Data Structures
struct	N_CLOCK_SYNC
	clock synchronization estimator More...

Macros
#define	N_CLOCK_SYNC_INTERVAL 3.0
	default interval between sync requests in seconds

#define	N_CLOCK_SYNC_SAMPLE_COUNT 11
	number of samples for the median filter

Functions
static int	cmp_double (const void a, const void b)
	comparison function for qsort on doubles

static double	median_of (const double *samples, int count)
	compute the median of an array of doubles

void	n_clock_sync_delete (N_CLOCK_SYNC **cs)
	free a clock sync estimator

void	n_clock_sync_mark_sent (N_CLOCK_SYNC *cs, double local_now)
	mark that a sync request was just sent

N_CLOCK_SYNC *	n_clock_sync_new (void)
	allocate and initialize a new clock sync estimator

int	n_clock_sync_process_response (N_CLOCK_SYNC *cs, double client_send_time, double server_time, double local_now)
	record a sync response: client_send_time is the local time the request was sent, server_time is the server's timestamp from the response, local_now is the current local time when the response was received.

double	n_clock_sync_server_time (const N_CLOCK_SYNC *cs, double local_now)
	get estimated server time given a local time value

int	n_clock_sync_should_send (const N_CLOCK_SYNC *cs, double local_now)
	check if it's time to send a new sync request (returns TRUE/FALSE)

Detailed Description

Data Structure Documentation

◆ N_CLOCK_SYNC

struct N_CLOCK_SYNC

clock synchronization estimator

Examples: ex_clock_sync.c.

Definition at line 77 of file n_clock_sync.h.

Collaboration diagram for N_CLOCK_SYNC:

Data Fields
double	estimated_offset	add to local time to get estimated server time
double	estimated_rtt	current estimated round-trip time
double	last_sync_time	local time of last sync request sent
double	offset_samples[11]	circular buffer of offset estimates
double	rtt_samples[11]	circular buffer of RTT values
int	sample_count	number of samples collected so far
int	sample_index	current write position in circular buffer

Macro Definition Documentation

◆ N_CLOCK_SYNC_INTERVAL

#define N_CLOCK_SYNC_INTERVAL 3.0

default interval between sync requests in seconds

Definition at line 73 of file n_clock_sync.h.

◆ N_CLOCK_SYNC_SAMPLE_COUNT

#define N_CLOCK_SYNC_SAMPLE_COUNT 11

number of samples for the median filter

Definition at line 68 of file n_clock_sync.h.

Function Documentation

◆ cmp_double()

static int cmp_double	(	const void *	a,
		const void *	b
	)

static

comparison function for qsort on doubles

Definition at line 39 of file n_clock_sync.c.

Referenced by median_of().

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◆ median_of()

static double median_of	(	const double *	samples,
		int	count
	)

static

compute the median of an array of doubles

Definition at line 48 of file n_clock_sync.c.

References cmp_double(), and N_CLOCK_SYNC_SAMPLE_COUNT.

Referenced by n_clock_sync_process_response().

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◆ n_clock_sync_delete()

void n_clock_sync_delete ( N_CLOCK_SYNC ** cs )

free a clock sync estimator

Examples: ex_clock_sync.c.

Definition at line 78 of file n_clock_sync.c.

References __n_assert, and Free.

Referenced by run_client().

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◆ n_clock_sync_mark_sent()

void n_clock_sync_mark_sent	(	N_CLOCK_SYNC *	cs,
		double	local_now
	)

mark that a sync request was just sent

Examples: ex_clock_sync.c.

Definition at line 125 of file n_clock_sync.c.

References __n_assert, and N_CLOCK_SYNC::last_sync_time.

Referenced by run_client().

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◆ n_clock_sync_new()

N_CLOCK_SYNC * n_clock_sync_new ( void )

allocate and initialize a new clock sync estimator

Examples: ex_clock_sync.c.

Definition at line 62 of file n_clock_sync.c.

References __n_assert, N_CLOCK_SYNC::estimated_offset, N_CLOCK_SYNC::estimated_rtt, N_CLOCK_SYNC::last_sync_time, Malloc, N_CLOCK_SYNC_INTERVAL, N_CLOCK_SYNC::sample_count, and N_CLOCK_SYNC::sample_index.

Referenced by run_client().

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◆ n_clock_sync_process_response()

int n_clock_sync_process_response	(	N_CLOCK_SYNC *	cs,
		double	client_send_time,
		double	server_time,
		double	local_now
	)

record a sync response: client_send_time is the local time the request was sent, server_time is the server's timestamp from the response, local_now is the current local time when the response was received.

Updates estimated_offset and estimated_rtt. Returns TRUE on success, FALSE on error.