source: trunk/www.guidonia.net/wp/wp-includes/class-feed.php@ 44

<?php

if ( !class_exists('SimplePie') )
        require_once (ABSPATH . WPINC . '/class-simplepie.php');

class WP_Feed_Cache extends SimplePie_Cache {
        /**
         * Don't call the constructor. Please.
         *
         * @access private
         */
        function WP_Feed_Cache() {
                trigger_error('Please call SimplePie_Cache::create() instead of the constructor', E_USER_ERROR);
        }

        /**
         * Create a new SimplePie_Cache object
         *
         * @static
         * @access public
         */
        function create($location, $filename, $extension) {
                return new WP_Feed_Cache_Transient($location, $filename, $extension);
        }
}

class WP_Feed_Cache_Transient {
        var $name;
        var $mod_name;
        var $lifetime = 43200; //Default lifetime in cache of 12 hours

        function WP_Feed_Cache_Transient($location, $filename, $extension) {
                $this->name = 'feed_' . $filename;
                $this->mod_name = 'feed_mod_' . $filename;
                $this->lifetime = apply_filters('wp_feed_cache_transient_lifetime', $this->lifetime);
        }

        function save($data) {
                if ( is_a($data, 'SimplePie') )
                        $data = $data->data;

                set_transient($this->name, $data, $this->lifetime);
                set_transient($this->mod_name, time(), $this->lifetime);
                return true;
        }

        function load() {
                return get_transient($this->name);
        }

        function mtime() {
                return get_transient($this->mod_name);
        }

        function touch() {
                return set_transient($this->mod_name, time(), $this->lifetime);
        }

        function unlink() {
                delete_transient($this->name);
                delete_transient($this->mod_name);
                return true;
        }
}

class WP_SimplePie_File extends SimplePie_File {

        function WP_SimplePie_File($url, $timeout = 10, $redirects = 5, $headers = null, $useragent = null, $force_fsockopen = false) {
                $this->url = $url;
                $this->timeout = $timeout;
                $this->redirects = $redirects;
                $this->headers = $headers;
                $this->useragent = $useragent;

                $this->method = SIMPLEPIE_FILE_SOURCE_REMOTE;

                if ( preg_match('/^http(s)?:\/\//i', $url) ) {
                        $args = array( 'timeout' => $this->timeout, 'redirection' => $this->redirects);

                        if ( !empty($this->headers) )
                                $args['headers'] = $this->headers;

                        if ( SIMPLEPIE_USERAGENT != $this->useragent ) //Use default WP user agent unless custom has been specified
                                $args['user-agent'] = $this->useragent;

                        $res = wp_remote_request($url, $args);

                        if ( is_wp_error($res) ) {
                                $this->error = 'WP HTTP Error: ' . $res->get_error_message();
                                $this->success = false;
                        } else {
                                $this->headers = $res['headers'];
                                $this->body = $res['body'];
                                $this->status_code = $res['response']['code'];
                        }
                } else {
                        if ( ! $this->body = file_get_contents($url) ) {
                                $this->error = 'file_get_contents could not read the file';
                                $this->success = false;
                        }
                }
        }
}