chromium/base/containers/id_map.h

// Copyright 2011 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_CONTAINERS_ID_MAP_H_
#define BASE_CONTAINERS_ID_MAP_H_

#include <stddef.h>
#include <stdint.h>

#include <iterator>
#include <limits>
#include <memory>
#include <ostream>
#include <type_traits>
#include <unordered_map>
#include <utility>

#include "base/check.h"
#include "base/check_op.h"
#include "base/containers/flat_set.h"
#include "base/memory/raw_ptr.h"
#include "base/sequence_checker.h"

namespace base {

// This object maintains a list of IDs that can be quickly converted to
// pointers to objects. It is implemented as a hash table, optimized for
// relatively small data sets (in the common case, there will be exactly one
// item in the list).
//
// Items can be inserted into the container with arbitrary ID, but the caller
// must ensure they are unique. Inserting IDs and relying on automatically
// generated ones is not allowed because they can collide.
//
// The map's value type (the V param) can be any dereferenceable type, such as a
// raw pointer or smart pointer, and must be comparable with nullptr.
template <typename V, typename K = int32_t>
class IDMap final { … };

}  // namespace base

#endif  // BASE_CONTAINERS_ID_MAP_H_