Add SampleMap and use it in SparseHistogram

base/metrics/sample_map_unittest.cc

Index: base/metrics/sample_map_unittest.cc
diff --git a/base/metrics/sample_map_unittest.cc b/base/metrics/sample_map_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e461affd0997b7df95824d0466f7035ee3f4a235
--- /dev/null
+++ b/base/metrics/sample_map_unittest.cc
@@ -0,0 +1,123 @@
+// 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 "base/memory/scoped_ptr.h"
+#include "base/metrics/sample_map.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace {
+
+TEST(SampleMapTest, AccumulateTest) {
+  SampleMap samples;
+
+  samples.Accumulate(1, 100);
+  samples.Accumulate(2, 200);
+  samples.Accumulate(1, -300);

[Ilya Sherman, 2012/10/01 21:24:50]

What does it mean for a bucket to have a negative count?  I'm surprised that
this isn't something we'd want to treat as an error, i.e. trip a DCHECK for.

[kaiwang, 2012/10/01 22:38:52]

Because HistogramSamples support Subtract, it's hard to avoid negative counts.
(and in my opinion, may not worth, because the perception is histogram can be
corrupted at anytime).

+  EXPECT_EQ(-200, samples.GetCount(1));
+  EXPECT_EQ(200, samples.GetCount(2));
+
+  EXPECT_EQ(200, samples.sum());
+  EXPECT_EQ(0, samples.redundant_count());
+  EXPECT_EQ(0, samples.TotalCount());
+}
+
+TEST(SampleMapTest, AddSubtractTest) {
+  SampleMap samples1;
+  SampleMap samples2;
+
+  samples1.Accumulate(1, 100);
+  samples1.Accumulate(2, 100);
+  samples1.Accumulate(3, 100);
+
+  samples2.Accumulate(1, 200);
+  samples2.Accumulate(2, 200);
+  samples2.Accumulate(4, 200);
+
+  samples1.Add(samples2);
+  EXPECT_EQ(300, samples1.GetCount(1));
+  EXPECT_EQ(300, samples1.GetCount(2));
+  EXPECT_EQ(100, samples1.GetCount(3));
+  EXPECT_EQ(200, samples1.GetCount(4));
+  EXPECT_EQ(2000, samples1.sum());
+  EXPECT_EQ(900, samples1.TotalCount());
+  EXPECT_EQ(samples1.redundant_count(), samples1.TotalCount());
+
+  samples1.Subtract(samples2);
+  EXPECT_EQ(100, samples1.GetCount(1));
+  EXPECT_EQ(100, samples1.GetCount(2));
+  EXPECT_EQ(100, samples1.GetCount(3));
+  EXPECT_EQ(0, samples1.GetCount(4));
+  EXPECT_EQ(600, samples1.sum());
+  EXPECT_EQ(300, samples1.TotalCount());
+  EXPECT_EQ(samples1.redundant_count(), samples1.TotalCount());
+}
+
+TEST(SampleMapIteratorTest, IterateTest) {
+  SampleMap samples;
+  samples.Accumulate(1, 100);
+  samples.Accumulate(2, 200);
+  samples.Accumulate(4, -300);
+  samples.Accumulate(5, 0);
+
+  scoped_ptr<SampleCountIterator> it = samples.Iterator();
+
+  HistogramBase::Sample min;
+  HistogramBase::Sample max;
+  HistogramBase::Count count;
+
+  it->Get(&min, &max, &count);
+  EXPECT_EQ(1, min);
+  EXPECT_EQ(2, max);
+  EXPECT_EQ(100, count);
+  EXPECT_FALSE(it->GetBucketIndex(NULL));
+
+  it->Next();
+  it->Get(&min, &max, &count);
+  EXPECT_EQ(2, min);
+  EXPECT_EQ(3, max);
+  EXPECT_EQ(200, count);
+
+  it->Next();
+  it->Get(&min, &max, &count);
+  EXPECT_EQ(4, min);
+  EXPECT_EQ(5, max);
+  EXPECT_EQ(-300, count);
+
+  it->Next();
+  it->Get(&min, &max, &count);
+  EXPECT_EQ(5, min);
+  EXPECT_EQ(6, max);
+  EXPECT_EQ(0, count);
+
+  it->Next();
+  EXPECT_TRUE(it->Done());
+}
+
+#if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)) && GTEST_HAS_DEATH_TEST
+
+TEST(SampleMapIteratorDeathTest, IterateDoneTest) {
+  SampleMap samples;
+
+  scoped_ptr<SampleCountIterator> it = samples.Iterator();
+
+  EXPECT_TRUE(it->Done());
+
+  HistogramBase::Sample min;
+  HistogramBase::Sample max;
+  HistogramBase::Count count;
+  EXPECT_DEATH(it->Get(&min, &max, &count), "");
+
+  EXPECT_DEATH(it->Next(), "");
+
+  samples.Accumulate(1, 100);
+  it = samples.Iterator();
+  EXPECT_FALSE(it->Done());
+}
+
+#endif
+// (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)) && GTEST_HAS_DEATH_TEST
+
+}  // namespace
+}  // namespace base