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| 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_ | |
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