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[](https://travis-ci.org/gkostka/lwext4)
About
=====
The main goal of the lwext4 project is to provide ext2/3/4 filesystem for microcontrollers. It may be an interesting alternative for traditional MCU filesystem libraries (mostly based on FAT32).
Lwext4 may be used with SD/MMC card, USB flash drive or other block based memory device. However it is not good for flash memory–based storage devices.
Code is also available on github:
https://github.com/gkostka/lwext4
Feel free to contact me:
kostka.grzegorz@gmail.com
Credits
=====
The most of the source code of lwext4 was taken from HelenOS:
* http://helenos.org/
Some features are based on FreeBSD and Linux implementations.
KaHo Ng (https://github.com/ngkaho1234):
* advanced extents implementation
* xattr support
* metadata checksum support
* journal recovery
* many bugfixes & improvements
fuse-lwext4 project:
* https://github.com/ngkaho1234/fuse-lwext4
Features
=====
* filetypes: regular, directories, softlinks
* support for hardlinks
* multiple blocksize supported: 1KB, 2KB, 4KB ... 64KB
* little/big endian architectures supported
* multiple configurations (ext2/ext3/ext4)
* only C standard library dependency
* various CPU architectures supported (x86/64, cortex-mX, msp430 ...)
* small memory footprint
Memory footprint (for cortex-m4)
------------
* .text: 20KB - 40KB
* .data: 8KB (minimum 8 x 1KB block cache)
* .stack: 2KB
Supported ext2/3/4 features
=====
Features incompatible:
------------
* compression: no
* filetype: yes
* recover: no
* journal_dev: no
* meta_bg: yes
* extents: yes
* 64bit: yes
* mmp: no
* flex_bg: yes
* ea_inode: no
* dirdata: no
* bg_meta_csum: no
* largedir: no
* inline_data: no
Features compatible:
------------
* dir_prealloc: no
* imagic_inodes: no
* has_journal: yes (in progress)
* ext_attr: yes
* resize_inode: no
* dir_index: yes
Features read-only:
------------
* sparse_super: yes
* large_file: yes
* btree_dir: yes
* huge_file: yes
* gdt_csum: yes
* dir_nlink: yes
* extra_isize: yes
* quota: no
* bigalloc: no
* metadata_csum: yes
Project tree
=====
* blockdev - block devices set, supported blockdev
* fs_test - test suite, mkfs and demo application
* lwext4 - internals of the lwext4 library
* toolchain - specific toolchain cmake files
* CMakeLists.txt - CMake config file
* ext_images.7z - compressed ext2/3/4 100MB images
* fs_test.mk - automatic tests definitions
* Makefile - helper makefile to generate cmake and run test suite
* readme.mediawiki - readme file
Compile
=====
Windows
------------
* CMake: http://www.cmake.org/cmake/resources/software.html
* MinGw: http://www.mingw.org/
* GnuWin: http://gnuwin32.sourceforge.net/
Linux
------------
* CMake, make, gcc
Generate makefiles
------------
```bash
make
```
Compile
------------
```bash
cd build_generic
make
```
Generic demo application
=====
Simple lwext4 library presentation:
* load ext2/3/4 images
* load linux block device with ext2/3/4 part
* load windows volume with ext2/3/4 filesystem
* directory speed test
* file write/read speed test
How to use for images/blockdevices:
```bash
cd build_generic
lwext4_generic -i ext_images/ext2
lwext4_generic -i ext_images/ext3
lwext4_generic -i ext_images/ext4
```
Build and run automatic tests
=====
Build automatic test tools:
```bash
make
cd build_generic
make
```
Uncompress ext/2/3/4 images:
```bash
make unpack_images
```
Run server for one of the image file:
```bash
make server_ext2
make server_ext3
make server_ext4
```
Execute tests:
```bash
make test
```
Cross compile standalone library
=====
Toolchains needed:
------------
* arm-none-eabi-gcc for cortex-mX
* avr-gcc for avr
* bfin-elf-gcc for bfin
* msp430-gcc for msp430
Build bf518 library:
------------
```bash
make bf518
cd build_bf518
make lwext4
```
Build avrxmega7 library:
------------
```bash
make avrxmega7
cd build_avrxmega7
make lwext4
```
Build cortex-m0 library:
------------
```bash
make cortex-m0
cd build_cortex-m0
make lwext4
```
Build cortex-m3 library:
------------
```bash
make cortex-m3
cd build_cortex-m3
make lwext4
```
Build cortex-m4 library:
------------
```bash
make cortex-m4
cd build_cortex-m4
make lwext4
```
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