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+// Copyright 2019 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/base/internal/periodic_sampler.h"
+
+#include <atomic>
+
+#include "absl/base/internal/exponential_biased.h"
+
+namespace absl {
+namespace base_internal {
+
+int64_t PeriodicSamplerBase::GetExponentialBiased(int period) noexcept {
+ return rng_.Get(period);
+}
+
+bool PeriodicSamplerBase::SubtleConfirmSample() noexcept {
+ int current_period = period();
+
+ // Deal with period case 0 (always off) and 1 (always on)
+ if (ABSL_PREDICT_FALSE(current_period < 2)) {
+ stride_ = 0;
+ return current_period == 1;
+ }
+
+ // Check if this is the first call to Sample()
+ if (ABSL_PREDICT_FALSE(stride_ == 1)) {
+ stride_ = -1 - GetExponentialBiased(current_period);
+ if (stride_ < -1) {
+ ++stride_;
+ return false;
+ }
+ }
+ stride_ = -1 - GetExponentialBiased(current_period);
+ return true;
+}
+
+} // namespace base_internal
+} // namespace absl