mirror of
https://github.com/eledio-devices/thirdparty-littlefs.git
synced 2025-10-31 08:42:40 +01:00
d7e4abad0b
This is a minor tweak that resulted from looking at some other use cases for the littlefs data-structure on disk. Consider an implementation that does not need to buffer inline-files in RAM. In this case we should have as large a tag size field as possible. Unfortunately, we don't have much space to work with in the 32-bit tag struct, so we have to make some compromises. These limitations could be removed with a 64-bit tag struct, at the cost of code size. 32-bit tag structure: [--- 32 ---] [1|- 9 -|- 9 -|-- 13 --] ^ ^ ^ ^- entry length | | \-------- file id | \-------------- tag type \------------------ valid bit
45 lines
1.1 KiB
Python
Executable File
45 lines
1.1 KiB
Python
Executable File
#!/usr/bin/env python
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import struct
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import sys
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import os
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import argparse
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def corrupt(block):
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with open(block, 'r+b') as file:
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# skip rev
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file.read(4)
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# go to last commit
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tag = 0xffffffff
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while True:
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try:
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ntag, = struct.unpack('<I', file.read(4))
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except struct.error:
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break
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tag ^= ntag
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size = (tag & 0x1fff) if (tag & 0x1fff) != 0x1fff else 0
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file.seek(size, os.SEEK_CUR)
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# lob off last 3 bytes
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file.seek(-(size + 3), os.SEEK_CUR)
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file.truncate()
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def main(args):
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if args.n or not args.blocks:
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with open('blocks/.history', 'rb') as file:
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for i in range(int(args.n or 1)):
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last, = struct.unpack('<I', file.read(4))
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args.blocks.append('blocks/%x' % last)
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for block in args.blocks:
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print 'corrupting %s' % block
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corrupt(block)
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if __name__ == "__main__":
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parser = argparse.ArgumentParser()
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parser.add_argument('-n')
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parser.add_argument('blocks', nargs='*')
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main(parser.parse_args())
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