Implement remote procedure calls.

src/RpcServer.cpp

@@ -0,0 +1,119 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2015. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "RpcServer.h"
+
+#include "Log.h"
+
+using namespace nt;
+
+ATOMIC_STATIC_INIT(RpcServer)
+
+RpcServer::RpcServer() {
+  m_active = false;
+  m_terminating = false;
+}
+
+RpcServer::~RpcServer() {
+  Stop();
+  m_terminating = true;
+  m_poll_cond.notify_all();
+}
+
+void RpcServer::Start() {
+  {
+    std::lock_guard<std::mutex> lock(m_mutex);
+    if (m_active) return;
+    m_active = true;
+  }
+  m_thread = std::thread(&RpcServer::ThreadMain, this);
+}
+
+void RpcServer::Stop() {
+  m_active = false;
+  if (m_thread.joinable()) {
+    // send notification so the thread terminates
+    m_call_cond.notify_one();
+    m_thread.join();
+  }
+}
+
+void RpcServer::ProcessRpc(StringRef name, std::shared_ptr<Message> msg,
+                           RpcCallback func, unsigned int conn_id,
+                           SendMsgFunc send_response) {
+  std::unique_lock<std::mutex> lock(m_mutex);
+
+  if (func)
+    m_call_queue.emplace(name, msg, func, conn_id, send_response);
+  else
+    m_poll_queue.emplace(name, msg, func, conn_id, send_response);
+
+  lock.unlock();
+
+  if (func)
+    m_call_cond.notify_one();
+  else
+    m_poll_cond.notify_one();
+}
+
+bool RpcServer::PollRpc(bool blocking, RpcCallInfo* call_info) {
+  std::unique_lock<std::mutex> lock(m_mutex);
+  while (m_poll_queue.empty()) {
+    if (!blocking || m_terminating) return false;
+    m_poll_cond.wait(lock);
+  }
+
+  auto& item = m_poll_queue.front();
+  unsigned int call_uid = (item.conn_id << 16) | item.msg->seq_num_uid();
+  call_info->rpc_id = item.msg->id();
+  call_info->call_uid = call_uid;
+  call_info->name = std::move(item.name);
+  call_info->params = item.msg->str();
+  m_response_map.insert(std::make_pair(std::make_pair(item.msg->id(), call_uid),
+                                       item.send_response));
+  m_poll_queue.pop();
+  return true;
+}
+
+void RpcServer::PostRpcResponse(unsigned int rpc_id, unsigned int call_uid,
+                                llvm::StringRef result) {
+  auto i = m_response_map.find(std::make_pair(rpc_id, call_uid));
+  if (i == m_response_map.end()) {
+    WARNING("posting RPC response to nonexistent call (or duplicate response)");
+    return;
+  }
+  (i->getSecond())(Message::RpcResponse(rpc_id, call_uid, result));
+  m_response_map.erase(i);
+}
+
+void RpcServer::ThreadMain() {
+  std::unique_lock<std::mutex> lock(m_mutex);
+  std::string tmp;
+  while (m_active) {
+    while (m_call_queue.empty()) {
+      m_call_cond.wait(lock);
+      if (!m_active) return;
+    }
+
+    while (!m_call_queue.empty()) {
+      auto item = std::move(m_call_queue.front());
+      m_call_queue.pop();
+
+      DEBUG4("rpc calling " << item.name);
+
+      if (item.name.empty() || !item.msg || !item.func || !item.send_response)
+        continue;
+
+      // Don't hold mutex during callback execution!
+      lock.unlock();
+      auto result = item.func(item.name, item.msg->str());
+      item.send_response(Message::RpcResponse(item.msg->id(),
+                                              item.msg->seq_num_uid(), result));
+      lock.lock();
+    }
+  }
+}