__peter__ at web.de
Fri Oct 16 13:30:37 CEST 2009
Richard Brodie wrote:
> "pjcoup" <pjcoup at gmail.com> wrote in message
> news:b1537079-6e3a-43e1-814b-7ccf185fb9c3 at v15g2000prn.googlegroups.com...
>> I would have expected calcsize('BhhhhB') to be either 10 or 12
>> (padding), but 11? Is there a simple explanation of what is going
>> on here?
> The purpose of the padding is to align the words 'naturally'.
> That is, when reading two bytes, to start at an even number.
> B X B h1
> h1 h1 h1 h2
> h2 h2 h2 h3
> h3 h3 h3 h4
> h4 h4 h4 B
> B Y
> The padding at X lines up h1-h4. There isn't any point
> putting padding at Y.
I would have expected "native size and alignment" (as stated in the
documentation) to mean that I can read the output of struct.pack("bhhhhb")
into a C
short b1, b2, b3, b4;
but that has a size of 12 bytes on my 64 bit Ubuntu.
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