RAPPOR implementation

components/rappor/byte_vector_utils_unittest.cc

+// 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.
+
+#include "components/rappor/byte_vector_utils.h"
+
+#include "base/rand_util.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+

[Alexei Svitkine (slow), 2014/01/21 18:14:04]

Nit: Remove one blank line.

[Steven Holte, 2014/01/21 20:25:14]

Done.

+namespace rappor {
+
+namespace {
+
+int CountBits(const ByteVector& v) {
+  int bit_count = 0;
+  for(size_t i = 0; i < v.size(); i++) {

[Alexei Svitkine (slow), 2014/01/21 18:14:04]

Nit: space after for. also after "if" below.

Also, prefer ++i over i++ (here and below).

[Steven Holte, 2014/01/21 20:25:14]

Done.

+    uint8_t byte = v[i];
+    for (int j = 0; j < 8 ; j++) {
+      if(byte & 1 << j) {

[Alexei Svitkine (slow), 2014/01/21 18:14:04]

Nit: No {}'s.

Also, please but parens around one of the sub expression (so a person reading
the code doesn't need to remember order of operations between & and <<.

[Steven Holte, 2014/01/21 20:25:14]

Done.

+        bit_count++;
+      }
+    }
+  }
+  return bit_count;
+}
+
+}  // namespace
+
+TEST(ByteVectorTest, TestOr) {
+  ByteVector lhs(2);
+  lhs[1] = 0x12;
+  ByteVector rhs(2);
+  rhs[1] = 0x03;
+
+  EXPECT_EQ(0x13, (*ByteVectorOr(lhs, &rhs))[1]);
+}
+
+TEST(ByteVectorTest, TestMerge) {
+  ByteVector lhs(2);
+  lhs[1] = 0x33;
+  ByteVector rhs(2);
+  rhs[1] = 0x55;
+  ByteVector mask(2);
+  mask[1] = 0x0f;
+
+  EXPECT_EQ(0x35, (*ByteVectorMerge(mask, lhs, &rhs))[1]);
+}
+
+TEST(ByteVectorTest, TestGenerator) {
+  ByteVectorGenerator generator(2u);
+  ByteVector random_50 = generator.GetWeightedRandomByteVector(PROBABILITY_50);
+  EXPECT_EQ(random_50.size(), 2u);
+  ByteVector random_75 = generator.GetWeightedRandomByteVector(PROBABILITY_75);
+  EXPECT_EQ(random_75.size(), 2u);
+}
+
+TEST(ByteVectorTest, TestHmacGeneratorDeterminism) {
+  HmacByteVectorGenerator generator(2u, "MySecret");
+  ByteVector random_50 = generator.GetWeightedRandomByteVector(PROBABILITY_50);
+  EXPECT_EQ(random_50.size(), 2u);
+  EXPECT_EQ(random_50[0], 0x16);
+  ByteVector random_75 = generator.GetWeightedRandomByteVector(PROBABILITY_75);
+  EXPECT_EQ(random_75.size(), 2u);
+  EXPECT_EQ(random_75[0], 0xef);
+}
+
+TEST(ByteVectorTest, TestStatistic50) {
+  ByteVectorGenerator generator(50u);
+  ByteVector random = generator.GetWeightedRandomByteVector(PROBABILITY_50);
+  int bit_count = CountBits(random);
+  // Check bounds on bit counts that are true with 99.999% probability.
+  EXPECT_GT(bit_count, 155); // Binomial(400, .5) CDF(155) ~= 0.000004
+  EXPECT_LE(bit_count, 244); // Binomial(400, .5) CDF(244) ~= 0.999996
+}
+
+TEST(ByteVectorTest, TestStatistic75) {
+  ByteVectorGenerator generator(50u);
+  ByteVector random = generator.GetWeightedRandomByteVector(PROBABILITY_75);
+  int bit_count = CountBits(random);
+  // Check bounds on bit counts that are true with 99.999% probability.
+  EXPECT_GT(bit_count, 259); // Binomial(400, .75) CDF(259) ~= 0.000003
+  EXPECT_LE(bit_count, 337); // Binomial(400, .75) CDF(337) ~= 0.999997
+}
+
+TEST(ByteVectorTest, TestHmacStatistic50) {
+  HmacByteVectorGenerator generator(50u, base::RandBytesAsString(128));
+  ByteVector random = generator.GetWeightedRandomByteVector(PROBABILITY_50);
+  int bit_count = CountBits(random);
+  // Check bounds on bit counts that are true with 99.999% probability.
+  EXPECT_GT(bit_count, 155); // Binomial(400, .5) CDF(155) ~= 0.000004
+  EXPECT_LE(bit_count, 244); // Binomial(400, .5) CDF(244) ~= 0.999996
+}
+
+TEST(ByteVectorTest, TestHmacStatistic75) {
+  HmacByteVectorGenerator generator(50u, base::RandBytesAsString(128));
+  ByteVector random = generator.GetWeightedRandomByteVector(PROBABILITY_75);
+  int bit_count = CountBits(random);
+  // Check bounds on bit counts that are true with 99.999% probability.
+  EXPECT_GT(bit_count, 259); // Binomial(400, .75) CDF(259) ~= 0.000003
+  EXPECT_LE(bit_count, 337); // Binomial(400, .75) CDF(337) ~= 0.999997
+}
+
+}  // namespace rappor