chromium/third_party/grpc/src/src/core/lib/gprpp/sorted_pack.h

// Copyright 2022 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_GPRPP_SORTED_PACK_H
#define GRPC_SRC_CORE_LIB_GPRPP_SORTED_PACK_H

#include <grpc/support/port_platform.h>

#include <type_traits>

namespace grpc_core {

namespace sorted_pack_detail {

// A list of types
template <typename... A>
struct Typelist { … };

// Find the smallest element of Args, and the rest of the elements
template <template <typename, typename> class Cmp, typename Args>
struct Smallest;

Smallest<Cmp, Typelist<Arg, Args...>>;

Smallest<Cmp, Typelist<Arg>>;

// Sort a list of types into a typelist
template <template <typename, typename> class Cmp, typename Args>
struct Sorted;

Sorted<Cmp, Typelist<Args...>>;

Sorted<Cmp, Typelist<Arg>>;

Sorted<Cmp, Typelist<>>;

}  // namespace sorted_pack_detail

// Given a type T<A...>, and a type comparator Cmp<P,Q>, and some set of types
// Args...:
// Sort Args... using Cmp into SortedArgs..., then instantiate T<SortedArgs...>
// as Type.
// Cmp<P,Q> should have a single constant `kValue` that is true if P < Q.
template <template <typename...> class T,
          template <typename, typename> class Cmp, typename... Args>
struct WithSortedPack { … };

}  // namespace grpc_core

#endif  // GRPC_SRC_CORE_LIB_GPRPP_SORTED_PACK_H