Re: Faster StrNCpy

Thanks for the results on your machines Dave, Luke, and Tom. Interesting.

On Mon, Oct 02, 2006 at 02:30:11PM -0400, Tom Lane wrote:
> It appears that these results are a bit platform-dependent; on my x86_64
> (Xeon) Fedora 5 box, I get

*nod*

> Anyway, I looked at glibc's strncpy and determined that on this machine
> the only real optimization that's been done to it is to unroll the data
> copying loop four times. I did the same to strlcpy (attached) and got
> numbers like these:

> So the unroll seems to get us to the point of not losing compared to the
> original strncpy code for any string length, and so I propose doing
> that, if it holds up on other architectures.

Sounds reasonable. strlcpy() is the best match. I'm not sure why GLIBC
doesn't come with strlcpy(). Apparently some philosophical differences
against it by the GLIBC maintainers... :-)

memcpy() makes too many assumptions, that would be difficult to prove
in each case, or may be difficult to ensure that they remain true. I
only mentioned it as a possibility, to keep the options open, and to
show the sort of effects we are dealing with.

Cheers,
mark

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