Multi-dimension rappor metrics

components/rappor/rappor_metric.h

 // Copyright 2014 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.
 
 #ifndef COMPONENTS_RAPPOR_RAPPOR_METRIC_H_
 #define COMPONENTS_RAPPOR_RAPPOR_METRIC_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/macros.h"
-#include "components/rappor/bloom_filter.h"
 #include "components/rappor/byte_vector_utils.h"
 #include "components/rappor/rappor_parameters.h"
 
 namespace rappor {
 
-// A RapporMetric is an object that collects string samples into a Bloom filter,
+namespace internal {
+
+// Use byte vectors to store samples.
+typedef ByteVector Sample;
+
+// Given a string and flags, pack a bloom filter representing the string
+// and the flags directly into a single sample that supports seperable
+// analysis.  |parameters| will determine how many bytes are used for each
+// part of the sample.
+void SetSampleBits(const RapporParameters& parameters, int32_t cohort_seed,
+                   const std::string& str, uint64_t flags, Sample* output);
+
+// A RapporMetric is an object that collects samples of a metric
 // and generates randomized reports about the collected data.
 //
 // This class should not be used directly by metrics clients.  Record metrics
 // using RapporService::RecordSample instead.
 //
 // For a full description of the rappor metrics, see
 // http://www.chromium.org/developers/design-documents/rappor
 class RapporMetric {
  public:
   // Takes the |metric_name| that this will be reported to the server with,
   // a |parameters| describing size and probability weights used in recording
-  // this metric, and a |cohort| value, which determines the hash functions
-  // used in the Bloom filter.
+  // this metric.
   RapporMetric(const std::string& metric_name,
-               const RapporParameters& parameters,
-               int32_t cohort);
+               const RapporParameters& parameters);
   ~RapporMetric();
 
-  // Records an additional sample in the Bloom filter.
+  // Records an additional sample.
   // A random sample will be used when reporting this metric when more than one
   // sample is collected in the same reporting interval.
-  void AddSample(const std::string& str);
+  void AddSample(const Sample& str);
 
-  // Retrieves the current Bloom filter bits.
-  const ByteVector& bytes() const { return bloom_filter_.bytes(); }
+  // Retrieves the current Sample.
+  const Sample& bytes() const { return sample_; }
 
   // Gets the parameter values this metric was constructed with.
   const RapporParameters& parameters() const { return parameters_; }
 
   // Generates the bits to report for this metric.  Using the secret as a seed,
   // randomly selects bits for redaction.  Then flips coins to generate the
   // final report bits.
   ByteVector GetReport(const std::string& secret) const;
 
-  // Specify the bytes to generate a report from, for testing purposes.
-  void SetBytesForTesting(const ByteVector& bytes);
+  // Specify the Sample to generate a report from, for testing purposes.
+  void SetSampleForTesting(const Sample& bytes);
 
  private:
   const std::string metric_name_;
   const RapporParameters parameters_;
   uint32_t sample_count_;
-  BloomFilter bloom_filter_;
+  Sample sample_;
 
   DISALLOW_COPY_AND_ASSIGN(RapporMetric);
 };
 
+}  // namespace internal
+
 }  // namespace rappor
 
 #endif  // COMPONENTS_RAPPOR_RAPPOR_METRIC_H_