use a string based buffer for Read/Write streams

src/StringBuffer.php

@@ -0,0 +1,61 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2021 Robin Appelman <robin@icewind.nl>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace Icewind\SMB;
+
+class StringBuffer {
+	private $buffer = "";
+	private $pos = 0;
+
+	public function clear() {
+		$this->buffer = "";
+		$this->pos = 0;
+	}
+
+	public function push(string $data) {
+		$this->buffer = $this->flush() . $data;
+		return strlen($data);
+	}
+
+	public function remaining(): int {
+		return strlen($this->buffer) - $this->pos;
+	}
+
+	public function read(int $count): string {
+		$chunk = substr($this->buffer, $this->pos, $this->pos + $count);
+		$this->pos += strlen($chunk);
+		return $chunk;
+	}
+
+	public function flush(): string {
+		if ($this->pos === 0) {
+			$remaining = $this->buffer;
+		} else {
+			$remaining = substr($this->buffer, $this->pos);
+		}
+
+		$this->clear();
+
+		return $remaining;
+	}
+}