+ // Call pointer instance
+ return $this->getPointerInstance()->rewind();
+ }
+
+ /**
+ * Checks wether the current entry is valid (not at the end of the file).
+ * This method will return TRUE if an emptied (nulled) entry has been found.
+ *
+ * @return $isValid Whether the next entry is valid
+ */
+ public function valid () {
+ // First calculate minimum block length
+ $length = $this->getBlockInstance()->caluclateMinimumBlockLength();
+
+ // Short be more than zero!
+ assert($length > 0);
+
+ // Get current seek position
+ $seekPosition = $this->key();
+
+ // Then try to read it
+ $data = $this->read($length);
+
+ // If some bytes could be read, all is fine
+ $isValid = ((is_string($data)) && (strlen($data) > 0));
+
+ // Get header size
+ $headerSize = $this->getBlockInstance()->getHeaderSize();
+
+ // Is the seek position at or beyond the header?
+ if ($seekPosition >= $headerSize) {
+ // Seek back to old position
+ $this->seek($seekPosition);
+ } else {
+ // Seek directly behind the header
+ $this->seek($headerSize);
+ }
+
+ // Return result
+ return $isValid;