2103fd9acd
-- d447fdcb801036cf08197eece193a5a706661120 by Gennadiy Rozental <rogeeff@google.com>: Eliminate the need for static function holding help message. This decreases the cost of ABSL_FLAG abstraction by 120 bytes under clang. PiperOrigin-RevId: 281107806 -- 0aa6b91189f0e8b2381438c33465673a7ae02487 by Derek Mauro <dmauro@google.com>: Disable the weak symbol CCTZ extension in the time test_util on MinGW, which does not support it. PiperOrigin-RevId: 280719769 -- 67322c41c3e776eb541de90fa4526bdb49422eb6 by Abseil Team <absl-team@google.com>: Tune PeriodicSampler implementation (for internal-use only) PiperOrigin-RevId: 280708943 -- 3a48c346340c7ed03816645cd327e1ff07729aa4 by Abseil Team <absl-team@google.com>: Clean up public headers not to have warnings for "-Wcomma" PiperOrigin-RevId: 280695373 -- 981acd1ef3b13a83a84f04f11c8931f4ed4451c9 by Matthew Brown <matthewbr@google.com>: Release absl::int128. PiperOrigin-RevId: 280690817 -- d30fae9d2ec30b81322d2eb5afe7e13e45b4b422 by Derek Mauro <dmauro@google.com>: Fix -Wundef warnings in random platform detection PiperOrigin-RevId: 280669598 GitOrigin-RevId: d447fdcb801036cf08197eece193a5a706661120 Change-Id: Ie5e10e567c54b7de211833607689f233d4ddf734
50 lines
1.5 KiB
C++
50 lines
1.5 KiB
C++
// 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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namespace base_internal {
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int64_t PeriodicSamplerBase::GetExponentialBiased(int period) noexcept {
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return rng_.Get(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>(-1 - 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>(-1 - GetExponentialBiased(current_period));
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return true;
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}
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} // namespace base_internal
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} // namespace absl
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