Time

NNG supports has support for time in the form of access to a system clock, and supporting timeouts for certain operations.

Time Type

typedef uint64_t nng_time;

The nng_time type is used to represent a clock offset from a common base time, measured in milliseconds.

The reference, or zero value, is some arbitrary point in time, most often sytem boot, but can be process start time or any other convenient reference.

All threads within a process will use the same reference time, but be aware that different processes may use a different reference time.

Duration Type

typedef int64_t nng_duration;

#define NNG_DURATION_INFINITE (-1)
#define NNG_DURATION_DEFAULT  (-2)
#define NNG_DURATION_ZERO     (0)

The nng_duration time measures a time duration in milliseconds. Normally durations are positive, but some specific negative values are reserved.

• NNG_DURATION_INFINITE: The duration essentially means forever. This is most often used with a timeout to indicate that there is no timeout, the operation should wait until it is complete, even forever.

• NNG_DURATION_DEFAULT: This special value is used in some circumstances to prevent overriding a default timeout. Some operations have a default maximum time, and this value means that the previously established default should be used. The precise meaning is context-specific.

• NNG_DURATION_ZERO: A zero length duration is used to performan an immediate poll.

Get the Current Time

nng_time nng_clock(void);

The nng_clock function returns the number of elapsed milliseconds since some arbitrary time in the past. The resolution of the clock depends on the underlying timing facilities of the system. This function may be used for timing, but applications should not expect very fine-grained values.

Wait for Duration

void nng_msleep(nng_duration msec);

The nng_msleep function blocks the calling thread for at least the specified number of milliseconds.

Wait Asynchronously

void nng_sleep_aio(nng_duration msec, nng_aio *aio);

It is possible to wait as the action on an nng_aio, which in effect acts like scheduling a callback to run after a specified period of time.

The nng_sleep_aio function provides this capability. After msec milliseconds have passed, then aio’s callback will be executed. If this sleep waits without interruption, and then completes, the result from nng_aio_result will be zero.

See Also

Asynchronous Operations, Synchronization