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// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/reporting/util/rate_limiter_token_bucket.h"
#include <cmath>
#include <cstddef>
#include "base/check.h"
#include "base/memory/weak_ptr.h"
#include "base/sequence_checker.h"
#include "base/task/sequenced_task_runner.h"
#include "base/time/time.h"
namespace reporting {
RateLimiterTokenBucket::RateLimiterTokenBucket(size_t max_level,
base::TimeDelta filling_time,
base::TimeDelta filling_period)
: max_level_(max_level),
filling_time_(filling_time),
filling_period_(filling_period) {
CHECK_GT(max_level_, 0u);
CHECK_GT(filling_time_, base::TimeDelta());
// Make sure filling rate is reasonable - at least 1 token per period!
CHECK_LT(filling_time_ / max_level_, filling_period_);
DETACH_FROM_SEQUENCE(sequence_checker_);
// Empty initially, start filling in.
ScheduleNextFill();
}
RateLimiterTokenBucket::~RateLimiterTokenBucket() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
}
bool RateLimiterTokenBucket::Acquire(size_t event_size) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (event_size > max_level_) {
return false; // The event is too large, will never be accepted.
}
if (event_size > current_level_) {
return false; // The bucket does not have enough tokens.
}
// Accept and account for the new event.
current_level_ -= event_size;
// Resume filling in, if it was not ongoing (that is, if the bucket was full
// before we removed the event).
if (current_level_ + event_size >= max_level_) {
ScheduleNextFill();
}
return true;
}
void RateLimiterTokenBucket::NextFill() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
current_level_ += std::ceil(max_level_ * filling_period_ / filling_time_);
if (current_level_ > max_level_) {
current_level_ = max_level_;
} else if (current_level_ < max_level_) {
ScheduleNextFill();
}
}
void RateLimiterTokenBucket::ScheduleNextFill() {
base::SequencedTaskRunner::GetCurrentDefault()->PostDelayedTask(
FROM_HERE,
base::BindOnce(&RateLimiterTokenBucket::NextFill,
weak_ptr_factory_.GetWeakPtr()),
filling_period_);
}
} // namespace reporting
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