# Crow: include/crow/middleware.h Source File

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middleware.h
#pragma once
#include "crow/http_request.h"
#include "crow/http_response.h"
#include "crow/utility.h"
#include <tuple>
#include <type_traits>
#include <iostream>
#include <utility>
namespace crow // NOTE: Already documented in "crow/app.h"
{
/// Local middleware should extend ILocalMiddleware
struct ILocalMiddleware
{
using call_global = std::false_type;
};
namespace detail
{
template<typename MW>
struct check_before_handle_arity_3_const
{
template<typename T, void (T::*)(request&, response&, typename MW::context&) const = &T::before_handle>
struct get
{};
};
template<typename MW>
struct check_before_handle_arity_3
{
template<typename T, void (T::*)(request&, response&, typename MW::context&) = &T::before_handle>
struct get
{};
};
template<typename MW>
struct check_after_handle_arity_3_const
{
template<typename T, void (T::*)(request&, response&, typename MW::context&) const = &T::after_handle>
struct get
{};
};
template<typename MW>
struct check_after_handle_arity_3
{
template<typename T, void (T::*)(request&, response&, typename MW::context&) = &T::after_handle>
struct get
{};
};
template<typename MW>
struct check_global_call_false
{
template<typename T, typename std::enable_if<T::call_global::value == false, bool>::type = true>
struct get
{};
};
template<typename T>
struct is_before_handle_arity_3_impl
{
template<typename C>
static std::true_type f(typename check_before_handle_arity_3_const<T>::template get<C>*);
template<typename C>
static std::true_type f(typename check_before_handle_arity_3<T>::template get<C>*);
template<typename C>
static std::false_type f(...);
public:
static const bool value = decltype(f<T>(nullptr))::value;
};
template<typename T>
struct is_after_handle_arity_3_impl
{
template<typename C>
static std::true_type f(typename check_after_handle_arity_3_const<T>::template get<C>*);
template<typename C>
static std::true_type f(typename check_after_handle_arity_3<T>::template get<C>*);
template<typename C>
static std::false_type f(...);
public:
static constexpr bool value = decltype(f<T>(nullptr))::value;
};
template<typename MW>
struct is_middleware_global
{
template<typename C>
static std::false_type f(typename check_global_call_false<MW>::template get<C>*);
template<typename C>
static std::true_type f(...);
static const bool value = decltype(f<MW>(nullptr))::value;
};
template<typename MW, typename Context, typename ParentContext>
typename std::enable_if<!is_before_handle_arity_3_impl<MW>::value>::type
before_handler_call(MW& mw, request& req, response& res, Context& ctx, ParentContext& /*parent_ctx*/)
{
mw.before_handle(req, res, ctx.template get<MW>(), ctx);
}
template<typename MW, typename Context, typename ParentContext>
typename std::enable_if<is_before_handle_arity_3_impl<MW>::value>::type
before_handler_call(MW& mw, request& req, response& res, Context& ctx, ParentContext& /*parent_ctx*/)
{
mw.before_handle(req, res, ctx.template get<MW>());
}
template<typename MW, typename Context, typename ParentContext>
typename std::enable_if<!is_after_handle_arity_3_impl<MW>::value>::type
after_handler_call(MW& mw, request& req, response& res, Context& ctx, ParentContext& /*parent_ctx*/)
{
mw.after_handle(req, res, ctx.template get<MW>(), ctx);
}
template<typename MW, typename Context, typename ParentContext>
typename std::enable_if<is_after_handle_arity_3_impl<MW>::value>::type
after_handler_call(MW& mw, request& req, response& res, Context& ctx, ParentContext& /*parent_ctx*/)
{
mw.after_handle(req, res, ctx.template get<MW>());
}
template<typename CallCriteria,
int N, typename Context, typename Container>
typename std::enable_if<(N < std::tuple_size<typename std::remove_reference<Container>::type>::value), bool>::type
middleware_call_helper(const CallCriteria& cc, Container& middlewares, request& req, response& res, Context& ctx)
{
using CurrentMW = typename std::tuple_element<N, typename std::remove_reference<Container>::type>::type;
if (!cc.template enabled<CurrentMW>(N))
{
return middleware_call_helper<CallCriteria, N + 1, Context, Container>(cc, middlewares, req, res, ctx);
}
using parent_context_t = typename Context::template partial<N - 1>;
before_handler_call<CurrentMW, Context, parent_context_t>(std::get<N>(middlewares), req, res, ctx, static_cast<parent_context_t&>(ctx));
if (res.is_completed())
{
after_handler_call<CurrentMW, Context, parent_context_t>(std::get<N>(middlewares), req, res, ctx, static_cast<parent_context_t&>(ctx));
return true;
}
if (middleware_call_helper<CallCriteria, N + 1, Context, Container>(cc, middlewares, req, res, ctx))
{
after_handler_call<CurrentMW, Context, parent_context_t>(std::get<N>(middlewares), req, res, ctx, static_cast<parent_context_t&>(ctx));
