Fix various compatibility issues with PHP 8

libs/swiftmailer/classes/Swift/OutputByteStream.php

@@ -0,0 +1,46 @@
+<?php
+
+/*
+ * This file is part of SwiftMailer.
+ * (c) 2004-2009 Chris Corbyn
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/**
+ * An abstract means of reading data.
+ *
+ * Classes implementing this interface may use a subsystem which requires less
+ * memory than working with large strings of data.
+ *
+ * @author Chris Corbyn
+ */
+interface Swift_OutputByteStream
+{
+    /**
+     * Reads $length bytes from the stream into a string and moves the pointer
+     * through the stream by $length.
+     *
+     * If less bytes exist than are requested the remaining bytes are given instead.
+     * If no bytes are remaining at all, boolean false is returned.
+     *
+     * @param int $length
+     *
+     * @throws Swift_IoException
+     *
+     * @return string|bool
+     */
+    public function read($length);
+
+    /**
+     * Move the internal read pointer to $byteOffset in the stream.
+     *
+     * @param int $byteOffset
+     *
+     * @throws Swift_IoException
+     *
+     * @return bool
+     */
+    public function setReadPointer($byteOffset);
+}