exec::stopped_by

include/stdexec/__detail/__matching_completion_signature.hpp

@@ -0,0 +1,104 @@
+/*
+ * SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ *                         Copyright (c) 2026 Robert Leahy. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ *
+ * Licensed under the Apache License, Version 2.0 with LLVM Exceptions (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://llvm.org/LICENSE.txt
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include "__completion_signatures.hpp"
+
+#include <cstddef>
+#include <type_traits>
+
+namespace STDEXEC
+{
+
+  namespace __matching_completion_signature
+  {
+
+    template <typename>
+    struct __canonicalize;
+
+    template <typename _Tag, typename... _Args>
+    struct __canonicalize<_Tag(_Args...)>
+    {
+      using type = _Tag(_Args&&...);
+    };
+
+    template <typename _Signature>
+    using __canonicalize_t = typename __canonicalize<_Signature>::type;
+
+    template <typename _Needle, typename _Signature>
+    inline constexpr bool __is_canonical_match =
+      std::is_same_v<__canonicalize_t<_Needle>, __canonicalize_t<_Signature>>;
+
+    template <typename _Needle, typename _Signatures>
+    struct __canonical_match_count;
+
+    template <typename _Needle, typename... _Signatures>
+    struct __canonical_match_count<_Needle, completion_signatures<_Signatures...>>
+      : std::integral_constant<std::size_t, (__is_canonical_match<_Needle, _Signatures> + ... + 0)>
+    {};
+
+    template <typename _Needle, typename... _Signatures>
+    struct __find_canonical_match;
+
+    template <typename _Needle>
+    struct __find_canonical_match<_Needle>
+    {};
+
+    template <typename _Needle, typename _Signature, typename... _Rest>
+    struct __find_canonical_match<_Needle, _Signature, _Rest...>
+      : std::conditional_t<__is_canonical_match<_Needle, _Signature>,
+                           std::type_identity<_Signature>,
+                           __find_canonical_match<_Needle, _Rest...>>
+    {};
+
+    template <typename _Signatures,
+              typename _Signature,
+              std::size_t _Matches = __canonical_match_count<_Signature, _Signatures>::value>
+    struct __matching_completion_signature
+    {};
+
+    template <typename _Signature, typename... _Signatures>
+    struct __matching_completion_signature<completion_signatures<_Signatures...>, _Signature, 1>
+      : __find_canonical_match<_Signature, _Signatures...>
+    {};
+
+  }  // namespace __matching_completion_signature
+
+  template <typename _Signatures, typename _Tag, typename... _Args>
+  using matching_completion_signature_t =
+    typename __matching_completion_signature::__matching_completion_signature<_Signatures,
+                                                                              _Tag(_Args...)>::type;
+
+  template <typename _Signatures, typename _Tag, typename... _Args>
+  inline constexpr bool has_matching_completion_signature_v = requires {
+    typename matching_completion_signature_t<_Signatures, _Tag, _Args...>;
+  };
+
+  template <typename _Signatures, typename _Tag, typename... _Args>
+  struct matching_completion_signature
+  {
+    using type = matching_completion_signature_t<_Signatures, _Tag, _Args...>;
+  };
+
+  template <typename _Signatures, typename _Tag, typename... _Args>
+  struct has_matching_completion_signature
+    : std::bool_constant<has_matching_completion_signature_v<_Signatures, _Tag, _Args...>>
+  {};
+
+}  // namespace STDEXEC