fixes #143 Protocols and transports should be "configurable"

This makes all the protocols and transports optional.  All
of them except ZeroTier are enabled by default, but you can
now disable them (remove from the build) with cmake options.

The test suite is modified so that tests still run as much
as they can, but skip over things caused by missing functionality
from the library (due to configuration).

Further, the constant definitions and prototypes for functions
that are specific to transports or protocols are moved into
appropriate headers, which should be included directly by
applications wishing to use these.

We have also added and improved documentation -- all of the
transports are documented, and several more man pages for
protocols have been added.  (Req/Rep and Surveyor are still
missing.)

9 files changed, 156 insertions, 8 deletions

diff --git a/src/transport/inproc/CMakeLists.txt b/src/transport/inproc/CMakeLists.txt
new file mode 100644
index 00000000..a445da85
--- /dev/null
+++ b/src/transport/inproc/CMakeLists.txt
@@ -0,0 +1,18 @@
+#
+# Copyright 2017 Garrett D'Amore <garrett@damore.org>
+# Copyright 2017 Capitar IT Group BV <info@capitar.com>
+#
+# This software 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.
+#
+
+# inproc protocol
+
+if (NNG_TRANSPORT_INPROC)
+    set(INPROC_SOURCES transport/inproc/inproc.c transport/inproc/inproc.h)
+    install(FILES inproc.h DESTINATION include/nng/transport/inproc)
+endif()
+
+set(NNG_SOURCES ${NNG_SOURCES} ${INPROC_SOURCES} PARENT_SCOPE)
diff --git a/src/transport/inproc/inproc.c b/src/transport/inproc/inproc.c
index c747f7dc..ae64263c 100644
--- a/src/transport/inproc/inproc.c
+++ b/src/transport/inproc/inproc.c
@@ -475,9 +475,8 @@ struct nni_tran nni_inproc_tran = {
 	.tran_fini    = nni_inproc_fini,
 };
 
-
 int
 nng_inproc_register(void)
 {
-        return (nni_tran_register(&nni_inproc_tran));
+	return (nni_tran_register(&nni_inproc_tran));
 }
diff --git a/src/transport/ipc/CMakeLists.txt b/src/transport/ipc/CMakeLists.txt
new file mode 100644
index 00000000..1a5496cf
--- /dev/null
+++ b/src/transport/ipc/CMakeLists.txt
@@ -0,0 +1,18 @@
+#
+# Copyright 2017 Garrett D'Amore <garrett@damore.org>
+# Copyright 2017 Capitar IT Group BV <info@capitar.com>
+#
+# This software 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.
+#
+
+# ipc protocol
+
+if (NNG_TRANSPORT_IPC)
+    set(IPC_SOURCES transport/ipc/ipc.c transport/ipc/ipc.h)
+    install(FILES ipc.h DESTINATION include/nng/transport/ipc)
+endif()
+
+set(NNG_SOURCES ${NNG_SOURCES} ${IPC_SOURCES} PARENT_SCOPE)
diff --git a/src/transport/ipc/ipc.c b/src/transport/ipc/ipc.c
index afe8afa8..c13dbd34 100644
--- a/src/transport/ipc/ipc.c
+++ b/src/transport/ipc/ipc.c
@@ -704,9 +704,7 @@ static nni_tran_ep nni_ipc_ep_ops = {
 	.ep_options = nni_ipc_ep_options,
 };
 
-// This is the IPC transport linkage, and should be the only global
-// symbol in this entire file.
-struct nni_tran nni_ipc_tran = {
+static nni_tran nni_ipc_tran = {
 	.tran_version = NNI_TRANSPORT_VERSION,
 	.tran_scheme  = "ipc",
 	.tran_ep      = &nni_ipc_ep_ops,
@@ -714,3 +712,9 @@ struct nni_tran nni_ipc_tran = {
 	.tran_init    = nni_ipc_tran_init,
 	.tran_fini    = nni_ipc_tran_fini,
 };
+
+int
+nng_ipc_register(void)
+{
+	return (nni_tran_register(&nni_ipc_tran));
+}
diff --git a/src/transport/ipc/ipc.h b/src/transport/ipc/ipc.h
new file mode 100644
index 00000000..f19762c7
--- /dev/null
+++ b/src/transport/ipc/ipc.h
@@ -0,0 +1,19 @@
+//
+// Copyright 2017 Garrett D'Amore <garrett@damore.org>
+// Copyright 2017 Capitar IT Group BV <info@capitar.com>
+//
+// This software 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.
+//
+
+#ifndef NNG_TRANSPORT_IPC_IPC_H
+#define NNG_TRANSPORT_IPC_IPC_H
+
+// ipc transport.  This is used for inter-process communication on
+// the same host computer.
+
+extern int nng_ipc_register(void);
+
+#endif // NNG_TRANSPORT_IPC_IPC_H
diff --git a/src/transport/tcp/CMakeLists.txt b/src/transport/tcp/CMakeLists.txt
new file mode 100644
index 00000000..305c357a
--- /dev/null
+++ b/src/transport/tcp/CMakeLists.txt
@@ -0,0 +1,18 @@
+#
+# Copyright 2017 Garrett D'Amore <garrett@damore.org>
+# Copyright 2017 Capitar IT Group BV <info@capitar.com>
+#
+# This software 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.
+#
+
+# TCP protocol
+
+if (NNG_TRANSPORT_TCP)
+    set(TCP_SOURCES transport/tcp/tcp.c transport/tcp/tcp.h)
+    install(FILES tcp.h DESTINATION include/nng/transport/tcp)
+endif()
+
+set(NNG_SOURCES ${NNG_SOURCES} ${TCP_SOURCES} PARENT_SCOPE)
diff --git a/src/transport/tcp/tcp.c b/src/transport/tcp/tcp.c
index 43b2890d..e33db865 100644
--- a/src/transport/tcp/tcp.c
+++ b/src/transport/tcp/tcp.c
@@ -854,9 +854,7 @@ static nni_tran_ep nni_tcp_ep_ops = {
 	.ep_options = nni_tcp_ep_options,
 };
 
