src/Stream.php
public function seek($offset, $whence = SEEK_SET)
    {
        if (!is_resource($this->fp) || fseek($this->fp, $offset, $whence) == -1) {
            throw new \RuntimeException('Unable to seek stream');
        }
    }
public function seek($offset, $whence = SEEK_SET)
    {
        if (!is_resource($this->fp) || fseek($this->fp, $offset, $whence) == -1) {
            throw new \RuntimeException('Unable to seek stream');
        }
    }
Seek to a position in the stream.

@link http://www.php.net/manual/en/function.fseek.php

@param int $offset Stream offset
@param int $whence Specifies how the cursor position will be calculated
based on the seek offset. Valid values are identical to the built-in
PHP $whence values for `fseek()`.  SEEK_SET: Set position equal to
offset bytes SEEK_CUR: Set position to current location plus offset
SEEK_END: Set position to end-of-stream plus offset.

@throws \RuntimeException on failure.