+ +

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.

+ + tip +

This function may block for longer than requested. +The actual wait time is determined by the capabilities of the +underlying system.

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.

+ + note +

If a timeout shorter than msec is set on aio using nng_aio_set_timeout, +then the sleep will wake up early, with a result code of NNG_ETIMEDOUT.

NNG Reference Manual (DRAFT)