gecko-dev/gfx/thebes/gfxReusableSharedImageSurfaceWrapper.cpp

/* 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 "gfxReusableSharedImageSurfaceWrapper.h"
#include "gfxSharedImageSurface.h"
#include "mozilla/layers/ISurfaceAllocator.h"

using mozilla::ipc::Shmem;
using mozilla::layers::ISurfaceAllocator;

gfxReusableSharedImageSurfaceWrapper::gfxReusableSharedImageSurfaceWrapper(ISurfaceAllocator* aAllocator,
                                                                           gfxSharedImageSurface* aSurface)
  : mAllocator(aAllocator)
  , mSurface(aSurface)
{
  MOZ_COUNT_CTOR(gfxReusableSharedImageSurfaceWrapper);
  ReadLock();
}

gfxReusableSharedImageSurfaceWrapper::~gfxReusableSharedImageSurfaceWrapper()
{
  MOZ_COUNT_DTOR(gfxReusableSharedImageSurfaceWrapper);
  ReadUnlock();
}

void
gfxReusableSharedImageSurfaceWrapper::ReadLock()
{
  NS_ASSERT_OWNINGTHREAD(gfxReusableSharedImageSurfaceWrapper);
  mSurface->ReadLock();
}

void
gfxReusableSharedImageSurfaceWrapper::ReadUnlock()
{
  int32_t readCount = mSurface->ReadUnlock();
  MOZ_ASSERT(readCount >= 0, "Read count should not be negative");

  if (readCount == 0) {
    mAllocator->DeallocShmem(mSurface->GetShmem());
  }
}

gfxReusableSurfaceWrapper*
gfxReusableSharedImageSurfaceWrapper::GetWritable(gfxImageSurface** aSurface)
{
  NS_ASSERT_OWNINGTHREAD(gfxReusableSharedImageSurfaceWrapper);

  int32_t readCount = mSurface->GetReadCount();
  MOZ_ASSERT(readCount > 0, "A ReadLock must be held when calling GetWritable");
  if (readCount == 1) {
    *aSurface = mSurface;
    return this;
  }

  // Something else is reading the surface, copy it
  RefPtr<gfxSharedImageSurface> copySurface =
    gfxSharedImageSurface::CreateUnsafe(mAllocator.get(), mSurface->GetSize(), mSurface->Format());
  copySurface->CopyFrom(mSurface);
  *aSurface = copySurface;

  // We need to create a new wrapper since this wrapper has an external ReadLock
  gfxReusableSurfaceWrapper* wrapper = new gfxReusableSharedImageSurfaceWrapper(mAllocator, copySurface);

  // No need to release the ReadLock on the surface, this will happen when
  // the wrapper is destroyed.

  return wrapper;
}

const unsigned char*
gfxReusableSharedImageSurfaceWrapper::GetReadOnlyData() const
{
  MOZ_ASSERT(mSurface->GetReadCount() > 0, "Should have read lock");
  return mSurface->Data();
}

gfxImageFormat
gfxReusableSharedImageSurfaceWrapper::Format()
{
  return mSurface->Format();
}

Shmem&
gfxReusableSharedImageSurfaceWrapper::GetShmem()
{
  return mSurface->GetShmem();
}

/* static */ already_AddRefed<gfxReusableSharedImageSurfaceWrapper>
gfxReusableSharedImageSurfaceWrapper::Open(ISurfaceAllocator* aAllocator, const Shmem& aShmem)
{
  RefPtr<gfxSharedImageSurface> sharedImage = gfxSharedImageSurface::Open(aShmem);
  RefPtr<gfxReusableSharedImageSurfaceWrapper> wrapper = new gfxReusableSharedImageSurfaceWrapper(aAllocator, sharedImage);
  wrapper->ReadUnlock();
  return wrapper.forget();
}