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The C program we have (generate-windows-test-vectors.c) uses a higher
level API than MS-XCA refers to, which plays tricks like refusing to
do compression if the result would be larger than the original. It
does that because I could not successfully compile something using the
correct RtlCompressBuffer API in Cygwin.
It turns out you don't need to compile anything; using the Python
ctypes library, the Windows libraries are available to Python.
The compression *is* the same, which is what we expected.
Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Ralph Boehme <slow@samba.org>
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Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
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Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
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If compiled on Windows using Cygwin, MSYS2, or similar, this will output
compressed versions of files exactly as specified by MZ-XCA, if the
following conditions are met:
1. The file > 300 bytes.
2. The compressed file is smaller than the decompressed file.
Otherwise it returns the data unchanged. Without warning; that's just
how the API works.
Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
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Compression uses a 3 byte hash remember LZ77 matches in a 14-bit table.
This script runs the hash over all 16M combinations, then again over
all ASCII combinations, counting collisions to find hot-spots.
If you think you have a better hash, you are probably right, but you
should try it here -- alter h() -- before committing to it. This one is
literally the first one I thought of.
Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
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Huffman tree re-quantisation and perhaps other code paths are only
triggered by pathological data like this.
Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
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Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
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