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os: Add os_precise_sleeper.

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Mostly to be able to use a timer on Windows.
This commit is contained in:
Ryan Pavlik 2021-03-30 11:20:39 -05:00
parent 47bf17a0cc
commit aa3d1c1f6a
1 changed files with 71 additions and 1 deletions
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72
src/xrt/auxiliary/os/os_time.h
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@ -81,7 +81,77 @@ os_nanosleep(int32_t nsec)
#endif
}
#ifdef XRT_HAVE_TIMESPEC
/*!
* @brief A structure for storing state as needed for more precise sleeping, mostly for compositor use.
* @ingroup aux_os_time
*/
struct os_precise_sleeper
{
#if defined(XRT_OS_WINDOWS)
HANDLE timer;
#else
int unused_;
#endif
};
/*!
* @brief Initialize members of @ref os_precise_sleeper.
* @public @memberof os_precise_sleeper
*/
static inline void
os_precise_sleeper_init(struct os_precise_sleeper *ops)
{
#if defined(XRT_OS_WINDOWS)
ops->timer = CreateWaitableTimer(NULL, TRUE, NULL);
#endif
}
/*!
* @brief De-initialize members of @ref os_precise_sleeper, and free resources, without actually freeing the given
* pointer.
* @public @memberof os_precise_sleeper
*/
static inline void
os_precise_sleeper_deinit(struct os_precise_sleeper *ops)
{
#if defined(XRT_OS_WINDOWS)
if (ops->timer) {
CloseHandle(ops->timer);
ops->timer = NULL;
}
#endif
}
/*!
* @brief Sleep the given number of nanoseconds, trying harder to be precise.
*
* On some platforms, there is no way to improve sleep precision easily with some OS-specific state, so we just forward
* to os_nanosleep().
*
* Note that on all platforms, the system scheduler has the final say.
*
* @public @memberof os_precise_sleeper
*/
static inline void
os_precise_sleeper_nanosleep(struct os_precise_sleeper *ops, int32_t nsec)
{
#if defined(XRT_OS_WINDOWS)
if (ops->timer) {
LARGE_INTEGER timeperiod;
timeperiod.QuadPart = -nsec;
if (SetWaitableTimer(ops->timer, &timeperiod, 0, NULL, NULL, FALSE)) {
// OK we could set up the timer, now let's wait.
WaitForSingleObject(ops->timer, INFINITE);
return;
}
}
#endif
// If we fall through from an implementation, or there's no implementation needed for a platform, we just
// delegate to the regular os_nanosleep.
os_nanosleep(nsec);
}
#if defined(XRT_HAVE_TIMESPEC)
/*!
* @brief Convert a timespec struct to nanoseconds.
*