flow_many_sender.h

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/*
 * Copyright 2018-present Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#pragma once

#include <folly/experimental/pushmi/flow_receiver.h>
#include <folly/experimental/pushmi/executor.h>
#include <folly/experimental/pushmi/trampoline.h>

namespace folly {
namespace pushmi {

template <class PE, class PV, class E, class... VN>
class any_flow_many_sender {
  union data {
    void* pobj_ = nullptr;
    char buffer_[sizeof(std::tuple<VN...>)]; // can hold a V in-situ
  } data_{};
  template <class Wrapped>
  static constexpr bool insitu() {
    return sizeof(Wrapped) <= sizeof(data::buffer_) &&
        std::is_nothrow_move_constructible<Wrapped>::value;
  }
  struct vtable {
    static void s_op(data&, data*) {}
    static any_executor<E> s_executor(data&) { return {}; }
    static void s_submit(data&, any_flow_receiver<PE, PV, E, VN...>) {}
    void (*op_)(data&, data*) = vtable::s_op;
    any_executor<E> (*executor_)(data&) = vtable::s_executor;
    void (*submit_)(data&, any_flow_receiver<PE, PV, E, VN...>) = vtable::s_submit;
  };
  static constexpr vtable const noop_ {};
  vtable const* vptr_ = &noop_;
  template <class Wrapped>
  any_flow_many_sender(Wrapped obj, std::false_type) : any_flow_many_sender() {
    struct s {
      static void op(data& src, data* dst) {
        if (dst)
          dst->pobj_ = std::exchange(src.pobj_, nullptr);
        delete static_cast<Wrapped const*>(src.pobj_);
      }
      static any_executor<E> executor(data& src) {
        return any_executor<E>{
            ::folly::pushmi::executor(*static_cast<Wrapped*>(src.pobj_))};
      }
      static void submit(data& src, any_flow_receiver<PE, PV, E, VN...> out) {
        ::folly::pushmi::submit(
            *static_cast<Wrapped*>(src.pobj_), std::move(out));
      }
    };
    static const vtable vtbl{s::op, s::executor, s::submit};
    data_.pobj_ = new Wrapped(std::move(obj));
    vptr_ = &vtbl;
  }
  template <class Wrapped>
  any_flow_many_sender(Wrapped obj, std::true_type) noexcept
    : any_flow_many_sender() {
    struct s {
      static void op(data& src, data* dst) {
        if (dst)
          new (dst->buffer_) Wrapped(
              std::move(*static_cast<Wrapped*>((void*)src.buffer_)));
        static_cast<Wrapped const*>((void*)src.buffer_)->~Wrapped();
      }
      static any_executor<E> executor(data& src) {
        return any_executor<E>{::folly::pushmi::executor(
            *static_cast<Wrapped*>((void*)src.buffer_))};
      }
      static void submit(data& src, any_flow_receiver<PE, PV, E, VN...> out) {
        ::folly::pushmi::submit(
            *static_cast<Wrapped*>((void*)src.buffer_), std::move(out));
      }
    };
    static const vtable vtbl{s::op, s::executor, s::submit};
    new (data_.buffer_) Wrapped(std::move(obj));
    vptr_ = &vtbl;
  }
  template <class T, class U = std::decay_t<T>>
  using wrapped_t =
    std::enable_if_t<!std::is_same<U, any_flow_many_sender>::value, U>;
 public:
  using properties = property_set<is_sender<>, is_flow<>, is_many<>>;

  any_flow_many_sender() = default;
  any_flow_many_sender(any_flow_many_sender&& that) noexcept
      : any_flow_many_sender() {
    that.vptr_->op_(that.data_, &data_);
    std::swap(that.vptr_, vptr_);
  }
  PUSHMI_TEMPLATE (class Wrapped)
    (requires FlowSender<wrapped_t<Wrapped>, is_many<>>)
  explicit any_flow_many_sender(Wrapped obj) noexcept(insitu<Wrapped>())
    : any_flow_many_sender{std::move(obj), bool_<insitu<Wrapped>()>{}} {}
  ~any_flow_many_sender() {
    vptr_->op_(data_, nullptr);
  }
  any_flow_many_sender& operator=(any_flow_many_sender&& that) noexcept {
    this->~any_flow_many_sender();
    new ((void*)this) any_flow_many_sender(std::move(that));
    return *this;
  }
  any_executor<E> executor() {
    return vptr_->executor_(data_);
  }
  void submit(any_flow_receiver<PE, PV, E, VN...> out) {
    vptr_->submit_(data_, std::move(out));
  }
};

