ref: 922fc6faa00ab4e0f46b9f3d3c6bbd25a1c2201d
dir: /sys/src/libc/port/memccpy.c/
#include	<u.h>
#include	<libc.h>
void*
memccpy(void *a1, void *a2, int c, ulong n)
{
	uchar *s1, *s2;
	s1 = a1;
	s2 = a2;
	c &= 0xFF;
	while(n > 0) {
		if((*s1++ = *s2++) == c)
			return s1;
		n--;
	}
	return 0;
}