implement fseek for sftp read stream

Signed-off-by: Robin Appelman <[email protected]>

apps/files_external/lib/Lib/Storage/SFTP.php

@@ -381,11 +381,12 @@ public function fopen($path, $mode) {
 			switch ($mode) {
 				case 'r':
 				case 'rb':
-					if (!$this->file_exists($path)) {
+					$stat = $this->stat($path);
+					if (!$stat) {
 						return false;
 					}
 					SFTPReadStream::register();
-					$context = stream_context_create(['sftp' => ['session' => $connection]]);
+					$context = stream_context_create(['sftp' => ['session' => $connection, 'size' => $stat['size']]]);
 					$handle = fopen('sftpread://' . trim($absPath, '/'), 'r', false, $context);
 					return RetryWrapper::wrap($handle);
 				case 'w':

apps/files_external/lib/Lib/Storage/SFTPReadStream.php

@@ -50,6 +50,7 @@ class SFTPReadStream implements File {
 
 	private $buffer = '';
 	private bool $pendingRead = false;
+	private int $size = 0;
 
 	public static function register($protocol = 'sftpread') {
 		if (in_array($protocol, stream_get_wrappers(), true)) {
@@ -76,6 +77,9 @@ protected function loadContext($name) {
 		} else {
 			throw new \BadMethodCallException('Invalid context, session not set');
 		}
+		if (isset($context['size'])) {
+			$this->size = $context['size'];
+		}
 		return $context;
 	}
 
@@ -119,7 +123,25 @@ public function stream_open($path, $mode, $options, &$opened_path) {
 	}
 
 	public function stream_seek($offset, $whence = SEEK_SET) {
-		return false;
+		switch ($whence) {
+			case SEEK_SET:
+				$this->seekTo($offset);
+				break;
+			case SEEK_CUR:
+				$this->seekTo($this->readPosition + $offset);
+				break;
+			case SEEK_END:
+				$this->seekTo($this->size + $offset);
+				break;
+		}
+		return true;
+	}
+
+	private function seekTo(int $offset) {
+		$this->internalPosition = $offset;
+		$this->readPosition = $offset;
+		$this->buffer = '';
+		$this->request_chunk(256 * 1024);
 	}
 
 	public function stream_tell() {
@@ -143,6 +165,10 @@ public function stream_read($count) {
 	}
 
 	private function request_chunk($size) {
+		if ($this->pendingRead) {
+			$this->sftp->_get_sftp_packet();
+		}
+
 		$packet = pack('Na*N3', strlen($this->handle), $this->handle, $this->internalPosition / 4294967296, $this->internalPosition, $size);
 		$this->pendingRead = true;
 		return $this->sftp->_send_sftp_packet(NET_SFTP_READ, $packet);