On 6/29/2020 10:30 AM, Taco Hoekwater wrote:
On 28 Jun 2020, at 03:26, Reinhard Kotucha <[email protected]> wrote:
As far as I understand it's sufficient that the relevant
functions read{cardinal,integer}{2,4} obey a flag which tells
them whether byte re-ordering is necessary. The flag has to be
set if host and file byte orders are different. I don't know
whether we have to consider 64 bit integers too.
that adds passing parameters and checking them for each call
... you can then as well use lua's 'read' function and convert with
string.byte/char which is then about equally fast
This is what I actually did. It took 14 s to process a PNM file, way
too much if I have to process hundreds or thousands files. I ported
the script to C and could process the file within 270 ms. I can't
imagine that obeying a variable in C can slow down everything so much.
The quick way to fix this without noticeable overhead would be to add
a few extra function definitions for read{cardinal,integer}{2,4} in
the byte permutations that are likely to actually happen. There are
not *that* many of those.
that was indeed the idea ... (i'll do it this week)
Hans
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