media: Create Mojo StructTraits for VideoFrame

media/mojo/interfaces/video_frame_struct_traits.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/mojo/interfaces/video_frame_struct_traits.h"
+
+#include <utility>
+#include <vector>
+
+#include "base/logging.h"
+#include "media/mojo/common/mojo_shared_buffer_video_frame.h"
+
+namespace mojo {
+
+namespace {
+
+media::mojom::VideoFrameDataPtr MakeVideoFrameData(
+    const scoped_refptr<media::VideoFrame>& input) {
+  // EOS frames contain no data.
+  if (input->metadata()->IsTrue(media::VideoFrameMetadata::END_OF_STREAM))
+    return nullptr;
+
+  if (input->storage_type() == media::VideoFrame::STORAGE_MOJO_SHARED_BUFFER) {
+    media::MojoSharedBufferVideoFrame* mojo_frame =
+        static_cast<media::MojoSharedBufferVideoFrame*>(input.get());
+
+    mojo::ScopedSharedBufferHandle dup = mojo_frame->Handle().Clone();
+    DCHECK(dup.is_valid());
+
+    return media::mojom::VideoFrameData::NewSharedBufferData(
+        media::mojom::SharedBufferVideoFrameData::New(
+            std::move(dup), mojo_frame->MappedSize(),
+            mojo_frame->stride(media::VideoFrame::kYPlane),
+            mojo_frame->stride(media::VideoFrame::kUPlane),
+            mojo_frame->stride(media::VideoFrame::kVPlane),
+            mojo_frame->PlaneOffset(media::VideoFrame::kYPlane),
+            mojo_frame->PlaneOffset(media::VideoFrame::kUPlane),
+            mojo_frame->PlaneOffset(media::VideoFrame::kVPlane)));
+  }
+
+  if (input->HasTextures()) {
+    std::vector<gpu::MailboxHolder> mailbox_holder(
+        media::VideoFrame::kMaxPlanes);
+    size_t num_planes = media::VideoFrame::NumPlanes(input->format());
+    for (size_t i = 0; i < num_planes; i++)
+      mailbox_holder[i] = input->mailbox_holder(i);
+    return media::mojom::VideoFrameData::NewMailboxData(
+        media::mojom::MailboxVideoFrameData::New(std::move(mailbox_holder)));
+  }
+
+  NOTREACHED() << "Unsupported VideoFrame conversion";

[dcheng, 2017/06/09 21:52:23]

As mentioned, there shouldn't be any CHECKs/DCHECKs in struct traits
deserialization, so let's remove these in a followup--we need to handle these
cases gracefully. I think we can assume that the Clone() on line 28 works though
(though yzshen should correct me on that if I'm wrong)

[sandersd (OOO until July 31), 2017/06/09 22:07:01]

I disagree here; we really don't support serializing all the kinds of
VideoFrames yet. A DCHECK to ensure we don't try seems entirely reasonable to me
(and the release behavior is safe too).

[dcheng, 2017/06/10 00:39:32]

OK, I got confused and missed that this was for serialization. This is fine.

+  return nullptr;
+}
+
+}  // namespace
+
+// static
+void* StructTraits<media::mojom::VideoFrameDataView,
+                   scoped_refptr<media::VideoFrame>>::
+    SetUpContext(const scoped_refptr<media::VideoFrame>& input) {
+  return new media::mojom::VideoFrameDataPtr(MakeVideoFrameData(input));
+}
+
+// static
+void StructTraits<media::mojom::VideoFrameDataView,
+                  scoped_refptr<media::VideoFrame>>::
+    TearDownContext(const scoped_refptr<media::VideoFrame>& input,
+                    void* context) {
+  delete static_cast<media::mojom::VideoFrameDataPtr*>(context);
+}
+
+// static
+media::mojom::VideoFrameDataPtr&
+StructTraits<media::mojom::VideoFrameDataView,
+             scoped_refptr<media::VideoFrame>>::
+    data(const scoped_refptr<media::VideoFrame>& input, void* context) {
+  return *static_cast<media::mojom::VideoFrameDataPtr*>(context);
+}
+
+// static
+bool StructTraits<media::mojom::VideoFrameDataView,
+                  scoped_refptr<media::VideoFrame>>::
+    Read(media::mojom::VideoFrameDataView input,
+         scoped_refptr<media::VideoFrame>* output) {
+  // View of the |data| member of the input media::mojom::VideoFrame.
+  media::mojom::VideoFrameDataDataView data;
+  input.GetDataDataView(&data);
+
+  DCHECK_EQ(input.end_of_stream(), data.is_null());

