RAPPOR implementation

components/rappor/rappor_metric.cc

+// Copyright (c) 2012 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.
+
+#include "components/rappor/rappor_metric.h"
+
+namespace rappor {
+
+RapporMetric::RapporMetric(const RapporParameters& parameters)
+    : parameters_(parameters),
+      bloom_(parameters.bloom_filter_size_bytes,
+             parameters.bloom_filter_hash_count) {}
+
+void RapporMetric::AddSamples(const std::vector<std::string>& strings) {
+  bloom_.AddStrings(strings);
+}
+
+void RapporMetric::AddSample(const std::string& str) { bloom_.AddString(str); }
+
+const ByteVector& RapporMetric::GetBytes() const { return bloom_.bytes(); }

[Ilya Sherman, 2014/01/10 11:00:32]

nit: It's fine to name this method "bytes()" and inline the implementation if
you want to, since the operation is cheap.

[Steven Holte, 2014/01/14 00:47:54]

Done.

+
+ByteVector RapporMetric::GetReport(const std::string& secret) const {

[Ilya Sherman, 2014/01/10 11:00:32]

It would be very useful to include comments in this implementation function
explaining the algorithmic reasoning behind the operations performed.

[Steven Holte, 2014/01/14 00:47:54]

Done.

+  const ByteVector real_bits(GetBytes());
+
+  HmacByteVectorGenerator hmac_generator(real_bits.size(),
+                                         secret + parameters()->rappor_name);
+  const ByteVector fake_mask =
+      hmac_generator.GetWeightedRandomByteVector(parameters()->fake_prob);
+  ByteVector fake_ones =
+      hmac_generator.GetWeightedRandomByteVector(parameters()->fake_one_prob);
+
+  const ByteVector* onebits = ByteVectorMerge(fake_mask, real_bits, &fake_ones);
+
+  ByteVectorGenerator coinGenerator(real_bits.size());

[Ilya Sherman, 2014/01/10 11:00:32]

nit: coinGenerator -> coin_generator

[Steven Holte, 2014/01/14 00:47:54]

Done.

+  const ByteVector zero_coins =
+      coinGenerator.GetWeightedRandomByteVector(parameters()->zero_coin_prob);
+  ByteVector one_coins =
+      coinGenerator.GetWeightedRandomByteVector(parameters()->one_coin_prob);
+
+  const ByteVector* output = ByteVectorMerge(*onebits, zero_coins, &one_coins);
+
+  return *output;
+}
+
+}  // namespace rappor