forked from Imagelibrary/littlefs
bd70270e11
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.
121 lines
3.0 KiB
Python
Executable File
121 lines
3.0 KiB
Python
Executable File
#!/usr/bin/env python3
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# prevent local imports
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if __name__ == "__main__":
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__import__('sys').path.pop(0)
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import io
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import math as mt
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import os
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import struct
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import sys
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# open with '-' for stdin/stdout
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def openio(path, mode='r', buffering=-1):
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import os
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if path == '-':
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if 'r' in mode:
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return os.fdopen(os.dup(sys.stdin.fileno()), mode, buffering)
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else:
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return os.fdopen(os.dup(sys.stdout.fileno()), mode, buffering)
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else:
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return open(path, mode, buffering)
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def fromleb128(data, j=0):
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word = 0
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d = 0
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while j+d < len(data):
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b = data[j+d]
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word |= (b & 0x7f) << 7*d
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word &= 0xffffffff
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if not b & 0x80:
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return word, d+1
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d += 1
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return word, d
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def dbg_leb128s(data, *,
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word_bits=32):
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# figure out leb128 size in bytes
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if word_bits != 0:
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n = mt.ceil(word_bits / 7)
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# parse leb128s
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lines = []
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j = 0
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while j < len(data):
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# bounded leb128s?
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if word_bits != 0:
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word, d = fromleb128(data[j:j+n])
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# unbounded?
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else:
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word, d = fromleb128(data, j)
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lines.append((
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' '.join('%02x' % b for b in data[j:j+d]),
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word))
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j += d
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# figure out widths
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w = [0]
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for l in lines:
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w[0] = max(w[0], len(l[0]))
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# then print results
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for l in lines:
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print('%-*s %s' % (
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w[0], l[0],
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l[1]))
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def main(leb128s, *,
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hex=False,
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input=None,
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word_bits=32):
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hex_ = hex; del hex
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# interpret as a sequence of hex bytes
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if hex_:
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bytes_ = [b for leb128 in leb128s for b in leb128.split()]
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dbg_leb128s(bytes(int(b, 16) for b in bytes_),
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word_bits=word_bits)
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# parse leb128s in a file
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elif input:
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with openio(input, 'rb') as f:
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dbg_leb128s(f.read(),
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word_bits=word_bits)
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# we don't currently have a default interpretation
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else:
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print("error: no -x/--hex or -i/--input?",
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file=sys.stderr)
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sys.exit(1)
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if __name__ == "__main__":
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import argparse
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import sys
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parser = argparse.ArgumentParser(
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description="Decode leb128s.",
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allow_abbrev=False)
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parser.add_argument(
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'leb128s',
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nargs='*',
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help="Leb128s to decode.")
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parser.add_argument(
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'-x', '--hex',
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action='store_true',
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help="Interpret as a sequence of hex bytes.")
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parser.add_argument(
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'-i', '--input',
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help="Read leb128s from this file. Can use - for stdin.")
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parser.add_argument(
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'-w', '--word-bits',
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nargs='?',
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type=lambda x: int(x, 0),
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const=0,
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help="Word size in bits. 0 is unbounded. Defaults to 32.")
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sys.exit(main(**{k: v
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for k, v in vars(parser.parse_intermixed_args()).items()
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if v is not None}))
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