Fix overflow bug in histogram sample data structures

base/metrics/sparse_histogram_unittest.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 "base/metrics/sparse_histogram.h"
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram_base.h"
@@ skipping 63 matching lines @@
   EXPECT_EQ(15, snapshot1->GetCount(100));
 
   histogram->AddCount(100, 15);
   histogram->AddCount(101, 25);
   scoped_ptr<HistogramSamples> snapshot2(histogram->SnapshotSamples());
   EXPECT_EQ(55, snapshot2->TotalCount());
   EXPECT_EQ(30, snapshot2->GetCount(100));
   EXPECT_EQ(25, snapshot2->GetCount(101));
 }
 
+TEST_F(SparseHistogramTest, AddCount_LargeValuesDontOverflow) {
+  scoped_ptr<SparseHistogram> histogram(NewSparseHistogram("Sparse"));
+  scoped_ptr<HistogramSamples> snapshot(histogram->SnapshotSamples());
+  EXPECT_EQ(0, snapshot->TotalCount());
+  EXPECT_EQ(0, snapshot->sum());
+
+  histogram->AddCount(1000000000, 15);
+  scoped_ptr<HistogramSamples> snapshot1(histogram->SnapshotSamples());
+  EXPECT_EQ(15, snapshot1->TotalCount());
+  EXPECT_EQ(15, snapshot1->GetCount(1000000000));
+
+  histogram->AddCount(1000000000, 15);
+  histogram->AddCount(1010000000, 25);
+  scoped_ptr<HistogramSamples> snapshot2(histogram->SnapshotSamples());
+  EXPECT_EQ(55, snapshot2->TotalCount());
+  EXPECT_EQ(30, snapshot2->GetCount(1000000000));
+  EXPECT_EQ(25, snapshot2->GetCount(1010000000));
+  EXPECT_EQ(55250000000LL, snapshot2->sum());
+}
+
 TEST_F(SparseHistogramTest, MacroBasicTest) {
   UMA_HISTOGRAM_SPARSE_SLOWLY("Sparse", 100);
   UMA_HISTOGRAM_SPARSE_SLOWLY("Sparse", 200);
   UMA_HISTOGRAM_SPARSE_SLOWLY("Sparse", 100);
 
   StatisticsRecorder::Histograms histograms;
   StatisticsRecorder::GetHistograms(&histograms);
 
   ASSERT_EQ(1U, histograms.size());
   HistogramBase* sparse_histogram = histograms[0];
@@ skipping 46 matching lines @@
 
   int flag;
   EXPECT_TRUE(iter.ReadInt(&flag));
   EXPECT_EQ(HistogramBase::kIPCSerializationSourceFlag, flag);
 
   // No more data in the pickle.
   EXPECT_FALSE(iter.SkipBytes(1));
 }
 
 }  // namespace base