printf在kernel中的实现

static void
putch(int ch, int cnt)
{
cputchar(ch);
cnt++;
}

int
vcprintf(const char *fmt, va_list ap)
{
int cnt = 0;

vprintfmt((void*)putch, &cnt, fmt, ap);
return cnt;

}

int
cprintf(const char *fmt, …)
{
va_list ap;
int cnt;

va_start(ap, fmt);
cnt = vcprintf(fmt, ap);
va_end(ap);

return cnt;

}