= nng_thread_create(3supp)
//
// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
// Copyright 2018 Capitar IT Group BV <info@capitar.com>
//
// This document is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt).  A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//

== NAME

nng_thread_create - create thread

== SYNOPSIS

[source, c]
----
#include <nng/nng.h>
#include <nng/supplemental/util/platform.h>

typedef struct nng_thread nng_thread;

int nng_thread_create(nng_thread **thrp, void (*func)(void *), void *arg);
----

== DESCRIPTION

The `nng_thread_create()` function creates a single thread of execution,
running _func_ with the argument _arg_.
The thread is started immediately.
A pointer to the thread object is returned in _thrp_.

The intention of this program is to facilitate writing parallel programs.
Threads created by this program will be based upon the underlying
threading mechanism of the system that _NNG_ is running on.
This may include use of so-called "`green threads`" or coroutines.

Using threads created by this function can make it easy to write
programs that use simple sequential execution, using functions in the
_NNG_ suite that would otherwise normally "`block`".

When the thread is no longer needed, the
xref:nng_thread_destroy.3supp.adoc[`nng_thread_destroy()`]
function should be used to reap it.
(This function will block waiting for _func_ to return.)

IMPORTANT: Thread objects created by this function may not be "`real`"
threads capable of performing blocking I/O operations using normal blocking
system calls.
If use of blocking system calls is required (not including APIs provided
by the _NNG_ library itself of course), then real OS-specific threads
should be created instead (such as with `pthread_create()` or similar
functions.)

IMPORTANT: Thread objects created by this function cannot be passed
to any system threading functions.

TIP: The system may impose limits on the number of threads that can be
created.
Typically applications should not create more than a dozen of these.
If greater concurrency or scalability is needed, consider instead using
an asynchronous model using xref:nng_aio.5.adoc[`nng_aio`] structures.

TIP: Threads can be synchronized using
xref:nng_mtx_alloc.3supp.adoc[mutexes] and
xref:nng_cv_alloc.3supp.adoc[condition variables].

== RETURN VALUES

This function returns 0 on success, and non-zero otherwise.

== ERRORS

[horizontal]
`NNG_ENOMEM`:: Insufficient free memory exists.

== SEE ALSO

[.text-left]
xref:nng_strerror.3.adoc[nng_strerror(3)],
xref:nng_cv_alloc.3supp.adoc[nng_cv_alloc(3supp)],
xref:nng_mtx_alloc.3supp.adoc[nng_mtx_alloc(3supp)],
xref:nng_thread_destroy.3supp.adoc[nng_thread_destroy(3supp)],
xref:nng_aio.5.adoc[nng_aio(5)],
xref:nng.7.adoc[nng(7)]