Hi,

David Miller wrote:

From: Lothar Waßmann <redacted>
Date: Tue, 4 Nov 2014 11:29:12 +0100

quoted

Hi David,

Lothar Waßmann wrote:

quoted

David Miller wrote:

quoted

From: Lothar Waßmann <redacted>
Date: Thu, 30 Oct 2014 07:51:04 +0100

quoted

quoted

Also, I don't thnk your DIV_ROUND_UP() eliminate for the loop
in swap_buffer() is valid.  The whole point is that the current
code handles buffers which have a length which is not a multiple
of 4 properly, after your change it will no longer do so.

Do you really think so?

Yes, because you're rounding down so you'll miss the final
partial word (if any).

Nope. DIV_ROUND_UP() would give '1' as upper bound for lengths from 1 to
4, '2' for lengths from 5 to 8 and so on.

The loop with increment 4 and i < len does exactly the same.
Try it for yourself, if you don't believe it.

Do you still think, the loop without DIV_ROUND_UP() is incorrect,
or can this patch be applied?

I haven't had the time to fully re-look into the details, I'm busy
with many other things at the moment.

But looking at DIV_ROUND_UP() macro it rounds up.  It gives an
upper bound of 4 for any value 1 to 4.  Unlike what you claim.

You're missing the 'DIV' part of DIV_ROUND_UP().

Because it goes "(n + (d - 1)) / d"

Which for 'd' of 4 gives:

1 --> 4
2 --> 4
3 --> 4
4 --> 4

'1', not '4'.
The loop has to be done once for each (probably partial) WORD of input
data, not for each BYTE.

Without dividing and incrementing by four the loop
counter will be 0 for the first word which is less than any length > 0.
Thus the loop will be run once for any number of bytes from 1 thru 4.
If incremented by 4 after the first loop, it will be run again for any
length > 5 and so forth.


Lothar Waßmann
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