| // Copyright 2020 The Pigweed 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 |
| // |
| // https://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. |
| |
| #include "pw_containers/intrusive_list.h" |
| |
| #include "pw_assert/assert.h" |
| |
| namespace pw::intrusive_list_impl { |
| |
| List::Item::~Item() { unlist(); } |
| |
| void List::Item::unlist(Item* prev) { |
| if (prev == nullptr) { |
| prev = previous(); |
| } |
| // Skip over this. |
| prev->next_ = next_; |
| |
| // Retain the invariant that unlisted items are self-cycles. |
| next_ = this; |
| } |
| |
| List::Item* List::Item::previous() { |
| // Follow the cycle around to find the previous element; O(N). |
| Item* prev = next_; |
| while (prev->next_ != this) { |
| prev = prev->next_; |
| } |
| return prev; |
| } |
| |
| void List::insert_after(Item* pos, Item& item) { |
| PW_CHECK( |
| item.unlisted(), |
| "Cannot add an item to a pw::IntrusiveList that is already in a list"); |
| item.next_ = pos->next_; |
| pos->next_ = &item; |
| } |
| |
| void List::erase_after(Item* pos) { pos->next_->unlist(pos); } |
| |
| List::Item* List::before_end() noexcept { return before_begin()->previous(); } |
| |
| void List::clear() { |
| while (!empty()) { |
| erase_after(before_begin()); |
| } |
| } |
| |
| bool List::remove(const Item& item_to_remove) { |
| for (Item* pos = before_begin(); pos->next_ != end(); pos = pos->next_) { |
| if (pos->next_ == &item_to_remove) { |
| erase_after(pos); |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| size_t List::size() const { |
| size_t total = 0; |
| Item* item = head_.next_; |
| while (item != &head_) { |
| item = item->next_; |
| total++; |
| } |
| return total; |
| } |
| |
| } // namespace pw::intrusive_list_impl |