sync/ullist.js

/*
The MIT License (MIT)
Copyright (c) 2013 Calvin Montgomery

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.
*/

/*
    ullist.js

    Description: Defines ULList, which represents a doubly linked list
    in which each item has a unique identifier stored in the `uid` field.

*/

function ULList() {
    this.first = null;
    this.last = null;
    this.length = 0;
}

/* Add an item to the beginning of the list */
ULList.prototype.prepend = function(item) {
    if(this.first !== null) {
        item.next = this.first;
        this.first.prev = item;
    }
    else {
        this.last = item;
    }
    this.first = item;
    this.first.prev = null;
    this.length++;
    return true;
}

/* Add an item to the end of the list */
ULList.prototype.append = function(item) {
    if(this.last !== null) {
        item.prev = this.last;
        this.last.next = item;
    }
    else {
        this.first = item;
    }
    this.last = item;
    this.last.next = null;
    this.length++;
    return true;
}

/* Insert an item after one which has a specified UID */
ULList.prototype.insertAfter = function(item, uid) {
    var after = this.find(uid);

    if(!after)
        return false;

    // Update links
    item.next = after.next;
    if(item.next)
        item.next.prev = item;
    item.prev = after;
    after.next = item;

    // New end of list
    if(after == this.last)
        this.last = item;

    this.length++;

    return true;
}

/* Insert an item before one that has a specified UID */
ULList.prototype.insertBefore = function(item, uid) {
    var before = this.find(uid);

    if(!before)
        return false;

    // Update links
    item.next = before;
    item.prev = before.prev;
    if(item.prev)
        item.prev.next = item;
    before.prev = item;

    // New beginning of list
    if(before == this.first)
        this.first = item;

    this.length++;

    return true;
}

/* Remove an item from the list */
ULList.prototype.remove = function(uid) {
    var item = this.find(uid);
    if(!item)
        return false;

    // Boundary conditions
    if(item == this.first)
        this.first = item.next;
    if(item == this.last)
        this.last = item.prev;

    // General case
    if(item.prev)
        item.prev.next = item.next;
    if(item.next)
        item.next.prev = item.prev;

    this.length--;
    return true;
}

/* Find an element in the list, return false if specified UID not found */
ULList.prototype.find = function(uid) {
    // Can't possibly find it in an empty list
    if(this.first === null)
        return false;

    var item = this.first;
    var iter = this.first;
    while(iter !== null && item.uid != uid) {
        item = iter;
        iter = iter.next;
    }

    if(item && item.uid == uid)
        return item;
    return false;
}

/* Clear all elements from the list */
ULList.prototype.clear = function() {
    this.first = null;
    this.last = null;
    this.length = 0;
}

/* Dump the contents of the list into an array */
ULList.prototype.toArray = function(pack) {
    var arr = new Array(this.length);
    var item = this.first;
    var i = 0;
    while(item !== null) {
        if(pack !== false && typeof item.pack == "function")
            arr[i++] = item.pack();
        else
            arr[i++] = item;
        item = item.next;
    }
    return arr;
}

/* iterate across the playlist */
ULList.prototype.forEach = function (fn) {
    var item = this.first;
    while(item !== null) {
        fn(item);
        item = item.next;
    }
};

exports.ULList = ULList;