freebsd-nq/contrib/ntp/libntp/refidsmear.c

59 lines
1.1 KiB
C
Raw Normal View History

#include <config.h>
#include <ntp.h>
#include <ntp_fp.h>
#include <refidsmear.h>
/*
* we want to test a refid format of:
* 254.x.y.x
*
* where x.y.z are 24 bits containing 2 (signed) integer bits
* and 22 fractional bits.
*
*/
l_fp
convertRefIDToLFP(uint32_t r)
{
l_fp temp;
r = ntohl(r);
// printf("%03d %08x: ", (r >> 24) & 0xFF, (r & 0x00FFFFFF) );
temp.l_uf = (r << 10); /* 22 fractional bits */
temp.l_ui = (r >> 22) & 0x3;
temp.l_ui |= ~(temp.l_ui & 2) + 1;
return temp;
}
uint32_t
convertLFPToRefID(l_fp num)
{
uint32_t temp;
/* round the input with the highest bit to shift out from the
* fraction, then keep just two bits from the integral part.
*
* TODO: check for overflows; should we clamp/saturate or just
* complain?
*/
L_ADDUF(&num, 0x200);
num.l_ui &= 3;
/* combine integral and fractional part to 24 bits */
temp = (num.l_ui << 22) | (num.l_uf >> 10);
/* put in the leading 254.0.0.0 */
temp |= UINT32_C(0xFE000000);
// printf("%03d %08x: ", (temp >> 24) & 0xFF, (temp & 0x00FFFFFF) );
return htonl(temp);
}