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82 lines
2.0 KiB
82 lines
2.0 KiB
// Copyright 2020 The Pigweed Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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#include "pw_containers/intrusive_list.h"
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#include "pw_assert/assert.h"
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namespace pw::intrusive_list_impl {
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List::Item::~Item() { unlist(); }
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void List::Item::unlist(Item* prev) {
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if (prev == nullptr) {
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prev = previous();
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}
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// Skip over this.
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prev->next_ = next_;
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// Retain the invariant that unlisted items are self-cycles.
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next_ = this;
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}
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List::Item* List::Item::previous() {
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// Follow the cycle around to find the previous element; O(N).
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Item* prev = next_;
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while (prev->next_ != this) {
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prev = prev->next_;
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}
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return prev;
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}
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void List::insert_after(Item* pos, Item& item) {
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PW_CHECK(
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item.unlisted(),
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"Cannot add an item to a pw::IntrusiveList that is already in a list");
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item.next_ = pos->next_;
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pos->next_ = &item;
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}
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void List::erase_after(Item* pos) { pos->next_->unlist(pos); }
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List::Item* List::before_end() noexcept { return before_begin()->previous(); }
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void List::clear() {
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while (!empty()) {
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erase_after(before_begin());
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}
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}
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bool List::remove(const Item& item_to_remove) {
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for (Item* pos = before_begin(); pos->next_ != end(); pos = pos->next_) {
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if (pos->next_ == &item_to_remove) {
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erase_after(pos);
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return true;
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}
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}
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return false;
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}
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size_t List::size() const {
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size_t total = 0;
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Item* item = head_.next_;
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while (item != &head_) {
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item = item->next_;
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total++;
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}
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return total;
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}
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} // namespace pw::intrusive_list_impl
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