aboutsummaryrefslogtreecommitdiff
path: root/src/common/callback.hpp
diff options
context:
space:
mode:
Diffstat (limited to 'src/common/callback.hpp')
-rw-r--r--src/common/callback.hpp97
1 files changed, 97 insertions, 0 deletions
diff --git a/src/common/callback.hpp b/src/common/callback.hpp
new file mode 100644
index 00000000..ac5ff1c5
--- /dev/null
+++ b/src/common/callback.hpp
@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2021, The OpenThread Authors.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the copyright holder nor the
+ * names of its contributors may be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef OTBR_COMMON_CALLBACK_HPP_
+#define OTBR_COMMON_CALLBACK_HPP_
+
+#include <functional>
+#include <type_traits>
+
+namespace otbr {
+
+template <class T> class OnceCallback;
+
+/**
+ * A callback which can be invoked at most once.
+ *
+ * IsNull is guaranteed to return true once the callback has been invoked.
+ *
+ * Example usage:
+ * OnceCallback<int(int)> square([](int x) { return x * x; });
+ * std::move(square)(5); // Returns 25.
+ * std::move(square)(6); // Crashes since `square` has already run.
+ * square(7); // Compiling error.
+ *
+ * Inspired by Chromium base::OnceCallback
+ * (https://chromium.googlesource.com/chromium/src.git/+/refs/heads/main/base/callback.h).
+ *
+ */
+template <typename R, typename... Args> class OnceCallback<R(Args...)>
+{
+public:
+ // Constructs a new `OnceCallback` instance with a callable.
+ //
+ // This constructor is for matching std::function<> and lambda and the
+ // `std::enable_if_t` check is only required for working around gcc 4.x
+ // compiling issue which trying to instantiate this template constructor
+ // for use cases like `::mOnceCallback(aOnceCallback)`.
+ template <typename T, typename = typename std::enable_if<!std::is_same<OnceCallback, T>::value>::type>
+ OnceCallback(T &&func)
+ : mFunc(std::forward<T>(func))
+ {
+ }
+
+ OnceCallback(const OnceCallback &) = delete;
+ OnceCallback &operator=(const OnceCallback &) = delete;
+ OnceCallback(OnceCallback &&) = default;
+ OnceCallback &operator=(OnceCallback &&) = default;
+
+ R operator()(Args...) const &
+ {
+ static_assert(!sizeof(*this), "OnceCallback::() can only be invoked on a non-const "
+ "rvalue, i.e. std::move(callback)().");
+ }
+
+ R operator()(Args... args) &&
+ {
+ // Move `this` to a local variable to clear internal state
+ // before invoking the callback function.
+ OnceCallback cb = std::move(*this);
+
+ return cb.mFunc(std::forward<Args>(args)...);
+ }
+
+ bool IsNull() const { return mFunc == nullptr; }
+
+private:
+ std::function<R(Args...)> mFunc;
+};
+
+} // namespace otbr
+
+#endif // OTBR_COMMON_CALLBACK_HPP_