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       1             : /* -*-  Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
       2             : /* This Source Code Form is subject to the terms of the Mozilla Public
       3             :  * License, v. 2.0. If a copy of the MPL was not distributed with this
       4             :  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
       5             : 
       6             : #ifndef KeyedStackCapturer_h__
       7             : #define KeyedStackCapturer_h__
       8             : 
       9             : #include "Telemetry.h"
      10             : #include "nsString.h"
      11             : #include "nsClassHashtable.h"
      12             : #include "mozilla/Mutex.h"
      13             : #include "CombinedStacks.h"
      14             : 
      15             : struct JSContext;
      16             : 
      17             : namespace mozilla {
      18             : namespace Telemetry {
      19             : 
      20             : /**
      21             : * Allows taking a snapshot of a call stack on demand. Captured stacks are
      22             : * indexed by a string key in a hash table. The stack is only captured Once
      23             : * for each key. Consequent captures with the same key result in incrementing
      24             : * capture counter without re-capturing the stack.
      25             : */
      26           0 : class KeyedStackCapturer
      27             : {
      28             : public:
      29           3 :   KeyedStackCapturer()
      30           3 :     : mStackCapturerMutex("Telemetry::StackCapturerMutex")
      31           3 :   {}
      32             : 
      33             :   /**
      34             :    * Captures a stack for the given key.
      35             :    */
      36             :   void Capture(const nsACString& aKey);
      37             : 
      38             :   /**
      39             :    * Transforms captured stacks into a JS object.
      40             :    */
      41             :    NS_IMETHODIMP ReflectCapturedStacks(
      42             :     JSContext *cx, JS::MutableHandle<JS::Value> ret);
      43             : 
      44             :   /**
      45             :    * Resets captured stacks and the information related to them.
      46             :    */
      47             :   void Clear();
      48             : 
      49             : private:
      50             :   /**
      51             :    * Describes how often a stack was captured.
      52             :    */
      53             :   struct StackFrequencyInfo {
      54             :     // A number of times the stack was captured.
      55             :     uint32_t mCount;
      56             :     // Index of the stack inside stacks array.
      57             :     uint32_t mIndex;
      58             : 
      59           0 :     StackFrequencyInfo(uint32_t aCount, uint32_t aIndex)
      60           0 :       : mCount(aCount)
      61           0 :       , mIndex(aIndex)
      62           0 :     {}
      63             :   };
      64             : 
      65             :   typedef nsClassHashtable<nsCStringHashKey, StackFrequencyInfo> FrequencyInfoMapType;
      66             : 
      67             :   FrequencyInfoMapType mStackInfos;
      68             :   CombinedStacks mStacks;
      69             :   Mutex mStackCapturerMutex;
      70             : };
      71             : 
      72             : } // namespace Telemetry
      73             : } // namespace mozilla
      74             : 
      75             : #endif // KeyedStackCapturer_h__