Abseil Common Libraries (C++) (grcp 依赖)
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46 lines
1.5 KiB
46 lines
1.5 KiB
// Copyright 2018 The Abseil 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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#include "absl/container/internal/raw_hash_set.h" |
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#include <atomic> |
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#include <cstddef> |
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#include "absl/base/config.h" |
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namespace absl { |
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namespace container_internal { |
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constexpr size_t Group::kWidth; |
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// Returns "random" seed. |
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inline size_t RandomSeed() { |
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#if ABSL_HAVE_THREAD_LOCAL |
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static thread_local size_t counter = 0; |
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size_t value = ++counter; |
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#else // ABSL_HAVE_THREAD_LOCAL |
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static std::atomic<size_t> counter(0); |
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size_t value = counter.fetch_add(1, std::memory_order_relaxed); |
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#endif // ABSL_HAVE_THREAD_LOCAL |
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return value ^ static_cast<size_t>(reinterpret_cast<uintptr_t>(&counter)); |
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} |
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bool ShouldInsertBackwards(size_t hash, ctrl_t* ctrl) { |
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// To avoid problems with weak hashes and single bit tests, we use % 13. |
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// TODO(kfm,sbenza): revisit after we do unconditional mixing |
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return (H1(hash, ctrl) ^ RandomSeed()) % 13 > 6; |
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} |
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} // namespace container_internal |
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} // namespace absl
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