time.c File Reference

Helper functions for dealing with time values. More...

#include "para.h"

Functions
long unsigned	tv2ms (const struct timeval *tv)
	Convert struct timeval to milliseconds. More...
void	ms2tv (long unsigned n, struct timeval *tv)
	Convert milliseconds to a struct timeval. More...
int	tv_diff (const struct timeval *b, const struct timeval *a, struct timeval *diff)
	Compute the difference of two time values. More...
void	tv_add (const struct timeval *a, const struct timeval *b, struct timeval *sum)
	Add two time values. More...
void	tv_scale (const unsigned long mult, const struct timeval *tv, struct timeval *result)
	Compute integer multiple of given struct timeval. More...
void	tv_divide (const unsigned long divisor, const struct timeval *tv, struct timeval *result)
	Compute a fraction of given struct timeval. More...
int	tv_convex_combination (const long a, const struct timeval *tv1, const long b, const struct timeval *tv2, struct timeval *result)
	Compute a convex combination of two time values. More...
void	compute_chunk_time (long unsigned chunk_num, struct timeval *chunk_tv, struct timeval *stream_start, struct timeval *result)
	Compute when to send a chunk of an audio file. More...
struct timeval *	clock_get_realtime (struct timeval *tv)
	Retrieve the time of the realtime clock. More...

Detailed Description

Helper functions for dealing with time values.

Function Documentation

tv2ms()

long unsigned tv2ms

(

const struct timeval *

tv

)

Convert struct timeval to milliseconds.

Parameters

tv	The time value value to convert.

Returns

The number of milliseconds in tv.

Referenced by sched_request_timeout(), and vss_init().

ms2tv()

void ms2tv	(	long unsigned	n,
		struct timeval *	tv
	)

Convert milliseconds to a struct timeval.

Parameters

n	The number of milliseconds.
tv	Result pointer.

Referenced by sched_request_timeout_ms(), and vss_init().

tv_diff()

int tv_diff	(	const struct timeval *	b,
		const struct timeval *	a,
		struct timeval *	diff
	)

Compute the difference of two time values.

Parameters

b	Minuend.
a	Subtrahend.
diff	Result pointer.

If diff is not NULL, it contains the absolute value |b - a| on return.

Returns

If b < a, this function returns -1, otherwise it returns 1.

Referenced by audiod_get_btr_root(), sched_request_barrier(), sched_request_barrier_or_min_delay(), and tv_convex_combination().

tv_add()

void tv_add	(	const struct timeval *	a,
		const struct timeval *	b,
		struct timeval *	sum
	)

Add two time values.

Parameters

a	First addend.
b	Second addend.
sum	Contains the sum a + b on return.

Referenced by compute_chunk_time(), and tv_convex_combination().

tv_scale()

void tv_scale	(	const unsigned long	mult,
		const struct timeval *	tv,
		struct timeval *	result
	)

Compute integer multiple of given struct timeval.

Parameters

mult	The integer value to multiply with.
tv	The timevalue to multiply.
result	Contains mult * tv on return.

Referenced by compute_chunk_time(), and tv_convex_combination().

tv_divide()

void tv_divide	(	const unsigned long	divisor,
		const struct timeval *	tv,
		struct timeval *	result
	)

Compute a fraction of given struct timeval.

Parameters

divisor	The integer value to divide by.
tv	The timevalue to divide.
result	Contains (1 / mult) * tv on return.

Referenced by tv_convex_combination().

tv_convex_combination()

int tv_convex_combination	(	const long	a,
		const struct timeval *	tv1,
		const long	b,
		const struct timeval *	tv2,
		struct timeval *	result
	)

Compute a convex combination of two time values.

Parameters

a	The first coefficient.
tv1	The first time value.
b	The second coefficient.
tv2	The second time value.
result	Contains the convex combination upon return.

Compute x := (a * tv1 + b * tv2) / (|a| + |b|) and store |x| in result. Both a and b may be negative.

Returns

Zero, 1 or -1, if x is zero, positive or negative, respectively.

References PARA_ABS, tv_add(), tv_diff(), tv_divide(), and tv_scale().

compute_chunk_time()

void compute_chunk_time	(	long unsigned	chunk_num,
		struct timeval *	chunk_tv,
		struct timeval *	stream_start,
		struct timeval *	result
	)

Compute when to send a chunk of an audio file.

Parameters

chunk_num	The number of the chunk.
chunk_tv	The duration of one chunk.
stream_start	When the first chunk was sent.
result	The time when to send chunk number chunk_num.

This function computes stream_start + chunk_num * chunk_time.

References tv_add(), and tv_scale().

clock_get_realtime()

struct timeval* clock_get_realtime

(

struct timeval *

tv

)

Retrieve the time of the realtime clock.

Parameters

tv	Where to store the result.

Gets the current value of the system-wide real-time clock (identified by id CLOCK_REALTIME). If tv is NULL, the value is stored in a static buffer, otherwise it is stored at the location given by tv.

Returns

This function aborts on errors. On success it returns a pointer to memory containing the current time.

See also

clock_gettime(2), gettimeofday(2).

Referenced by schedule().