Squashed 'third_party/abseil/' content from commit ddf8e52a2
Change-Id: I330cdc687395c6605ad027b855e313ff4a2059e9
git-subtree-dir: third_party/abseil
git-subtree-split: ddf8e52a2918dd0ccec75d3e2426125fa3926724
diff --git a/absl/container/internal/raw_hash_set.cc b/absl/container/internal/raw_hash_set.cc
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+++ b/absl/container/internal/raw_hash_set.cc
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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