https://bugs.freedesktop.org/show_bug.cgi?id=55786
Thomas Kluyver <tho...@kluyver.me.uk> changed:
What |Removed |Added
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CC| |tho...@kluyver.me.uk
--- Comment #13 from Thomas Kluyver <tho...@kluyver.me.uk> ---
I had to spend a while digging into an old WK4 file to extract some data. I
thought I'd document my main finding here:
opcode 0x17 appears to be a 10-byte extended precision float. After the record
header, there is a two byte row number, one byte sheet number, and one byte
column number. These are common to a few record types. The remainder of it is
the value, in the format described here:
http://en.wikipedia.org/wiki/Extended_precision#x86_Extended_Precision_Format
I was able to extract these, at least for the small positive numbers in my
sample, using the following Python code:
a = int.from_bytes(r.data[-2:], 'little')
sign = -1 if (a & (1<<15)) else 1
e = a - (a & (1 << 15)) - 16383
m = int.from_bytes(r.data[4:-2], 'little')
val = m / (1<<(63-e))
0x16 is a label, with the same row/sheet/column fields.
I started looking into making a patch, but I got confused because there appear
to be opcode lookup tables both in optab.cxx and as switch statements in
lotread.cxx, with different opcodes in them.
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