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// Copyright 2021 gRPC authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// 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.
#ifndef GRPC_SRC_CORE_LIB_GPRPP_MATCH_H
#define GRPC_SRC_CORE_LIB_GPRPP_MATCH_H
#include <grpc/support/port_platform.h>
#include <type_traits>
#include "y_absl/types/variant.h"
#include "src/core/lib/gprpp/overload.h"
namespace grpc_core {
namespace detail {
template <typename... Cases>
struct MatchPointerExtractor {
OverloadType<Cases...> cases;
template <typename T>
auto operator()(T& value) -> decltype(cases(&value)) {
return cases(&value);
}
};
} // namespace detail
/// Match on a variant.
/// Given variant \a value, and a set of callables \a fs, call the appropriate
/// callable based on the type contained in \a value.
///
/// Example (prints "hoorah"):
/// variant<int, string> v = 42;
/// Match(v,
/// [](int i) { puts("hoorah"); },
/// [](string s) { puts("boo"); });
template <typename... Fs, typename T0, typename... Ts>
auto Match(const y_absl::variant<T0, Ts...>& value, Fs... fs)
-> decltype(std::declval<OverloadType<Fs...>>()(std::declval<T0>())) {
return y_absl::visit(Overload(std::move(fs)...), value);
}
/// A version of Match that takes a mutable pointer to a variant and calls its
/// overload callables with a mutable pointer to the current variant value.
///
/// Example:
/// variant<int, string> v = 42;
/// MatchMutable(&v,
/// [](int* i) { *i = 1; },
/// [](string* s) { *s = "foo"; });
/// // v now contains 1.
template <typename... Fs, typename T0, typename... Ts>
auto MatchMutable(y_absl::variant<T0, Ts...>* value, Fs... fs)
-> decltype(std::declval<OverloadType<Fs...>>()(std::declval<T0*>())) {
return y_absl::visit(detail::MatchPointerExtractor<Fs...>{OverloadType<Fs...>(
std::move(fs)...)},
*value);
}
} // namespace grpc_core
#endif // GRPC_SRC_CORE_LIB_GPRPP_MATCH_H
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