/*

 * Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

#ifndef SHARE_GC_Z_ZLIST_HPP

#define SHARE_GC_Z_ZLIST_HPP

#include "memory/allocation.hpp"

#include "utilities/debug.hpp"

template <typename T> class ZList;

// Element in a doubly linked list

template <typename T>

class ZListNode {

  friend class ZList<T>;

private:

  ZListNode* _next;

  ZListNode* _prev;

  ZListNode(ZListNode* next, ZListNode* prev) :

      _next(next),

      _prev(prev) {}

  void set_unused() {

    _next = NULL;

    _prev = NULL;

  }

public:

  ZListNode() {

    set_unused();

  }

  ~ZListNode() {

    set_unused();

  }

  bool is_unused() const {

    return _next == NULL && _prev == NULL;

  }

};

// Doubly linked list

template <typename T>

class ZList {

private:

  ZListNode<T> _head;

  size_t       _size;

  // Passing by value and assignment is not allowed

  ZList(const ZList<T>& list);

  ZList<T>& operator=(const ZList<T>& list);

  void verify() const {

    assert(_head._next->_prev == &_head, "List corrupt");

    assert(_head._prev->_next == &_head, "List corrupt");

  }

  void insert(ZListNode<T>* before, ZListNode<T>* node) {

    verify();

    assert(node->is_unused(), "Already in a list");

    node->_prev = before;

    node->_next = before->_next;

    before->_next = node;

    node->_next->_prev = node;

    _size++;

  }

  ZListNode<T>* cast_to_inner(T* elem) const {

    return &elem->_node;

  }

  T* cast_to_outer(ZListNode<T>* node) const {

    return (T*)((uintptr_t)node - offset_of(T, _node));

  }

public:

  ZList() :

      _head(&_head, &_head),

      _size(0) {

    verify();

  }

  size_t size() const {

    verify();

    return _size;

  }

  bool is_empty() const {

    return _size == 0;

  }

  T* first() const {

    return is_empty() ? NULL : cast_to_outer(_head._next);

  }

  T* last() const {

    return is_empty() ? NULL : cast_to_outer(_head._prev);

  }

  T* next(T* elem) const {

    verify();

    ZListNode<T>* next = cast_to_inner(elem)->_next;

    return (next == &_head) ? NULL : cast_to_outer(next);

  }

  T* prev(T* elem) const {

    verify();

    ZListNode<T>* prev = cast_to_inner(elem)->_prev;

    return (prev == &_head) ? NULL : cast_to_outer(prev);

  }

  void insert_first(T* elem) {

    insert(&_head, cast_to_inner(elem));

  }

  void insert_last(T* elem) {

    insert(_head._prev, cast_to_inner(elem));

  }

  void insert_before(T* before, T* elem) {

    insert(cast_to_inner(before)->_prev, cast_to_inner(elem));

  }

  void insert_after(T* after, T* elem) {

    insert(cast_to_inner(after), cast_to_inner(elem));

  }

  void remove(T* elem) {

    verify();

    ZListNode<T>* const node = cast_to_inner(elem);

    assert(!node->is_unused(), "Not in a list");

    ZListNode<T>* const next = node->_next;

    ZListNode<T>* const prev = node->_prev;

    assert(next->_prev == node, "List corrupt");

    assert(prev->_next == node, "List corrupt");

    prev->_next = next;

    next->_prev = prev;

    node->set_unused();

    _size--;

  }

  T* remove_first() {

    T* elem = first();

    if (elem != NULL) {

      remove(elem);

    }

    return elem;

  }

  T* remove_last() {

    T* elem = last();

    if (elem != NULL) {

      remove(elem);

    }

    return elem;

  }

  void transfer(ZList<T>* list) {

    verify();

    if (!list->is_empty()) {

      list->_head._next->_prev = _head._prev;

      list->_head._prev->_next = _head._prev->_next;

      _head._prev->_next = list->_head._next;

      _head._prev = list->_head._prev;

      list->_head._next = &list->_head;

      list->_head._prev = &list->_head;

      _size += list->_size;

      list->_size = 0;

      list->verify();

      verify();

    }

  }

};

template <typename T, bool forward>

class ZListIteratorImpl : public StackObj {

private:

  const ZList<T>* const _list;

  T*                    _next;

public:

  ZListIteratorImpl(const ZList<T>* list);

  bool next(T** elem);

};

// Iterator types

#define ZLIST_FORWARD        true

#define ZLIST_REVERSE        false

template <typename T>

class ZListIterator : public ZListIteratorImpl<T, ZLIST_FORWARD> {

public:

  ZListIterator(const ZList<T>* list) :

      ZListIteratorImpl<T, ZLIST_FORWARD>(list) {}

};

template <typename T>

class ZListReverseIterator : public ZListIteratorImpl<T, ZLIST_REVERSE> {

public:

  ZListReverseIterator(const ZList<T>* list) :

      ZListIteratorImpl<T, ZLIST_REVERSE>(list) {}

};

#endif // SHARE_GC_Z_ZLIST_HPP