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/*
* This file is Copyright (c) 2015 by the GPSD project
* SPDX-License-Identifier: BSD-2-clause
*/
#ifndef GPSD_NTPSHM_H
#define GPSD_NTPSHM_H
#include <stdbool.h>
#include <time.h>
#include <sys/time.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#define NTPD_BASE 0x4e545030 /* "NTP0" */
/*
* How to read and write fields in an NTP shared segment.
* This definition of shmTime is from ntpd source ntpd/refclock_shm.c
*
* The fields aren't documented there. It appears the only use of
* nsamples is internal to the (obsolete and deprecated) EES M201
* receiver refclock. The precision field is nominally log(2) of the
* source's jitter in seconds:
* -1 is about 100mSec jitter
* -10 is about 1 mSec jitter (GR-601W or other USB with 1ms poll interval)
* -13 is about 100 uSec
* -20 is about 1 uSec (typical for serial PPS)
*/
struct shmTime
{
int mode; /* 0 - if valid set
* use values,
* clear valid
* 1 - if valid set
* if count before and after read of values is equal,
* use values
* clear valid
*/
volatile int count;
time_t clockTimeStampSec;
int clockTimeStampUSec;
time_t receiveTimeStampSec;
int receiveTimeStampUSec;
int leap; /* not leapsecond offset, a notification code */
int precision; /* log(2) of source jitter */
int nsamples; /* not used */
volatile int valid;
unsigned clockTimeStampNSec; /* Unsigned ns timestamps */
unsigned receiveTimeStampNSec; /* Unsigned ns timestamps */
int dummy[8];
};
/*
* These types are internal to GPSD
*/
enum segstat_t {OK, NO_SEGMENT, NOT_READY, BAD_MODE, CLASH};
struct shm_stat_t {
enum segstat_t status;
struct timespec tvc; /* System time when SHM read, for debug only */
struct timespec tvr; /* System time at GPS time */
struct timespec tvt; /* GPS time */
int precision;
int leap;
};
#ifndef TIMEDELTA_DEFINED
struct timedelta_t {
struct timespec real;
struct timespec clock;
};
#define TIMEDELTA_DEFINED
#endif /* TIMEDELTA_DEFINED */
struct shmTime *shm_get(int, bool, bool);
extern char *ntp_name(const int);
enum segstat_t ntp_read(struct shmTime *, struct shm_stat_t *, const bool);
void ntp_write(volatile struct shmTime *, struct timedelta_t *, int, int);
#endif /* GPSD_NTPSHM_H */
/* end */
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