blob: e6cf0a5c8e2400f3481b1c75498fcbf561a650d5 [file] [log] [blame]
// Copyright 2018 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <algorithm>
#include <stack>
#include <unordered_map>
#include <utility>
#include <base/logging.h>
#include <base/macros.h>
namespace smbprovider {
// Class that maps an int32_t ID to another type. Each new ID is not currently
// in use, but IDs can be reused after that item is removed from the map.
// Primarily used for handing out pseudo file descriptors.
template <typename T>
class IdMap {
using MapType = std::unordered_map<int32_t, T>;
explicit IdMap(int initial_value)
: initial_id_(initial_value), next_unused_id_(initial_value) {}
IdMap(const IdMap&) = delete;
IdMap& operator=(const IdMap&) = delete;
~IdMap() = default;
int32_t Insert(T value) {
const int32_t next_id = GetNextId();
DCHECK_EQ(0, ids_.count(next_id));
ids_.emplace(next_id, std::move(value));
return next_id;
typename MapType::const_iterator Find(int32_t id) const {
return ids_.find(id);
typename MapType::iterator Find(int32_t id) { return ids_.find(id); }
const T& At(int32_t id) const { return; }
bool Contains(int32_t id) const { return ids_.count(id) > 0; }
bool Remove(int32_t id) {
// If the id was being used add to the free list to be reused.
if (ids_.erase(id) > 0) {
return true;
return false;
void Reset() {
// Empty out |free_ids_|.
free_ids_ = {};
next_unused_id_ = initial_id_;
size_t Count() const { return ids_.size(); }
bool Empty() const { return ids_.empty(); }
typename MapType::const_iterator Begin() const { return ids_.begin(); }
typename MapType::iterator Begin() { return ids_.begin(); }
typename MapType::const_iterator End() const { return ids_.end(); }
typename MapType::iterator End() { return ids_.end(); }
// Returns the next ID and updates the internal state to ensure that
// an ID that is already in use is not returned.
int32_t GetNextId() {
if (!free_ids_.empty()) {
int32_t next_id =;
return next_id;
return next_unused_id_++;
MapType ids_;
std::stack<int32_t> free_ids_;
const int32_t initial_id_;
int32_t next_unused_id_;
} // namespace smbprovider