nng_cv_until()

NAME

nng_cv_until — wait for condition or timeout

SYNOPSIS

#include <nng/nng.h>
#include <nng/supplemental/util/platform.h>

int nng_cv_until(nng_cv *cv, nng_time when);

The nng_cv_until() waits until either the condition variable cv is signaled by another thread calling either nng_cv_wake() or nng_cv_wake1(), or the system clock (as tracked by nng_clock()) reaches when.

The caller must have have ownership of the mutex that was used when cv was allocated. This function will drop the ownership of that mutex, and reacquire it atomically just before returning to the caller. (The waiting is done without holding the mutex.)

Spurious wakeups can occur.

tip

Any condition may be used or checked, but the condition must be checked, as it is possible for this function to wake up spuriously. The best way to do this is inside a loop that repeats until the condition tests for true.

EXAMPLE

The following example demonstrates use of this function:

Example 1: Waiting for the condition

    expire = nng_clock() + 1000; // 1 second in the future
    nng_mtx_lock(m);  // assume cv was allocated using m
    while (!condition_true) {
        if (nng_cv_until(cv, expire) == NNG_ETIMEDOUT) {
            printf("Time out reached!\n");
            break;
        }
    }
    // condition_true is true
    nng_mtx_unlock(m);

Example 2: Signaling the condition

    nng_mtx_lock(m);
    condition_true = true;
    nng_cv_wake(cv);
    nng_mtx_unlock(m);

NNG Reference Manual