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[event_engine] Add SliceCast (#31831)
* [event_engine] Add SliceCast * Automated change: Fix sanity tests * windows-fix * comments * comments * comments * build-fix * fix * Update port_platform.h Co-authored-by: ctiller <ctiller@users.noreply.github.com>pull/31923/head
Craig Tiller
2 years ago
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GitHub
parent
580569358f
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72c296a3c2
20 changed files with 147 additions and 6 deletions
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// Copyright 2022 gRPC authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef GRPC_EVENT_ENGINE_INTERNAL_SLICE_CAST_H |
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#define GRPC_EVENT_ENGINE_INTERNAL_SLICE_CAST_H |
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namespace grpc_event_engine { |
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namespace experimental { |
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namespace internal { |
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// Opt-in trait class for slice conversions.
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// Declare a specialization of this class for any types that are compatible
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// with `SliceCast`. Both ways need to be declared (i.e. if
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// ConstRefSliceCastable<A,B> exists, you should declare
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// ConstRefSliceCastable<B,A> too).
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// The type has no members, it's just the existance of the specialization that
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// unlocks SliceCast usage for a type pair.
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template <typename Result, typename T> |
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struct ConstRefSliceCastable; |
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// This is strictly too wide, but consider all types to be SliceCast-able to
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// themselves.
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// Unfortunately this allows `const int& x = SliceCast<int>(x);` which is kind
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// of bogus.
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template <typename A> |
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struct ConstRefSliceCastable<A, A> {}; |
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// Cast to `const Result&` from `const T&` without any runtime checks.
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// This is only valid if `sizeof(Result) == sizeof(T)`, and if `Result`, `T` are
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// opted in as compatible via `ConstRefSliceCastable`.
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template <typename Result, typename T> |
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const Result& SliceCast(const T& value, ConstRefSliceCastable<Result, T> = {}) { |
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// Insist upon sizes being equal to catch mismatches.
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// We assume if sizes are opted in and sizes are equal then yes, these two
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// types are expected to be layout compatible and actually appear to be.
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static_assert(sizeof(Result) == sizeof(T), "size mismatch"); |
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return reinterpret_cast<const Result&>(value); |
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} |
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} // namespace internal
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} // namespace experimental
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} // namespace grpc_event_engine
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#endif // GRPC_EVENT_ENGINE_INTERNAL_SLICE_CAST_H
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