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).
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). Library has some cool and unique features in microcontrollers world:
- directory indexing - fast file find and list operations
- extents - fast big file truncate
- journaling transactions & recovery - power loss resistance
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.
Lwext4 is an excellent choice for 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:
Feel free to contact me:
kostka.grzegorz@gmail.com
kostka.grzegorz@gmail.com
@ -20,16 +20,17 @@ Credits
The most of the source code of lwext4 was taken from HelenOS:
The most of the source code of lwext4 was taken from HelenOS:
* http://helenos.org/
* http://helenos.org/
Some features are based on FreeBSD and Linux implementations.
Some features are based on FreeBSD and Linux implementations.
KaHo Ng (https://github.com/ngkaho1234):
KaHo Ng (https://github.com/ngkaho1234):
* advanced extents implementation
* advanced extents implementation
* xattr support
* xattr support
* metadata checksum support
* metadata checksum support
* journal recovery
* journal recovery& transactions
* many bugfixes & improvements
* many bugfixes & improvements
fuse-lwext4 project:
Lwext4 could be used also as fuse internals. Here is a nice project which uses lwext4 as a filesystem base:
* https://github.com/ngkaho1234/fuse-lwext4
* https://github.com/ngkaho1234/fuse-lwext4
Features
Features
@ -43,13 +44,22 @@ Features
* only C standard library dependency
* only C standard library dependency
* various CPU architectures supported (x86/64, cortex-mX, msp430 ...)
* various CPU architectures supported (x86/64, cortex-mX, msp430 ...)
* small memory footprint
* small memory footprint
* flexible configurations
Memory footprint
Memory footprint (for cortex-m4)
------------
------------
* .text: 20KB - 40KB
* .data: 8KB (minimum 8 x 1KB block cache)
Advanced ext4 filesystem features, like extents or journaling require some memory.
* .stack: 2KB
However most of the memory expensive features could be disabled at compile time.
Here is a brief summary for cortex-m4 processor:
* .text: 20KB - only ext2 fs support , 50KB - full ext4 fs feature set
* .data: 8KB - minimum 8 x 1KB block cache, 12KB - when journaling and extents are enabled
* .stack: 2KB - is enough (not measured precisely)
Blocks are allocated dynamically. Previous versions of library could work without
malloc but from 1.0.0 dynamic memory allocation is required. However, block cache
should not allocate more than CONFIG_BLOCK_DEV CACHE_SIZE.
gkostka
9 years ago