// Copyright 2016 The Chromium Authors // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #ifndef BASE_METRICS_HISTOGRAM_MACROS_INTERNAL_H_ #define BASE_METRICS_HISTOGRAM_MACROS_INTERNAL_H_ #include <stdint.h> #include <atomic> #include <limits> #include <memory> #include <type_traits> #include "base/dcheck_is_on.h" #include "base/metrics/histogram.h" #include "base/metrics/sparse_histogram.h" #include "base/time/time.h" #include "base/types/cxx23_to_underlying.h" // This is for macros and helpers internal to base/metrics. They should not be // used outside of this directory. For writing to UMA histograms, see // histogram_macros.h. namespace base::internal { // Helper trait for deducing the boundary value for enums. template <typename Enum> requires(std::is_enum_v<Enum>) struct EnumSizeTraits { … }; } // namespace base::internal // TODO(rkaplow): Improve commenting of these methods. //------------------------------------------------------------------------------ // Histograms are often put in areas where they are called many many times, and // performance is critical. As a result, they are designed to have a very low // recurring cost of executing (adding additional samples). Toward that end, // the macros declare a static pointer to the histogram in question, and only // take a "slow path" to construct (or find) the histogram on the first run // through the macro. We leak the histograms at shutdown time so that we don't // have to validate using the pointers at any time during the running of the // process. // In some cases (integration into 3rd party code), it's useful to separate the // definition of |atomic_histogram_pointer| from its use. To achieve this we // define HISTOGRAM_POINTER_USE, which uses an |atomic_histogram_pointer|, and // STATIC_HISTOGRAM_POINTER_BLOCK, which defines an |atomic_histogram_pointer| // and forwards to HISTOGRAM_POINTER_USE. #define HISTOGRAM_POINTER_USE( \ atomic_histogram_pointer, constant_histogram_name, \ histogram_add_method_invocation, histogram_factory_get_invocation) … // This is a helper macro used by other macros and shouldn't be used directly. // Defines the static |atomic_histogram_pointer| and forwards to // HISTOGRAM_POINTER_USE. #define STATIC_HISTOGRAM_POINTER_BLOCK(constant_histogram_name, \ histogram_add_method_invocation, \ histogram_factory_get_invocation) … // This is a helper macro used by other macros and shouldn't be used directly. #define INTERNAL_HISTOGRAM_CUSTOM_COUNTS_WITH_FLAG(name, sample, min, max, \ bucket_count, flag) … // This is a helper macro used by other macros and shouldn't be used directly. // The bucketing scheme is linear with a bucket size of 1. For N items, // recording values in the range [0, N - 1] creates a linear histogram with N + // 1 buckets: // [0, 1), [1, 2), ..., [N - 1, N) // and an overflow bucket [N, infinity). // // Code should never emit to the overflow bucket; only to the other N buckets. // This allows future versions of Chrome to safely increase the boundary size. // Otherwise, the histogram would have [N - 1, infinity) as its overflow bucket, // and so the maximal value (N - 1) would be emitted to this overflow bucket. // But, if an additional value were later added, the bucket label for // the value (N - 1) would change to [N - 1, N), which would result in different // versions of Chrome using different bucket labels for identical data. #define INTERNAL_HISTOGRAM_EXACT_LINEAR_WITH_FLAG(name, sample, boundary, \ flag) … // While this behaves the same as the above macro, the wrapping of a linear // histogram with another object to do the scaling means the POINTER_BLOCK // macro can't be used as it is tied to HistogramBase #define INTERNAL_HISTOGRAM_SCALED_EXACT_LINEAR_WITH_FLAG( \ name, sample, count, boundary, scale, flag) … // Helper for 'overloading' UMA_HISTOGRAM_ENUMERATION with a variable number of // arguments. #define INTERNAL_UMA_HISTOGRAM_ENUMERATION_GET_MACRO(_1, _2, NAME, ...) … #define INTERNAL_UMA_HISTOGRAM_ENUMERATION_DEDUCE_BOUNDARY(name, sample, \ flags) … // Note: The value in |sample| must be strictly less than |enum_size|. #define INTERNAL_UMA_HISTOGRAM_ENUMERATION_SPECIFY_BOUNDARY(name, sample, \ enum_size, flags) … // Similar to the previous macro but intended for enumerations. This delegates // the work to the previous macro, but supports scoped enumerations as well by // forcing an explicit cast to the HistogramBase::Sample integral type. // // Note the range checks verify two separate issues: // - that the declared enum size isn't out of range of HistogramBase::Sample // - that the declared enum size is > 0 // // TODO(dcheng): This should assert that the passed in types are actually enum // types. #define INTERNAL_HISTOGRAM_ENUMERATION_WITH_FLAG(name, sample, boundary, flag) … #define INTERNAL_HISTOGRAM_SCALED_ENUMERATION_WITH_FLAG(name, sample, count, \ scale, flag) … // This is a helper macro used by other macros and shouldn't be used directly. // This is necessary to expand __COUNTER__ to an actual value. #define INTERNAL_SCOPED_UMA_HISTOGRAM_TIMER_EXPANDER(name, timing, key) … // This is a helper macro used by other macros and shouldn't be used directly. #define INTERNAL_SCOPED_UMA_HISTOGRAM_TIMER_UNIQUE(name, timing, key) … #endif // BASE_METRICS_HISTOGRAM_MACROS_INTERNAL_H_
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