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myfs

Simple and buggy user-space file system implementation

It's based on a simple file, in Unix-like file system you can mount /dev/* devices and it will potentially work with real device. It's very simple and has bugs.

The following features are supported:

  • mounting file as a device
  • file creation
  • hard links
  • sym links
  • directories
  • directory navigation (and relative paths (with bugs))
  • file and inode statistics

It uses the following layout:

  • device consits of blocks (512-bytes by default, easily changeble)
  • at the beginning device uses a few blocks as a bitmask for maintating other blocks (note: potential improvement here - use in-RAM caching)
  • each file has a descriptor (aka inode)
  • There are 3 types of files: directories, regular files, symlinks
  • directories contain an array of (hard) Links to other files
  • regular files contain whatever you want
  • symlinks contain only a name of the file they're pointing to.

Known bugs:

  • bad handling of .. and . in directory paths
  • not full support for big files.
  • some functions are just hanging if some incorrect data is passed. They should return some error code etc.

There are the following command aliases:

  • create <-> touch
  • read <-> cat
  • l <-> ls .
  • unlink <-> rm
  • filestat <-> stat

Example usage

>>> mount dev/hda
File system mounted!
>>> touch a
File created
>>> l
a
>>> write a
Write some text to the file. When you want to finish writing write "end" in UPPERCASE symbols
END
Data successfully written
>>> cat a
Write some text to the file. When you want to finish writing write "end" in UPPERCASE symbols
>>> stat a
Type: regular
Inode: 2
Blocks uses(1): #4 
Size: 93 bytes
Number of (hard) links: 1
>>> mkdir dir
Dir created
>>> cd dir
cwd changed
>>> write f
/dir/f
END
File with name 'f' doesn't exist
>>> create f
File created
>>> write f
/dir/f
END
Data successfully written
>>> ln f f_alias
Link created
>>> stat f
Type: regular
Inode: 6
Blocks uses(1): #8 
Size: 6 bytes
Number of (hard) links: 2
>>> stat f_alias
Type: regular
Inode: 6
Blocks uses(1): #8 
Size: 6 bytes
Number of (hard) links: 2
>>> stat .
Type: directory
Contains files: 2
Inode: 5
Blocks uses(1): #7 
Size: 40 bytes
Number of (hard) links: 1
>>> cd ..
cwd changed
>>> ls
.
a
dir
>>> ls dir
f
f_alias
>>> ln dir/f qw
Link created
>>> stat qw
Type: regular
Inode: 6
Blocks uses(1): #8 
Size: 6 bytes
Number of (hard) links: 3
>>> write qw
One of three aliases
END
Data successfully written
>>> cat dir/f
One of three aliases
>>> rm dir/f
Hard link was removed
>>> cat dir/f_alias
One of three aliases
>>> rm dir/f_alias
Hard link was removed
>>> stat f
File with name 'f' doesn't exist
>>> stat qw
Type: regular
Inode: 6
Blocks uses(1): #8 
Size: 20 bytes
Number of (hard) links: 1
>>> l
a
dir
qw
>>> symlink qs slink
Target file doesn't exist
>>> symlink qw slink
Symlink created
>>> cat slink
One of three aliases
>>> write slink
The only file
END
Data successfully written
>>> cat slink
The only file
>>> cat qw
The only file
>>> rm slink
Hard link was removed
>>> ls
.
a
dir
qw
>>> rmdir dir
Dir successfully removed
>>> rm qw
Hard link was removed
>>> rm a
Hard link was removed
>>> umount
File system unmounted!