littlefs

## littlefs

A little fail-safe filesystem designed for microcontrollers.

```
   | | |     .---._____
  .-----.   |          |
--|o    |---| littlefs |
--|     |---|          |
  '-----'   '----------'
   | | |
```

**Power-loss resilience** - littlefs is designed to handle random power
failures. All file operations have strong copy-on-write guarantees and if
power is lost the filesystem will fall back to the last known good state.

**Dynamic wear leveling** - littlefs is designed with flash in mind, and
provides wear leveling over dynamic blocks. Additionally, littlefs can
detect bad blocks and work around them.

**Bounded RAM/ROM** - littlefs is designed to work with a small amount of
memory. RAM usage is strictly bounded, which means RAM consumption does not
change as the filesystem grows. The filesystem contains no unbounded
recursion and dynamic memory is limited to configurable buffers that can be
provided statically.

## Example

Here's a simple example that updates a file named `boot_count` every time
main runs. The program can be interrupted at any time without losing track
of how many times it has been booted and without corrupting the filesystem:

``` c
#include "lfs.h"

// variables used by the filesystem
lfs_t lfs;
lfs_file_t file;

// configuration of the filesystem is provided by this struct
const struct lfs_config cfg = {
    // block device operations
    .read  = user_provided_block_device_read,
    .prog  = user_provided_block_device_prog,
    .erase = user_provided_block_device_erase,
    .sync  = user_provided_block_device_sync,

    // block device configuration
    .read_size = 16,
    .prog_size = 16,
    .block_size = 4096,
    .block_count = 128,
    .cache_size = 16,
    .lookahead_size = 16,
    .block_cycles = 500,
};

// entry point
int main(void) {
    // mount the filesystem
    int err = lfs_mount(&lfs, &cfg);

    // reformat if we can't mount the filesystem
    // this should only happen on the first boot
    if (err) {
        lfs_format(&lfs, &cfg);
        lfs_mount(&lfs, &cfg);
    }

    // read current count
    uint32_t boot_count = 0;
    lfs_file_open(&lfs, &file, "boot_count", LFS_O_RDWR | LFS_O_CREAT);
    lfs_file_read(&lfs, &file, &boot_count, sizeof(boot_count));

    // update boot count
    boot_count += 1;
    lfs_file_rewind(&lfs, &file);
    lfs_file_write(&lfs, &file, &boot_count, sizeof(boot_count));

    // remember the storage is not updated until the file is closed successfully
    lfs_file_close(&lfs, &file);

    // release any resources we were using
    lfs_unmount(&lfs);

    // print the boot count
    printf("boot_count: %d\n", boot_count);
}
```

## Usage

Detailed documentation (or at least as much detail as is currently available)
can be found in the comments in [lfs.h](lfs.h).

littlefs takes in a configuration structure that defines how the filesystem
operates. The configuration struct provides the filesystem with the block
device operations and dimensions, tweakable paramete