gecko-dev/toolkit/components/telemetry/other/KeyedStackCapturer.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef KeyedStackCapturer_h__
#define KeyedStackCapturer_h__
#include "CombinedStacks.h"
#include "mozilla/Mutex.h"
#include "mozilla/Telemetry.h"
#include "nsClassHashtable.h"
#include "nsString.h"
struct JSContext;
namespace mozilla {
namespace Telemetry {
/**
* Allows taking a snapshot of a call stack on demand. Captured stacks are
* indexed by a string key in a hash table. The stack is only captured Once
* for each key. Consequent captures with the same key result in incrementing
* capture counter without re-capturing the stack.
*/
class KeyedStackCapturer {
public:
KeyedStackCapturer() : mStackCapturerMutex("Telemetry::StackCapturerMutex") {}
/**
* Captures a stack for the given key.
*/
void Capture(const nsACString& aKey);
/**
* Transforms captured stacks into a JS object.
*/
NS_IMETHODIMP ReflectCapturedStacks(JSContext* cx,
JS::MutableHandle<JS::Value> ret);
/**
* Resets captured stacks and the information related to them.
*/
void Clear();
size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
private:
/**
* Describes how often a stack was captured.
*/
struct StackFrequencyInfo {
// A number of times the stack was captured.
uint32_t mCount;
// Index of the stack inside stacks array.
uint32_t mIndex;
StackFrequencyInfo(uint32_t aCount, uint32_t aIndex)
: mCount(aCount), mIndex(aIndex) {}
};
typedef nsClassHashtable<nsCStringHashKey, StackFrequencyInfo>
FrequencyInfoMapType;
FrequencyInfoMapType mStackInfos;
CombinedStacks mStacks;
Mutex mStackCapturerMutex;
};
} // namespace Telemetry
} // namespace mozilla
#endif // KeyedStackCapturer_h__