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Diffstat (limited to 'absl/base/internal/periodic_sampler.cc')
-rw-r--r-- | absl/base/internal/periodic_sampler.cc | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/absl/base/internal/periodic_sampler.cc b/absl/base/internal/periodic_sampler.cc new file mode 100644 index 00000000..439745d0 --- /dev/null +++ b/absl/base/internal/periodic_sampler.cc @@ -0,0 +1,50 @@ +// 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 |