[FFmpeg-devel] [RFC] av_strlcpy instead of pstrcpy

[Michael Niedermayer]

Hi

On Sat, Jun 23, 2007 at 08:33:35PM +0100, M?ns Rullg?rd wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> 
> > Hi
> >
> > On Sat, Jun 23, 2007 at 05:10:26PM +0200, Reimar D?ffinger wrote:
> >> Hello,
> >> attached incomplete patch (no uses changed) would replace pstrcpy and
> >> pstrcat by av_strlcpy and av_strlcat which behave like the (BSD-only)
> >> strlcpy and strlcat functions (documentation here:
> >> http://developer.apple.com/documentation/Darwin/Reference/Manpages/man3/strlcpy.3.html).
> >> While I don't think we will ever really need the "return value vodoo" ;-) of these
> >> functions it seems preferable to not have yet another different
> >> implementation (of course that is only true if you check that my
> >> implementations really are right).
> >> It might also allow to use the real system functions if available like
> >> MPlayer does (but of course in a less ugly-hackish way).
> >
> > iam in favor of this in principle ...
> >
> > [...]
> >> -void pstrcpy(char *buf, int buf_size, const char *str)
> >> +size_t av_strlcpy(char *buf, const char *str, size_t buf_size)
> >>  {
> >> +    size_t i = 0;
> >>      if (buf_size <= 0)
> >> -        return;
> >> +        goto out;
> >>  
> >> -    while (buf_size-- > 1 && *str)
> >> -        *buf++ = *str++;
> >> -    *buf = 0;
> >> +    while (buf_size-- > 1 && *str) {
> >> +        buf[i] = str[i];
> >
> > uhm, *str and src[i]?
> >
> >> +    }
> >> +    buf[i] = 0;
> >> +out:
> >> +    while (str[i]) i++;
> >> +    return i;
> >
> > maybe the following is less buggy (or maybe not ...)
> >
> > size_t av_strlcpy(char *buf, const char *str, size_t buf_size)
> > {
> >     const char *org= src;
> >     while (buf_size-- > 1 && *str)
> >         *buf++ = *str++;
> >     if(buf_size>0)
> >         *buf = 0;
> >     return src-org+strlen(src);
> > }
> 
> This breaks if buf_size == 0 (size_t is unsigned).
> 
> My take:
> 
> size_t av_strlcpy(char *dst, const char *src, size_t size)
> {
>     size_t len = 0;
>     while (++len < size && *src)
>         *dst++ = *src++;
>     if (len <= size)
>         *dst = 0;
>     return len + strlen(src) - 1;
> }
> 
> size_t av_strlcat(char *dst, const char *src, size_t size)
> {
>     size_t len = strlen(dst);
>     if (size <= len + 1)
>         return len + strlen(src);
>     return len + av_strlcpy(dst + len, src, size - len);
> }
> 
> Did I overlook anything?

probably not

and iam fine with the code and API

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I hate to see young programmers poisoned by the kind of thinking
Ulrich Drepper puts forward since it is simply too narrow -- Roman Shaposhnik
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