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54 lines
1.5 KiB
54 lines
1.5 KiB
4 months ago
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// Copyright 2019 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "absl/base/internal/periodic_sampler.h"
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#include <atomic>
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#include "absl/base/internal/exponential_biased.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace base_internal {
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int64_t PeriodicSamplerBase::GetExponentialBiased(int period) noexcept {
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return rng_.GetStride(period);
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}
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bool PeriodicSamplerBase::SubtleConfirmSample() noexcept {
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int current_period = period();
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// Deal with period case 0 (always off) and 1 (always on)
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if (ABSL_PREDICT_FALSE(current_period < 2)) {
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stride_ = 0;
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return current_period == 1;
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}
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// Check if this is the first call to Sample()
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if (ABSL_PREDICT_FALSE(stride_ == 1)) {
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stride_ = static_cast<uint64_t>(-GetExponentialBiased(current_period));
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if (static_cast<int64_t>(stride_) < -1) {
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++stride_;
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return false;
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}
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}
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stride_ = static_cast<uint64_t>(-GetExponentialBiased(current_period));
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return true;
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}
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} // namespace base_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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