mirror of
https://github.com/eledio-devices/thirdparty-littlefs.git
synced 2025-10-31 16:14:16 +01:00
b989b4a89f
Before, the tag format's type field was limited to 9-bits. This sounds
like a lot, but this field needed to encode up to 256 user-specified
types. This limited the flexibility of the encoded types. As time went
on, more bits in the type field were repurposed for various things,
leaving a rather fragile type field.
Here we make the jump to full 11-bit type fields. This comes at the cost
of a smaller length field, however the use of the length field was
always going to come with a RAM limitation. Rather than putting pressure
on RAM for inline files, the new type field lets us encode a chunk
number, splitting up inline files into multiple updatable units. This
actually pushes the theoretical inline max from 8KiB to 256KiB! (Note
that we only allow a single 1KiB chunk for now, chunky inline files
is just a theoretical future improvement).
Here is the new 32-bit tag format, note that there are multiple levels
of types which break down into more info:
[---- 32 ----]
[1|-- 11 --|-- 10 --|-- 10 --]
^. ^ . ^ ^- entry length
|. | . \------------ file id chunk info
|. \-----.------------------ type info (type3)
\.-----------.------------------ valid bit
[-3-|-- 8 --]
^ ^- chunk info
\------- type info (type1)
Additionally, I've split the CREATE tag into separate SPLICE and NAME
tags. This simplified the new compact logic a bit. For now, littlefs
still follows the rule that a NAME tag precedes any other tags related
to a file, but this can change in the future.
113 lines
3.0 KiB
Python
Executable File
113 lines
3.0 KiB
Python
Executable File
#!/usr/bin/env python2
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import struct
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import binascii
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TYPES = {
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(0x700, 0x400): 'splice',
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(0x7ff, 0x401): 'create',
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(0x7ff, 0x4ff): 'delete',
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(0x700, 0x000): 'name',
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(0x7ff, 0x001): 'name reg',
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(0x7ff, 0x002): 'name dir',
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(0x7ff, 0x0ff): 'name superblock',
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(0x700, 0x200): 'struct',
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(0x7ff, 0x200): 'struct dir',
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(0x7ff, 0x202): 'struct ctz',
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(0x7ff, 0x201): 'struct inline',
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(0x700, 0x300): 'userattr',
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(0x700, 0x600): 'tail',
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(0x7ff, 0x600): 'tail soft',
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(0x7ff, 0x601): 'tail hard',
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(0x700, 0x700): 'gstate',
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(0x7ff, 0x7ff): 'gstate move',
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(0x700, 0x500): 'crc',
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}
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def typeof(type):
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for prefix in range(12):
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mask = 0x7ff & ~((1 << prefix)-1)
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if (mask, type & mask) in TYPES:
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return TYPES[mask, type & mask] + (
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' %0*x' % (prefix/4, type & ((1 << prefix)-1))
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if prefix else '')
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else:
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return '%02x' % type
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def main(*blocks):
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# find most recent block
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file = None
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rev = None
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crc = None
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versions = []
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for block in blocks:
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try:
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nfile = open(block, 'rb')
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ndata = nfile.read(4)
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ncrc = binascii.crc32(ndata)
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nrev, = struct.unpack('<I', ndata)
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assert rev != nrev
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if not file or ((rev - nrev) & 0x80000000):
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file = nfile
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rev = nrev
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crc = ncrc
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versions.append((nrev, '%s (rev %d)' % (block, nrev)))
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except (IOError, struct.error):
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pass
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if not file:
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print 'Bad metadata pair {%s}' % ', '.join(blocks)
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return 1
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print "--- %s ---" % ', '.join(v for _,v in sorted(versions, reverse=True))
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# go through each tag, print useful information
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print "%-4s %-8s %-14s %3s %4s %s" % (
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'off', 'tag', 'type', 'id', 'len', 'dump')
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tag = 0xffffffff
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off = 4
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while True:
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try:
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data = file.read(4)
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crc = binascii.crc32(data, crc)
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ntag, = struct.unpack('>I', data)
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except struct.error:
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break
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tag ^= ntag
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off += 4
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type = (tag & 0x7ff00000) >> 20
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id = (tag & 0x000ffc00) >> 10
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size = (tag & 0x000003ff) >> 0
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iscrc = (type & 0x700) == 0x500
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data = file.read(size if size != 0x3ff else 0)
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if iscrc:
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crc = binascii.crc32(data[:4], crc)
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else:
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crc = binascii.crc32(data, crc)
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print '%04x: %08x %-15s %3s %4s %-23s %-8s' % (
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off, tag,
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typeof(type) + (' bad!' if iscrc and ~crc else ''),
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id if id != 0x3ff else '.',
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size if size != 0x3ff else 'x',
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' '.join('%02x' % ord(c) for c in data[:8]),
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''.join(c if c >= ' ' and c <= '~' else '.' for c in data[:8]))
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off += size if size != 0x3ff else 0
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if iscrc:
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crc = 0
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tag ^= (type & 1) << 31
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return 0
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if __name__ == "__main__":
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import sys
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sys.exit(main(*sys.argv[1:]))
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