tor-browser

Tools.h (6053B)

---

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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_GFX_TOOLS_H_
#define MOZILLA_GFX_TOOLS_H_

#include <math.h>

#include <utility>

#include "Point.h"
#include "Types.h"
#include "mozilla/CheckedInt.h"
#include "mozilla/MemoryReporting.h"  // for MallocSizeOf

namespace mozilla {
namespace gfx {

static inline bool IsOperatorBoundByMask(CompositionOp aOp) {
 switch (aOp) {
   case CompositionOp::OP_IN:
   case CompositionOp::OP_OUT:
   case CompositionOp::OP_DEST_IN:
   case CompositionOp::OP_DEST_ATOP:
   case CompositionOp::OP_SOURCE:
     return false;
   default:
     return true;
 }
}

template <class T>
struct ClassStorage {
 char bytes[sizeof(T)];

 const T* addr() const { return (const T*)bytes; }
 T* addr() { return (T*)(void*)bytes; }
};

static inline bool FuzzyEqual(Float aA, Float aB, Float aErr) {
 if ((aA + aErr >= aB) && (aA - aErr <= aB)) {
   return true;
 }
 return false;
}

static inline void NudgeToInteger(float* aVal) {
 float r = floorf(*aVal + 0.5f);
 // The error threshold should be proportional to the rounded value. This
 // bounds the relative error introduced by the nudge operation. However,
 // when the rounded value is 0, the error threshold can't be proportional
 // to the rounded value (we'd never round), so we just choose the same
 // threshold as for a rounded value of 1.
 if (FuzzyEqual(r, *aVal, r == 0.0f ? 1e-6f : fabs(r * 1e-6f))) {
   *aVal = r;
 }
}

static inline void NudgeToInteger(float* aVal, float aErr) {
 float r = floorf(*aVal + 0.5f);
 if (FuzzyEqual(r, *aVal, aErr)) {
   *aVal = r;
 }
}

static inline void NudgeToInteger(double* aVal) {
 float f = float(*aVal);
 NudgeToInteger(&f);
 *aVal = f;
}

static inline Float Distance(Point aA, Point aB) {
 return hypotf(aB.x - aA.x, aB.y - aA.y);
}

template <typename T, int alignment = 16>
struct AlignedArray final {
 typedef T value_type;

 AlignedArray() : mPtr(nullptr), mStorage(nullptr), mCount(0) {}

 explicit MOZ_ALWAYS_INLINE AlignedArray(size_t aCount, bool aZero = false)
     : mPtr(nullptr), mStorage(nullptr), mCount(0) {
   Realloc(aCount, aZero);
 }

 MOZ_ALWAYS_INLINE ~AlignedArray() { Dealloc(); }

 void Dealloc() {
   // If we fail this assert we'll need to uncomment the loop below to make
   // sure dtors are properly invoked. If we do that, we should check that the
   // comment about compiler dead code elimination is in fact true for all the
   // compilers that we care about.
   static_assert(std::is_trivially_destructible<T>::value,
                 "Destructors must be invoked for this type");
#if 0
   for (size_t i = 0; i < mCount; ++i) {
     // Since we used the placement |operator new| function to construct the
     // elements of this array we need to invoke their destructors manually.
     // For types where the destructor does nothing the compiler's dead code
     // elimination step should optimize this loop away.
     mPtr[i].~T();
   }
#endif

   free(mStorage);
   mStorage = nullptr;
   mPtr = nullptr;
 }

 MOZ_ALWAYS_INLINE void Realloc(size_t aCount, bool aZero = false) {
   free(mStorage);
   CheckedInt32 storageByteCount =
       CheckedInt32(sizeof(T)) * aCount + (alignment - 1);
   if (!storageByteCount.isValid()) {
     mStorage = nullptr;
     mPtr = nullptr;
     mCount = 0;
     return;
   }
   // We don't create an array of T here, since we don't want ctors to be
   // invoked at the wrong places if we realign below.
   if (aZero) {
     // calloc can be more efficient than new[] for large chunks,
     // so we use calloc/malloc/free for everything.
     mStorage = static_cast<uint8_t*>(calloc(1u, storageByteCount.value()));
   } else {
     mStorage = static_cast<uint8_t*>(malloc(storageByteCount.value()));
   }
   if (!mStorage) {
     mStorage = nullptr;
     mPtr = nullptr;
     mCount = 0;
     return;
   }
   if (uintptr_t(mStorage) % alignment) {
     // Our storage does not start at a <alignment>-byte boundary. Make sure
     // mPtr does!
     mPtr = (T*)(uintptr_t(mStorage) + alignment -
                 (uintptr_t(mStorage) % alignment));
   } else {
     mPtr = (T*)(mStorage);
   }
   // Now that mPtr is pointing to the aligned position we can use placement
   // |operator new| to invoke any ctors at the correct positions. For types
   // that have a no-op default constructor the compiler's dead code
   // elimination step should optimize this away.
   mPtr = new (mPtr) T[aCount];
   mCount = aCount;
 }

 void Swap(AlignedArray<T, alignment>& aOther) {
   std::swap(mPtr, aOther.mPtr);
   std::swap(mStorage, aOther.mStorage);
   std::swap(mCount, aOther.mCount);
 }

 size_t HeapSizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
   return aMallocSizeOf(mStorage);
 }

 MOZ_ALWAYS_INLINE operator T*() { return mPtr; }

 T* mPtr;

private:
 uint8_t* mStorage;
 size_t mCount;
};

/**
* Returns aWidth * aBytesPerPixel increased, if necessary, so that it divides
* exactly into |alignment|.
*
* Note that currently |alignment| must be a power-of-2. If for some reason we
* want to support NPOT alignment we can revert back to this functions old
* implementation.
*/
template <int alignment>
int32_t GetAlignedStride(int32_t aWidth, int32_t aBytesPerPixel) {
 static_assert(alignment > 0 && (alignment & (alignment - 1)) == 0,
               "This implementation currently require power-of-two alignment");
 const int32_t mask = alignment - 1;
 CheckedInt32 stride =
     CheckedInt32(aWidth) * CheckedInt32(aBytesPerPixel) + CheckedInt32(mask);
 if (stride.isValid()) {
   return stride.value() & ~mask;
 }
 return 0;
}

}  // namespace gfx
}  // namespace mozilla

#endif /* MOZILLA_GFX_TOOLS_H_ */