Rename our allwpilib (which is now 2020) to not have 2019 in the name

Change-Id: I3c07f85ed32ab8b97db765a9b43f2a6ce7da964a
diff --git a/wpiutil/src/main/native/cpp/SafeThread.cpp b/wpiutil/src/main/native/cpp/SafeThread.cpp
new file mode 100644
index 0000000..3a906bd
--- /dev/null
+++ b/wpiutil/src/main/native/cpp/SafeThread.cpp
@@ -0,0 +1,86 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2015-2019 FIRST. 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 "wpi/SafeThread.h"
+
+using namespace wpi;
+
+detail::SafeThreadProxyBase::SafeThreadProxyBase(
+    std::shared_ptr<SafeThread> thr)
+    : m_thread(std::move(thr)) {
+  if (!m_thread) return;
+  m_lock = std::unique_lock<wpi::mutex>(m_thread->m_mutex);
+  if (!m_thread->m_active) {
+    m_lock.unlock();
+    m_thread = nullptr;
+    return;
+  }
+}
+
+detail::SafeThreadOwnerBase::~SafeThreadOwnerBase() {
+  if (m_joinAtExit)
+    Join();
+  else
+    Stop();
+}
+
+void detail::SafeThreadOwnerBase::Start(std::shared_ptr<SafeThread> thr) {
+  std::scoped_lock lock(m_mutex);
+  if (auto thr = m_thread.lock()) return;
+  m_stdThread = std::thread([=] { thr->Main(); });
+  thr->m_threadId = m_stdThread.get_id();
+  m_thread = thr;
+}
+
+void detail::SafeThreadOwnerBase::Stop() {
+  std::scoped_lock lock(m_mutex);
+  if (auto thr = m_thread.lock()) {
+    thr->m_active = false;
+    thr->m_cond.notify_all();
+    m_thread.reset();
+  }
+  if (m_stdThread.joinable()) m_stdThread.detach();
+}
+
+void detail::SafeThreadOwnerBase::Join() {
+  std::unique_lock lock(m_mutex);
+  if (auto thr = m_thread.lock()) {
+    auto stdThread = std::move(m_stdThread);
+    m_thread.reset();
+    lock.unlock();
+    thr->m_active = false;
+    thr->m_cond.notify_all();
+    stdThread.join();
+  } else if (m_stdThread.joinable()) {
+    m_stdThread.detach();
+  }
+}
+
+void detail::swap(SafeThreadOwnerBase& lhs, SafeThreadOwnerBase& rhs) noexcept {
+  using std::swap;
+  if (&lhs == &rhs) return;
+  std::scoped_lock lock(lhs.m_mutex, rhs.m_mutex);
+  std::swap(lhs.m_stdThread, rhs.m_stdThread);
+  std::swap(lhs.m_thread, rhs.m_thread);
+}
+
+detail::SafeThreadOwnerBase::operator bool() const {
+  std::scoped_lock lock(m_mutex);
+  return !m_thread.expired();
+}
+
+std::thread::native_handle_type
+detail::SafeThreadOwnerBase::GetNativeThreadHandle() {
+  std::scoped_lock lock(m_mutex);
+  return m_stdThread.native_handle();
+}
+
+std::shared_ptr<SafeThread> detail::SafeThreadOwnerBase::GetThreadSharedPtr()
+    const {
+  std::scoped_lock lock(m_mutex);
+  return m_thread.lock();
+}