uv: Add reuse to pipe (#1577)

Needed for a reconnection API

wpiutil/src/main/native/cpp/uv/Pipe.cpp

@@ -25,6 +25,25 @@ std::shared_ptr<Pipe> Pipe::Create(Loop& loop, bool ipc) {
   return h;
 }
 
+void Pipe::Reuse(std::function<void()> callback, bool ipc) {
+  if (IsClosing()) return;
+  if (!m_reuseData) m_reuseData = std::make_unique<ReuseData>();
+  m_reuseData->callback = callback;
+  m_reuseData->ipc = ipc;
+  uv_close(GetRawHandle(), [](uv_handle_t* handle) {
+    Pipe& h = *static_cast<Pipe*>(handle->data);
+    if (!h.m_reuseData) return;
+    auto data = std::move(h.m_reuseData);
+    auto err =
+        uv_pipe_init(h.GetLoopRef().GetRaw(), h.GetRaw(), data->ipc ? 1 : 0);
+    if (err < 0) {
+      h.ReportError(err);
+      return;
+    }
+    data->callback();
+  });
+}
+
 std::shared_ptr<Pipe> Pipe::Accept() {
   auto client = Create(GetLoopRef(), GetRaw()->ipc);
   if (!client) return nullptr;

wpiutil/src/main/native/include/wpi/uv/Pipe.h

@@ -56,6 +56,18 @@ class Pipe final : public NetworkStreamImpl<Pipe, uv_pipe_t> {
     return Create(*loop, ipc);
   }
 
+  /**
+   * Reuse this handle.  This closes the handle, and after the close completes,
+   * reinitializes it (identically to Create) and calls the provided callback.
+   * Unlike Close(), it does NOT emit the closed signal, however, IsClosing()
+   * will return true until the callback is called.  This does nothing if
+   * IsClosing() is true (e.g. if Close() was called).
+   *
+   * @param ipc IPC
+   * @param callback Callback
+   */
+  void Reuse(std::function<void()> callback, bool ipc = false);
+
   /**
    * Accept incoming connection.
    *
@@ -176,6 +188,12 @@ class Pipe final : public NetworkStreamImpl<Pipe, uv_pipe_t> {
 
  private:
   Pipe* DoAccept() override;
+
+  struct ReuseData {
+    std::function<void()> callback;
+    bool ipc;
+  };
+  std::unique_ptr<ReuseData> m_reuseData;
 };
 
 /**