Re: [lwip-users] TCP checksumming

[Jonathan Larmour]

Bill Auerbach wrote:
> 
>> And perhaps 
>> we should include an example in the contrib folder to clarify 
>> this for the future...?
> 
> Sure.  Or clarify the comments in inet_chksum.c since they are the only
> reference I've seen to mention performance gains by optimizing the checksum
> routine and it already provides a hint about how to go about it.  I don't
> mind doing this if you can tell me quickly how are you generating patch
> files that I've seen others submit.

Correcting the comment seems right, so I've done this. I've also changed
the selection of the algorithm from a bunch of "#if 1"s and "#if 0"s to use
an optional define test since it's a trivial improvement. That way you can
select the algorithm used from lwipopts.h rather than editting inet_chksum.c.

Just for the future, generating patches is done with the diff utility. To
just compare two files with GNU diff, you can usually get away with "diff
-u <oldfile> <newfile>". To diff large trees of files also use -r. Using -p
adds a helpful comment in the diff about the function name. Personally I
use the following macro in my bash shell:

alias jdiff="diff -x CVS -x \*~ -x .#\* -urpN "

Or you can make a short bash script to do the same thing:
#!/bin/bash
diff -x CVS -x \*~ -x .#\* -urpN "$@"

Hope this helps,

Jifl
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