tor-browser

gfxBaseSharedMemorySurface.h (5500B)

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// vim:set ts=4 sts=2 sw=2 et cin:
/* -*- 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/. */

#ifndef GFX_SHARED_MEMORYSURFACE_H
#define GFX_SHARED_MEMORYSURFACE_H

#include "mozilla/gfx/2D.h"
#include "mozilla/ipc/Shmem.h"

#include "gfxASurface.h"
#include "gfxImageSurface.h"
#include "pratom.h"

typedef struct _cairo_user_data_key cairo_user_data_key_t;

struct SharedImageInfo {
 int32_t width;
 int32_t height;
 gfxImageFormat format;
 int32_t readCount;
};

inline SharedImageInfo* GetShmInfoPtr(const mozilla::ipc::Shmem& aShmem) {
 return reinterpret_cast<SharedImageInfo*>(
     aShmem.get<char>() + aShmem.Size<char>() - sizeof(SharedImageInfo));
}

extern const cairo_user_data_key_t SHM_KEY;

template <typename Base, typename Sub>
class gfxBaseSharedMemorySurface : public Base {
 typedef mozilla::ipc::Shmem Shmem;

protected:
 virtual ~gfxBaseSharedMemorySurface() {
   MOZ_COUNT_DTOR(gfxBaseSharedMemorySurface);
 }

public:
 /**
  * Return a new gfxSharedImageSurface around a shmem segment newly
  * allocated by this function.  |aAllocator| is the object used to
  * allocate the new shmem segment.  Null is returned if creating
  * the surface failed.
  *
  * NB: the *caller* is responsible for freeing the Shmem allocated
  * by this function.
  */
 template <class ShmemAllocator>
 static already_AddRefed<Sub> Create(ShmemAllocator* aAllocator,
                                     const mozilla::gfx::IntSize& aSize,
                                     gfxImageFormat aFormat) {
   return Create<ShmemAllocator, false>(aAllocator, aSize, aFormat);
 }

 /**
  * Return a new gfxSharedImageSurface that wraps a shmem segment
  * already created by the Create() above.  Bad things will happen
  * if an attempt is made to wrap any other shmem segment.  Null is
  * returned if creating the surface failed.
  */
 static already_AddRefed<Sub> Open(const Shmem& aShmem) {
   SharedImageInfo* shmInfo = GetShmInfoPtr(aShmem);
   mozilla::gfx::IntSize size(shmInfo->width, shmInfo->height);
   if (!mozilla::gfx::Factory::CheckSurfaceSize(size)) return nullptr;

   gfxImageFormat format = shmInfo->format;
   long stride = gfxImageSurface::ComputeStride(size, format);

   RefPtr<Sub> s = new Sub(size, stride, format, aShmem);
   // We didn't create this Shmem and so don't free it on errors
   return (s->CairoStatus() != 0) ? nullptr : s.forget();
 }

 template <class ShmemAllocator>
 static already_AddRefed<Sub> CreateUnsafe(ShmemAllocator* aAllocator,
                                           const mozilla::gfx::IntSize& aSize,
                                           gfxImageFormat aFormat) {
   return Create<ShmemAllocator, true>(aAllocator, aSize, aFormat);
 }

 Shmem& GetShmem() { return mShmem; }

 static bool IsSharedImage(gfxASurface* aSurface) {
   return (aSurface && aSurface->GetType() == gfxSurfaceType::Image &&
           aSurface->GetData(&SHM_KEY));
 }

protected:
 gfxBaseSharedMemorySurface(const mozilla::gfx::IntSize& aSize, long aStride,
                            gfxImageFormat aFormat, const Shmem& aShmem)
     : Base(aShmem.get<unsigned char>(), aSize, aStride, aFormat) {
   MOZ_COUNT_CTOR(gfxBaseSharedMemorySurface);

   mShmem = aShmem;
   this->SetData(&SHM_KEY, this, nullptr);
 }

private:
 void WriteShmemInfo() {
   SharedImageInfo* shmInfo = GetShmInfoPtr(mShmem);
   shmInfo->width = this->mSize.width;
   shmInfo->height = this->mSize.height;
   shmInfo->format = this->mFormat;
   shmInfo->readCount = 0;
 }

 int32_t ReadLock() {
   SharedImageInfo* shmInfo = GetShmInfoPtr(mShmem);
   return PR_ATOMIC_INCREMENT(&shmInfo->readCount);
 }

 int32_t ReadUnlock() {
   SharedImageInfo* shmInfo = GetShmInfoPtr(mShmem);
   return PR_ATOMIC_DECREMENT(&shmInfo->readCount);
 }

 int32_t GetReadCount() {
   SharedImageInfo* shmInfo = GetShmInfoPtr(mShmem);
   return shmInfo->readCount;
 }

 static size_t GetAlignedSize(const mozilla::gfx::IntSize& aSize,
                              long aStride) {
#define MOZ_ALIGN_WORD(x) (((x) + 3) & ~3)
   return MOZ_ALIGN_WORD(sizeof(SharedImageInfo) + aSize.height * aStride);
 }

 template <class ShmemAllocator, bool Unsafe>
 static already_AddRefed<Sub> Create(ShmemAllocator* aAllocator,
                                     const mozilla::gfx::IntSize& aSize,
                                     gfxImageFormat aFormat) {
   if (!mozilla::gfx::Factory::CheckSurfaceSize(aSize)) return nullptr;

   Shmem shmem;
   long stride = gfxImageSurface::ComputeStride(aSize, aFormat);
   size_t size = GetAlignedSize(aSize, stride);
   if (!Unsafe) {
     if (!aAllocator->AllocShmem(size, &shmem)) return nullptr;
   } else {
     if (!aAllocator->AllocUnsafeShmem(size, &shmem)) return nullptr;
   }

   RefPtr<Sub> s = new Sub(aSize, stride, aFormat, shmem);
   if (s->CairoStatus() != 0) {
     aAllocator->DeallocShmem(shmem);
     return nullptr;
   }
   s->WriteShmemInfo();
   return s.forget();
 }

 Shmem mShmem;

 // Calling these is very bad, disallow it
 gfxBaseSharedMemorySurface(const gfxBaseSharedMemorySurface&);
 gfxBaseSharedMemorySurface& operator=(const gfxBaseSharedMemorySurface&);
};

#endif /* GFX_SHARED_MEMORYSURFACE_H */