blob: b6928f1f5290e627bfd50aabedb3582afaf516ef [file] [log] [blame]
// 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.
#include <limits.h>
#include <stddef.h>
#include <stdint.h>
#include <memory>
#include <string>
#include <vector>
#include "base/atomicops.h"
#include "base/base_export.h"
#include "base/macros.h"
#include "base/strings/string_piece.h"
#include "base/time/time.h"
namespace base {
class DictionaryValue;
class HistogramBase;
class HistogramSamples;
class ListValue;
class Pickle;
class PickleIterator;
// This enum is used to facilitate deserialization of histograms from other
// processes into the browser. If you create another class that inherits from
// HistogramBase, add new histogram types and names below.
enum HistogramType {
// Controls the verbosity of the information when the histogram is serialized to
// a JSON.
// GENERATED_JAVA_ENUM_PACKAGE: org.chromium.base.metrics
enum JSONVerbosityLevel {
// The histogram is completely serialized.
// The bucket information is not serialized.
std::string HistogramTypeToString(HistogramType type);
// This enum is used for reporting how many histograms and of what types and
// variations are being created. It has to be in the main .h file so it is
// visible to files that define the various histogram types.
enum HistogramReport {
// Count the number of reports created. The other counts divided by this
// number will give the average per run of the program.
// Count the total number of histograms created. It is the limit against
// which all others are compared.
// Count the total number of histograms looked-up. It's better to cache
// the result of a single lookup rather than do it repeatedly.
// These count the individual histogram types. This must follow the order
// of HistogramType above.
// These indicate the individual flags that were set.
// This must be last.
// Create or find existing histogram that matches the pickled info.
// Returns NULL if the pickled data has problems.
BASE_EXPORT HistogramBase* DeserializeHistogramInfo(base::PickleIterator* iter);
class BASE_EXPORT HistogramBase {
typedef int32_t Sample; // Used for samples.
typedef subtle::Atomic32 AtomicCount; // Used to count samples.
typedef int32_t Count; // Used to manipulate counts in temporaries.
static const Sample kSampleType_MAX; // INT_MAX
enum Flags {
kNoFlags = 0x0,
// Histogram should be UMA uploaded.
kUmaTargetedHistogramFlag = 0x1,
// Indicates that this is a stability histogram. This flag exists to specify
// which histograms should be included in the initial stability log. Please
// refer to |MetricsService::PrepareInitialStabilityLog|.
kUmaStabilityHistogramFlag = kUmaTargetedHistogramFlag | 0x2,
// Indicates that the histogram was pickled to be sent across an IPC
// Channel. If we observe this flag on a histogram being aggregated into
// after IPC, then we are running in a single process mode, and the
// aggregation should not take place (as we would be aggregating back into
// the source histogram!).
kIPCSerializationSourceFlag = 0x10,
// Indicates that a callback exists for when a new sample is recorded on
// this histogram. We store this as a flag with the histogram since
// histograms can be in performance critical code, and this allows us
// to shortcut looking up the callback if it doesn't exist.
kCallbackExists = 0x20,
// Indicates that the histogram is held in "persistent" memory and may
// be accessible between processes. This is only possible if such a
// memory segment has been created/attached, used to create a Persistent-
// MemoryAllocator, and that loaded into the Histogram module before this
// histogram is created.
kIsPersistent = 0x40,
// Histogram data inconsistency types.
enum Inconsistency : uint32_t {
// Construct the base histogram. The name is not copied; it's up to the
// caller to ensure that it lives at least as long as this object.
explicit HistogramBase(const char* name);
virtual ~HistogramBase();
const char* histogram_name() const { return histogram_name_; }
// Comapres |name| to the histogram name and triggers a DCHECK if they do not
// match. This is a helper function used by histogram macros, which results in
// in more compact machine code being generated by the macros.
void CheckName(const StringPiece& name) const;
// Get a unique ID for this histogram's samples.
virtual uint64_t name_hash() const = 0;
// Operations with Flags enum.
int32_t flags() const { return subtle::NoBarrier_Load(&flags_); }
void SetFlags(int32_t flags);
void ClearFlags(int32_t flags);
virtual HistogramType GetHistogramType() const = 0;
// Whether the histogram has construction arguments as parameters specified.
