| // Copyright 2023 gRPC authors. |
| // |
| // 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. |
| |
| #ifndef GRPC_SRC_CORE_LIB_PROMISE_SWITCH_H |
| #define GRPC_SRC_CORE_LIB_PROMISE_SWITCH_H |
| |
| #include <memory> |
| #include <utility> |
| |
| #include <grpc/support/port_platform.h> |
| |
| #include "src/core/lib/promise/detail/promise_factory.h" |
| #include "src/core/lib/promise/if.h" |
| |
| namespace grpc_core { |
| |
| namespace promise_detail { |
| template <typename D, typename F> |
| struct Case { |
| D discriminator; |
| F factory; |
| }; |
| |
| template <typename F> |
| struct Default { |
| F factory; |
| }; |
| } // namespace promise_detail |
| |
| template <typename D, typename PromiseFactory> |
| auto Case(D discriminator, PromiseFactory f) { |
| return promise_detail::Case<D, PromiseFactory>{discriminator, std::move(f)}; |
| } |
| |
| template <typename PromiseFactory> |
| auto Default(PromiseFactory f) { |
| return promise_detail::Default<PromiseFactory>{std::move(f)}; |
| } |
| |
| // Given a list of cases that result in promise factories, return a single |
| // promise chosen by the discriminator (the first argument of this function). |
| // e.g.: |
| // Switch(1, Case<1>([] { return 43; }), Case<2>([] { return 44; })) |
| // resolves to 43. |
| // TODO(ctiller): consider writing a code-generator like we do for seq/join |
| // so that this lowers into a C switch statement. |
| template <typename D, typename F> |
| auto Switch(D, promise_detail::Default<F> def) { |
| return promise_detail::OncePromiseFactory<void, F>(std::move(def.factory)) |
| .Make(); |
| } |
| |
| template <typename D, typename F, typename... Others> |
| auto Switch(D discriminator, promise_detail::Case<D, F> c, Others... others) { |
| return If(discriminator == c.discriminator, std::move(c.factory), |
| Switch(discriminator, std::move(others)...)); |
| } |
| |
| } // namespace grpc_core |
| |
| #endif // GRPC_SRC_CORE_LIB_PROMISE_SWITCH_H |