[RSS] introducing query param 'limit' to restrict the number of items to display...

[github/wallabag/wallabag.git] / inc / 3rdparty / htmlpurifier / HTMLPurifier / Queue.php

<?php\r
\r
/**\r
 * A simple array-backed queue, based off of the classic Okasaki\r
 * persistent amortized queue.  The basic idea is to maintain two\r
 * stacks: an input stack and an output stack.  When the output\r
 * stack runs out, reverse the input stack and use it as the output\r
 * stack.\r
 *\r
 * We don't use the SPL implementation because it's only supported\r
 * on PHP 5.3 and later.\r
 *\r
 * Exercise: Prove that push/pop on this queue take amortized O(1) time.\r
 *\r
 * Exercise: Extend this queue to be a deque, while preserving amortized\r
 * O(1) time.  Some care must be taken on rebalancing to avoid quadratic\r
 * behaviour caused by repeatedly shuffling data from the input stack\r
 * to the output stack and back.\r
 */\r
class HTMLPurifier_Queue {\r
    private $input;\r
    private $output;\r
\r
    public function __construct($input = array()) {\r
        $this->input = $input;\r
        $this->output = array();\r
    }\r
\r
    /**\r
     * Shifts an element off the front of the queue.\r
     */\r
    public function shift() {\r
        if (empty($this->output)) {\r
            $this->output = array_reverse($this->input);\r
            $this->input = array();\r
        }\r
        if (empty($this->output)) {\r
            return NULL;\r
        }\r
        return array_pop($this->output);\r
    }\r
\r
    /**\r
     * Pushes an element onto the front of the queue.\r
     */\r
    public function push($x) {\r
        array_push($this->input, $x);\r
    }\r
\r
    /**\r
     * Checks if it's empty.\r
     */\r
    public function isEmpty() {\r
        return empty($this->input) && empty($this->output);\r
    }\r
}\r