method_matcher.hpp

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/*
 * RESTinio
 */

/**
 * @file
 * @brief Stuff related to method_matchers.
 *
 * @since v.0.6.6
 */

#pragma once

#include <restinio/http_headers.hpp>

#include <initializer_list>
#include <vector>

namespace restinio
{

namespace router
{

//
// method_matcher_t
//
/*!
 * @brief An interface of method_matcher.
 *
 * Method_matchers are used by routers to detect an applicability
 * of an incoming request to a route. If method_matcher_t::match()
 * returns `true` then HTTP method from an incoming request is
 * applicable to a route.
 *
 * @since v.0.6.6
 */
struct method_matcher_t
{
    method_matcher_t( const method_matcher_t & ) = default;
    method_matcher_t &
    operator=( const method_matcher_t & ) = default;

    method_matcher_t( method_matcher_t && ) = default;
    method_matcher_t &
    operator=( method_matcher_t && ) = default;

    method_matcher_t() = default;
    virtual ~method_matcher_t() = default;

    //! Is the specified method can be applied to a route?
    /*!
     * \retval true if @a method can be applied to a route.
     * \retval false if @a method can't be applied to a route.
     */
    RESTINIO_NODISCARD
    virtual bool
    match( const http_method_id_t & method ) const noexcept = 0;
};

namespace impl
{

//
// allocated_matcher_proxy_t
//
/*!
 * @brief A proxy for actual method_matcher that will be allocated
 * in dynamic memory.
 *
 * An instance of Matcher class will be allocated automatically in
 * the constructor of allocated_matcher_proxy_t.
 *
 * @note
 * This is a moveable class.
 *
 * @since v.0.6.6
 */
template< typename Matcher >
class allocated_matcher_proxy_t : public method_matcher_t
{
    std::unique_ptr< Matcher > m_matcher;

public :
    template< typename... Args >
    allocated_matcher_proxy_t( Args && ...args )
        :   m_matcher{ std::make_unique<Matcher>( std::forward<Args>(args)... ) }
    {}

    RESTINIO_NODISCARD
    bool
    match( const http_method_id_t & method ) const noexcept override
    {
        return m_matcher->match( method );
    }
};

//
// simple_matcher_t
//
/*!
 * @brief A simple method_matcher that compares just one user-specified
 * value.
 *
 * The allowed value is specified in the constructor and can't be changed
 * after that.
 *
 * @since v.0.6.6
 */
class simple_matcher_t : public method_matcher_t
{
    http_method_id_t m_method;

public :
    simple_matcher_t( http_method_id_t method )
        :   m_method{ std::move(method) }
    {}

    RESTINIO_NODISCARD
    bool
    match( const http_method_id_t & method ) const noexcept override
    {
        return m_method == method;
    }
};

//
// fixed_size_any_of_matcher_t
//
/*!
 * @brief A matcher that finds a value in the vector of allowed values
 * of fixed size.
 *
 * A method is allowed if it's found in the vector of allowed values.
 *
 * @since v.0.6.6
 */
template< std::size_t Size >
class fixed_size_any_of_matcher_t : public method_matcher_t
{
    std::array< http_method_id_t, Size > m_methods;

public :
    /*!
     * @brief Initializing constructor.
     *
     * @attention
     * The values.size() is expected to be equal to Size. The behavior is
     * undefined otherwise.
     */
    fixed_size_any_of_matcher_t(
        std::initializer_list< http_method_id_t > values )
    {
        assert( Size == values.size() );

        std::copy( values.begin(), values.end(), m_methods.begin() );
    }

    RESTINIO_NODISCARD
    bool
    match( const http_method_id_t & method ) const noexcept override
    {
        for( const auto & m : m_methods )
            if( m == method )
                return true;

        return false;
    }
};

//
// fixed_size_none_of_matcher_t
//
/*!
 * @brief A matcher that finds a value in the vector of disabled values
 * of fixed size.
 *
 * A method is allowed if it isn't found in the vector of disabled values.
 *
 * @since v.0.6.6
 */
template< std::size_t Size >
class fixed_size_none_of_matcher_t
    : public fixed_size_any_of_matcher_t<Size>
{
    using base_type_t = fixed_size_any_of_matcher_t<Size>;

public :
    using base_type_t::base_type_t;

    RESTINIO_NODISCARD
    bool
    match( const http_method_id_t & method ) const noexcept override
    {
        return !base_type_t::match( method );
    }
};

//
// buffered_matcher_holder_t
//
/*!
 * @brief A special class that allows to hold a copy of small-size
 * method_matchers or a pointer to dynamically allocated large-size
 * method_matchers.
 *
 * An instance of this class looks like a smart pointer to
 * method_matcher_t. This smart pointer is moveable, but not
 * copyable (it's like unique_ptr).
 *
 * A value is set by assign() method:
 * @code
 * buffered_matcher_holder_t matcher;
 * matcher.assign<fixed_size_any_of_matcher_t<10>>(
 *  std::initializer_list<http_method_id_t>{
 *      http_method_get(),
 *      http_method_head(),
 *      ...
 *  });
 * @endcode
 *
 * @since v.0.6.6
 */
class buffered_matcher_holder_t
{
    //! The size of the internal buffer.
    static constexpr std::size_t buffer_size =
            sizeof(fixed_size_any_of_matcher_t<4>);