// Class static definitions:
template <class PE, class PV, class E, class... VN>
constexpr typename any_flow_many_sender<PE, PV, E, VN...>::vtable const
    any_flow_many_sender<PE, PV, E, VN...>::noop_;

template <class SF, class EXF>
class flow_many_sender<SF, EXF> {
  SF sf_;
  EXF exf_;

 public:
  using properties = property_set<is_sender<>, is_flow<>, is_many<>>;

  constexpr flow_many_sender() = default;
  constexpr explicit flow_many_sender(SF sf)
      : sf_(std::move(sf)) {}
  constexpr flow_many_sender(SF sf, EXF exf)
      : sf_(std::move(sf)), exf_(std::move(exf)) {}

  auto executor() { return exf_(); }
  PUSHMI_TEMPLATE(class Out)
    (requires FlowReceiver<Out> && Invocable<SF&, Out>)
  void submit(Out out) {
    sf_(std::move(out));
  }
};

template <PUSHMI_TYPE_CONSTRAINT(Sender<is_many<>, is_flow<>>) Data, class DSF, class DEXF>
class flow_many_sender<Data, DSF, DEXF> {
  Data data_;
  DSF sf_;
  DEXF exf_;

 public:
  using properties = property_set_insert_t<properties_t<Data>, property_set<is_sender<>, is_flow<>, is_many<>>>;

  constexpr flow_many_sender() = default;
  constexpr explicit flow_many_sender(Data data)
      : data_(std::move(data)) {}
  constexpr flow_many_sender(Data data, DSF sf)
      : data_(std::move(data)), sf_(std::move(sf)) {}
  constexpr flow_many_sender(Data data, DSF sf, DEXF exf)
      : data_(std::move(data)), sf_(std::move(sf)), exf_(std::move(exf)) {}

  auto executor() { return exf_(data_); }
  PUSHMI_TEMPLATE(class Out)
    (requires PUSHMI_EXP(lazy::FlowReceiver<Out> PUSHMI_AND
        lazy::Invocable<DSF&, Data&, Out>))
  void submit(Out out) {
    sf_(data_, std::move(out));
  }
};

template <>
class flow_many_sender<>
    : public flow_many_sender<ignoreSF, trampolineEXF> {
public:
  flow_many_sender() = default;
};

// make_flow_many_sender
PUSHMI_INLINE_VAR constexpr struct make_flow_many_sender_fn {
  inline auto operator()() const {
    return flow_many_sender<ignoreSF, trampolineEXF>{};
  }
  PUSHMI_TEMPLATE(class SF)
    (requires True<> PUSHMI_BROKEN_SUBSUMPTION(&& not Sender<SF>))
  auto operator()(SF sf) const {
    return flow_many_sender<SF, trampolineEXF>{std::move(sf)};
  }
  PUSHMI_TEMPLATE(class SF, class EXF)
    (requires True<> && Invocable<EXF&> PUSHMI_BROKEN_SUBSUMPTION(&& not Sender<SF>))
  auto operator()(SF sf, EXF exf) const {
    return flow_many_sender<SF, EXF>{std::move(sf), std::move(exf)};
  }
  PUSHMI_TEMPLATE(class Data)
    (requires True<> && Sender<Data, is_many<>, is_flow<>>)
  auto operator()(Data d) const {
    return flow_many_sender<Data, passDSF, passDEXF>{std::move(d)};
  }
  PUSHMI_TEMPLATE(class Data, class DSF)
    (requires Sender<Data, is_many<>, is_flow<>>)
  auto operator()(Data d, DSF sf) const {
    return flow_many_sender<Data, DSF, passDEXF>{std::move(d), std::move(sf)};
  }
  PUSHMI_TEMPLATE(class Data, class DSF, class DEXF)
    (requires Sender<Data, is_many<>, is_flow<>> && Invocable<DEXF&, Data&>)
  auto operator()(Data d, DSF sf, DEXF exf) const {
    return flow_many_sender<Data, DSF, DEXF>{std::move(d), std::move(sf), std::move(exf)};
  }
} const make_flow_many_sender {};

// deduction guides
#if __cpp_deduction_guides >= 201703
flow_many_sender() -> flow_many_sender<ignoreSF, trampolineEXF>;

PUSHMI_TEMPLATE(class SF)
  (requires True<> PUSHMI_BROKEN_SUBSUMPTION(&& not Sender<SF>))
flow_many_sender(SF) -> flow_many_sender<SF, trampolineEXF>;

PUSHMI_TEMPLATE(class SF, class EXF)
  (requires True<> && Invocable<EXF&> PUSHMI_BROKEN_SUBSUMPTION(&& not Sender<SF>))
flow_many_sender(SF, EXF) -> flow_many_sender<SF, EXF>;

PUSHMI_TEMPLATE(class Data)
  (requires True<> && Sender<Data, is_many<>, is_flow<>>)
flow_many_sender(Data) -> flow_many_sender<Data, passDSF, passDEXF>;

PUSHMI_TEMPLATE(class Data, class DSF)
  (requires Sender<Data, is_many<>, is_flow<>>)
flow_many_sender(Data, DSF) -> flow_many_sender<Data, DSF, passDEXF>;

PUSHMI_TEMPLATE(class Data, class DSF, class DEXF)
  (requires Sender<Data, is_many<>, is_flow<>> && Invocable<DEXF&, Data&>)
flow_many_sender(Data, DSF, DEXF) -> flow_many_sender<Data, DSF, DEXF>;
#endif

template<>
struct construct_deduced<flow_many_sender>
  : make_flow_many_sender_fn {};

// // TODO constrain me
// template <class V, class E = std::exception_ptr, Sender Wrapped>
// auto erase_cast(Wrapped w) {
//   return flow_many_sender<V, E>{std::move(w)};
// }

} // namespace pushmi
} // namespace folly