WHile I don't know what ptr2 does, you might try putting the test for end
of the first string into the for loop's termination condition. Or add a
'break' statement to your if. They both accomplish the same thing; it is
primarily a style issue.

Off the top of my head, I have to admit I'd probably do something
semi-illegible like:

char *strncpy( char *s1, const char *s2, int n)
{
   int x;

   for ( x = 0; ( x < n) && *s2;)
      *s1++ = *s2++;

   if ( x < n)
      *s1 = 0;

   return s1;

(And, yes, it's possible to fold my 'if' statement into the loop, but I
don't feel it would look very good, nor would it gain you much).

  Bob
--
  Bob           One good thing about being wrong is the joy it brings to others

As Robert mentioned, if(*ptr2) looks fishy.  How did this function manage to
work?  You probably meant if(*s2) instead.

Except that, now, it's not a valid implementation of strncpy().

#include <stddef.h>

char * my_strncpy(char *s1, const char *s2, size_t n)
{
   while (n--) *s1++ = (*s2) ? (*s2++) : (*s2);
   return s1;

would be the implementation of my choice, but it shouldn't be
significantly faster (or slower) than the (corrected) version of the
function from the original post.  Any attempt to do loop unrolling,
etc., would be classified as micro-optimization, which probably wouldn't
help, and if it did, the optimization wouldn't be portable to all
platforms anyway.

So, my advice is, if the version you have works correctly, stick with it.

--

http://www.cs.wustl.edu/~jxh/        Washington University in Saint Louis

Bob...

I think it might be helpful either to increment x or decrement n so as to leave
the loop if the destination field is used up before a NUL is found.

Can I play? I like while loops:

char *strncpy(char *d,char *s,int n)
{       char *x = d;
        while (n-- && *s) *d++ = *s++;
        if (n) *d = '\0';
        return x;

Morris Dovey

Des Moines, Iowa, USA

This function does not satisfy the definition of strncpy().  Even if you
changed the parameter list to match what the Standard says it should be:

char *strncpy(char *d,const char *s,size_t n)

The result of the function still fails to comply.

--

http://www.cs.wustl.edu/~jxh/        Washington University in Saint Louis