    //! Alignment to be used by the internal buffer.
    static constexpr std::size_t alignment =
            std::max( {
                    alignof(simple_matcher_t),
                    alignof(fixed_size_any_of_matcher_t<4>),
                    alignof(allocated_matcher_proxy_t<
                            fixed_size_any_of_matcher_t<20>>) } );

    //! A type of free function to be used to move a value of
    //! an object to the specified buffer.
    /*!
     * This function should allocate a new instance in @a buffer and
     * move the content of @a object into it. The pointer to the allocated
     * instance should be returned.
     */
    using pfn_move_t = method_matcher_t* (*)(void* object, void* buffer);

    //! A pointer to actual matcher allocated inside the internall buffer.
    /*!
     * Can be nullptr. For example: just after the creation and before
     * the call to assign(). Or after a move-constructor or move-operator.
     */
    method_matcher_t * m_matcher{ nullptr };

    //! The internal buffer.
    alignas(alignment) std::array<char, buffer_size> m_buffer;

    //! An actual move-function.
    /*!
     * Can be nullptr if assign() is not called yet.
     */
    pfn_move_t m_mover{ nullptr };

    void
    cleanup()
    {
        if( m_matcher ) m_matcher->~method_matcher_t();
    }

    void
    move_from( buffered_matcher_holder_t & other )
    {
        if( other.m_matcher )
        {
            m_matcher = other.m_mover( other.m_matcher, m_buffer.data() );
            m_mover = other.m_mover;

            other.m_matcher = nullptr;
            other.m_mover = nullptr;
        }
    }

public :
    buffered_matcher_holder_t() = default;

    ~buffered_matcher_holder_t() noexcept
    {
        cleanup();
    }

    buffered_matcher_holder_t(
        const buffered_matcher_holder_t & ) = delete;

    buffered_matcher_holder_t &
    operator=(
        const buffered_matcher_holder_t & ) = delete;

    buffered_matcher_holder_t(
        buffered_matcher_holder_t && other ) noexcept
    {
        move_from( other );
    }

    buffered_matcher_holder_t &
    operator=( buffered_matcher_holder_t && other ) noexcept
    {
        if( this != &other )
        {
            cleanup();
            move_from( other );
        }

        return *this;
    }

    /*!
     * @brief Creates an instance of Target_Type and initializes it
     * with arguments Args.
     *
     * Previous value of buffered_matcher_holder_t will be destroyed.
     *
     * A new object is created in the internal buffer if its size is
     * not greater than buffer_size. Otherwise a new object is created
     * in dynamic memory and allocated_matcher_proxy_t for it
     * is placed into the internal buffer.
     *
     */
    template< typename Target_Type, typename... Args >
    void
    assign( Args &&... args )
    {
        static_assert( alignof(Target_Type) <= alignment,
                "Target_Type should have appropriate alignment" );

        cleanup();

        if( sizeof(Target_Type) <= buffer_size )
        {
            m_matcher = new(m_buffer.data()) Target_Type{ std::forward<Args>(args)... };
            m_mover = [](void * raw_what, void * dest_storage) -> method_matcher_t * {
                auto * what = reinterpret_cast<Target_Type *>(raw_what);
                return new(dest_storage) Target_Type{ std::move(*what) };
            };
        }
        else
        {
            using actual_type = allocated_matcher_proxy_t<Target_Type>;
            m_matcher = new(m_buffer.data()) actual_type{ std::forward<Args>(args)... };
            m_mover = [](void * raw_what, void * dest_storage) -> method_matcher_t * {
                auto * what = reinterpret_cast<actual_type *>(raw_what);
                return new(dest_storage) actual_type{ std::move(*what) };
            };
        }
    }

    //! Get the pointer to actual matcher inside the holder.
    RESTINIO_NODISCARD
    method_matcher_t *
    get() const noexcept { return m_matcher; }

    //! Get the pointer to actual matcher inside the holder.
    RESTINIO_NODISCARD
    method_matcher_t *
    operator->() const noexcept { return m_matcher; }

    //! Get a reference to actual matcher inside the holder.
    RESTINIO_NODISCARD
    method_matcher_t &
    operator*() const noexcept { return *m_matcher; }

    friend void
    assign( buffered_matcher_holder_t & holder, http_method_id_t method )
    {
        holder.assign< simple_matcher_t >( std::move(method) );
    }

    template< typename Arg >
    friend void
    assign( buffered_matcher_holder_t & holder, Arg && method_matcher )
    {
        using pure_method_matcher_type = std::decay_t<Arg>;

        static_assert( std::is_base_of<
                method_matcher_t, pure_method_matcher_type >::value,
                "Arg should be derived from method_matcher_t" );

        holder.assign< pure_method_matcher_type >(
                std::forward<Arg>(method_matcher) );
    }
};

