| // 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. |
| // |
| // BucketRanges stores the vector of ranges that delimit what samples are |
| // tallied in the corresponding buckets of a histogram. Histograms that have |
| // same ranges for all their corresponding buckets should share the same |
| // BucketRanges object. |
| // |
| // E.g. A 5 buckets LinearHistogram with 1 as minimal value and 4 as maximal |
| // value will need a BucketRanges with 6 ranges: |
| // 0, 1, 2, 3, 4, INT_MAX |
| // |
| // TODO(kaiwang): Currently we keep all negative values in 0~1 bucket. Consider |
| // changing 0 to INT_MIN. |
| |
| #ifndef BASE_METRICS_BUCKET_RANGES_H_ |
| #define BASE_METRICS_BUCKET_RANGES_H_ |
| |
| #include <stddef.h> |
| #include <stdint.h> |
| |
| #include <vector> |
| |
| #include <limits.h> |
| |
| #include "base/atomicops.h" |
| #include "base/base_export.h" |
| #include "base/macros.h" |
| #include "base/metrics/histogram_base.h" |
| |
| namespace base { |
| |
| class BASE_EXPORT BucketRanges { |
| public: |
| typedef std::vector<HistogramBase::Sample> Ranges; |
| |
| explicit BucketRanges(size_t num_ranges); |
| ~BucketRanges(); |
| |
| size_t size() const { return ranges_.size(); } |
| HistogramBase::Sample range(size_t i) const { return ranges_[i]; } |
| void set_range(size_t i, HistogramBase::Sample value) { |
| DCHECK_LT(i, ranges_.size()); |
| DCHECK_GE(value, 0); |
| ranges_[i] = value; |
| } |
| uint32_t checksum() const { return checksum_; } |
| void set_checksum(uint32_t checksum) { checksum_ = checksum; } |
| |
| // A bucket is defined by a consecutive pair of entries in |ranges|, so there |
| // is one fewer bucket than there are ranges. For example, if |ranges| is |
| // [0, 1, 3, 7, INT_MAX], then the buckets in this histogram are |
| // [0, 1), [1, 3), [3, 7), and [7, INT_MAX). |
| size_t bucket_count() const { return ranges_.size() - 1; } |
| |
| // Checksum methods to verify whether the ranges are corrupted (e.g. bad |
| // memory access). |
| uint32_t CalculateChecksum() const; |
| bool HasValidChecksum() const; |
| void ResetChecksum(); |
| |
| // Return true iff |other| object has same ranges_ as |this| object's ranges_. |
| bool Equals(const BucketRanges* other) const; |
| |
| // Set and get a reference into persistent memory where this bucket data |
| // can be found (and re-used). These calls are internally atomic with no |
| // safety against overwriting an existing value since though it is wasteful |
| // to have multiple identical persistent records, it is still safe. |
| void set_persistent_reference(uint32_t ref) const { |
| subtle::Release_Store(&persistent_reference_, ref); |
| } |
| uint32_t persistent_reference() const { |
| return subtle::Acquire_Load(&persistent_reference_); |
| } |
| |
| private: |
| // A monotonically increasing list of values which determine which bucket to |
| // put a sample into. For each index, show the smallest sample that can be |
| // added to the corresponding bucket. |
| Ranges ranges_; |
| |
| // Checksum for the conntents of ranges_. Used to detect random over-writes |
| // of our data, and to quickly see if some other BucketRanges instance is |
| // possibly Equal() to this instance. |
| // TODO(kaiwang): Consider change this to uint64_t. Because we see a lot of |
| // noise on UMA dashboard. |
| uint32_t checksum_; |
| |
| // A reference into a global PersistentMemoryAllocator where the ranges |
| // information is stored. This allows for the record to be created once and |
| // re-used simply by having all histograms with the same ranges use the |
| // same reference. |
| mutable subtle::Atomic32 persistent_reference_ = 0; |
| |
| DISALLOW_COPY_AND_ASSIGN(BucketRanges); |
| }; |
| |
| ////////////////////////////////////////////////////////////////////////////// |
| // Expose only for test. |
| BASE_EXPORT extern const uint32_t kCrcTable[256]; |
| uint32_t Crc32(uint32_t sum, HistogramBase::Sample value); |
| |
| } // namespace base |
| |
| #endif // BASE_METRICS_BUCKET_RANGES_H_ |