return true;
}
return false;
}
template<typename CallCriteria, int N, typename Context, typename Container>
typename std::enable_if<(N >= std::tuple_size<typename std::remove_reference<Container>::type>::value), bool>::type
middleware_call_helper(const CallCriteria& /*cc*/, Container& /*middlewares*/, request& /*req*/, response& /*res*/, Context& /*ctx*/)
{
return false;
}
template<typename CallCriteria, int N, typename Context, typename Container>
typename std::enable_if<(N < 0)>::type
after_handlers_call_helper(const CallCriteria& /*cc*/, Container& /*middlewares*/, Context& /*context*/, request& /*req*/, response& /*res*/)
{
}
template<typename CallCriteria, int N, typename Context, typename Container>
typename std::enable_if<(N == 0)>::type after_handlers_call_helper(const CallCriteria& cc, Container& middlewares, Context& ctx, request& req, response& res)
{
using parent_context_t = typename Context::template partial<N - 1>;
using CurrentMW = typename std::tuple_element<N, typename std::remove_reference<Container>::type>::type;
if (cc.template enabled<CurrentMW>(N))
{
after_handler_call<CurrentMW, Context, parent_context_t>(std::get<N>(middlewares), req, res, ctx, static_cast<parent_context_t&>(ctx));
}
}
template<typename CallCriteria, int N, typename Context, typename Container>
typename std::enable_if<(N > 0)>::type after_handlers_call_helper(const CallCriteria& cc, Container& middlewares, Context& ctx, request& req, response& res)
{
using parent_context_t = typename Context::template partial<N - 1>;
using CurrentMW = typename std::tuple_element<N, typename std::remove_reference<Container>::type>::type;
if (cc.template enabled<CurrentMW>(N))
{
after_handler_call<CurrentMW, Context, parent_context_t>(std::get<N>(middlewares), req, res, ctx, static_cast<parent_context_t&>(ctx));
}
after_handlers_call_helper<CallCriteria, N - 1, Context, Container>(cc, middlewares, ctx, req, res);
}
// A CallCriteria that accepts only global middleware
struct middleware_call_criteria_only_global
{
template<typename MW>
constexpr bool enabled(int) const
{
return is_middleware_global<MW>::value;
}
};
template<typename F, typename... Args>
typename std::enable_if<black_magic::CallHelper<F, black_magic::S<Args...>>::value, void>::type
wrapped_handler_call(crow::request& /*req*/, crow::response& res, const F& f, Args&&... args)
{
static_assert(!std::is_same<void, decltype(f(std::declval<Args>()...))>::value,
"Handler function cannot have void return type; valid return types: string, int, crow::response, crow::returnable");
res = crow::response(f(std::forward<Args>(args)...));
res.end();
}
template<typename F, typename... Args>
typename std::enable_if<
!black_magic::CallHelper<F, black_magic::S<Args...>>::value &&
black_magic::CallHelper<F, black_magic::S<crow::request&, Args...>>::value,
void>::type
wrapped_handler_call(crow::request& req, crow::response& res, const F& f, Args&&... args)
{
static_assert(!std::is_same<void, decltype(f(std::declval<crow::request>(), std::declval<Args>()...))>::value,
"Handler function cannot have void return type; valid return types: string, int, crow::response, crow::returnable");
res = crow::response(f(req, std::forward<Args>(args)...));
res.end();
}
template<typename F, typename... Args>
typename std::enable_if<
!black_magic::CallHelper<F, black_magic::S<Args...>>::value &&
!black_magic::CallHelper<F, black_magic::S<crow::request&, Args...>>::value &&
black_magic::CallHelper<F, black_magic::S<crow::response&, Args...>>::value,
void>::type
wrapped_handler_call(crow::request& /*req*/, crow::response& res, const F& f, Args&&... args)
{
static_assert(std::is_same<void, decltype(f(std::declval<crow::response&>(), std::declval<Args>()...))>::value,
"Handler function with response argument should have void return type");
f(res, std::forward<Args>(args)...);
}
template<typename F, typename... Args>
typename std::enable_if<
!black_magic::CallHelper<F, black_magic::S<Args...>>::value &&
!black_magic::CallHelper<F, black_magic::S<crow::request&, Args...>>::value &&
!black_magic::CallHelper<F, black_magic::S<crow::response&, Args...>>::value &&
black_magic::CallHelper<F, black_magic::S<const crow::request&, crow::response&, Args...>>::value,
void>::type
wrapped_handler_call(crow::request& req, crow::response& res, const F& f, Args&&... args)
{
static_assert(std::is_same<void, decltype(f(std::declval<crow::request&>(), std::declval<crow::response&>(), std::declval<Args>()...))>::value,
"Handler function with response argument should have void return type");
f(req, res, std::forward<Args>(args)...);
}
// wrapped_handler_call transparently wraps a handler call behind (req, res, args...)
