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include/ littlefsv2 | 1 year ago | ||
littlefs | 3 years ago | ||
source | 3 years ago | ||
tests/ TESTS | 3 years ago | ||
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CMakeLists.txt | 2 years ago | ||
README.md | 3 years ago | ||
mbed_lib.json | 3 years ago |
This is the Mbed OS API for littlefs, a little fail-safe filesystem designed for embedded systems.
| | | .---._____ .-----. | | --|o |---| littlefs | --| |---| | '-----' '----------' | | |
Bounded RAM/ROM - The littlefs is designed to work with a limited amount of memory. Recursion is avoided, and dynamic memory is limited to configurable buffers that can be provided statically.
Power-loss resilient - The littlefs is designed for systems that may have random power failures. The littlefs has strong copy-on-write guarantees, and storage on disk is always kept in a valid state.
Wear leveling - Because the most common form of embedded storage is erodible flash memories, littlefs provides a form of dynamic wear leveling for systems that cannot fit a full flash translation layer.
If you are already using a filesystem in Mbed, adopting the littlefs should just require a name change to use the LittleFileSystem2 class.
Here is a simple example that updates a file named "boot_count" every time the application runs:
#include "LittleFileSystem2.h" #include "SPIFBlockDevice.h" // Physical block device, can be any device that supports the BlockDevice API SPIFBlockDevice bd(PTE2, PTE4, PTE1, PTE5); // Storage for the littlefs LittleFileSystem2 fs("fs"); // Entry point int main() { // Mount the filesystem int err = fs.mount(&bd); if (err) { // Reformat if we can't mount the filesystem, // this should only happen on the first boot LittleFileSystem2::format(&bd); fs.mount(&bd); } // Read the boot count uint32_t boot_count = 0; FILE *f = fopen("/fs/boot_count", "r+"); if (!f) { // Create the file if it doesn't exist f = fopen("/fs/boot_count", "w+"); } fread(&boot_count, sizeof(boot_count), 1, f); // Update the boot count boot_count += 1; rewind(f); fwrite(&boot_count, sizeof(boot_count), 1, f); // Remember that storage may not be updated until the file // is closed successfully fclose(f); // Release any resources we were using fs.unmount(); // Print the boot count printf("boot_count: %ld\n", boot_count); }
DESIGN.md - DESIGN.md contains a fully detailed dive into how littlefs actually works. We encourage you to read it because the solutions and tradeoffs at work here are quite interesting.
SPEC.md - SPEC.md contains the on-disk specification of littlefs with all the nitty-gritty details. This can be useful for developing tooling.
littlefs - Where the core of littlefs currently lives.
littlefs-fuse - A FUSE wrapper for littlefs. The project allows you to mount littlefs directly in a Linux machine. This can be useful for debugging littlefs if you have an SD card handy.
littlefs-js - A JavaScript wrapper for littlefs. I'm not sure why you would want this, but it is handy for demos. You can see it in action here.