On Wed, 6 Sep 2017 13:59:27 +0000 David Laight <david.lai...@aculab.com> wrote:
> 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 Zeroing the bytes after the first null character should not be a big issue other than a few nanoseconds extra work.
