68 lines
2.4 KiB
C++
68 lines
2.4 KiB
C++
// 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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// https://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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ABSL_NAMESPACE_BEGIN
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namespace container_internal {
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alignas(16) ABSL_CONST_INIT ABSL_DLL const ctrl_t kEmptyGroup[16] = {
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ctrl_t::kSentinel, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,
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ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,
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ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,
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ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty};
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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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#ifdef 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, const 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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void ConvertDeletedToEmptyAndFullToDeleted(ctrl_t* ctrl, size_t capacity) {
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assert(ctrl[capacity] == ctrl_t::kSentinel);
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assert(IsValidCapacity(capacity));
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for (ctrl_t* pos = ctrl; pos < ctrl + capacity; pos += Group::kWidth) {
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Group{pos}.ConvertSpecialToEmptyAndFullToDeleted(pos);
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}
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// Copy the cloned ctrl bytes.
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std::memcpy(ctrl + capacity + 1, ctrl, NumClonedBytes());
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ctrl[capacity] = ctrl_t::kSentinel;
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}
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// Extern template instantiotion for inline function.
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template FindInfo find_first_non_full(const ctrl_t*, size_t, size_t);
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} // namespace container_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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