-// This is the TCP transport linkage, and should be the only global
-// symbol in this entire file.
-struct nni_tran nni_tcp_tran = {
+static nni_tran nni_tcp_tran = {
 	.tran_version = NNI_TRANSPORT_VERSION,
 	.tran_scheme  = "tcp",
 	.tran_ep      = &nni_tcp_ep_ops,
@@ -864,3 +862,9 @@ struct nni_tran nni_tcp_tran = {
 	.tran_init    = nni_tcp_tran_init,
 	.tran_fini    = nni_tcp_tran_fini,
 };
+
+int
+nng_tcp_register(void)
+{
+	return (nni_tran_register(&nni_tcp_tran));
+}
diff --git a/src/transport/tcp/tcp.h b/src/transport/tcp/tcp.h
new file mode 100644
index 00000000..b4c79461
--- /dev/null
+++ b/src/transport/tcp/tcp.h
@@ -0,0 +1,18 @@
+//
+// Copyright 2017 Garrett D'Amore <garrett@damore.org>
+// Copyright 2017 Capitar IT Group BV <info@capitar.com>
+//
+// This software 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.
+//
+
+#ifndef NNG_TRANSPORT_TCP_TCP_H
+#define NNG_TRANSPORT_TCP_TCP_H
+
+// TCP transport.  This is used for communication over TCP/IP.
+
+extern int nng_tcp_register(void);
+
+#endif // NNG_TRANSPORT_TCP_TCP_H
diff --git a/src/transport/zerotier/CMakeLists.txt b/src/transport/zerotier/CMakeLists.txt
new file mode 100644
index 00000000..c1bb0c35
--- /dev/null
+++ b/src/transport/zerotier/CMakeLists.txt
@@ -0,0 +1,50 @@
+#
+# Copyright 2017 Garrett D'Amore <garrett@damore.org>
+# Copyright 2017 Capitar IT Group BV <info@capitar.com>
+#
+# This software 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.
+#
+
+# ZeroTier protocol
+
+set (NNG_TRANSPORT_ZEROTIER_SOURCE "" CACHE PATH "Location of ZeroTier source tree.")
+
+if (NNG_TRANSPORT_ZEROTIER)
+
+    # We use the libzerotiercore.a library, which is unfortunately a C++ object
+    # even though it exposes only public C symbols.  It would be extremely
+    # helpful if libzerotiercore didn't make us carry the whole C++ runtime
+    # behind us.  The user must specify the location of the ZeroTier source
+    # tree (dev branch for now, and already compiled please) by setting the
+    # NNG_ZEROTIER_SOURCE macro.
+    # NB: This needs to be the zerotierone tree, not the libzt library.
+    # This is because we don't access the API, but instead use the low
+    # level zerotiercore functionality directly.
+    # NB: As we wind up linking libzerotiercore.a into the application,
+    # this means that your application will *also* need to either be licensed
+    # under the GPLv3, or you will need to have a commercial license from
+    # ZeroTier permitting its use elsewhere.
+    
+    enable_language(CXX)
+    find_library(NNG_LIBZTCORE zerotiercore PATHS ${NNG_TRANSPORT_ZEROTIER_SOURCE})
+    if (NNG_LIBZTCORE)
+        set(CMAKE_REQUIRED_INCLUDES ${NNG_TRANSPORT_ZEROTIER_SOURCE}/include)
+        message(STATUS "C++ ${CMAKE_CXX_IMPLICIT_LINK_LIBRARIES}")
+        set(CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES} ${NNG_LIBZTCORE} ${CMAKE_CXX_IMPLICIT_LINK_LIBRARIES})
+        set(NNG_REQUIRED_LIBRARIES ${NNG_REQUIRED_LIBRARIES} ${NNG_LIBZTCORE} ${CMAKE_CXX_IMPLICIT_LINK_LIBRARIES} PARENT_SCOPE)
+        set(NNG_REQUIRED_INCLUDES ${NNG_REQUIRED_INCLUDES} ${NNG_TRANSPORT_ZEROTIER_SOURCE}/include PARENT_SCOPE)
+        nng_check_sym(ZT_Node_join ZeroTierOne.h HAVE_ZTCORE)
+    endif()
+    if (NOT HAVE_ZTCORE)
+        message (FATAL_ERROR "Cannot find ZeroTier components")
+    endif()
+    message(STATUS "Found ZeroTier at ${NNG_LIBZTCORE}")
+
+    set(ZT_SOURCES transport/zerotier/zerotier.c transport/zerotier/zerotier.h)
+    install(FILES zerotier.h DESTINATION include/nng/transport/zerotier)
+endif()
+
+set(NNG_SOURCES ${NNG_SOURCES} ${ZT_SOURCES} PARENT_SCOPE)