folly/folly/container/View.h

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * 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/Portability.h>
#include <folly/functional/Invoke.h>
#include <folly/lang/CustomizationPoint.h>

namespace folly {

//  order_preserving_reinsertion_view_fn
//  order_preserving_reinsertion_view
//
//  Extension point for containers to provide an order such that if entries are
//  inserted into a new instance in that order, iteration order of the new
//  instance matches the original's. This can be useful for containers that have
//  defined but non-FIFO iteration order, such as F14Vector*.
//
//  Should return an iterable view (a type that provides begin() and end()).
//
//  Containers should provide overloads via tag-invoke.
struct order_preserving_reinsertion_view_fn { … };
FOLLY_DEFINE_CPO(
    order_preserving_reinsertion_view_fn, order_preserving_reinsertion_view)

//  order_preserving_reinsertion_view_or_default_fn
//  order_preserving_reinsertion_view_or_default
//
//  If a tag-invoke extension of order_preserving_reinsertion_view is available
//  over the given argument, forwards to that. Otherwise, returns the argument.
struct order_preserving_reinsertion_view_or_default_fn { … };
FOLLY_DEFINE_CPO(
    order_preserving_reinsertion_view_or_default_fn,
    order_preserving_reinsertion_view_or_default)

} // namespace folly