The Tor Browser: gfx/layers/LayerUtils.cpp@97036ab72558

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

     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/. */

     6 #include "LayerUtils.h"

     7 #include "PremultiplyTables.h"

     8 #include "mozilla/Endian.h"

    10 namespace mozilla {

    11 namespace layers {

    13 using namespace mozilla::gfx;

    15 static inline const uint8_t PremultiplyValue(uint8_t a, uint8_t v) {

    16   return PremultiplyTable[a*256+v];

    17 }

    19 static inline const uint8_t UnpremultiplyValue(uint8_t a, uint8_t v) {

    20   return UnpremultiplyTable[a*256+v];

    21 }

    23 #ifdef DEBUG

    24 static bool IsLittleEndian()

    25 {

    26     // Violate strict aliasing, because violating strict aliasing is how

    27     // we always pack and unpack between uint32_t and uint8_t[].

    28     uint16_t testShort;

    29     static const uint8_t testBytes[2] = { 0xAA, 0xBB };

    30     memcpy(&testShort, testBytes, sizeof(testBytes));

    31     return testShort == 0xBBAA;

    32 }

    33 #endif // DEBUG

    35 #ifdef MOZ_LITTLE_ENDIAN

    36 #define ASSERT_ENDIAN() MOZ_ASSERT(IsLittleEndian(), "Defined as little endian, but actually big!")

    37 #else

    38 #define ASSERT_ENDIAN() MOZ_ASSERT(!IsLittleEndian(), "Defined as big endian, but actually little!")

    39 #endif

    41 void

    42 PremultiplySurface(DataSourceSurface* srcSurface,

    43                    DataSourceSurface* destSurface)

    44 {

    45   if (!destSurface)

    46     destSurface = srcSurface;

    48   IntSize srcSize = srcSurface->GetSize();

    49   MOZ_ASSERT(srcSurface->GetFormat() == destSurface->GetFormat() &&

    50              srcSize.width  == destSurface->GetSize().width &&

    51              srcSize.height  == destSurface->GetSize().height &&

    52              srcSurface->Stride() == destSurface->Stride(),

    53              "Source and destination surfaces don't have identical characteristics");

    55   MOZ_ASSERT(srcSurface->Stride() == srcSize.width * 4,

    56              "Source surface stride isn't tightly packed");

    58   // Only premultiply ARGB32

    59   if (srcSurface->GetFormat() != SurfaceFormat::B8G8R8A8) {

    60     if (destSurface != srcSurface) {

    61       memcpy(destSurface->GetData(), srcSurface->GetData(),

    62              srcSurface->Stride() * srcSize.height);

    63     }

    64     return;

    65   }

    67   uint8_t *src = srcSurface->GetData();

    68   uint8_t *dst = destSurface->GetData();

    70   // Assert that our endian define is correct.

    71   ASSERT_ENDIAN();

    73   uint32_t dim = srcSize.width * srcSize.height;

    74   for (uint32_t i = 0; i < dim; ++i) {

    75 #ifdef MOZ_LITTLE_ENDIAN

    76     uint8_t b = *src++;

    77     uint8_t g = *src++;

    78     uint8_t r = *src++;

    79     uint8_t a = *src++;

    81     *dst++ = PremultiplyValue(a, b);

    82     *dst++ = PremultiplyValue(a, g);

    83     *dst++ = PremultiplyValue(a, r);

    84     *dst++ = a;

    85 #else

    86     uint8_t a = *src++;

    87     uint8_t r = *src++;

    88     uint8_t g = *src++;

    89     uint8_t b = *src++;

    91     *dst++ = a;

    92     *dst++ = PremultiplyValue(a, r);

    93     *dst++ = PremultiplyValue(a, g);

    94     *dst++ = PremultiplyValue(a, b);

    95 #endif

    96   }

    97 }

   100 }

   101 }

The Tor Browser / file revision

gfx/layers/LayerUtils.cpp@97036ab72558

gfx/layers/LayerUtils.cpp