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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.
#ifndef COMPONENTS_SEGMENTATION_PLATFORM_INTERNAL_DATABASE_SIGNAL_SAMPLE_VIEW_H_
#define COMPONENTS_SEGMENTATION_PLATFORM_INTERNAL_DATABASE_SIGNAL_SAMPLE_VIEW_H_
#include <optional>
#include <vector>
#include "base/memory/raw_ptr.h"
#include "base/time/time.h"
#include "components/segmentation_platform/internal/database/signal_database.h"
#include "components/segmentation_platform/public/proto/types.pb.h"
namespace segmentation_platform {
// A container "view" on top of all the signal database sample list, that helps
// to query a particular histogram / user action or enum histograms.
class SignalSampleView {
public:
using Entries = std::vector<SignalDatabase::DbEntry>;
// Object to query a particular signal to be included.
struct Query {
Query(proto::SignalType type,
uint64_t metric_hash,
base::Time start,
base::Time end,
const std::vector<int>& enum_ids = {});
~Query();
Query(const Query&);
// Returns true if the `sample` matches the view query.
bool IsFeatureMatching(const SignalDatabase::DbEntry& sample) const;
// The metric type and hash to filter in.
const proto::SignalType type = proto::SignalType::UNKNOWN_SIGNAL_TYPE;
const uint64_t metric_hash = 0;
// The time period to filter in, start and end inclusive.
const base::Time start;
const base::Time end;
// List of enum values to include. If empty, then all signals are included.
const std::vector<int> enum_ids;
};
// Use begin() to create iterator, and ++ operator to increment the iterator.
struct Iterator {
Iterator(const SignalSampleView* view, size_t current);
~Iterator();
Iterator(Iterator& other);
const SignalDatabase::DbEntry& operator*() { return samples_[current_]; }
const SignalDatabase::DbEntry* operator->() { return &samples_[current_]; }
Iterator& operator++() {
current_ = view_->FindNext(current_);
return *this;
}
bool operator==(const Iterator& other) const {
CHECK_EQ(view_, other.view_);
return current_ == other.current_;
}
// Current index the iterator points to. Prefer to use * operator instead:
// `*it`.
size_t current() const { return current_; }
private:
const raw_ptr<const SignalSampleView> view_;
const Entries& samples_;
size_t current_;
};
// Creates a view on the database samples. `query` specifies the filter to
// apply on the samples for the view. If `query` is empty, all samples are
// included, just acts like a vector.
SignalSampleView(const std::vector<SignalDatabase::DbEntry>& samples,
const std::optional<Query>& query);
~SignalSampleView();
SignalSampleView(const SignalSampleView&) = delete;
// C++ iterable object methods.
Iterator begin() const { return Iterator(this, FindNext(-1)); }
Iterator end() const { return Iterator(this, EndIndex()); }
// Returns the last element in the view, if view is empty, returns end().
Iterator Last() const { return Iterator(this, FindPrev(samples_.size())); }
// The empty() and size() methods take O(n) time, on the size of the samples.
bool empty() const { return size() == 0; }
size_t size() const;
private:
// Returns the index that represents the "end()" iterator of this object.
size_t EndIndex() const { return samples_.size(); }
// Finds the next index that matches the given query.
size_t FindNext(int index) const;
// Finds the previous index that matches the given query.
size_t FindPrev(int index) const;
const std::vector<SignalDatabase::DbEntry>& samples_;
std::optional<Query> query_;
};
} // namespace segmentation_platform
#endif // COMPONENTS_SEGMENTATION_PLATFORM_INTERNAL_DATABASE_SIGNAL_SAMPLE_VIEW_H_
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