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‎.travis.yml

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script:
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- CFLAGS="-DLFS_READ_SIZE=16 -DLFS_PROG_SIZE=16" make test
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- CFLAGS="-DLFS_READ_SIZE=1 -DLFS_PROG_SIZE=1" make test
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- CFLAGS="-DLFS_READ_SIZE=512 -DLFS_PROG_SIZE=512" make test

‎DESIGN.md

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‎LICENSE.md

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Apache License
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Version 2.0, January 2004
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http://www.apache.org/licenses/
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‎Makefile

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TARGET = lfs
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CC = gcc
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AR = ar
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SIZE = size
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SRC += $(wildcard *.c emubd/*.c)
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OBJ := $(SRC:.c=.o)
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DEP := $(SRC:.c=.d)
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ASM := $(SRC:.c=.s)
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TEST := $(patsubst tests/%.sh,%,$(wildcard tests/test_*))
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ifdef DEBUG
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CFLAGS += -O0 -g3
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else
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CFLAGS += -Os
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endif
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ifdef WORD
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CFLAGS += -m$(WORD)
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endif
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CFLAGS += -I.
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CFLAGS += -std=c99 -Wall -pedantic
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all: $(TARGET)
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asm: $(ASM)
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size: $(OBJ)
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$(SIZE) -t $^
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.SUFFIXES:
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test: test_format test_dirs test_files test_seek test_parallel \
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test_alloc test_paths test_orphan test_corrupt
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test_%: tests/test_%.sh
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./$<
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-include $(DEP)
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$(TARGET): $(OBJ)
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$(CC) $(CFLAGS) $^ $(LFLAGS) -o $@
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%.a: $(OBJ)
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$(AR) rcs $@ $^
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%.o: %.c
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$(CC) -c -MMD $(CFLAGS) $< -o $@
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%.s: %.c
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$(CC) -S $(CFLAGS) $< -o $@
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clean:
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rm -f $(TARGET)
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rm -f $(OBJ)
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rm -f $(DEP)
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rm -f $(ASM)

‎README.md

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## The little filesystem
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A little fail-safe filesystem designed for embedded systems.
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```
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| | | .---._____
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.-----. | |
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--|o |---| littlefs |
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--| |---| |
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'-----' '----------'
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| | |
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```
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**Fail-safe** - The littlefs is designed to work consistently with random
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power failures. During filesystem operations the storage on disk is always
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kept in a valid state. The filesystem also has strong copy-on-write garuntees.
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When updating a file, the original file will remain unmodified until the
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file is closed, or sync is called.
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**Wear awareness** - While the littlefs does not implement static wear
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leveling, the littlefs takes into account write errors reported by the
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underlying block device and uses a limited form of dynamic wear leveling
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to manage blocks that go bad during the lifetime of the filesystem.
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**Bounded ram/rom** - The littlefs is designed to work in a
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limited amount of memory, recursion is avoided, and dynamic memory is kept
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to a minimum. The littlefs allocates two fixed-size buffers for general
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operations, and one fixed-size buffer per file. If there is only ever one file
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in use, all memory can be provided statically and the littlefs can be used
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in a system without dynamic memory.
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## Example
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Here's a simple example that updates a file named `boot_count` every time
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main runs. The program can be interrupted at any time without losing track
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of how many times it has been booted and without corrupting the filesystem:
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``` c
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#include "lfs.h"
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// variables used by the filesystem
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lfs_t lfs;
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lfs_file_t file;
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// configuration of the filesystem is provided by this struct
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const struct lfs_config cfg = {
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// block device operations
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.read = user_provided_block_device_read,
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.prog = user_provided_block_device_prog,
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.erase = user_provided_block_device_erase,
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.sync = user_provided_block_device_sync,
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// block device configuration
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.read_size = 16,
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.prog_size = 16,
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.block_size = 4096,
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.block_count = 128,
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.lookahead = 128,
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};
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// entry point
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int main(void) {
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// mount the filesystem
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int err = lfs_mount(&lfs, &cfg);
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// reformat if we can't mount the filesystem
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// this should only happen on the first boot
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if (err) {
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lfs_format(&lfs, &cfg);
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lfs_mount(&lfs, &cfg);
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}
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// read current count
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uint32_t boot_count = 0;
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lfs_file_open(&lfs, &file, "boot_count", LFS_O_RDWR | LFS_O_CREAT);
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lfs_file_read(&lfs, &file, &boot_count, sizeof(boot_count));
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// update boot count
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boot_count += 1;
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printf("boot_count: %ld\n", boot_count);
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lfs_file_rewind(&lfs, &file);
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lfs_file_write(&lfs, &file, &boot_count, sizeof(boot_count));
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// remember the storage is not updated until the file is closed successfully
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lfs_file_close(&lfs, &file);
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// release any resources we were using
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lfs_unmount(&lfs);
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}
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```
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## Usage
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Detailed documentation (or at least as much detail as is currently available)
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can be cound in the comments in [lfs.h](lfs.h).
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As you may have noticed, the littlefs takes in a configuration structure that
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defines how the filesystem operates. The configuration struct provides the
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filesystem with the block device operations and dimensions, tweakable
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parameters that tradeoff memory usage for performance, and optional
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static buffers if the user wants to avoid dynamic memory.
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The state of the littlefs is stored in the `lfs_t` type which is left up
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to the user to allocate, allowing multiple filesystems to be in use
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simultaneously. With the `lfs_t` and configuration struct, a user can either
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format a block device or mount the filesystem.
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Once mounted, the littlefs provides a full set of posix-like file and
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directory functions, with the deviation that the allocation of filesystem
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structures must be provided by the user. An important addition is that
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no file updates will actually be written to disk until a sync or close
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is called.
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## Other notes
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All littlefs have the potential to return a negative error code. The errors
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can be either one of those found in the `enum lfs_error` in [lfs.h](lfs.h),
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or an error returned by the user's block device operations.
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It should also be noted that the littlefs does not do anything to insure
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that the data written to disk is machine portable. It should be fine as
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long as the machines involved share endianness and don't have really
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strange padding requirements. If the question does come up, the littlefs
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metadata should be stored on disk in little-endian format.
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## Design
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the littlefs was developed with the goal of learning more about filesystem
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design by tackling the relative unsolved problem of managing a robust
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filesystem resilient to power loss on devices with limited RAM and ROM.
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More detail on the solutions and tradeoffs incorporated into this filesystem
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can be found in [DESIGN.md](DESIGN.md).
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## Testing
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The littlefs comes with a test suite designed to run on a pc using the
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[emulated block device](emubd/lfs_emubd.h) found in the emubd directory.
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The tests assume a linux environment and can be started with make:
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``` bash
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make test
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```

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