std_regex_engine.hpp

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/*
    restinio
*/

/*!
    Regex engine for using std::regex.
*/

#pragma once

#include <regex>

namespace restinio
{

namespace router
{

//
// std_regex_engine_t
//

//! Regex engine implementation for using with standard regex implementation.
struct std_regex_engine_t
{
    using compiled_regex_t = std::regex;
    using match_results_t = std::vector< std::pair< std::size_t, size_t > >;
    using matched_item_descriptor_t = match_results_t::value_type;

    static constexpr std::size_t
    max_capture_groups()
    {
        // The size of match results for standard regexes cannot be reserved
        // and grows as needed, so no limits beforehand.
        return std::numeric_limits< std::size_t >::max();
    }

    //! Create compiled regex object for a given route.
    static auto
    compile_regex(
        //! Regular expression (the pattern).
        string_view_t r,
        //! Option for case sensativity.
        bool is_case_sensative )
    {
        auto regex_flags = std::regex::ECMAScript;

        if( !is_case_sensative )
        {
            regex_flags |= std::regex::icase;
        }

        return compiled_regex_t{ r.data(), r.size(), regex_flags };
    }

    //! Wrapper function for matching logic invokation.
    static auto
    try_match(
        string_view_t target_path,
        const compiled_regex_t & r,
        match_results_t & match_results )
    {
        std::cmatch matches;
        if(
            std::regex_search(
                target_path.data(),
                target_path.data() + target_path.size(),
                matches,
                r ) )
        {
            std::transform(
                matches.begin(),
                matches.end(),
                std::back_inserter( match_results ),
                [ begin = target_path.data() ]( const auto & m ){
                    return matched_item_descriptor_t{ m.first - begin, m.second - begin };
                } );

            return true;
        }
        return false;
    }

    //! Get the beginning of a submatch.
    static auto
    submatch_begin_pos( const matched_item_descriptor_t & m )
    {
        return m.first;
    }

    //! Get the end of a submatch.
    static auto
    submatch_end_pos( const matched_item_descriptor_t & m )
    {
        return m.second;
    }
};

} /* namespace router */

} /* namespace restinio */