RE: gzip use of memcpy

[Alain Magloire]

> From: Jim Meyering [mailto:address@hidden
> Sent: Tuesday, January 12, 2010 2:53 AM
> To: Yuxi Zhang
> Cc: Alain Magloire; address@hidden
> Subject: Re: gzip use of memcpy
>

Bonjour,
 
> Yuxi Zhang wrote:
> > It would be nice to declare the delta inside the function scope.
> 
> Why?
> I find it less readable and less maintainable.
> Do you have to use a compiler for which that is required?
> If so, please give its name and version number.
> 

Ouch! You are a hard man to please 8-).

We were using the watcom cc, but we stop its use, now out of (bad)
habit, the testers/developers still do the declaration at the beginning
of the block.  But you are right it should not be a problem.  

You're patch was tested on a SH4a and it seems to be fine.


> > 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.