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 <stddef.h> 21 #include <stdint.h> 22 23 #include <vector> 24 25 #include <limits.h> 26 27 #include "base/base_export.h" 28 #include "base/macros.h" 29 #include "base/metrics/histogram_base.h" 30 31 namespace base { 32 33 class BASE_EXPORT BucketRanges { 34 public: 35 typedef std::vector<HistogramBase::Sample> Ranges; 36 37 explicit BucketRanges(size_t num_ranges); 38 ~BucketRanges(); 39 40 size_t size() const { return ranges_.size(); } 41 HistogramBase::Sample range(size_t i) const { return ranges_[i]; } 42 void set_range(size_t i, HistogramBase::Sample value); 43 uint32_t checksum() const { return checksum_; } 44 void set_checksum(uint32_t checksum) { checksum_ = checksum; } 45 46 // A bucket is defined by a consecutive pair of entries in |ranges|, so there 47 // is one fewer bucket than there are ranges. For example, if |ranges| is 48 // [0, 1, 3, 7, INT_MAX], then the buckets in this histogram are 49 // [0, 1), [1, 3), [3, 7), and [7, INT_MAX). 50 size_t bucket_count() const { return ranges_.size() - 1; } 51 52 // Checksum methods to verify whether the ranges are corrupted (e.g. bad 53 // memory access). 54 uint32_t CalculateChecksum() const; 55 bool HasValidChecksum() const; 56 void ResetChecksum(); 57 58 // Return true iff |other| object has same ranges_ as |this| object's ranges_. 59 bool Equals(const BucketRanges* other) const; 60 61 private: 62 // A monotonically increasing list of values which determine which bucket to 63 // put a sample into. For each index, show the smallest sample that can be 64 // added to the corresponding bucket. 65 Ranges ranges_; 66 67 // Checksum for the conntents of ranges_. Used to detect random over-writes 68 // of our data, and to quickly see if some other BucketRanges instance is 69 // possibly Equal() to this instance. 70 // TODO(kaiwang): Consider change this to uint64_t. Because we see a lot of 71 // noise on UMA dashboard. 72 uint32_t checksum_; 73 74 DISALLOW_COPY_AND_ASSIGN(BucketRanges); 75 }; 76 77 ////////////////////////////////////////////////////////////////////////////// 78 // Expose only for test. 79 BASE_EXPORT extern const uint32_t kCrcTable[256]; 80 81 } // namespace base 82 83 #endif // BASE_METRICS_BUCKET_RANGES_H_ 84