template<typename F, typename... Args>
typename std::enable_if<
!black_magic::CallHelper<F, black_magic::S<Args...>>::value &&
!black_magic::CallHelper<F, black_magic::S<crow::request&, Args...>>::value &&
!black_magic::CallHelper<F, black_magic::S<crow::response&, Args...>>::value &&
!black_magic::CallHelper<F, black_magic::S<const crow::request&, crow::response&, Args...>>::value,
void>::type
wrapped_handler_call(crow::request& req, crow::response& res, const F& f, Args&&... args)
{
static_assert(std::is_same<void, decltype(f(std::declval<crow::request&>(), std::declval<crow::response&>(), std::declval<Args>()...))>::value,
"Handler function with response argument should have void return type");
f(req, res, std::forward<Args>(args)...);
}
template<bool Reversed>
struct middleware_call_criteria_dynamic
{};
template<>
struct middleware_call_criteria_dynamic<false>
{
middleware_call_criteria_dynamic(const std::vector<int>& indices):
indices(indices), slider(0) {}
template<typename>
bool enabled(int mw_index) const
{
if (slider < int(indices.size()) && indices[slider] == mw_index)
{
slider++;
return true;
}
return false;
}
private:
const std::vector<int>& indices;
mutable int slider;
};
template<>
struct middleware_call_criteria_dynamic<true>
{
middleware_call_criteria_dynamic(const std::vector<int>& indices):
indices(indices), slider(int(indices.size()) - 1) {}
template<typename>
bool enabled(int mw_index) const
{
if (slider >= 0 && indices[slider] == mw_index)
{
slider--;
return true;
}
return false;
}
private:
const std::vector<int>& indices;
mutable int slider;
};
} // namespace detail
} // namespace crow
crow
The main namespace of the library. In this namespace is defined the most important classes and functi...
crow::ILocalMiddleware
Local middleware should extend ILocalMiddleware.
Definition middleware.h:17
crow::detail::check_after_handle_arity_3::get
Definition middleware.h:52
crow::detail::check_after_handle_arity_3_const::get
Definition middleware.h:44
crow::detail::check_after_handle_arity_3_const
Definition middleware.h:41
crow::detail::check_after_handle_arity_3
Definition middleware.h:49
crow::detail::check_before_handle_arity_3::get
Definition middleware.h:36
crow::detail::check_before_handle_arity_3_const::get
Definition middleware.h:28
crow::detail::check_before_handle_arity_3_const
Definition middleware.h:25
crow::detail::check_before_handle_arity_3
Definition middleware.h:33
crow::detail::check_global_call_false::get
Definition middleware.h:60
crow::detail::check_global_call_false
Definition middleware.h:57
crow::detail::is_after_handle_arity_3_impl
Definition middleware.h:81
crow::detail::is_before_handle_arity_3_impl
Definition middleware.h:65
crow::detail::is_middleware_global
Definition middleware.h:97
crow::detail::middleware_call_criteria_dynamic
Definition middleware.h:284
crow::detail::middleware_call_criteria_only_global
Definition middleware.h:204
crow::request
An HTTP request.
Definition http_request.h:36
crow::response
HTTP response.
Definition http_response.h:34
crow::response::end
void end()
Set the response completion flag and call the handler (to send the response).
Definition http_response.h:237