= nng_cv_wait(3supp)
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//
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// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
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// Copyright 2018 Capitar IT Group BV <info@capitar.com>
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//
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// This document is supplied under the terms of the MIT License, a
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// copy of which should be located in the distribution where this
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// file was obtained (LICENSE.txt). A copy of the license may also be
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// found online at https://opensource.org/licenses/MIT.
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//
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== NAME
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nng_cv_wait - wait for condition
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== SYNOPSIS
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[source, c]
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----
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#include <nng/nng.h>
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#include <nng/supplemental/util/platform.h>
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void nng_cv_wait(nng_cv *cv);
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----
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== DESCRIPTION
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The `nng_cv_wait()` waits for the condition variable _cv_ to be signaled
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by another thread calling either xref:nng_cv_wake.3supp.adoc[`nng_cv_wake()`] or
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xref:nng_cv_wake1.3supp.adoc[`nng_cv_wake1()`].
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The caller must have have ownership of the mutex that was used when
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_cv_ was allocated.
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This function will drop the ownership of that mutex, and reacquire it
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atomically just before returning to the caller.
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(The waiting is done without holding the mutex.)
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NOTE: Any condition may be used or checked, but the condition must be
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checked, as it is possible for this function to wake up spuriously.
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The best way to do this is inside a loop that repeats until the condition
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tests for true.
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== EXAMPLE
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The following example demonstrates use of this function:
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.Example 1: Waiting for the condition
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[source, c]
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----
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nng_mtx_lock(m); // assume cv was allocated using m
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while (!condition_true) {
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nng_cv_wait(cv);
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}
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// condition_true is true
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nng_mtx_unlock(m);
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----
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.Example 2: Signaling the condition
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[source, c]
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----
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nng_mtx_lock(m);
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condition_true = true;
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nng_cv_wake(cv);
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nng_mtx_unlock(m);
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----
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== RETURN VALUES
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None.
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== ERRORS
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None.
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== SEE ALSO
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[.text-left]
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xref:nng_cv_alloc.3supp.adoc[nng_cv_alloc(3supp)],
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xref:nng_cv_until.3supp.adoc[nng_cv_until(3supp)],
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xref:nng_cv_wake.3supp.adoc[nng_cv_wake(3supp)],
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xref:nng_cv_wake1.3supp.adoc[nng_cv_wake1(3supp)],
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xref:nng_mtx_alloc.3supp.adoc[nng_mtx_alloc(3supp)],
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xref:nng_mtx_lock.3supp.adoc[nng_mtx_lock(3supp)],
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xref:nng_mtx_unlock.3supp.adoc[nng_mtx_unlock(3supp)],
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xref:nng.7.adoc[nng(7)]
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