1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef COMPONENTS_RAPPOR_RAPPOR_METRIC_H_
6#define COMPONENTS_RAPPOR_RAPPOR_METRIC_H_
7
8#include <string>
9
10#include "base/basictypes.h"
11#include "base/macros.h"
12#include "components/rappor/bloom_filter.h"
13#include "components/rappor/byte_vector_utils.h"
14#include "components/rappor/rappor_parameters.h"
15
16namespace rappor {
17
18// A RapporMetric is an object that collects string samples into a Bloom filter,
19// and generates randomized reports about the collected data.
20//
21// This class should not be used directly by metrics clients.  Record metrics
22// using RapporService::RecordSample instead.
23//
24// For a full description of the rappor metrics, see
25// http://www.chromium.org/developers/design-documents/rappor
26class RapporMetric {
27 public:
28  // Takes the |metric_name| that this will be reported to the server with,
29  // a |parameters| describing size and probability weights used in recording
30  // this metric, and a |cohort| value, which determines the hash functions
31  // used in the Bloom filter.
32  RapporMetric(const std::string& metric_name,
33               const RapporParameters& parameters,
34               int32_t cohort);
35  ~RapporMetric();
36
37  // Records an additional sample in the Bloom filter.
38  void AddSample(const std::string& str);
39
40  // Retrieves the current Bloom filter bits.
41  const ByteVector& bytes() const { return bloom_filter_.bytes(); }
42
43  // Gets the parameter values this metric was constructed with.
44  const RapporParameters& parameters() const { return parameters_; }
45
46  // Generates the bits to report for this metric.  Using the secret as a seed,
47  // randomly selects bits for redaction.  Then flips coins to generate the
48  // final report bits.
49  ByteVector GetReport(const std::string& secret) const;
50
51 private:
52  const std::string metric_name_;
53  const RapporParameters parameters_;
54  BloomFilter bloom_filter_;
55
56  DISALLOW_COPY_AND_ASSIGN(RapporMetric);
57};
58
59}  // namespace rappor
60
61#endif  // COMPONENTS_RAPPOR_RAPPOR_METRIC_H_
62