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Implement Sys_LongTime and wrap it with Sys_DoubleTime.

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Sys_LongTime returns time in microseconds as a 64-bit int. Sys_DoubleTime
uses Sys_LongTime, converts to double and offsets 0 time by 4G (2**32).
This gives us consistent sub-microsecond precision for a very long time.

See http://randomascii.wordpress.com/2012/02/13/dont-store-that-in-a-float/
This commit is contained in:
Bill Currie 2013-02-27 14:29:28 +09:00
parent 32b76b3576
commit 8e86ce9de9
2 changed files with 23 additions and 18 deletions
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1
include/QF/sys.h
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@ -73,6 +73,7 @@ void Sys_Error (const char *error, ...) __attribute__((format(printf,1,2), noret
void Sys_Quit (void) __attribute__((noreturn));
void Sys_Shutdown (void);
void Sys_RegisterShutdown (void (*func) (void));
int64_t Sys_LongTime (void);
double Sys_DoubleTime (void);
void Sys_TimeOfDay(date_t *date);

40
libs/util/sys.c
View file

@ -305,8 +305,8 @@ Sys_MaskPrintf (int mask, const char *fmt, ...)
va_end (args);
}
VISIBLE double
Sys_DoubleTime (void)
VISIBLE int64_t
Sys_LongTime (void)
{
static qboolean first = true;
#ifdef _WIN32
@ -332,13 +332,13 @@ Sys_DoubleTime (void)
# else
// MH's solution combining timeGetTime for stability and
// QueryPerformanceCounter for precision.
static __int64 qpcfreq = 0;
static __int64 currqpccount = 0;
static __int64 lastqpccount = 0;
static double qpcfudge = 0;
DWORD currtime = 0;
static DWORD lasttime = 0;
static DWORD starttime = 0;
static int64_t qpcfreq = 0;
static int64_t currqpccount = 0;
static int64_t lastqpccount = 0;
static int64_t qpcfudge = 0;
int64_t currtime = 0;
static int64_t lasttime = 0;
static int64_t starttime = 0;
if (first) {
timeBeginPeriod (1);
@ -360,9 +360,8 @@ Sys_DoubleTime (void)
// store back times and calc a fudge factor as timeGetTime can
// overshoot on a sub-millisecond scale
qpcfudge = (((double) (currqpccount - lastqpccount)
/ (double) qpcfreq))
- ((double) (currtime - lasttime) * 0.001);
qpcfudge = (( (currqpccount - lastqpccount) * 1000000 / qpcfreq))
- ((currtime - lasttime) * 1000);
lastqpccount = currqpccount;
lasttime = currtime;
} else {
@ -370,19 +369,18 @@ Sys_DoubleTime (void)
}
// the final time is the base from timeGetTime plus an addition from QPC
return ((double) (currtime - starttime) * 0.001)
+ ((double) (currqpccount - lastqpccount) / (double) qpcfreq)
+ qpcfudge;
return (((currtime - starttime) * 1000)
+ ((currqpccount - lastqpccount) * 1000000 / qpcfreq) + qpcfudge);
# endif
#else
struct timeval tp;
struct timezone tzp;
double now;
static double start_time;
int64_t now;
static int64_t start_time;
gettimeofday (&tp, &tzp);
now = tp.tv_sec + tp.tv_usec / 1e6;
now = tp.tv_sec * 1000000 + tp.tv_usec;
if (first) {
first = false;
@ -393,6 +391,12 @@ Sys_DoubleTime (void)
#endif
}
VISIBLE double
Sys_DoubleTime (void)
{
return (__INT64_C (4294967296000000) + Sys_LongTime ()) / 1e6;
}
VISIBLE void
Sys_TimeOfDay (date_t *date)
{