1 files changed, 50 insertions, 0 deletions
diff --git a/absl/base/internal/periodic_sampler.cc b/absl/base/internal/periodic_sampler.cc
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+++ b/absl/base/internal/periodic_sampler.cc
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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