protected function validateFileContents() {
		if (!$this->fileName) {
			throw new \LogicException("Missing file's path. Looks like severe internal error.");
		}
		$this->validateFilePath($this->fileName);
		if (!$this->sha1hash) {
			throw new \LogicException("Missing file's SHA1 hash. Looks like severe internal error.");
		}
		if ($this->sha1hash !== sha1_file($this->fileName)) {
			throw new IOException("The file on disk has changed and this " . get_class($this) . " class instance is no longer valid for use. Please create fresh instance.");
		}
		return true;
	}