how to download NIOS II programme using a external processor

Hi, everyone!

I am trying to implement loading Cyclone III FPGA firmware (FPGA hardware configuration and NIOS II software programme) by using a external processor (arm processor).

After some search on altera knowledge database, I found a JTAG + jrunner solution on configuring FPGA using external processor. However I don't find any materials about how to download and start runing NIOS II programme to FPGA by using a external processor.

I know the nios2-download command could do the thing I wanted to, but I doesn't has its source code.

Does anyone have done such thing before? Any related information will be appreciated. Thanks.