Convert nng_socket_pair.

Also some cleanups on the organization of the mdbook.

docs/man/libnng.3.adoc

@@ -297,7 +297,7 @@ as a convenience to aid in creating portable applications.
 // |xref:nng_mtx_unlock.3supp.adoc[nng_mtx_unlock()]|unlock mutex
 |xref:nng_opts_parse.3supp.adoc[nng_opts_parse()]|parse command line options
 // |xref:nng_random.3supp.adoc[nng_random()]|get random number
-|xref:nng_socket_pair.3supp.adoc[nng_socket_pair()]|create connected pair of BSD sockets
+// |xref:nng_socket_pair.3supp.adoc[nng_socket_pair()]|create connected pair of BSD sockets
 |xref:nng_thread_create.3supp.adoc[nng_thread_create()]|create thread
 |xref:nng_thread_destroy.3supp.adoc[nng_thread_destroy()]|reap thread
 |xref:nng_thread_set_name.3supp.adoc[nng_thread_set_name()]|set thread name

docs/ref/SUMMARY.md

@@ -1,8 +1,8 @@
 # Summary
 
-- [API](./api.md)
+- [API](./api/index.md)
 
-  - [Threading Functions](./api/thr/index.md)
+  - [Threading and Synchronization](./api/thr/index.md)
 
     - [nng_cv](./api/thr/nng_cv.md)
     - [nng_mtx](./api/thr/nng_mtx.md)
@@ -14,6 +14,7 @@
     - [nng_id_map](./api/util/nng_id_map.md)
     - [nng_msleep](./api/util/nng_msleep.md)
     - [nng_random](./api/util/nng_random.md)
+    - [nng_socket_pair](./api/util/nng_socket_pair.md)
     - [nng_strdup](./api/util/nng_strdup.md)
     - [nng_strerror](./api/util/nng_strerror.md)
     - [nng_version](./api/util/nng_version.md)

docs/ref/api/index.md

@@ -0,0 +1,4 @@
+# API
+
+- [Threading and Synchronization](api/thr/)
+- [Utility Functions](api/util/)

docs/ref/api/thr/index.md

@@ -1,4 +1,8 @@
-# Threading Functions
+# Threading and Synchronization
+
+These interfaces are likely to be useful when implementing concurrent designs.
+Furthermore, because NNG itself is based on concurrency, the synchronization primitives
+are likely to be useful in callback functions and similar situations.
 
 - [nng_cv](nng_cv.md)
 - [nng_mtx](nng_mtx.md)

docs/ref/api/util/index.md

@@ -2,14 +2,15 @@
 
 This section documents various utility functions that may help
 with application portability. These are not fundamental to NNG
-or Scalability Protocols, but we find them useful for a variety
+or Scalability Protocols, but they are likely useful for a variety
 of other uses.
 
-- [nng_alloc](nng_alloc.md)
-- [nng_clock](nng_clock.md)
-- [nng_id_map](nng_id_map.md)
-- [nng_msleep](nng_msleep.md)
-- [nng_random](nng_random.md)
-- [nng_strdup](nng_strdup.md)
-- [nng_strerror](nng_strerror.md)
-- [nng_version](nng_version.md)
+- [nng_alloc](nng_alloc.md) --- allocate memory
+- [nng_clock](nng_clock.md) --- get time
+- [nng_id_map](nng_id_map.md) --- identifier based mapping table
+- [nng_msleep](nng_msleep.md) --- sleep milliseconds
+- [nng_random](nng_random.md) --- get random number
+- [nng_socket_pair](nng_socket_pair.md) --- create a connected pair of BSD sockets
+- [nng_strdup](nng_strdup.md) --- duplicate string
+- [nng_strerror](nng_strerror.md) --- return an error description
+- [nng_version](nng_version.md) --- report library version

docs/ref/tran/socket.md

@@ -4,10 +4,10 @@
 
 The {{i:_socket_ transport}} supports communication between
 peers across arbitrary BSD sockets, such as those that are
-created with [`nng_socket_pair()`][nng_socket_pair].
+created with [`nng_socket_pair`][nng_socket_pair].
 
 This transport only supports [listeners][listener],
-using [`nng_listener_create()`][nng_listener_create].
+using [`nng_listener_create`][nng_listener_create].
 
 > [!NOTE]
 > Attempts to create [dialers][dialer] using this transport will result in `NNG_ENOTSUP`.
@@ -63,7 +63,7 @@ Additionally, the following options may be supported on pipes when the platform
 [dialer]: [TODO.md]
 [nng_sockaddr]: [TODO.md]
 [nng_listener_create]: [TODO.md]
-[nng_socket_pair]: [TODO.md]
+[nng_socket_pair]: ../../api/util/nng_socket_pair.md
 [NNG_OPT_LOCADDR]: [TODO.md]
 [NNG_OPT_REMADDR]: [TODO.md]
 [NNG_OPT_URL]: [TODO.md]