safe_dslist

/* -*- mode: c++; indent-tabs-mode: nil -*- */
/*
    safe_dslist
 
    Qore Programming Language
 
    Copyright (C) 2003 - 2024 Qore Technologies, s.r.o.
 
    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
    to deal in the Software without restriction, including without limitation
    the rights to use, copy, modify, merge, publish, distribute, sublicense,
    and/or sell copies of the Software, and to permit persons to whom the
    Software is furnished to do so, subject to the following conditions:
 
    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.
 
    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
 
    Note that the Qore library is released under a choice of three open-source
    licenses: MIT (as above), LGPL 2+, or GPL 2+; see README-LICENSE for more
    information.
*/
 
#ifndef _QORE_SAFE_DSLIST
 
#define _QORE_SAFE_DSLIST
 
#include <stdlib.h>
#include <string.h>
 
#include <algorithm>
#include <functional>
 
//! defines a node in a safe_dslist
template<typename T> hashdecl _qore_list_node {
    typedef _qore_list_node self_t;
    self_t* next;
    T data;
 
    DLLLOCAL _qore_list_node(T d, self_t* n) {
        next = n;
        data = d;
    }
    DLLLOCAL _qore_list_node(T d) {
        next = 0;
        data = d;
    }
};
 
//! defines an iterator for a safe_dslist
template<typename T> hashdecl _qore_list_iterator {
    typedef _qore_list_node<T> node_t;
    typedef _qore_list_iterator<T> self_t;
 
    // data for the node
    node_t* node;
 
    DLLLOCAL _qore_list_iterator(node_t* n) {
        node = n;
    }
    DLLLOCAL _qore_list_iterator() {
        node = nullptr;
    }
    DLLLOCAL self_t operator++(int) {
        self_t _tmp = *this;
        node = node->next;
        return _tmp;
    }
    DLLLOCAL self_t operator++() {
        node = node->next;
        return *this;
    }
    DLLLOCAL T operator*() {
        return node->data;
    }
    DLLLOCAL bool operator!=(const self_t& n) {
        return n.node != node;
    }
    DLLLOCAL bool operator==(const self_t& n) {
        return n.node == node;
    }
};
 
//! defines a const iterator for a safe_dslist
template<typename T> hashdecl _qore_list_const_iterator {
    typedef _qore_list_node<T> node_t;
    typedef _qore_list_const_iterator<T> self_t;
 
    // data for the node
    const node_t* node;
 
    DLLLOCAL _qore_list_const_iterator(_qore_list_iterator<T> i) {
        node = i.node;
    }
    DLLLOCAL _qore_list_const_iterator(const node_t* n) {
        node = n;
    }
    DLLLOCAL _qore_list_const_iterator() {
        node = nullptr;
    }
    DLLLOCAL self_t operator++(int) {
        self_t _tmp = *this;
        node = node->next;
        return _tmp;
    }
    DLLLOCAL self_t operator++() {
        node = node->next;
        return *this;
    }
    DLLLOCAL T operator*() const {
        return node->data;
    }
    DLLLOCAL bool operator!=(const self_t& n) {
        return n.node != node;
    }
    DLLLOCAL bool operator==(const self_t& n) {
        return n.node == node;
    }
};
 
//! templated class for a double-ended singly-linked list that can be safely read from multiple threads without locking as long as writes are locked
/**
   Reading in multiple threads is safe as long as writes (appends at the end or beginning) are locked.
   Implements a singly-linked list with constant-time inserts at the beginning and end that
   can be read in a multi-threaded context without locking.  Writes must be performed in a lock; however
   this class does not provide any locking; locking must be provided and performed externally to the
   class.  Provides an STL-like interface.
*/
template<typename T> class safe_dslist {
public:
    typedef _qore_list_iterator<T> iterator;
    typedef _qore_list_const_iterator<T> const_iterator;
    typedef _qore_list_node<T> node_t;
    typedef safe_dslist<T> self_t;
 
protected:
    DLLLOCAL void clear_intern() {
        node_t* w = head;
        while (w) {
            node_t* n = w->next;
            delete w;
            w = n;
        }
    }
 
private:
    node_t* head = nullptr,
        * tail = nullptr;
 
public:
    DLLLOCAL safe_dslist() {
    }
 
    DLLLOCAL ~safe_dslist() {
        clear_intern();
    }
 
    //! empties the list
    DLLLOCAL void clear() {
        clear_intern();
        head = tail = nullptr;
    }
 
