misc/141682: Fester version of stncpy function

[Maxim Zakharov]

>Number:         141682
>Category:       misc
>Synopsis:       Fester version of stncpy function
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          change-request
>Submitter-Id:   current-users
>Arrival-Date:   Wed Dec 16 14:20:01 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     Maxim Zakharov
>Release:        7.1-BETA2
>Organization:
>Environment:
FreeBSD max.maxime.net.ru 7.1-BETA2 FreeBSD 7.1-BETA2 #0: Mon Oct 13 04:23:28 UTC 2008     root at logan.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  i386
>Description:
I would like to propose a faster version of strncpy function (/usr/src/lib/libc/string/strncpy.c). It's about 30% faster on aligned data, and about two times faster on unaligned data on modern pipelined processors (Intel Duo E8400 3MHz in particular).
>How-To-Repeat:

>Fix:
void * dps_strncpy(char *dst0, char *src0, size_t length) {
  if (length) {
    register size_t n = (length + 7) / 8;
    register size_t r = (length % 8);
    register char *dst = dst0, *src = src0;
    if (r == 0) r = 8;
    if (!(dst[0] = src[0])) return dst0;
    if (r > 1) { if (!(dst[1] = src[1])) return dst0;
    if (r > 2) { if (!(dst[2] = src[2])) return dst0;
    if (r > 3) { if (!(dst[3] = src[3])) return dst0;
    if (r > 4) { if (!(dst[4] = src[4])) return dst0;
    if (r > 5) { if (!(dst[5] = src[5])) return dst0;
    if (r > 6) { if (!(dst[6] = src[6])) return dst0;
    if (r > 7) { if (!(dst[7] = src[7])) return dst0;
    }}}}}}}
    src += r; dst += r;
    while (--n > 0) {
      if (!(dst[0] = src[0])) break;
      if (!(dst[1] = src[1])) break;
      if (!(dst[2] = src[2])) break;
      if (!(dst[3] = src[3])) break;
      if (!(dst[4] = src[4])) break;
      if (!(dst[5] = src[5])) break;
      if (!(dst[6] = src[6])) break;
      if (!(dst[7] = src[7])) break;
      src += 8; dst += 8;
    }
    if (dst < dst0 + length) *dst = '\0';
  }
  return dst0;
}


>Release-Note:
>Audit-Trail:
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