From: Stephen Hemminger [mailto:step...@networkplumber.org]
> Sent: 04 September 2017 19:25
> On Mon, 4 Sep 2017 17:00:15 +0200
> Phil Sutter <p...@nwl.cc> wrote:
>
> > On Mon, Sep 04, 2017 at 02:49:20PM +0000, David Laight wrote:
> > > From: Phil Sutter
> > > > Sent: 01 September 2017 17:53
> > > > By making use of strncpy(), both implementations are really simple so
> > > > there is no need to add libbsd as additional dependency.
> > > >
> > > ...
> > > > +
> > > > +size_t strlcpy(char *dst, const char *src, size_t size)
> > > > +{
> > > > + if (size) {
> > > > + strncpy(dst, src, size - 1);
> > > > + dst[size - 1] = '\0';
> > > > + }
> > > > + return strlen(src);
> > > > +}
> > >
> > > Except that isn't really strlcpy().
> > > Better would be:
> > > len = strlen(src) + 1;
> > > if (len <= size)
> > > memcpy(dst, src, len);
> > > else if (size) {
> > > dst[size - 1] = 0;
> > > memcpy(dst, src, size - 1);
> > > }
> > > return len - 1;
> >
> > Please elaborate: Why isn't my version "really" strlcpy()? Why is your
> > proposed version better?
> >
> > Thanks, Phil
>
> Linux kernel:
> size_t strlcpy(char *dest, const char *src, size_t size)
> {
> size_t ret = strlen(src);
>
> if (size) {
> size_t len = (ret >= size) ? size - 1 : ret;
> memcpy(dest, src, len);
> dest[len] = '\0';
> }
> return ret;
> }
>
> FreeBSD:
> size_t
> strlcpy(char * __restrict dst, const char * __restrict src, size_t dsize)
> {
> const char *osrc = src;
> size_t nleft = dsize;
>
> /* Copy as many bytes as will fit. */
> if (nleft != 0) {
> while (--nleft != 0) {
> if ((*dst++ = *src++) == '\0')
> break;
> }
> }
>
> /* Not enough room in dst, add NUL and traverse rest of src. */
> if (nleft == 0) {
> if (dsize != 0)
> *dst = '\0'; /* NUL-terminate dst */
> while (*src++)
> ;
> }
>
> return(src - osrc - 1); /* count does not include NUL */
> }
>
>
> They all give the same results for some basic tests.
> Test FreeBSD Linux Iproute2
> "",0: 0 "JUNK" 0 "JUNK" 0 "JUNK"
> "",1: 0 "" 0 "" 0 ""
> "",8: 0 "" 0 "" 0 ""
> "foo",0: 3 "JUNK" 3 "JUNK" 3 "JUNK"
> "foo",3: 3 "fo" 3 "fo" 3 "fo"
> "foo",4: 3 "foo" 3 "foo" 3 "foo"
> "foo",8: 3 "foo" 3 "foo" 3 "foo"
> "longstring",0: 10 "JUNK" 10 "JUNK" 10 "JUNK"
> "longstring",8: 10 "longstr" 10 "longstr" 10 "longstr"
You need to look at the contents of the destination buffer after the
first '\0'.
strlcpy() shouldn't change it.
David
