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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// This class loads a client-side model and lets you compute a phishing score
// for a set of previously extracted features. The phishing score corresponds
// to the probability that the features are indicative of a phishing site.
//
// For more details on how the score is actually computed for a given model
// and a given set of features read the comments in client_model.proto file.
//
// See features.h for a list of features that are currently used.
#ifndef CHROME_RENDERER_SAFE_BROWSING_SCORER_H_
#define CHROME_RENDERER_SAFE_BROWSING_SCORER_H_
#include <stddef.h>
#include <stdint.h>
#include <string>
#include "base/containers/hash_tables.h"
#include "base/macros.h"
#include "base/strings/string_piece.h"
#include "chrome/common/safe_browsing/client_model.pb.h"
namespace safe_browsing {
class FeatureMap;
// Scorer methods are virtual to simplify mocking of this class.
class Scorer {
public:
virtual ~Scorer();
// Factory method which creates a new Scorer object by parsing the given
// model. If parsing fails this method returns NULL.
static Scorer* Create(const base::StringPiece& model_str);
// This method computes the probability that the given features are indicative
// of phishing. It returns a score value that falls in the range [0.0,1.0]
// (range is inclusive on both ends).
virtual double ComputeScore(const FeatureMap& features) const;
// Returns the version number of the loaded client model.
int model_version() const;
// -- Accessors used by the page feature extractor ---------------------------
// Returns a set of hashed page terms that appear in the model in binary
// format.
const base::hash_set<std::string>& page_terms() const;
// Returns a set of hashed page words that appear in the model in binary
// format.
const base::hash_set<uint32_t>& page_words() const;
// Return the maximum number of words per term for the loaded model.
size_t max_words_per_term() const;
// Returns the murmurhash3 seed for the loaded model.
uint32_t murmurhash3_seed() const;
// Return the maximum number of unique shingle hashes per page.
size_t max_shingles_per_page() const;
// Return the number of words in a shingle.
size_t shingle_size() const;
protected:
// Most clients should use the factory method. This constructor is public
// to allow for mock implementations.
Scorer();
private:
friend class PhishingScorerTest;
// Computes the score for a given rule and feature map. The score is computed
// by multiplying the rule weight with the product of feature weights for the
// given rule. The feature weights are stored in the feature map. If a
// particular feature does not exist in the feature map we set its weight to
// zero.
double ComputeRuleScore(const ClientSideModel::Rule& rule,
const FeatureMap& features) const;
ClientSideModel model_;
base::hash_set<std::string> page_terms_;
base::hash_set<uint32_t> page_words_;
DISALLOW_COPY_AND_ASSIGN(Scorer);
};
} // namespace safe_browsing
#endif // CHROME_RENDERER_SAFE_BROWSING_SCORER_H_
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