  The current implementation jumps through some unpleasant hoops in

// order to deal with signed character types.  As a std::codecvt_base::result,

// it is necessary  for the ExternType to be convertible to unsigned  char.

// I chose not to tie the extern_type explicitly to char. But if any combination

// of types other than <wchar_t,char_t> is used, then std::codecvt must be

// specialized on those types for this to work.

#include <hpx/program_options/config.hpp>

#include <cstddef>    // for std::size_t

#include <cwchar>     // for mbstate_t

#include <locale>

//----------------------------------------------------------------------------//

//                                                                            //

//                          utf8_codecvt_facet                                //

//                                                                            //

//            See utf8_codecvt_facet.cpp for the implementation.              //

//----------------------------------------------------------------------------//

namespace hpx::program_options::detail {

    HPX_CXX_EXPORT struct HPX_CORE_EXPORT utf8_codecvt_facet

      : public std::codecvt<wchar_t, char, std::mbstate_t>

    {

    public:

        explicit utf8_codecvt_facet(std::size_t no_locale_manage = 0);

        virtual ~utf8_codecvt_facet();

    protected:

        std::codecvt_base::result do_in(std::mbstate_t& state, char const* from,

            char const* from_end, char const*& from_next, wchar_t* to,

            wchar_t* to_end, wchar_t*& to_next) const override;

        std::codecvt_base::result do_out(std::mbstate_t& state,

            wchar_t const* from, wchar_t const* from_end,

            wchar_t const*& from_next, char* to, char* to_end,

            char*& to_next) const override;

        static bool invalid_continuing_octet(unsigned char octet_1) noexcept

        {

            return (octet_1 < 0x80 || 0xbf < octet_1);

        }

        static bool invalid_leading_octet(unsigned char octet_1) noexcept

        {

            return (0x7f < octet_1 && octet_1 < 0xc0) || (octet_1 > 0xfd);

        }

        static unsigned int get_cont_octet_count(

            unsigned char lead_octet) noexcept

        {

            return get_octet_count(lead_octet) - 1;

        static unsigned int get_octet_count(unsigned char lead_octet) noexcept;

        // How many "continuing octets" will be needed for this word

        // ==   total octets - 1.

        int get_cont_octet_out_count(wchar_t word) const noexcept;

        bool do_always_noconv() const noexcept override

        {

            return false;

        }

        // UTF-8 isn't really stateful since we rewind on partial conversions

        std::codecvt_base::result do_unshift(std::mbstate_t&, char* from,

            char* /*to*/, char*& next) const override

            next = from;

        }

        int do_encoding() const noexcept override

            constexpr int variable_byte_external_encoding = 0;

            return variable_byte_external_encoding;

        // How many char objects can I process to get <= max_limit

        // wchar_t objects?

            std::size_t max_limit) const noexcept override;

        virtual int do_length(std::mbstate_t const& s,    //-V835

            char const* from, char const* from_end,

            std::size_t max_limit) const noexcept

        {

            return do_length(

                const_cast<std::mbstate_t&>(s), from, from_end, max_limit);

        }

        int do_max_length() const noexcept override

        {

            return 6;    // largest UTF-8 encoding of a UCS-4 character

}    // namespace hpx::program_options::detail