I don't know how I completely missed that this doesn't actually work!
Using del _does_ work in Python's repl, but it makes sense the repl may
differ from actual function execution in this case.
The problem is Python still thinks the relevant builtin is a local
variables after deletion, raising an UnboundLocalError instead of
performing a global lookup. In theory this would work if the variable
could be made global, but since global/nonlocal statements are lifted,
Python complains with "SyntaxError: name 'list' is parameter and
global".
And that's A-Ok! Intentionally shadowing language builtins already puts
this code deep into ugly hacks territory.
This is limited to dbgle32.py, dbgleb128.py, and dbgtag.py for now.
This more closely matches how littlefs behaves, in that we read a
bounded number of bytes before leb128 decoding. This minimizes bugs
related to leb128 overflow and avoids reading inherently undecodable
data.
The previous unbounded behavior is still available with -w0.
Note this gives dbgle32.py much more flexibility in that it can now
decode other integer widths. Uh, ignore the name for now. At least it's
self documenting that the default is 32-bits...
---
Also fixed a bug in fromleb128 where size was reported incorrectly on
offset + truncated leb128.
Do you see the O(n^2) behavior in this loop?
j = 0
while j < len(data):
word, d = fromleb(data[j:])
j += d
The slice, data[j:], creates a O(n) copy every iteration of the loop.
A bit tricky. Or at least I found it tricky to notice. Maybe because
array indexing being cheap is baked into my brain...
Long story short, this repeated slicing resulted in O(n^2) behavior in
Rbyd.fetch and probably some other functions. Even though we don't care
_too_ much about performance in these scripts, having Rbyd.fetch run in
O(n^2) isn't great.
Tweaking all from* functions to take an optional index solves this, at
least on paper.
---
In practice I didn't actually find any measurable performance gain. I
guess array slicing in Python is optimized enough that the constant
factor takes over?
(Maybe it's being helped by us limiting Rbyd.fetch to block_size in most
scripts? I haven't tested NAND block sizes yet...)
Still, it's good to at least know this isn't a bottleneck.
These mimic dbgtag.py, but provide debugging for the lower-level integer
primitives in littlefs:
$ ./scripts/dbgleb128.py -x 2a 80 80 a8 01
2a 42
80 80 a8 01 2752512
$ ./scripts/dbgle32.py -x 2a 00 00 00 00 00 2a 00
2a 00 00 00 42
00 00 2a 00 2752512
dbgleb128.py is probably going to be more useful, but I figured we might
as well include both for completeness. Though dbgle32.py is begging to
be generalized.
