#
actix_service/
boxed.rs

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    //! Trait object forms of services and service factories.

    use alloc::{boxed::Box, rc::Rc};
    use core::{future::Future, pin::Pin};

    use paste::paste;

    use crate::{Service, ServiceFactory};

    /// A boxed future with no send bound or lifetime parameters.
    pub type BoxFuture<T> = Pin<Box<dyn Future<Output = T>>>;

    macro_rules! service_object {
        ($name: ident, $type: tt, $fn_name: ident) => {
            paste! {
                #[doc = "Type alias for service trait object using `" $type "`."]
                pub type $name<Req, Res, Err> = $type<
                    dyn Service<Req, Response = Res, Error = Err, Future = BoxFuture<Result<Res, Err>>>,
                >;

                #[doc = "Wraps service as a trait object using [`" $name "`]."]
                pub fn $fn_name<S, Req>(service: S) -> $name<Req, S::Response, S::Error>
                where
                    S: Service<Req> + 'static,
                    Req: 'static,
                    S::Future: 'static,
                {
                    $type::new(ServiceWrapper::new(service))
                }
            }
        };
    }

    service_object!(BoxService, Box, service);
    service_object!(RcService, Rc, rc_service);

    struct ServiceWrapper<S> {
        inner: S,
    }

    impl<S> ServiceWrapper<S> {
        fn new(inner: S) -> Self {
            Self { inner }
        }
    }

    impl<S, Req, Res, Err> Service<Req> for ServiceWrapper<S>
    where
        S: Service<Req, Response = Res, Error = Err>,
        S::Future: 'static,
    {
        type Response = Res;
        type Error = Err;
        type Future = BoxFuture<Result<Res, Err>>;

        crate::forward_ready!(inner);

        fn call(&self, req: Req) -> Self::Future {
            Box::pin(self.inner.call(req))
        }
    }

    /// Wrapper for a service factory that will map it's services to boxed trait object services.
    pub struct BoxServiceFactory<Cfg, Req, Res, Err, InitErr>(Inner<Cfg, Req, Res, Err, InitErr>);

    /// Wraps a service factory that returns service trait objects.
    pub fn factory<SF, Req>(
        factory: SF,
    ) -> BoxServiceFactory<SF::Config, Req, SF::Response, SF::Error, SF::InitError>
    where
        SF: ServiceFactory<Req> + 'static,
        Req: 'static,
        SF::Response: 'static,
        SF::Service: 'static,
        SF::Future: 'static,
        SF::Error: 'static,
        SF::InitError: 'static,
    {
        BoxServiceFactory(Box::new(FactoryWrapper(factory)))
    }

    type Inner<C, Req, Res, Err, InitErr> = Box<
        dyn ServiceFactory<
            Req,
            Config = C,
            Response = Res,
            Error = Err,
            InitError = InitErr,
            Service = BoxService<Req, Res, Err>,
            Future = BoxFuture<Result<BoxService<Req, Res, Err>, InitErr>>,
        >,
    >;

    impl<C, Req, Res, Err, InitErr> ServiceFactory<Req> for BoxServiceFactory<C, Req, Res, Err, InitErr>
    where
        Req: 'static,
        Res: 'static,
        Err: 'static,
        InitErr: 'static,
    {
        type Response = Res;
        type Error = Err;
        type Config = C;
        type Service = BoxService<Req, Res, Err>;
        type InitError = InitErr;

        type Future = BoxFuture<Result<Self::Service, InitErr>>;

        fn new_service(&self, cfg: C) -> Self::Future {
            self.0.new_service(cfg)
        }
    }

    struct FactoryWrapper<SF>(SF);

    impl<SF, Req, Cfg, Res, Err, InitErr> ServiceFactory<Req> for FactoryWrapper<SF>
    where
        Req: 'static,
        Res: 'static,
        Err: 'static,
        InitErr: 'static,
        SF: ServiceFactory<Req, Config = Cfg, Response = Res, Error = Err, InitError = InitErr>,
        SF::Future: 'static,
        SF::Service: 'static,
        <SF::Service as Service<Req>>::Future: 'static,
    {
        type Response = Res;
        type Error = Err;
        type Config = Cfg;
        type Service = BoxService<Req, Res, Err>;
        type InitError = InitErr;
        type Future = BoxFuture<Result<Self::Service, Self::InitError>>;

        fn new_service(&self, cfg: Cfg) -> Self::Future {
            let f = self.0.new_service(cfg);
            Box::pin(async { f.await.map(|s| Box::new(ServiceWrapper::new(s)) as _) })
        }
    }