Add seekable wrapper to make non seekable streams seekable

src/SeekableWrapper.php

@@ -0,0 +1,92 @@
+<?php
+/**
+ * Copyright (c) 2014 Robin Appelman <icewind@owncloud.com>
+ * This file is licensed under the Licensed under the MIT license:
+ * http://opensource.org/licenses/MIT
+ */
+
+namespace Icewind\Streams;
+
+/**
+ * Wrapper that provides callbacks for write, read and close
+ *
+ * The following options should be passed in the context when opening the stream
+ * [
+ *     'callback' => [
+ *        'source'  => resource
+ *     ]
+ * ]
+ *
+ * All callbacks are called after the operation is executed on the source stream
+ */
+class SeekableWrapper extends Wrapper {
+	/**
+	 * @var resource
+	 */
+	protected $cache;
+
+	/**
+	 * Wraps a stream to make it seekable
+	 *
+	 * @param resource $source
+	 * @return resource
+	 *
+	 * @throws \BadMethodCallException
+	 */
+	public static function wrap($source) {
+		$context = stream_context_create(array(
+			'callback' => array(
+				'source' => $source
+			)
+		));
+		return Wrapper::wrapSource($source, $context, 'callback', '\Icewind\Streams\SeekableWrapper');
+	}
+
+	public function dir_opendir($path, $options) {
+		return false;
+	}
+
+	public function stream_open($path, $mode, $options, &$opened_path) {
+		$this->loadContext('callback');
+		$this->cache = fopen('php://temp', 'w+');
+		return true;
+	}
+
+	protected function readTill($position) {
+		$current = ftell($this->source);
+		if ($position > $current) {
+			$data = parent::stream_read($position - $current);
+			$cachePosition = ftell($this->cache);
+			fseek($this->cache, $current);
+			fwrite($this->cache, $data);
+			fseek($this->cache, $cachePosition);
+		}
+	}
+
+	public function stream_read($count) {
+		$current = ftell($this->cache);
+		$this->readTill($current + $count);
+		return fread($this->cache, $count);
+	}
+
+	public function stream_seek($offset, $whence = SEEK_SET) {
+		if ($whence === SEEK_SET) {
+			$target = $offset;
+		} else if ($whence === SEEK_CUR) {
+			$current = ftell($this->cache);
+			$target = $current + $offset;
+		} else {
+			return false;
+		}
+		$this->readTill($target);
+		return fseek($this->cache, $target) === 0;
+	}
+
+	public function stream_tell() {
+		return ftell($this->cache);
+	}
+
+	public function stream_eof() {
+		return parent::stream_eof() and (ftell($this->source) === ftell($this->cache));
+	}
+}

tests/SeekableWrapper.php

@@ -0,0 +1,52 @@
+<?php
+/**
+ * Copyright (c) 2014 Robin Appelman <icewind@owncloud.com>
+ * This file is licensed under the Licensed under the MIT license:
+ * http://opensource.org/licenses/MIT
+ */
+
+namespace Icewind\Streams\Tests;
+
+class SeekableWrapper extends \PHPUnit_Framework_TestCase {
+	/**
+	 * @param resource $source
+	 * @return resource
+	 */
+	protected function wrapSource($source) {
+		return \Icewind\Streams\SeekableWrapper::wrap($source);
+	}
+
+	protected function getSource() {
+		$source = fopen('php://temp', 'w+');
+		fwrite($source, 'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.');
+		fseek($source, 0);
+		return $source;
+	}
+
+	public function testCantWrapDir() {
+		$source = opendir(__DIR__);
+		$this->assertFalse(@$this->wrapSource($source));
+	}
+
+	public function testSourceNotSeeked() {
+		$source = $this->getSource();
+		$wrapped = $this->wrapSource($source);
+		fseek($wrapped, 6);
+		$this->assertEquals(6, ftell($source));
+		$this->assertEquals(6, ftell($wrapped));
+		$this->assertEquals('ipsum', fread($wrapped, '5'));
+		fseek($wrapped, 6);
+		$this->assertEquals(6, ftell($wrapped));
+		$this->assertGreaterThan(6, ftell($source));
+	}
+
+	public function testSeekRelative() {
+		$source = $this->getSource();
+		$wrapped = $this->wrapSource($source);
+		fseek($wrapped, 6);
+		fseek($wrapped, 6, SEEK_CUR);
+		$this->assertEquals(12, ftell($source));
+		$this->assertEquals(12, ftell($wrapped));
+		$this->assertEquals('dolor', fread($wrapped, '5'));
+	}
+}