Add documentation for supplemental functions.

This includes platform portability stuff like mutexes and threads,
etc.  While here we fixed a problem with nng_opts_parse and we
addressed the type of the platform API.

1 files changed, 85 insertions, 0 deletions

diff --git a/docs/man/nng_thread_create.3supp.adoc b/docs/man/nng_thread_create.3supp.adoc
new file mode 100644
index 00000000..359dabab
--- /dev/null
+++ b/docs/man/nng_thread_create.3supp.adoc
@@ -0,0 +1,85 @@
+= 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
+<<nng_thread_destroy.3supp#,`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 few dozen of these.
+If greater concurrency or scalability is needed, consider instead using
+an asynchronous model using <<nng_aio.5#,`nng_aio`>> structures.
+
+TIP: Threads can be synchronized using
+<<nng_mtx_alloc.3supp#,mutexes>> and
+<<nng_cv_alloc.3supp#,condition variables>>.
+
+== RETURN VALUES
+
+This function returns 0 on success, and non-zero otherwise.
+
+== ERRORS
+
+`NNG_ENOMEM`:: Insufficient free memory exists.
+
+== SEE ALSO
+
+<<nng_strerror.3#,nng_strerror(3)>>,
+<<nng_cv_alloc.3supp#,nng_cv_alloc(3supp)>>,
+<<nng_mtx_alloc.3supp#,nng_mtx_alloc(3supp)>>,
+<<nng_thread_destroy.3supp#,nng_thread_destroy(3supp)>>,
+<<nng_aio.5#,nng_aio(5)>>,
+<<nng.7#,nng(7)>>