diff -r 000000000000 -r 6474c204b198 gfx/layers/ImageDataSerializer.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/layers/ImageDataSerializer.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,161 @@
+/* -*- Mode: C++; tab-width: 20; 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/. */
+
+#include "ImageDataSerializer.h"
+#include "gfx2DGlue.h"                  // for SurfaceFormatToImageFormat
+#include "gfxImageSurface.h"            // for gfxImageSurface
+#include "gfxPoint.h"                   // for gfxIntSize
+#include "mozilla/Assertions.h"         // for MOZ_ASSERT, etc
+#include "mozilla/gfx/2D.h"             // for DataSourceSurface, Factory
+#include "mozilla/gfx/Tools.h"          // for GetAlignedStride, etc
+#include "mozilla/mozalloc.h"           // for operator delete, etc
+
+namespace mozilla {
+namespace layers {
+
+using namespace gfx;
+
+// The Data is layed out as follows:
+//
+//  +-------------------+   -++ --+   <-- ImageDataSerializerBase::mData pointer
+//  | SurfaceBufferInfo |     |   |
+//  +-------------------+   --+   | offset
+//  |        ...        |         |
+//  +-------------------+   ------+
+//  |                   |
+//  |       data        |
+//  |                   |
+//  +-------------------+
+
+// Structure written at the beginning of the data blob containing the image
+// (as shown in the figure above). It contains the necessary informations to
+// read the image in the blob.
+namespace {
+struct SurfaceBufferInfo
+{
+  uint32_t width;
+  uint32_t height;
+  SurfaceFormat format;
+
+  static uint32_t GetOffset()
+  {
+    return GetAlignedStride<16>(sizeof(SurfaceBufferInfo));
+  }
+};
+} // anonymous namespace
+
+static SurfaceBufferInfo*
+GetBufferInfo(uint8_t* aData, size_t aDataSize)
+{
+  return aDataSize >= sizeof(SurfaceBufferInfo)
+         ? reinterpret_cast<SurfaceBufferInfo*>(aData)
+         : nullptr;
+}
+
+void
+ImageDataSerializer::InitializeBufferInfo(IntSize aSize,
+                                          SurfaceFormat aFormat)
+{
+  SurfaceBufferInfo* info = GetBufferInfo(mData, mDataSize);
+  MOZ_ASSERT(info); // OK to assert here, this method is client-side-only
+  info->width = aSize.width;
+  info->height = aSize.height;
+  info->format = aFormat;
+  Validate();
+}
+
+static inline uint32_t
+ComputeStride(SurfaceFormat aFormat, uint32_t aWidth)
+{
+  return GetAlignedStride<4>(BytesPerPixel(aFormat) * aWidth);
+}
+
+uint32_t
+ImageDataSerializerBase::ComputeMinBufferSize(IntSize aSize,
+                                          SurfaceFormat aFormat)
+{
+  uint32_t bufsize = aSize.height * ComputeStride(aFormat, aSize.width);
+  return SurfaceBufferInfo::GetOffset()
+       + GetAlignedStride<16>(bufsize);
+}
+
+void
+ImageDataSerializerBase::Validate()
+{
+  mIsValid = false;
+  if (!mData) {
+    return;
+  }
+  SurfaceBufferInfo* info = GetBufferInfo(mData, mDataSize);
+  if (!info) {
+    return;
+  }
+  size_t requiredSize =
+           ComputeMinBufferSize(IntSize(info->width, info->height), info->format);
+  mIsValid = requiredSize <= mDataSize;
+}
+
+uint8_t*
+ImageDataSerializerBase::GetData()
+{
+  MOZ_ASSERT(IsValid());
+  return mData + SurfaceBufferInfo::GetOffset();
+}
+
+uint32_t
+ImageDataSerializerBase::GetStride() const
+{
+  MOZ_ASSERT(IsValid());
+  SurfaceBufferInfo* info = GetBufferInfo(mData, mDataSize);
+  return ComputeStride(GetFormat(), info->width);
+}
+
+IntSize
+ImageDataSerializerBase::GetSize() const
+{
+  MOZ_ASSERT(IsValid());
+  SurfaceBufferInfo* info = GetBufferInfo(mData, mDataSize);
+  return IntSize(info->width, info->height);
+}
+
+SurfaceFormat
+ImageDataSerializerBase::GetFormat() const
+{
+  MOZ_ASSERT(IsValid());
+  return GetBufferInfo(mData, mDataSize)->format;
+}
+
+TemporaryRef<gfxImageSurface>
+ImageDataSerializerBase::GetAsThebesSurface()
+{
+  MOZ_ASSERT(IsValid());
+  IntSize size = GetSize();
+  return new gfxImageSurface(GetData(),
+                             gfxIntSize(size.width, size.height),
+                             GetStride(),
+                             SurfaceFormatToImageFormat(GetFormat()));
+}
+
+TemporaryRef<DrawTarget>
+ImageDataSerializerBase::GetAsDrawTarget(gfx::BackendType aBackend)
+{
+  MOZ_ASSERT(IsValid());
+  return gfx::Factory::CreateDrawTargetForData(aBackend,
+                                               GetData(), GetSize(),
+                                               GetStride(), GetFormat());
+}
+
+TemporaryRef<gfx::DataSourceSurface>
+ImageDataSerializerBase::GetAsSurface()
+{
+  MOZ_ASSERT(IsValid());
+  return Factory::CreateWrappingDataSourceSurface(GetData(),
+                                                  GetStride(),
+                                                  GetSize(),
+                                                  GetFormat());
+}
+
+} // namespace layers
+} // namespace mozilla