Repo created

TMessagesProj/jni/voip/webrtc/base/parameter_pack.h

@@ -0,0 +1,91 @@
+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_PARAMETER_PACK_H_
+#define BASE_PARAMETER_PACK_H_
+
+#include <stddef.h>
+
+#include <initializer_list>
+#include <tuple>
+#include <type_traits>
+
+#include "base/template_util.h"
+#include "build/build_config.h"
+
+namespace base {
+
+// Checks if any of the elements in |ilist| is true.
+// Similar to std::any_of for the case of constexpr initializer_list.
+inline constexpr bool any_of(std::initializer_list<bool> ilist) {
+  for (auto c : ilist) {
+    if (c)
+      return true;
+  }
+  return false;
+}
+
+// Checks if all of the elements in |ilist| are true.
+// Similar to std::all_of for the case of constexpr initializer_list.
+inline constexpr bool all_of(std::initializer_list<bool> ilist) {
+  for (auto c : ilist) {
+    if (!c)
+      return false;
+  }
+  return true;
+}
+
+// Counts the elements in |ilist| that are equal to |value|.
+// Similar to std::count for the case of constexpr initializer_list.
+template <class T>
+inline constexpr size_t count(std::initializer_list<T> ilist, T value) {
+  size_t c = 0;
+  for (const auto& v : ilist) {
+    c += (v == value);
+  }
+  return c;
+}
+
+constexpr size_t pack_npos = -1;
+
+template <typename... Ts>
+struct ParameterPack {
+  // Checks if |Type| occurs in the parameter pack.
+  template <typename Type>
+  using HasType = bool_constant<any_of({std::is_same<Type, Ts>::value...})>;
+
+  // Checks if the parameter pack only contains |Type|.
+  template <typename Type>
+  using OnlyHasType = bool_constant<all_of({std::is_same<Type, Ts>::value...})>;
+
+  // Checks if |Type| occurs only once in the parameter pack.
+  template <typename Type>
+  using IsUniqueInPack =
+      bool_constant<count({std::is_same<Type, Ts>::value...}, true) == 1>;
+
+  // Returns the zero-based index of |Type| within |Pack...| or |pack_npos| if
+  // it's not within the pack.
+  template <typename Type>
+  static constexpr size_t IndexInPack() {
+    size_t index = 0;
+    for (bool value : {std::is_same<Type, Ts>::value...}) {
+      if (value)
+        return index;
+      index++;
+    }
+    return pack_npos;
+  }
+
+  // Helper for extracting the Nth type from a parameter pack.
+  template <size_t N>
+  using NthType = std::tuple_element_t<N, std::tuple<Ts...>>;
+
+  // Checks if every type in the parameter pack is the same.
+  using IsAllSameType =
+      bool_constant<all_of({std::is_same<NthType<0>, Ts>::value...})>;
+};
+
+}  // namespace base
+
+#endif  // BASE_PARAMETER_PACK_H_