} /* namespace impl */

//
// any_of_methods
//
/*!
 * @brief A factory function that creates a method_matcher that allows
 * a method if it's found in the list of allowed methods.
 *
 * Usage example:
 * @code
 * router->add_handler(
 *  restinio::router::any_of_methods(
 *      restinio::http_method_get(), restinio::http_method_head()),
 *  "/users/:id",
 *  [](const auto & req, auto & params) {...});
 * @endcode
 *
 * @note
 * Returns the created object by value without any allocations.
 *
 * @since v.0.6.6
 */
template< typename... Args >
RESTINIO_NODISCARD
impl::fixed_size_any_of_matcher_t< sizeof...(Args) >
any_of_methods( Args && ...args )
{
    return { std::initializer_list<http_method_id_t>{ std::forward<Args>(args)... } };
}

//
// none_of_methods
//
/*!
 * @brief A factory function that creates a method_matcher that allows
 * a method if it isn't found in the list of disabled methods.
 *
 * Usage example:
 * @code
 * router->add_handler(
 *  restinio::router::none_of_methods(
 *      restinio::http_method_get(), restinio::http_method_head()),
 *  "/users/:id",
 *  [](const auto & req, auto &) {
 *      return req->create_response(status_method_not_allowed())
 *          .connection_close().done();
 *  });
 * @endcode
 *
 * @note
 * Returns the created object by value without any allocations.
 *
 * @since v.0.6.6
 */
template< typename... Args >
RESTINIO_NODISCARD
impl::fixed_size_none_of_matcher_t< sizeof...(Args) >
none_of_methods( Args && ...args )
{
    return { std::initializer_list<http_method_id_t>{ std::forward<Args>(args)... } };
}

//
// dynamic_any_of_methods_matcher_t
//
/*!
 * @brief An implementation of method_matcher that allows a method
 * if it's found in a dynamic list of allowed methods.
 *
 * Usage example:
 * @code
 * restinio::router::dynamic_any_of_methods_matcher_t matcher;
 * if(config.handle_get_method())
 *  matcher.add(restinio::http_method_get());
 * if(config.handle_head_method())
 *  matcher.add(restinio::http_method_head());
 * router->add_handler(matcher, // Or std::move(matcher) if matcher is no more needed.
 *  "/users/:id",
 *  [](const auto & req, auto & params) {...});
 * @endcode
 *
 * @since v.0.6.6
 */
class dynamic_any_of_methods_matcher_t : public method_matcher_t
{
    std::vector< http_method_id_t > m_methods;

public:
    dynamic_any_of_methods_matcher_t() = default;

    RESTINIO_NODISCARD
    bool
    match( const http_method_id_t & method ) const noexcept override
    {
        for( const auto & m : m_methods )
            if( m == method )
                return true;

        return false;
    }

    dynamic_any_of_methods_matcher_t &
    add( http_method_id_t method )
    {
        m_methods.emplace_back( std::move(method) );
        return *this;
    }

    RESTINIO_NODISCARD
    std::size_t
    size() const noexcept
    {
        return m_methods.size();
    }

    RESTINIO_NODISCARD
    bool
    empty() const noexcept
    {
        return m_methods.empty();
    }
};

//
// dynamic_none_of_methods_matcher_t
//
/*!
 * @brief An implementation of method_matcher that allows a method
 * if it isn't found in a dynamic list of disabled methods.
 *
 * Usage example:
 * @code
 * restinio::router::dynamic_none_of_methods_matcher_t matcher;
 * if(config.handle_get_method())
 *  matcher.add(restinio::http_method_get());
 * if(config.handle_head_method())
 *  matcher.add(restinio::http_method_head());
 * router->add_handler(matcher, // Or std::move(matcher) if matcher is no more needed.
 *  "/users/:id",
 *  [](const auto & req, auto & params) {...});
 * @endcode
 *
 * @since v.0.6.6
 */
class dynamic_none_of_methods_matcher_t : public method_matcher_t
{
    std::vector< http_method_id_t > m_methods;

public:
    dynamic_none_of_methods_matcher_t() = default;

    RESTINIO_NODISCARD
    bool
    match( const http_method_id_t & method ) const noexcept override
    {
        for( const auto & m : m_methods )
            if( m == method )
                return false;

        return true;
    }

    dynamic_none_of_methods_matcher_t &
    add( http_method_id_t method )
    {
        m_methods.emplace_back( std::move(method) );
        return *this;
    }

    RESTINIO_NODISCARD
    std::size_t
    size() const noexcept
    {
        return m_methods.size();
    }

    RESTINIO_NODISCARD
    bool
    empty() const noexcept
    {
        return m_methods.empty();
    }
};

} /* namespace router */

} /* namespace restinio */