// Copyright 2018 The Abseil 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 // // https://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. #include "absl/container/internal/raw_hash_set.h" #include <atomic> #include <cstddef> #include "absl/base/config.h" namespace absl { ABSL_NAMESPACE_BEGIN namespace container_internal { alignas(16) ABSL_CONST_INIT ABSL_DLL const ctrl_t kEmptyGroup[16] = { ctrl_t::kSentinel, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty}; constexpr size_t Group::kWidth; // Returns "random" seed. inline size_t RandomSeed() { #ifdef ABSL_HAVE_THREAD_LOCAL static thread_local size_t counter = 0; size_t value = ++counter; #else // ABSL_HAVE_THREAD_LOCAL static std::atomic<size_t> counter(0); size_t value = counter.fetch_add(1, std::memory_order_relaxed); #endif // ABSL_HAVE_THREAD_LOCAL return value ^ static_cast<size_t>(reinterpret_cast<uintptr_t>(&counter)); } bool ShouldInsertBackwards(size_t hash, const ctrl_t* ctrl) { // To avoid problems with weak hashes and single bit tests, we use % 13. // TODO(kfm,sbenza): revisit after we do unconditional mixing return (H1(hash, ctrl) ^ RandomSeed()) % 13 > 6; } void ConvertDeletedToEmptyAndFullToDeleted(ctrl_t* ctrl, size_t capacity) { assert(ctrl[capacity] == ctrl_t::kSentinel); assert(IsValidCapacity(capacity)); for (ctrl_t* pos = ctrl; pos < ctrl + capacity; pos += Group::kWidth) { Group{pos}.ConvertSpecialToEmptyAndFullToDeleted(pos); } // Copy the cloned ctrl bytes. std::memcpy(ctrl + capacity + 1, ctrl, NumClonedBytes()); ctrl[capacity] = ctrl_t::kSentinel; } // Extern template instantiotion for inline function. template FindInfo find_first_non_full(const ctrl_t*, size_t, size_t); } // namespace container_internal ABSL_NAMESPACE_END } // namespace absl