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// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "chrome/browser/privacy_budget/surface_set_with_valuation.h"
#include <algorithm>
#include <type_traits>
#include <utility>
#include <vector>
#include "base/check.h"
#include "base/rand_util.h"
#include "base/stl_util.h"
static_assert(std::is_same<RepresentativeSurface,
SurfaceSetWithValuation::key_type>::value,
"");
SurfaceSetWithValuation::SurfaceSetWithValuation(
const SurfaceSetValuation& valuation)
: valuation_(valuation) {}
SurfaceSetWithValuation::~SurfaceSetWithValuation() = default;
bool SurfaceSetWithValuation::TryAdd(RepresentativeSurface surface,
PrivacyBudgetCost budget) {
if (cost_ > budget)
return false;
auto it = surfaces_.find(surface);
if (it != surfaces_.end())
return true;
double new_cost = cost_ + valuation_->IncrementalCost(surfaces_, surface);
if (new_cost > budget)
return false;
cost_ = new_cost;
auto insertion_result = surfaces_.insert(surface);
DCHECK(insertion_result.second);
return true;
}
bool SurfaceSetWithValuation::TryAdd(blink::IdentifiableSurface surface,
PrivacyBudgetCost budget) {
return TryAdd(valuation_->equivalence().GetRepresentative(surface), budget);
}
void SurfaceSetWithValuation::AssignWithBudget(
RepresentativeSurfaceSet&& incoming_container,
double budget) {
Assign(std::move(incoming_container));
if (cost_ <= budget)
return;
// In case the budget doesn't accommodate all of `surfaces_`, we'll randomly
// drop elements until we meet the budget's restrictions.
auto container = std::move(surfaces_).extract();
base::RandomBitGenerator g;
std::ranges::shuffle(container, g);
auto new_beginning = container.begin();
for (; new_beginning != container.end() && cost_ > budget;
cost_ -= valuation_->Cost(*new_beginning), ++new_beginning) {
}
surfaces_ = container_type(new_beginning, container.end());
}
void SurfaceSetWithValuation::Assign(
RepresentativeSurfaceSet&& incoming_container) {
surfaces_ = std::move(incoming_container);
cost_ = valuation_->Cost(surfaces_);
}
void SurfaceSetWithValuation::Clear() {
cost_ = 0;
base::STLClearObject(&surfaces_);
}
RepresentativeSurfaceSet SurfaceSetWithValuation::Take() && {
cost_ = 0;
return std::move(surfaces_);
}
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