system/HTTP/DownloadResponse.php
private function sendBodyByFilePath()
	{
		$spl_file_object = $this->file->openFile('rb');

		// Flush 1MB chunks of data
		while (! $spl_file_object->eof() && ($data = $spl_file_object->fread(1048576)) !== false)
		{
			echo $data;
		}

		return $this;
	}
private function sendBodyByFilePath()
	{
		$spl_file_object = $this->file->openFile('rb');

		// Flush 1MB chunks of data
		while (! $spl_file_object->eof() && ($data = $spl_file_object->fread(1048576)) !== false)
		{
			echo $data;
		}

		return $this;
	}
output download text by file.

@return DownloadResponse