aiie/sdl/timeutil.h

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4.1 KiB
C
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#include <time.h>
#include <mach/mach_time.h>
// Derived from
// http://stackoverflow.com/questions/5167269/clock-gettime-alternative-in-mac-os-x
#define ORWL_NANO (+1.0E-9)
#define ORWL_GIGA UINT64_C(1000000000)
#define NANOSECONDS_PER_SECOND 1000000000UL
#define CYCLES_PER_SECOND 1023000UL
static double orwl_timebase = 0.0;
static uint64_t orwl_timestart = 0;
static void _init_darwin_shim(void) {
mach_timebase_info_data_t tb = { 0 };
mach_timebase_info(&tb);
orwl_timebase = tb.numer;
orwl_timebase /= tb.denom;
orwl_timestart = mach_absolute_time();
}
static int do_gettime(struct timespec *tp) {
double diff = (mach_absolute_time() - orwl_timestart) * orwl_timebase;
tp->tv_sec = diff * ORWL_NANO;
tp->tv_nsec = diff - (tp->tv_sec * ORWL_GIGA);
return 0;
}
// adds the number of nanoseconds that 'cycles' takes to *start and
// returns it in *out
static void timespec_add_cycles(struct timespec *start,
int32_t cycles,
struct timespec *out)
{
out->tv_sec = start->tv_sec;
out->tv_nsec = start->tv_nsec;
uint64_t nanosToAdd = (double)((double)cycles * (double) (NANOSECONDS_PER_SECOND) / (double)1023000);
out->tv_sec += (nanosToAdd / NANOSECONDS_PER_SECOND);
out->tv_nsec += (nanosToAdd % NANOSECONDS_PER_SECOND);
if (out->tv_nsec >= NANOSECONDS_PER_SECOND) {
out->tv_sec++ ;
out->tv_nsec -= NANOSECONDS_PER_SECOND;
}
}
static unsigned long cycles_since_time(struct timespec *start)
{
unsigned long ret = start->tv_sec * CYCLES_PER_SECOND;
ret += (double)((double)start->tv_nsec * (double)0.001023 + (double) 0.01); // 0.01 for rounding error; one cycle ~= 977517nS, and 977517 * .000001023 is only 0.999999891.
return ret;
}
// adds the number of microseconds given to *start and
// returns it in *out
static void timespec_add_us(struct timespec *start,
uint64_t micros,
struct timespec *out)
{
out->tv_sec = start->tv_sec;
out->tv_nsec = start->tv_nsec;
uint64_t nanosToAdd = micros * 1000L;
out->tv_sec += (nanosToAdd / NANOSECONDS_PER_SECOND);
out->tv_nsec += (nanosToAdd % NANOSECONDS_PER_SECOND);
if (out->tv_nsec >= 1000000000L) {
out->tv_sec++ ;
out->tv_nsec -= 1000000000L;
}
}
static void timespec_diff(struct timespec *start,
struct timespec *end,
struct timespec *diff,
bool *negative) {
struct timespec t;
if (negative)
{
*negative = false;
}
// if start > end, swizzle...
if ( (start->tv_sec > end->tv_sec) || ((start->tv_sec == end->tv_sec) && (start->tv_nsec > end->tv_nsec)) )
{
t=*start;
*start=*end;
*end=t;
if (negative)
{
*negative = true;
}
}
// assuming time_t is signed ...
if (end->tv_nsec < start->tv_nsec)
{
t.tv_sec = end->tv_sec - start->tv_sec - 1;
t.tv_nsec = 1000000000 + end->tv_nsec - start->tv_nsec;
}
else
{
t.tv_sec = end->tv_sec - start->tv_sec;
t.tv_nsec = end->tv_nsec - start->tv_nsec;
}
diff->tv_sec = t.tv_sec;
diff->tv_nsec = t.tv_nsec;
}
// tsCompare: return -1, 0, 1 for (a < b), (a == b), (a > b)
static int8_t tsCompare(struct timespec *A, struct timespec *B)
{
if (A->tv_sec < B->tv_sec)
return -1;
if (A->tv_sec > B->tv_sec)
return 1;
if (A->tv_nsec < B->tv_nsec)
return -1;
if (A->tv_nsec > B->tv_nsec)
return 1;
return 0;
}
// return time1 - time2. If time1 <= time2, then return 0.
static struct timespec tsSubtract(struct timespec time1, struct timespec time2)
{
struct timespec result;
if ((time1.tv_sec < time2.tv_sec) ||
((time1.tv_sec == time2.tv_sec) &&
(time1.tv_nsec <= time2.tv_nsec))) {/* TIME1 <= TIME2? */
result.tv_sec = result.tv_nsec = 0 ;
} else {/* TIME1 > TIME2 */
result.tv_sec = time1.tv_sec - time2.tv_sec ;
if (time1.tv_nsec < time2.tv_nsec) {
result.tv_nsec = time1.tv_nsec + 1000000000L - time2.tv_nsec ;
result.tv_sec-- ;/* Borrow a second. */
} else {
result.tv_nsec = time1.tv_nsec - time2.tv_nsec ;
}
}
return (result) ;
}