.\" Copyright (c) 2009-2022 Julien Nadeau Carriere <vedge@csoft.net>
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.Dd December 21, 2022
.Dt AG_TIME 3
.Os Agar 1.7
.Sh NAME
.Nm AG_Time
.Nd agar time interface
.Sh SYNOPSIS
.Bd -literal
#include <agar/core.h>
.Ed
.Sh DESCRIPTION
These functions provide a low-level interface to monotonically increasing
time sources.
Different time backends may be implemented (see
.Sx INTERNAL API
below).
Agar provides the following backends:
.Pp
.Bl -tag -width "agTimeOps_gettimeofday "
.It agTimeOps_dummy
No-op (timers will be unavailable).
.It agTimeOps_gettimeofday
BSD-style
.Fn gettimeofday
interface.
.It agTimeOps_posix
The POSIX
.Fn clock_gettime
interface.
.It agTimeOps_renderer
Monotonic clock which stops while graphical rendering is performed.
This is useful for applications performing offline rendering, where the
render may be influenced by different threads relying on Agar timers
or
.Fn AG_Delay
calls.
It requires the POSIX
.Fn clock_gettime
interface.
.It agTimeOps_win32
The MS Windows winmm API.
.El
.Sh INTERFACE
.nr nS 1
.Ft "Uint32"
.Fn AG_GetTicks "void"
.Pp
.Ft "void"
.Fn AG_Delay "Uint32 t"
.Pp
.Ft void
.Fn AG_SetTimeOps "const AG_TimeOps *ops"
.Pp
.nr nS 0
The
.Fn AG_GetTicks
function returns the current time in ticks.
One tick usually corresponds to one millisecond.
.Pp
The
.Fn AG_Delay
function blocks the current thread, waiting at least
.Fa t
ticks before returning.
The exact amount of time which
.Fn AG_Delay
waits is platform and backend dependent.
.Pp
The
.Fn AG_SetTimeOps
function selects a time backend (see below).
.\" MANLINK(AG_TimeOps)
.Sh BACKEND INTERFACE
The argument to
.Fn AG_SetTimeOps
should point to the following structure:
.Bd -literal
.\" SYNTAX(c)
typedef struct ag_time_ops {
	const char *name;
	void   (*Init)(void);
	void   (*Destroy)(void);
	Uint32 (*GetTicks)(void);
	void   (*Delay)(Uint32);
} AG_TimeOps;
.Ed
.Pp
.Fn Init
performs any necessary initialization.
.Fn Destroy
cleans up any allocated resources.
.Pp
The
.Fn GetTicks
operation is the backend to
.Fn AG_GetTicks
and
.Fn Delay
is the backend to
.Fn AG_Delay .
.Sh EXAMPLES
The following code uses
.Fn AG_GetTicks
to estimate the running time of a routine:
.Bd -literal -offset indent
.\" SYNTAX(c)
Uint32 t1, t2;

t1 = AG_GetTicks();
MyFunc();
t2 = AG_GetTicks();

AG_Verbose("MyFunc() ran for %u ticks\\n",
    t2 - t1);
.Ed
.Pp
The following code selects the rendering-aware time backend
.Va agTimeOps_renderer
if it's available:
.Bd -literal -offset indent
.\" SYNTAX(c)
#include <agar/config/have_clock_gettime.h>
#include <agar/config/have_pthreads.h>

#if defined(HAVE_CLOCK_GETTIME) && \\
    defined(HAVE_PTHREADS)
AG_SetTimeOps(&agTimeOps_renderer);
#endif
.Ed
.Sh SEE ALSO
.Xr AG_Intro 3 ,
.Xr AG_Timer 3
.Sh HISTORY
The
.Nm
interface first appeared in Agar 1.3.4.