Add RAII handles for libuv handle types

The `uv_*_t` handle types are closed by `uv_close`, but the semantics
are tricky.  Calling `uv_close` may not close immediately.  Instead it
hands ownership to the uv loop to which the handle is currently
attached.  When the loop decides to close it, a callback is used to
allow the `uv_close` caller to free resources.

Provide an abstraction layer as `cm::uv_*_ptr` types corresponding to
the `uv_*_t` handle types.  Each pointer is either empty (`nullptr`)
or has an initialized handle attached to a loop.  Use move semantics
to ensure a single owner of the handle so that clients can predict
when the handle is destroyed.

1 files changed, 198 insertions, 0 deletions

diff --git a/Source/cmUVHandlePtr.cxx b/Source/cmUVHandlePtr.cxx
new file mode 100644
index 0000000..214c7b2
--- /dev/null
+++ b/Source/cmUVHandlePtr.cxx
@@ -0,0 +1,198 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#define cmUVHandlePtr_cxx
+#include "cmUVHandlePtr.h"
+
+#include <assert.h>
+#include <stdlib.h>
+
+#include "cm_thread.hxx"
+#include "cm_uv.h"
+
+namespace cm {
+
+static void close_delete(uv_handle_t* h)
+{
+  free(h);
+}
+
+template <typename T>
+static void default_delete(T* type_handle)
+{
+  auto handle = reinterpret_cast<uv_handle_t*>(type_handle);
+  if (handle) {
+    assert(!uv_is_closing(handle));
+    if (!uv_is_closing(handle)) {
+      uv_close(handle, &close_delete);
+    }
+  }
+}
+
+/**
+ * Encapsulates delete logic for a given handle type T
+ */
+template <typename T>
+struct uv_handle_deleter
+{
+  void operator()(T* type_handle) const { default_delete(type_handle); }
+};
+
+template <typename T>
+void uv_handle_ptr_base_<T>::allocate(void* data)
+{
+  reset();
+
+  /*
+    We use calloc since we know all these types are c structs
+    and we just want to 0 init them. New would do the same thing;
+    but casting from uv_handle_t to certain other types -- namely
+    uv_timer_t -- triggers a cast_align warning on certain systems.
+  */
+  handle.reset(static_cast<T*>(calloc(1, sizeof(T))), uv_handle_deleter<T>());
+  handle->data = data;
+}
+
+template <typename T>
+void uv_handle_ptr_base_<T>::reset()
+{
+  handle.reset();
+}
+
+template <typename T>
+uv_handle_ptr_base_<T>::operator uv_handle_t*()
+{
+  return reinterpret_cast<uv_handle_t*>(handle.get());
+}
+
+template <typename T>
+T* uv_handle_ptr_base_<T>::operator->() const noexcept
+{
+  return handle.get();
+}
+
+template <typename T>
+T* uv_handle_ptr_base_<T>::get() const
+{
+  return handle.get();
+}
+
+template <typename T>
+uv_handle_ptr_<T>::operator T*() const
+{
+  return this->handle.get();
+}
+
+template <>
+struct uv_handle_deleter<uv_async_t>
+{
+  /***
+  * Wile uv_async_send is itself thread-safe, there are
+  * no strong guarantees that close hasn't already been
+  * called on the handle; and that it might be deleted
+  * as the send call goes through. This mutex guards
+  * against that.
+  *
+  * The shared_ptr here is to allow for copy construction
+  * which is mandated by the standard for Deleter on
+  * shared_ptrs.
+  */
+  std::shared_ptr<cm::mutex> handleMutex;
+
+  uv_handle_deleter()
+    : handleMutex(std::make_shared<cm::mutex>())
+  {
+  }
+
+  void operator()(uv_async_t* handle)
+  {
+    cm::lock_guard<cm::mutex> lock(*handleMutex);
+    default_delete(handle);
+  }
+};
+
+void uv_async_ptr::send()
+{
+  auto deleter = std::get_deleter<uv_handle_deleter<uv_async_t>>(this->handle);
+  assert(deleter);
+
+  cm::lock_guard<cm::mutex> lock(*deleter->handleMutex);
+  if (this->handle) {
+    uv_async_send(*this);
+  }
+}
+
+int uv_async_ptr::init(uv_loop_t& loop, uv_async_cb async_cb, void* data)
+{
+  allocate(data);
+  return uv_async_init(&loop, handle.get(), async_cb);
+}
+
+template <>
+struct uv_handle_deleter<uv_signal_t>
+{
+  void operator()(uv_signal_t* handle) const
+  {
+    if (handle) {
+      uv_signal_stop(handle);
+      default_delete(handle);
+    }
+  }
+};
+
+int uv_signal_ptr::init(uv_loop_t& loop, void* data)
+{
+  allocate(data);
+  return uv_signal_init(&loop, handle.get());
+}
+
+int uv_signal_ptr::start(uv_signal_cb cb, int signum)
+{
+  assert(handle);
+  return uv_signal_start(*this, cb, signum);
+}
+
+void uv_signal_ptr::stop()
+{
+  if (handle) {
+    uv_signal_stop(*this);
+  }
+}
+
+int uv_pipe_ptr::init(uv_loop_t& loop, int ipc, void* data)
+{
+  allocate(data);
+  return uv_pipe_init(&loop, *this, ipc);
+}
+
+uv_pipe_ptr::operator uv_stream_t*() const
+{
+  return reinterpret_cast<uv_stream_t*>(handle.get());
+}
+
+uv_tty_ptr::operator uv_stream_t*() const
+{
+  return reinterpret_cast<uv_stream_t*>(handle.get());
+}
+
+int uv_tty_ptr::init(uv_loop_t& loop, int fd, int readable, void* data)
+{
+  allocate(data);
+  return uv_tty_init(&loop, *this, fd, readable);
+}
+
+template class uv_handle_ptr_base_<uv_handle_t>;
+
+#define UV_HANDLE_PTR_INSTANTIATE_EXPLICIT(NAME)                              \
+  template class uv_handle_ptr_base_<uv_##NAME##_t>;                          \
+  template class uv_handle_ptr_<uv_##NAME##_t>;
+
+UV_HANDLE_PTR_INSTANTIATE_EXPLICIT(async)
+
+UV_HANDLE_PTR_INSTANTIATE_EXPLICIT(signal)
+
+UV_HANDLE_PTR_INSTANTIATE_EXPLICIT(pipe)
+
+UV_HANDLE_PTR_INSTANTIATE_EXPLICIT(stream)
+
+UV_HANDLE_PTR_INSTANTIATE_EXPLICIT(tty)
+}