Christopher Haster
2802880eaa
- primitive lfs_rbyd_fetch
- primitive lfs_rbyd_commit
- tag reading/progging and encoding machinery
The tag encoding scheme here uses pairs of leb128s, encoding either
a normal tag:
iiii iiiiiii iiiiiTT TTTTTTt ttttt0v
^--------^------^-^- 16-bit id
'------|-|- 8-bit type2
'-|- 6-bit type1
'- valid bit
llll lllllll lllllll lllllll lllllll
^- n-bit length
Or an alt pointer:
wwww wwwwwww wwwwwww wwwwwww wwwcd1v
^^^-^- 28-bit weight
'|-|- color bit
'-|- direction bit
'- valid bit
jjjj jjjjjjj jjjjjjj jjjjjjj jjjjjjj
^- n-bit jump
Note that two bits overlap the alt pointer dir/color encoding, this
is actually not a problem at all since some tags (crcs/fcrcs) don't
participate in the rbyd tree and can use these bits.
There's a number of benefits to using leb128s, which should probably
be written about, most notably is the abstraction of the device's
word-size. The "n-bits" above can be whatever word size works on the
device, trading off code-size for storage capabilities without breaking
compatibility with other devices. This will eventually be negotiated via
the superblock.
29 lines
539 B
TOML
29 lines
539 B
TOML
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# Test this inner rbyd data-structure
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[cases.rbyd_create]
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in = 'lfs.c'
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code = '''
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lfs_t lfs;
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lfs_init(&lfs, cfg) => 0;
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lfs_rbyd_t rbyd = {
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.block = 0,
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.trunk = 0,
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.noff = 0,
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.rev = 1,
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.crc = 0,
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.count = 0,
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.erased = true,
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};
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//lfs_rbyd_commit(&lfs, &rbyd, NULL) => 0;
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uint32_t data = 0xa5dfa5df;
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lfs_rbyd_commit(&lfs, &rbyd,
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LFS_MKRATTR(UATTR, 1, 0, &data, 4,
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LFS_MKRATTR(UATTR, 2, 0, &data, 4,
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NULL))) => 0;
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'''
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