IterableQueue.h

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/*
 * This is a part of the Uniot project.
 * Copyright (C) 2016-2024 Uniot <contact@uniot.io>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include "ClearQueue.h"

template <typename T>
class IterableQueue : public ClearQueue<T> {
 public:
  void begin() const;

  bool isEnd() const;

  const T& next() const;

  const T& current() const;

  bool deleteCurrent();
 
 protected:
  mutable typename ClearQueue<T>::pnode mCurrent;
};
 
template <typename T>
void IterableQueue<T>::begin() const {
  mCurrent = ClearQueue<T>::mHead;
}
 
template <typename T>
bool IterableQueue<T>::isEnd() const {
  return !mCurrent;
}
 
template <typename T>
const T& IterableQueue<T>::next() const {
  auto prevCurrent = mCurrent;
  mCurrent = mCurrent->next;
  return prevCurrent->value;
}
 
template <typename T>
const T& IterableQueue<T>::current() const {
  return mCurrent->value;
}
 
template <typename T>
bool IterableQueue<T>::deleteCurrent() {
  if (!mCurrent) {
    return false;
  }
 
  if (mCurrent == ClearQueue<T>::mHead) {
    ClearQueue<T>::hardPop();
    mCurrent = ClearQueue<T>::mHead;
    return true;
  }
 
  typename ClearQueue<T>::pnode prev = ClearQueue<T>::mHead;
  while (prev && prev->next != mCurrent) {
    prev = prev->next;
  }
 
  if (!prev) {
    return false;
  }
 
  auto nextNode = mCurrent->next;
  prev->next = nextNode;
 
  if (!nextNode) {
    ClearQueue<T>::mTail = prev;
  }
 
  delete mCurrent;
  mCurrent = nextNode;
 
  return true;
}