Re: generic strncpy - off-by-one error

Daniel Forrest
2003-08-16T10:04:22Z

On Sat, Aug 16, 2003 at 11:19:30AM +0200, Peter Kjellerstedt wrote:
>
> Actually, it should be:
>
> while (count && ((long)tmp & (sizeof(long) - 1)))
>

Oops, you're right, I forgot that the count could be small.

But, now that I think of it, maybe this would be best...

char *strncpy(char *dest, const char *src, size_t count)
{
char *tmp = dest;

while (count && *src) {
*tmp++ = *src++;
count--;
}

- if (count) {
+ if (count >= sizeof(long)) {
size_t count2;

- while (count && ((long)tmp & (sizeof(long) - 1))) {
+ while ((long)tmp & (sizeof(long) - 1)) {
*tmp++ = '\0';
count--;
}

count2 = count / sizeof(long);
while (count2) {
*((long *)tmp)++ = '\0';
count2--;
}

count &= (sizeof(long) - 1);
- while (count) {
- *tmp++ = '\0';
- count--;
- }
+ }
+
+ while (count) {
+ *tmp++ = '\0';
+ count--;
}

return dest;
}

--
Dan