add example RPC server/client

example/rpc_server.cpp

@@ -0,0 +1,91 @@
+/**
+ * Copyright - See the COPYRIGHT that is included with this distribution.
+ * pvxs is distributed subject to a Software License Agreement found
+ * in file LICENSE that is included with this distribution.
+ */
+/**
+ * Serves a single PV name.
+ * Only implements an RPC operation which adds two numbers.
+ *
+ *   ./rpc_server mypv
+ *
+ * Then in another shell run:
+ *
+ *   pvxcall mypv lhs=1 rhs=2
+ */
+
+#include <iostream>
+
+#include <epicsTime.h>
+
+#include <pvxs/sharedpv.h>
+#include <pvxs/server.h>
+#include <pvxs/nt.h>
+#include <pvxs/log.h>
+
+using namespace pvxs;
+
+int main(int argc, char* argv[])
+{
+    if(argc<=1) {
+        std::cerr<<"Usage: "<<argv[0]<<" <pvname>\n";
+        return 1;
+    }
+
+    // Read $PVXS_LOG from process environment and update
+    // logging configuration.  eg.
+    //    export PVXS_LOG=*=DEBUG
+    // makes a lot of noise.
+    logger_config_env();
+
+    // Actually creating the PV.
+    // buildReadonly() installs a default onPut() handler which
+    // rejects all Put operations.
+    server::SharedPV pv(server::SharedPV::buildReadonly());
+
+    // Provide an RPC handler
+    pv.onRPC([](server::SharedPV& pv,
+                std::unique_ptr<server::ExecOp>&& op,
+                Value&& top)
+    {
+        // Callback
+
+        // assume arguments encoded NTURI
+        auto rhs = top["query.rhs"].as<double>();
+        auto lhs = top["query.lhs"].as<double>();
+
+        auto reply(nt::NTScalar{TypeCode::Float64}.create());
+        reply["value"] = lhs + rhs;
+
+        op->reply(reply);
+        // Scale-able applications may reply outside of this callback,
+        // and from another thread.
+    });
+
+    // (Optional) Provide a data type for the PV.
+    // Provides a hint to users that Get, Put, or Monitor is not
+    // meaningful for this PV
+    Value initial = nt::NTScalar{TypeCode::String}.create();
+    initial["value"] = "RPC only";
+    pv.open(initial);
+
+    // Build server which will serve this PV
+    // Configure using process environment.
+    server::Server serv = server::Config::fromEnv()
+            .build()
+            .addPV(argv[1], pv);
+
+    // (optional) Print the configuration this server is using
+    // with any auto-address list expanded.
+    std::cout<<"Effective config\n"<<serv.config();
+
+    std::cout<<"Running\n";
+
+    // Start server and run forever, or until Ctrl+c is pressed.
+    // Returns on SIGINT or SIGTERM
+    serv.run();
+
+    std::cout<<"Done\n";
+
+    return 0;
+}