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authorVincent Ambo <tazjin@google.com>2020-05-20T01·32+0100
committerVincent Ambo <tazjin@google.com>2020-05-20T01·32+0100
commitfc8dc48020ac5b52731d0828a96ea4d2526c77ba (patch)
tree353204eea3268095a9ad3f5345720f32c2615c69 /third_party/abseil_cpp/absl/base/internal/periodic_sampler.cc
parentffb2ae54beb5796cd408fbe15d2d2da09ff37adf (diff)
parent768eb2ca2857342673fcd462792ce04b8bac3fa3 (diff)
Add 'third_party/abseil_cpp/' from commit '768eb2ca2857342673fcd462792ce04b8bac3fa3' r/781
git-subtree-dir: third_party/abseil_cpp
git-subtree-mainline: ffb2ae54beb5796cd408fbe15d2d2da09ff37adf
git-subtree-split: 768eb2ca2857342673fcd462792ce04b8bac3fa3
Diffstat (limited to 'third_party/abseil_cpp/absl/base/internal/periodic_sampler.cc')
-rw-r--r--third_party/abseil_cpp/absl/base/internal/periodic_sampler.cc53
1 files changed, 53 insertions, 0 deletions
diff --git a/third_party/abseil_cpp/absl/base/internal/periodic_sampler.cc b/third_party/abseil_cpp/absl/base/internal/periodic_sampler.cc
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+++ b/third_party/abseil_cpp/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 {
+ABSL_NAMESPACE_BEGIN
+namespace base_internal {
+
+int64_t PeriodicSamplerBase::GetExponentialBiased(int period) noexcept {
+  return rng_.GetStride(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_ = static_cast<uint64_t>(-GetExponentialBiased(current_period));
+    if (static_cast<int64_t>(stride_) < -1) {
+      ++stride_;
+      return false;
+    }
+  }
+
+  stride_ = static_cast<uint64_t>(-GetExponentialBiased(current_period));
+  return true;
+}
+
+}  // namespace base_internal
+ABSL_NAMESPACE_END
+}  // namespace absl