Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

fopen - Memory Mapped Files

Is there a way to have fopen read a file whose contents reside in flash/ram (i.e. not from stdin/stdout rs232/jtag)?

Using the nios-ide, I flashed a file into Flash where I have plenty of space, but at runtime I need to perform FILE type operations on it. If I just pass the (flash) memory address as the handle and cast it as FILE, it doesn't work, the typedef FILE has a host of elements, but the memory address contains just the data.

How is this generally done? Is there a way to mount a pointer that points to data such that fopen/fgetc/etc work? Since I'm low on ram, I'd hate to have to copy the same data just to serialize it! type=memory, memmapfile / MMFIO

1 Reply

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    If your file resides in CFI flash then would it work to just cast it as a char array? You'd have nice access for reads, but you'd have to manage the sector-at-a-time issues of flash when writing (erasing/programming).

    If not, then if it's read-only access you're after, rozip_fs might be enough. Otherwise, you're looking at more work to emulate filesystem-like behavior and/or porting an existing filesystem to Nios II HAL.

    Of course, none of this applies if you're using uClinux/Linux running on Nios II.

    Cheers,

    - slacker