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       1             : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2             : /* vim: set ts=8 sts=2 et sw=2 tw=80: */
       3             : /* This Source Code Form is subject to the terms of the Mozilla Public
       4             :  * License, v. 2.0. If a copy of the MPL was not distributed with this
       5             :  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
       6             : 
       7             : #ifndef mozilla_ChaosMode_h
       8             : #define mozilla_ChaosMode_h
       9             : 
      10             : #include "mozilla/Atomics.h"
      11             : #include "mozilla/EnumSet.h"
      12             : 
      13             : #include <stdint.h>
      14             : #include <stdlib.h>
      15             : 
      16             : namespace mozilla {
      17             : 
      18             : enum ChaosFeature {
      19             :   None = 0x0,
      20             :   // Altering thread scheduling.
      21             :   ThreadScheduling = 0x1,
      22             :   // Altering network request scheduling.
      23             :   NetworkScheduling = 0x2,
      24             :   // Altering timer scheduling.
      25             :   TimerScheduling = 0x4,
      26             :   // Read and write less-than-requested amounts.
      27             :   IOAmounts = 0x8,
      28             :   // Iterate over hash tables in random order.
      29             :   HashTableIteration = 0x10,
      30             :   // Randomly refuse to use cached version of image (when allowed by spec).
      31             :   ImageCache = 0x20,
      32             :   Any = 0xffffffff,
      33             : };
      34             : 
      35             : namespace detail {
      36             : extern MFBT_DATA Atomic<uint32_t> gChaosModeCounter;
      37             : extern MFBT_DATA ChaosFeature gChaosFeatures;
      38             : } // namespace detail
      39             : 
      40             : /**
      41             :  * When "chaos mode" is activated, code that makes implicitly nondeterministic
      42             :  * choices is encouraged to make random and extreme choices, to test more
      43             :  * code paths and uncover bugs.
      44             :  */
      45             : class ChaosMode
      46             : {
      47             : public:
      48           0 :   static void SetChaosFeature(ChaosFeature aChaosFeature)
      49             :   {
      50           0 :     detail::gChaosFeatures = aChaosFeature;
      51           0 :   }
      52             : 
      53        5044 :   static bool isActive(ChaosFeature aFeature)
      54             :   {
      55        5044 :     if (detail::gChaosModeCounter > 0) {
      56           0 :       return true;
      57             :     }
      58        5044 :     return detail::gChaosFeatures & aFeature;
      59             :   }
      60             : 
      61             :   /**
      62             :    * Increase the chaos mode activation level. An equivalent number of
      63             :    * calls to leaveChaosMode must be made in order to restore the original
      64             :    * chaos mode state. If the activation level is nonzero all chaos mode
      65             :    * features are activated.
      66             :    */
      67           0 :   static void enterChaosMode()
      68             :   {
      69           0 :     detail::gChaosModeCounter++;
      70           0 :   }
      71             : 
      72             :   /**
      73             :    * Decrease the chaos mode activation level. See enterChaosMode().
      74             :    */
      75           0 :   static void leaveChaosMode()
      76             :   {
      77           0 :     MOZ_ASSERT(detail::gChaosModeCounter > 0);
      78           0 :     detail::gChaosModeCounter--;
      79           0 :   }
      80             : 
      81             :   /**
      82             :    * Returns a somewhat (but not uniformly) random uint32_t < aBound.
      83             :    * Not to be used for anything except ChaosMode, since it's not very random.
      84             :    */
      85           0 :   static uint32_t randomUint32LessThan(uint32_t aBound)
      86             :   {
      87           0 :     MOZ_ASSERT(aBound != 0);
      88           0 :     return uint32_t(rand()) % aBound;
      89             :   }
      90             : };
      91             : 
      92             : } /* namespace mozilla */
      93             : 
      94             : #endif /* mozilla_ChaosMode_h */