/* -*-  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 "mozilla/Telemetry.h"

#include "nsString.h"

#include "nsClassHashtable.h"

#include "mozilla/Mutex.h"

#include "CombinedStacks.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__