chromium/third_party/grpc/src/src/core/lib/promise/try_join.h

// Copyright 2021 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_TRY_JOIN_H
#define GRPC_SRC_CORE_LIB_PROMISE_TRY_JOIN_H

#include <grpc/support/port_platform.h>

#include <type_traits>

#include "absl/meta/type_traits.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"

#include "src/core/lib/promise/detail/basic_join.h"
#include "src/core/lib/promise/detail/status.h"
#include "src/core/lib/promise/poll.h"

namespace grpc_core {

namespace promise_detail {

// Extract the T from a StatusOr<T>
template <typename T>
T IntoResult(absl::StatusOr<T>* status) { … }

// TryJoin returns a StatusOr<tuple<A,B,C>> for f()->Poll<StatusOr<A>>,
// g()->Poll<StatusOr<B>>, h()->Poll<StatusOr<C>>. If one of those should be a
// Status instead, we need a placeholder type to return, and this is it.
inline Empty IntoResult(absl::Status*) { … }

// Traits object to pass to BasicJoin
struct TryJoinTraits { … };

// Implementation of TryJoin combinator.
TryJoin;

}  // namespace promise_detail

// Run all promises.
// If any fail, cancel the rest and return the failure.
// If all succeed, return Ok(tuple-of-results).
template <typename... Promises>
promise_detail::TryJoin<Promises...> TryJoin(Promises... promises) { … }

}  // namespace grpc_core

#endif  // GRPC_SRC_CORE_LIB_PROMISE_TRY_JOIN_H