* @param string $path Path to normalize.
		 * @return string Normalized path.
		 */
		public static function normalizePath($path) {
			if ( function_exists('wp_normalize_path') ) {
				return wp_normalize_path($path);
			}
			$path = str_replace('\\', '/', $path);
			$path = preg_replace('|(?<=.)/+|', '/', $path);
			if ( substr($path, 1, 1) === ':' ) {
				$path = ucfirst($path);
			}
			return $path;
		}
		
		/**
		 * Check if the path points to a plugin file.
		 *
		 * @param string $absolutePath Normalized path.
		 * @return bool
		 */
		protected static function isPluginFile($absolutePath) {
			//Is the file inside the "plugins" or "mu-plugins" directory?
			$pluginDir = self::normalizePath(WP_PLUGIN_DIR);
			$muPluginDir = self::normalizePath(WPMU_PLUGIN_DIR);
			if ( (strpos($absolutePath, $pluginDir) === 0) || (strpos($absolutePath, $muPluginDir) === 0) ) {
				return true;
			}

			//Is it a file at all? Caution: is_file() can fail if the parent dir. doesn't have the +x permission set.
			if ( !is_file($absolutePath) ) {
				return false;
			}

			//Does it have a valid plugin header?
			//This is a last-ditch check for plugins symlinked from outside the WP root.
			if ( function_exists('get_file_data') ) {
				$headers = get_file_data($absolutePath, array('Name' => 'Plugin Name'), 'plugin');
				return !empty($headers['Name']);
			}

			return false;
		}

		/**
		 * Get the name of the theme's directory from a full path to a file inside that directory.
		 * E.g. "/abc/public_html/wp-content/themes/foo/whatever.php" => "foo".
		 *
		 * Note that subdirectories are currently not supported. For example,
		 * "/xyz/wp-content/themes/my-theme/includes/whatever.php" => NULL.
		 *
		 * @param string $absolutePath Normalized path.
		 * @return string|null Directory name, or NULL if the path doesn't point to a theme.
		 */
		protected static function getThemeDirectoryName($absolutePath) {
			if ( is_file($absolutePath) ) {
				$absolutePath = dirname($absolutePath);
			}

			if ( file_exists($absolutePath . '/style.css') ) {
				return basename($absolutePath);
			}
			return null;
		}

		/**
		 * Get the name of the hosting service that the URL points to.
		 *
		 * @param string $metadataUrl
		 * @return string|null
		 */
		private static function getVcsService($metadataUrl) {
			$service = null;

			//Which hosting service does the URL point to?
			$host = parse_url($metadataUrl, PHP_URL_HOST);
			$path = parse_url($metadataUrl, PHP_URL_PATH);

			//Check if the path looks like "/user-name/repository".
			//For GitLab.com it can also be "/user/group1/group2/.../repository".
			$repoRegex = '@^/?([^/]+?)/([^/#?&]+?)/?$@';
			if ( $host === 'gitlab.com' ) {
				$repoRegex = '@^/?(?:[^/#?&]++/){1,20}(?:[^/#?&]++)/?$@';
			}
			if ( preg_match($repoRegex, $path) ) {
				$knownServices = array(
					'github.com' => 'GitHub',
					'bitbucket.org' => 'BitBucket',
					'gitlab.com' => 'GitLab',
				);
				if ( isset($knownServices[$host]) ) {
					$service = $knownServices[$host];
				}
			}
			
			return apply_filters('puc_get_vcs_service', $service, $host, $path, $metadataUrl);
		}

		/**
		 * Get the latest version of the specified class that has the same major version number
		 * as this factory class.
		 *
		 * @param string $class Partial class name.
		 * @return string|null Full class name.
		 */
		protected static function getCompatibleClassVersion($class) {
			if ( isset(self::$classVersions[$class][self::$latestCompatibleVersion]) ) {
				return self::$classVersions[$class][self::$latestCompatibleVersion];
			}
			return null;
		}

		/**
		 * Get the specific class name for the latest available version of a class.
		 *
		 * @param string $class
		 * @return null|string
		 */
		public static function getLatestClassVersion($class) {
			if ( !self::$sorted ) {
				self::sortVersions();
			}

			if ( isset(self::$classVersions[$class]) ) {
				return reset(self::$classVersions[$class]);
			} else {
				return null;
			}
		}

		/**
		 * Sort available class versions in descending order (i.e. newest first).
		 */
		protected static function sortVersions() {
			foreach ( self::$classVersions as $class => $versions ) {
				uksort($versions, array(__CLASS__, 'compareVersions'));
				self::$classVersions[$class] = $versions;
			}
			self::$sorted = true;
		}

		protected static function compareVersions($a, $b) {
			return -version_compare($a, $b);
		}

		/**
		 * Register a version of a class.
		 *
		 * @access private This method is only for internal use by the library.
		 *
		 * @param string $generalClass Class name without version numbers, e.g. 'PluginUpdateChecker'.
		 * @param string $versionedClass Actual class name, e.g. 'PluginUpdateChecker_1_2'.
		 * @param string $version Version number, e.g. '1.2'.
		 */
		public static function addVersion($generalClass, $versionedClass, $version) {
			if ( empty(self::$myMajorVersion) ) {
				$nameParts = explode('_', __CLASS__, 3);
				self::$myMajorVersion = substr(ltrim($nameParts[1], 'v'), 0, 1);
			}

			//Store the greatest version number that matches our major version.
			$components = explode('.', $version);
			if ( $components[0] === self::$myMajorVersion ) {

				if (
					empty(self::$latestCompatibleVersion)
					|| version_compare($version, self::$latestCompatibleVersion, '>')
				) {
					self::$latestCompatibleVersion = $version;
				}

			}

			if ( !isset(self::$classVersions[$generalClass]) ) {
				self::$classVersions[$generalClass] = array();
			}
			self::$classVersions[$generalClass][$version] = $versionedClass;
			self::$sorted = false;
		}
	}

endif;