RE: [lwip-devel] Checksum optimizations

[Bill Auerbach]

> So the whole function can be effectively optimized away using:
> #define inet_chksum(x,y) ~LWIP_CHKSUM(x,y)
> ?

I tested this in inet_chksum.h:

#define inet_chksum(dataptr, len) ((u16_t) ~LWIP_CHKSUM(dataptr, len))

And before the function inet_chksum you need an #undef inet_chksum because
it's used by ipfrag.c.  I also commented out the while loop.

It works fine.  I didn't test for a speed improvement, but the code size has
to improve a little.  I added the cast because an ISO C compiler might do
the ~ as an int operation.

Bill