// For histograms that don't have the concept of minimum, maximum or
// bucket_count, this function always returns false.
virtual bool HasConstructionArguments(
Sample expected_minimum,
Sample expected_maximum,
uint32_t expected_bucket_count) const = 0;
virtual void Add(Sample value) = 0;
// In Add function the |value| bucket is increased by one, but in some use
// cases we need to increase this value by an arbitrary integer. AddCount
// function increases the |value| bucket by |count|. |count| should be greater
// than or equal to 1.
virtual void AddCount(Sample value, int count) = 0;
// 2 convenient functions that call Add(Sample).
void AddTime(const TimeDelta& time);
void AddBoolean(bool value);
virtual void AddSamples(const HistogramSamples& samples) = 0;
virtual bool AddSamplesFromPickle(base::PickleIterator* iter) = 0;
// Serialize the histogram info into |pickle|.
// Note: This only serializes the construction arguments of the histogram, but
// does not serialize the samples.
void SerializeInfo(base::Pickle* pickle) const;
// Try to find out data corruption from histogram and the samples.
// The returned value is a combination of Inconsistency enum.
virtual uint32_t FindCorruption(const HistogramSamples& samples) const;
// Snapshot the current complete set of sample data.
// Override with atomic/locked snapshot if needed.
// NOTE: this data can overflow for long-running sessions. It should be
// handled with care and this method is recommended to be used only
// in about:histograms and test code.
virtual std::unique_ptr<HistogramSamples> SnapshotSamples() const = 0;
// Calculate the change (delta) in histogram counts since the previous call
// to this method. Each successive call will return only those counts
// changed since the last call.
virtual std::unique_ptr<HistogramSamples> SnapshotDelta() = 0;
// Calculate the change (delta) in histogram counts since the previous call
// to SnapshotDelta() but do so without modifying any internal data as to
// what was previous logged. After such a call, no further calls to this
// method or to SnapshotDelta() should be done as the result would include
// data previously returned. Because no internal data is changed, this call
// can be made on "const" histograms such as those with data held in
// read-only memory.
virtual std::unique_ptr<HistogramSamples> SnapshotFinalDelta() const = 0;
// The following methods provide graphical histogram displays.
virtual void WriteHTMLGraph(std::string* output) const = 0;
virtual void WriteAscii(std::string* output) const = 0;
// TODO(bcwhite): Remove this after crbug/736675.
virtual bool ValidateHistogramContents(bool crash_if_invalid,
int corrupted_count) const;
// Produce a JSON representation of the histogram with |verbosity_level| as
// the serialization verbosity. This is implemented with the help of
// GetParameters and GetCountAndBucketData; overwrite them to customize the
// output.
void WriteJSON(std::string* output, JSONVerbosityLevel verbosity_level) const;
// Subclasses should implement this function to make SerializeInfo work.
virtual void SerializeInfoImpl(base::Pickle* pickle) const = 0;
// Writes information about the construction parameters in |params|.
virtual void GetParameters(DictionaryValue* params) const = 0;
// Writes information about the current (non-empty) buckets and their sample
// counts to |buckets|, the total sample count to |count| and the total sum
// to |sum|.
virtual void GetCountAndBucketData(Count* count,
int64_t* sum,
ListValue* buckets) const = 0;
//// Produce actual graph (set of blank vs non blank char's) for a bucket.
void WriteAsciiBucketGraph(double current_size,
double max_size,
std::string* output) const;
// Return a string description of what goes in a given bucket.
const std::string GetSimpleAsciiBucketRange(Sample sample) const;
// Write textual description of the bucket contents (relative to histogram).
// Output is the count in the buckets, as well as the percentage.
void WriteAsciiBucketValue(Count current,
double scaled_sum,
std::string* output) const;
// Retrieves the callback for this histogram, if one exists, and runs it
// passing |sample| as the parameter.
void FindAndRunCallback(Sample sample) const;
// Gets a permanent string that can be used for histogram objects when the
// original is not a code constant or held in persistent memory.
static const char* GetPermanentName(const std::string& name);
friend class HistogramBaseTest;
// A pointer to permanent storage where the histogram name is held. This can
// be code space or the output of GetPermanentName() or any other storage
// that is known to never change. This is not StringPiece because (a) char*
// is 1/2 the size and (b) StringPiece transparently casts from std::string
// which can easily lead to a pointer to non-permanent space.
// For persistent histograms, this will simply point into the persistent
// memory segment, thus avoiding duplication. For heap histograms, the
// GetPermanentName method will create the necessary copy.
const char* const histogram_name_;
// Additional information about the histogram.
AtomicCount flags_;
} // namespace base