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Commit Graph

8 Commits

Author SHA1 Message Date
Douglas Bagnall
637e7cbdba lzxpress: compress shortcut if we've reached maximum length
A simple degenerate case for our compressor has been a large number of
repeated bytes that will match the maximum length (~64k) at all 8192
search positions, 8191 of which searches are in vain because the
matches are not of greater length than the first one.

Here we recognise the inevitable and reduce runtime proportionately.

Credit to OSS-Fuzz.

REF: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=47428

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

Autobuild-User(master): Douglas Bagnall <dbagnall@samba.org>
Autobuild-Date(master): Tue May 17 23:11:21 UTC 2022 on sn-devel-184
2022-05-17 23:11:21 +00:00
Douglas Bagnall
04309bc682 lzxpress/test: time performance of long boring sequences
We get *very* slow when long runs of the bytes are the same. On this
laptop the test takes 18s; with the next commit it will be 0.006s.

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
2022-05-17 22:13:35 +00:00
Joseph Sutton
430bcd7a08 compression: Fix writing output flags
If indic_bit == 0, the shift amount of 32 - indic_bit == 32 will equal
the width of a 32-bit integer type, and these shifts will invoke
undefined behaviour, which is likely to cause incorrect output. Fix this
by not shifting a 32-bit integer type by 32 bits or more.

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
2022-05-12 02:22:35 +00:00
Joseph Sutton
69244b52ed compression: Use correct value for indic_pos
Previously, we were setting this to the wrong value and overwriting
existing output data.

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
2022-05-12 02:22:35 +00:00
Joseph Sutton
7fab9f90e8 compression: Use correct value for nibble_index
Previously, we were setting this to the wrong value and overwriting
existing output data.

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
2022-05-12 02:22:35 +00:00
Joseph Sutton
eb7f139dec compression tests: Add additional compression tests
Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
2022-05-12 02:22:35 +00:00
Matt Suiche
3c2f1f03c1 compression: fix lzxpress-compress
Signed-off-by: Matt Suiche <msuiche@comae.com>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
2022-05-12 02:22:35 +00:00
Matt Suiche
4bcdc3bf30 compression tests: add LZXpress tests based on [MS-XCA]
MS-XCA contains examples, and we should at least get those right.

Signed-off-by: Matt Suiche <msuiche@comae.com>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
2022-05-12 02:22:35 +00:00