[wpinet] Move network portions of wpiutil into new wpinet library (#4077)

wpinet/src/main/native/cpp/EventLoopRunner.cpp

@@ -0,0 +1,91 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "wpinet/EventLoopRunner.h"
+
+#include <wpi/SmallVector.h>
+#include <wpi/condition_variable.h>
+#include <wpi/mutex.h>
+
+#include "wpinet/uv/AsyncFunction.h"
+#include "wpinet/uv/Loop.h"
+
+using namespace wpi;
+
+class EventLoopRunner::Thread : public SafeThread {
+ public:
+  using UvExecFunc = uv::AsyncFunction<void(LoopFunc)>;
+
+  Thread() : m_loop(uv::Loop::Create()) {
+    // set up async handles
+    if (!m_loop) {
+      return;
+    }
+
+    // run function
+    m_doExec = UvExecFunc::Create(
+        m_loop, [loop = m_loop.get()](auto out, LoopFunc func) {
+          func(*loop);
+          out.set_value();
+        });
+  }
+
+  void Main() override {
+    if (m_loop) {
+      m_loop->Run();
+    }
+  }
+
+  // the loop
+  std::shared_ptr<uv::Loop> m_loop;
+
+  // run function
+  std::weak_ptr<UvExecFunc> m_doExec;
+};
+
+EventLoopRunner::EventLoopRunner() {
+  m_owner.Start();
+}
+
+EventLoopRunner::~EventLoopRunner() {
+  Stop();
+}
+
+void EventLoopRunner::Stop() {
+  ExecAsync([](uv::Loop& loop) {
+    // close all handles; this will (eventually) stop the loop
+    loop.Walk([](uv::Handle& h) {
+      h.SetLoopClosing(true);
+      h.Close();
+    });
+  });
+  m_owner.Join();
+}
+
+void EventLoopRunner::ExecAsync(LoopFunc func) {
+  if (auto thr = m_owner.GetThread()) {
+    if (auto doExec = thr->m_doExec.lock()) {
+      doExec->Call(std::move(func));
+    }
+  }
+}
+
+void EventLoopRunner::ExecSync(LoopFunc func) {
+  wpi::future<void> f;
+  if (auto thr = m_owner.GetThread()) {
+    if (auto doExec = thr->m_doExec.lock()) {
+      f = doExec->Call(std::move(func));
+    }
+  }
+  if (f.valid()) {
+    f.wait();
+  }
+}
+
+std::shared_ptr<uv::Loop> EventLoopRunner::GetLoop() {
+  if (auto thr = m_owner.GetThread()) {
+    return thr->m_loop;
+  }
+  return nullptr;
+}