initial sabre upgrade (needs lots of work - to wit: authentication, redo the browser interface, and rework event export/import)

vendor/sabre/vobject/lib/StringUtil.php

@@ -0,0 +1,66 @@
+<?php
+
+namespace Sabre\VObject;
+
+/**
+ * Useful utilities for working with various strings.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class StringUtil {
+
+    /**
+     * Returns true or false depending on if a string is valid UTF-8.
+     *
+     * @param string $str
+     *
+     * @return bool
+     */
+    static function isUTF8($str) {
+
+        // Control characters
+        if (preg_match('%[\x00-\x08\x0B-\x0C\x0E\x0F]%', $str)) {
+            return false;
+        }
+
+        return (bool)preg_match('%%u', $str);
+
+    }
+
+    /**
+     * This method tries its best to convert the input string to UTF-8.
+     *
+     * Currently only ISO-5991-1 input and UTF-8 input is supported, but this
+     * may be expanded upon if we receive other examples.
+     *
+     * @param string $str
+     *
+     * @return string
+     */
+    static function convertToUTF8($str) {
+
+        $encoding = mb_detect_encoding($str, ['UTF-8', 'ISO-8859-1', 'WINDOWS-1252'], true);
+
+        switch ($encoding) {
+            case 'ISO-8859-1' :
+                $newStr = utf8_encode($str);
+                break;
+            /* Unreachable code. Not sure yet how we can improve this
+             * situation.
+            case 'WINDOWS-1252' :
+                $newStr = iconv('cp1252', 'UTF-8', $str);
+                break;
+             */
+            default :
+                 $newStr = $str;
+
+        }
+
+        // Removing any control characters
+        return (preg_replace('%(?:[\x00-\x08\x0B-\x0C\x0E-\x1F\x7F])%', '', $newStr));
+
+    }
+
+}