    //! returns an iterator pointing to the first element of the list
    DLLLOCAL iterator begin() {
        return head;
    }
 
    //! returns an iterator pointing one element from the end of the list
    DLLLOCAL iterator end() {
        return nullptr;
    }
 
    //! returns an iterator pointing to the first element of the list
    DLLLOCAL const_iterator begin() const {
        return head;
    }
 
    //! returns an iterator pointing one element from the end of the list
    DLLLOCAL const_iterator end() const {
        return nullptr;
    }
 
    //! returns an iterator pointing to the last element in the list
    DLLLOCAL iterator last() {
        return tail;
    }
 
    //! returns an iterator pointing to the last element in the list
    DLLLOCAL const_iterator last() const {
        return tail;
    }
 
    //! returns an iterator either pointing to the element given if present in the list or pointing to one element from the end of the list if not
    DLLLOCAL iterator find(T data) {
        node_t* w = head;
        while (w) {
            if (w->data == data)
                return w;
            w = w->next;
        }
        return nullptr;
    }
 
    //! returns an iterator either pointing to the element given if present in the list or pointing to one element from the end of the list if not
    DLLLOCAL const_iterator find(T data) const {
        node_t* w = head;
        while (w) {
            if (w->data == data)
                return w;
            w = w->next;
        }
        return nullptr;
    }
 
    //! adds an element to the beginning of the list (constant time)
    DLLLOCAL void push_front(T data) {
        node_t* n = new node_t(data, head);
        if (!tail)
            tail = n;
        head = n;
    }
 
    //! adds an element to the end of the list (constant time)
    DLLLOCAL void push_back(T data) {
        node_t* n = new node_t(data);
        if (tail)
            tail->next = n;
        else
            head = n;
        tail = n;
    }
 
    //! removes an element from the beginning of the list
    DLLLOCAL void pop_front() {
        if (!tail)
            return;
        node_t* n = head;
        head = head->next;
        delete n;
        if (!head)
            tail = nullptr;
    }
 
    //! concatenates all elements of this list to the end of the list passed
    DLLLOCAL void populate(self_t& other) {
        iterator i = begin();
        while (i != end()) {
            other.push_back(*i);
            ++i;
        }
    }
 
    //! concatenates all elements of this list to the end of the list passed
    DLLLOCAL void populate(self_t* other) {
        iterator i = begin();
        while (i != end()) {
            other->push_back(*i);
            ++i;
        }
    }
 
    //! returns true if the list is empty
    DLLLOCAL bool empty() const {
        return !head;
    }
 
    //! returns true if the list contains only one element (constant time)
    DLLLOCAL bool singular() const {
        return head && head == tail;
    }
 
    //! returns true if the list contains more than one element (constant time)
    DLLLOCAL bool plural() const {
        return head != tail;
    }
 
    //! deletes the list element after the iterator argument and all other elements to the end of the list
    /** O(n) where n=length of list after the element given
        @note does not erase the element given by the iterator argument
    */
    DLLLOCAL void erase_to_end(iterator i) {
        if (!i.node) {
            clear();
            return;
        }
 
        node_t* w = i.node->next;
        i.node->next = nullptr;
        tail = i.node;
 
        while (w) {
            node_t* n = w->next;
            delete w;
            w = n;
        }
    }
 
    //! deletes the list element given by the iterator argument
    /** only constant time for the first element in the list, otherwise is O(n), linear with the length of the list
    */
    DLLLOCAL void erase(iterator i) {
        if (i.node == head) {
            head = i.node->next;
            if (!head) {
                tail = nullptr;
            }
        } else {
            // find previous entry
            node_t* n = head;
            while (n->next != i.node) {
                n = n->next;
            }
            n->next = i.node->next;
            if (i.node == tail) {
                tail = n;
            }
        }
        delete i.node;
    }
 
    DLLLOCAL size_t size() const {
        size_t i = 0;
        node_t* n = head;
        while (n) {
            ++i;
            n = n->next;
        }
        return i;
    }
};
 
#endif