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// 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 {
namespace container_internal {
constexpr size_t Group::kWidth;
// Returns "random" seed.
inline size_t RandomSeed() {
#if 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, 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;
}
} // namespace container_internal
} // namespace absl
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