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RE: gzip use of memcpy
From: |
Yuxi Zhang |
Subject: |
RE: gzip use of memcpy |
Date: |
Tue, 12 Jan 2010 09:12:05 -0500 |
> Why?
I just guess that would have some benefit for performance since we do
not need to declare the variable each time to enter the loop(it is a
just pure guess). That is my condiseration to put the declaration inside
the loop.
> I find it less readable and less maintainable.
Agree.
> Do you have to use a compiler for which that is required?
> If so, please give its name and version number.
No.
Thanks
Yuxi
>
> > Index: inflate.c
> > ===================================================================
> > --- inflate.c (revision 248271)
> > +++ inflate.c (working copy)
> > @@ -526,6 +526,7 @@
> > register unsigned e; /* table entry flag/number of extra bits */
> > unsigned n, d; /* length and index for copy */
> > unsigned w; /* current window position */
> > + unsigned delta; /* delta between slide+w and slide+d */
> > struct huft *t; /* pointer to table entry */
> > unsigned ml, md; /* masks for bl and bd bits */
> > register ulg b; /* bit buffer */
> > @@ -593,7 +594,9 @@
> > do {
> > n -= (e = (e = WSIZE - ((d &= WSIZE-1) > w ? d :
> w)) > n ? n :
> > e);
> > #if !defined(NOMEMCPY) && !defined(DEBUG)
> > - if (w - d >= e) /* (this test assumes unsigned
> > comparison) */
> > + /* make the unsigned comparision in positive range. */
> > + delta = w > d ? w - d : d - w;
> > + if (delta >= e) /* (this test assumes unsigned
> > comparison) */
>
> I know it is line with the style of the existing code, but
> that code certainly does not qualify as a role model.
>
- gzip use of memcpy, Alain Magloire, 2010/01/06
- Re: gzip use of memcpy, Jim Meyering, 2010/01/08
- RE: gzip use of memcpy, Alain Magloire, 2010/01/08
- RE: gzip use of memcpy, Alain Magloire, 2010/01/08
- Re: gzip use of memcpy, Jim Meyering, 2010/01/10
- RE: gzip use of memcpy, Alain Magloire, 2010/01/11
- Re: gzip use of memcpy, Jim Meyering, 2010/01/11
- RE: gzip use of memcpy, Yuxi Zhang, 2010/01/11
- Re: gzip use of memcpy, Jim Meyering, 2010/01/12
- RE: gzip use of memcpy,
Yuxi Zhang <=
- RE: gzip use of memcpy, Alain Magloire, 2010/01/12