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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
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