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/* -*- Mode: C++; tab-width: 8; 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 mozilla_ChaosMode_h
#define mozilla_ChaosMode_h
#include "mozilla/Atomics.h"
#include "mozilla/EnumSet.h"
#include <stdint.h>
#include <stdlib.h>
namespace mozilla {
enum ChaosFeature {
None = 0x0,
// Altering thread scheduling.
ThreadScheduling = 0x1,
// Altering network request scheduling.
NetworkScheduling = 0x2,
// Altering timer scheduling.
TimerScheduling = 0x4,
// Read and write less-than-requested amounts.
IOAmounts = 0x8,
// Iterate over hash tables in random order.
HashTableIteration = 0x10,
// Randomly refuse to use cached version of image (when allowed by spec).
ImageCache = 0x20,
Any = 0xffffffff,
};
namespace detail {
extern MFBT_DATA Atomic<uint32_t> gChaosModeCounter;
extern MFBT_DATA ChaosFeature gChaosFeatures;
} // namespace detail
/**
* When "chaos mode" is activated, code that makes implicitly nondeterministic
* choices is encouraged to make random and extreme choices, to test more
* code paths and uncover bugs.
*/
class ChaosMode
{
public:
static void SetChaosFeature(ChaosFeature aChaosFeature)
{
detail::gChaosFeatures = aChaosFeature;
}
static bool isActive(ChaosFeature aFeature)
{
if (detail::gChaosModeCounter > 0) {
return true;
}
return detail::gChaosFeatures & aFeature;
}
/**
* Increase the chaos mode activation level. An equivalent number of
* calls to leaveChaosMode must be made in order to restore the original
* chaos mode state. If the activation level is nonzero all chaos mode
* features are activated.
*/
static void enterChaosMode()
{
detail::gChaosModeCounter++;
}
/**
* Decrease the chaos mode activation level. See enterChaosMode().
*/
static void leaveChaosMode()
{
MOZ_ASSERT(detail::gChaosModeCounter > 0);
detail::gChaosModeCounter--;
}
/**
* Returns a somewhat (but not uniformly) random uint32_t < aBound.
* Not to be used for anything except ChaosMode, since it's not very random.
*/
static uint32_t randomUint32LessThan(uint32_t aBound)
{
MOZ_ASSERT(aBound != 0);
return uint32_t(rand()) % aBound;
}
};
} /* namespace mozilla */
#endif /* mozilla_ChaosMode_h */
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