Adding upstream version 16.2.11+ds.upstream/16.2.11+dsupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 111 insertions, 0 deletions

diff --git a/src/common/async/bind_handler.h b/src/common/async/bind_handler.h
new file mode 100644
index 000000000..516d8a5e8
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+++ b/src/common/async/bind_handler.h
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+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2018 Red Hat
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation. See file COPYING.
+ *
+ */
+
+#ifndef CEPH_ASYNC_BIND_HANDLER_H
+#define CEPH_ASYNC_BIND_HANDLER_H
+
+#include <tuple>
+#include <boost/asio.hpp>
+
+namespace ceph::async {
+
+/**
+ * A bound completion handler for use with boost::asio.
+ *
+ * A completion handler wrapper that allows a tuple of arguments to be forwarded
+ * to the original Handler. This is intended for use with boost::asio functions
+ * like defer(), dispatch() and post() which expect handlers which are callable
+ * with no arguments.
+ *
+ * The original Handler's associated allocator and executor are maintained.
+ *
+ * @see bind_handler
+ */
+template <typename Handler, typename Tuple>
+struct CompletionHandler {
+  Handler handler;
+  Tuple args;
+
+  CompletionHandler(Handler&& handler, Tuple&& args)
+    : handler(std::move(handler)),
+      args(std::move(args))
+  {}
+
+  void operator()() & {
+    std::apply(handler, args);
+  }
+  void operator()() const & {
+    std::apply(handler, args);
+  }
+  void operator()() && {
+    std::apply(std::move(handler), std::move(args));
+  }
+
+  using allocator_type = boost::asio::associated_allocator_t<Handler>;
+  allocator_type get_allocator() const noexcept {
+    return boost::asio::get_associated_allocator(handler);
+  }
+};
+
+} // namespace ceph::async
+
+namespace boost::asio {
+
+// specialize boost::asio::associated_executor<> for CompletionHandler
+template <typename Handler, typename Tuple, typename Executor>
+struct associated_executor<ceph::async::CompletionHandler<Handler, Tuple>, Executor> {
+  using type = boost::asio::associated_executor_t<Handler, Executor>;
+
+  static type get(const ceph::async::CompletionHandler<Handler, Tuple>& handler,
+                  const Executor& ex = Executor()) noexcept {
+    return boost::asio::get_associated_executor(handler.handler, ex);
+  }
+};
+
+} // namespace boost::asio
+
+namespace ceph::async {
+
+/**
+ * Returns a wrapped completion handler with bound arguments.
+ *
+ * Binds the given arguments to a handler, and returns a CompletionHandler that
+ * is callable with no arguments. This is similar to std::bind(), except that
+ * all arguments must be provided. Move-only argument types are supported as
+ * long as the CompletionHandler's 'operator() &&' overload is used, i.e.
+ * std::move(handler)().
+ *
+ * Example use:
+ *
+ *   // bind the arguments (5, "hello") to a callback lambda:
+ *   auto callback = [] (int a, std::string b) {};
+ *   auto handler = bind_handler(callback, 5, "hello");
+ *
+ *   // execute the bound handler on an io_context:
+ *   boost::asio::io_context context;
+ *   boost::asio::post(context, std::move(handler));
+ *   context.run();
+ *
+ * @see CompletionHandler
+ */
+template <typename Handler, typename ...Args>
+auto bind_handler(Handler&& h, Args&& ...args)
+{
+  return CompletionHandler{std::forward<Handler>(h),
+                           std::make_tuple(std::forward<Args>(args)...)};
+}
+
+} // namespace ceph::async
+
+#endif // CEPH_ASYNC_BIND_HANDLER_H