1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 // 5 // BucketRanges stores the vector of ranges that delimit what samples are 6 // tallied in the corresponding buckets of a histogram. Histograms that have 7 // same ranges for all their corresponding buckets should share the same 8 // BucketRanges object. 9 // 10 // E.g. A 5 buckets LinearHistogram with 1 as minimal value and 4 as maximal 11 // value will need a BucketRanges with 6 ranges: 12 // 0, 1, 2, 3, 4, INT_MAX 13 // 14 // TODO(kaiwang): Currently we keep all negative values in 0~1 bucket. Consider 15 // changing 0 to INT_MIN. 16 17 #ifndef BASE_METRICS_BUCKET_RANGES_H_ 18 #define BASE_METRICS_BUCKET_RANGES_H_ 19 20 #include <vector> 21 22 #include "base/base_export.h" 23 #include "base/basictypes.h" 24 #include "base/gtest_prod_util.h" 25 #include "base/metrics/histogram_base.h" 26 27 namespace base { 28 29 class BASE_EXPORT BucketRanges { 30 public: 31 typedef std::vector<HistogramBase::Sample> Ranges; 32 33 explicit BucketRanges(size_t num_ranges); 34 ~BucketRanges(); 35 36 size_t size() const { return ranges_.size(); } 37 HistogramBase::Sample range(size_t i) const { return ranges_[i]; } 38 void set_range(size_t i, HistogramBase::Sample value); 39 uint32 checksum() const { return checksum_; } 40 void set_checksum(uint32 checksum) { checksum_ = checksum; } 41 42 // A bucket is defined by a consecutive pair of entries in |ranges|, so there 43 // is one fewer bucket than there are ranges. For example, if |ranges| is 44 // [0, 1, 3, 7, INT_MAX], then the buckets in this histogram are 45 // [0, 1), [1, 3), [3, 7), and [7, INT_MAX). 46 size_t bucket_count() const { return ranges_.size() - 1; } 47 48 // Checksum methods to verify whether the ranges are corrupted (e.g. bad 49 // memory access). 50 uint32 CalculateChecksum() const; 51 bool HasValidChecksum() const; 52 void ResetChecksum(); 53 54 // Return true iff |other| object has same ranges_ as |this| object's ranges_. 55 bool Equals(const BucketRanges* other) const; 56 57 private: 58 // A monotonically increasing list of values which determine which bucket to 59 // put a sample into. For each index, show the smallest sample that can be 60 // added to the corresponding bucket. 61 Ranges ranges_; 62 63 // Checksum for the conntents of ranges_. Used to detect random over-writes 64 // of our data, and to quickly see if some other BucketRanges instance is 65 // possibly Equal() to this instance. 66 // TODO(kaiwang): Consider change this to uint64. Because we see a lot of 67 // noise on UMA dashboard. 68 uint32 checksum_; 69 70 DISALLOW_COPY_AND_ASSIGN(BucketRanges); 71 }; 72 73 ////////////////////////////////////////////////////////////////////////////// 74 // Expose only for test. 75 BASE_EXPORT_PRIVATE extern const uint32 kCrcTable[256]; 76 77 } // namespace base 78 79 #endif // BASE_METRICS_BUCKET_RANGES_H_ 80
