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Filename : gnu_gettext.hpp
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//
//  Copyright (c) 2009-2011 Artyom Beilis (Tonkikh)
//
//  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)
//
#ifndef BOOST_LOCLAE_GNU_GETTEXT_HPP
#define BOOST_LOCLAE_GNU_GETTEXT_HPP

#include <boost/locale/message.hpp>
#include <boost/function.hpp>
#include <stdexcept>

namespace boost {
namespace locale {
/// \addtogroup message
/// @{


///
/// \brief This namespace holds classes that provide GNU Gettext message catalogs support.
///
namespace gnu_gettext {

    ///
    /// \brief This structure holds all information required for creating gnu-gettext message catalogs,
    ///
    /// The user is expected to set its parameters to load these catalogs correctly. This structure
    /// also allows providing functions for charset conversion. Note, you need to provide them,
    /// so this structure is not useful for wide characters without subclassing and it will also
    /// ignore gettext catalogs that use a charset different from \a encoding.
    ///
    struct messages_info {
        messages_info() :
            language("C"),
            locale_category("LC_MESSAGES")
        {
        }

        std::string language;   ///< The language we load the catalog for, like "ru", "en", "de" 
        std::string country;    ///< The country we load the catalog for, like "US", "IL"
        std::string variant;    ///< Language variant, like "euro" so it would look for catalog like de_DE\@euro
        std::string encoding;   ///< Required target charset encoding. Ignored for wide characters.
                                ///< For narrow, should specify the correct encoding required for this catalog
        std::string locale_category; ///< Locale category, is set by default to LC_MESSAGES, but may be changed
        ///
        /// \brief This type represents GNU Gettext domain name for the messages.
        ///
        /// It consists of two parameters: 
        ///
        /// - name - the name of the domain - used for opening the file name
        /// - encoding - the encoding of the keys in the sources, default - UTF-8
        ///
        struct domain {

            std::string name; ///< The name of the domain
            std::string encoding;   ///< The character encoding for the domain
            domain() {}
            ///
            /// Create a domain object from the name that can hold an encoding after symbol "/"
            /// such that if n is "hello/cp1255" then the name would be "hello" and "encoding" would
            /// be "cp1255" and if n is "hello" then the name would be the same but encoding would be
            /// "UTF-8"
            ///
            domain(std::string const &n) 
            {
                size_t pos = n.find("/");
                if(pos==std::string::npos) {
                    name = n;
                    encoding = "UTF-8";
                }
                else {
                    name = n.substr(0,pos);
                    encoding = n.substr(pos+1);
                }

            }

            ///
            /// Check whether two objects are equivalent, only names are compared, encoding is ignored
            ///
            bool operator==(domain const &other) const
            {
                return name==other.name;
            }
            ///
            /// Check whether two objects are distinct, only names are compared, encoding is ignored
            ///
            bool operator!=(domain const &other) const
            {
                return !(*this==other);
            }

        };
        
        typedef std::vector<domain> domains_type;   ///< Type that defines a list of domains that are loaded
                                                    ///< The first one is the default one
        domains_type domains;           ///< Message domains - application name, like my_app. So files named my_app.mo
                                        ///< would be loaded
        std::vector<std::string> paths; ///< Paths to search files in. Under MS Windows it uses encoding
                                        ///< parameter to convert them to wide OS specific paths.
        
        ///
        /// The callback for custom file system support. This callback should read the file named \a file_name
        /// encoded in \a encoding character set into std::vector<char> and return it.
        ///
        /// - If the file does not exist, it should return an empty vector.
        /// - If a error occurs during file read it should throw a error.
        ///
        /// \note The user should support only the encodings the locales are created for. So if the user
        /// uses only one encoding or the file system is encoding agnostic, he may ignore the \a encoding parameter.
        ///
        typedef function<
                    std::vector<char>(
                        std::string const &file_name,
                        std::string const &encoding
                    ) 
                > callback_type;

        ///
        /// The callback for handling custom file systems, if it is empty, the real OS file-system
        /// is being used.
        /// 
        callback_type callback;

    };

    ///
    /// Create a message_format facet using GNU Gettext catalogs. It uses \a info structure to get
    /// information about where to read them from and uses it for character set conversion (if needed)
    ///

    template<typename CharType>
    message_format<CharType> *create_messages_facet(messages_info const &info);

    /// \cond INTERNAL
    
    template<>
    BOOST_LOCALE_DECL message_format<char> *create_messages_facet(messages_info const &info);
    
    template<>
    BOOST_LOCALE_DECL message_format<wchar_t> *create_messages_facet(messages_info const &info);

    #ifdef BOOST_LOCALE_ENABLE_CHAR16_T
    template<>
    BOOST_LOCALE_DECL message_format<char16_t> *create_messages_facet(messages_info const &info);
    #endif
    
    #ifdef BOOST_LOCALE_ENABLE_CHAR32_T
    template<>
    BOOST_LOCALE_DECL message_format<char32_t> *create_messages_facet(messages_info const &info);
    #endif

    /// \endcond

} // gnu_gettext

/// @}

} // locale
} // boost

#endif

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