[dcheng, 2017/06/09 21:52:23]

Ditto here: this needs to be handled gracefully (which I think it already is,
but there shouldn't be a DCHECK)

[sandersd (OOO until July 31), 2017/06/09 22:07:01]

Yes, in this case we just trust |end_of_stream|, which is not dangerous. There
is no serialization path for them to be out of sync, so this DCHECK isn't adding
anything beyond a sanity check of the serialization code.

That said, this also looks like a correct use of a DCHECK to me (that is, it
verifies a precondition). Why is it so important to remove DCHECKs?

I would propose that the correct solution here is actually to add another entry
to the VideoFrameData enum to signal EOS; then these fields cannot possibly be
out of sync. (EOS frames would still contain redundant fields, but there would
be no possible source for confusion.)

[dcheng, 2017/06/10 00:39:32]

But this is deserialization, and a bad process can write whatever it wants. If
/when we have mojo fuzzing, this DCHECK() will start getting tripped.

[sandersd (OOO until July 31), 2017/06/10 01:18:21]

Fuzzing false-positives is a very convincing answer :-)

+  if (input.end_of_stream()) {
+    *output = media::VideoFrame::CreateEOSFrame();
+    return !!*output;
+  }
+
+  media::VideoPixelFormat format;
+  if (!input.ReadFormat(&format))
+    return false;
+
+  gfx::Size coded_size;
+  if (!input.ReadCodedSize(&coded_size))
+    return false;
+
+  gfx::Rect visible_rect;
+  if (!input.ReadVisibleRect(&visible_rect))
+    return false;
+
+  // Coded size must contain the visible rect.
+  if (visible_rect.right() > coded_size.width() ||
+      visible_rect.bottom() > coded_size.height()) {
+    return false;
+  }
+
+  gfx::Size natural_size;
+  if (!input.ReadNaturalSize(&natural_size))
+    return false;
+
+  base::TimeDelta timestamp;
+  if (!input.ReadTimestamp(&timestamp))
+    return false;
+
+  if (data.is_shared_buffer_data()) {
+    media::mojom::SharedBufferVideoFrameDataDataView shared_buffer_data;
+    data.GetSharedBufferDataDataView(&shared_buffer_data);
+
+    // TODO(sandersd): Conversion from uint64_t to size_t could cause
+    // corruption. Platform-dependent types should be removed from the
+    // implementation (limiting to 32-bit offsets is fine).
+    *output = media::MojoSharedBufferVideoFrame::Create(
+        format, coded_size, visible_rect, natural_size,
+        shared_buffer_data.TakeFrameData(),
+        shared_buffer_data.frame_data_size(), shared_buffer_data.y_offset(),
+        shared_buffer_data.u_offset(), shared_buffer_data.v_offset(),
+        shared_buffer_data.y_stride(), shared_buffer_data.u_stride(),
+        shared_buffer_data.v_stride(), timestamp);
+    return !!*output;
+  }
+
+  if (data.is_mailbox_data()) {
+    media::mojom::MailboxVideoFrameDataDataView mailbox_data;
+    data.GetMailboxDataDataView(&mailbox_data);
+
+    std::vector<gpu::MailboxHolder> mailbox_holder;
+    if (!mailbox_data.ReadMailboxHolder(&mailbox_holder))
+      return false;
+
+    gpu::MailboxHolder mailbox_holder_array[media::VideoFrame::kMaxPlanes];
+    for (size_t i = 0; i < media::VideoFrame::kMaxPlanes; i++)
+      mailbox_holder_array[i] = mailbox_holder[i];
+
+    *output = media::VideoFrame::WrapNativeTextures(
+        format, mailbox_holder_array, media::VideoFrame::ReleaseMailboxCB(),
+        coded_size, visible_rect, natural_size, timestamp);
+    return !!*output;
+  }
+
+  // TODO(sandersd): Switch on the union tag to avoid this ugliness?
+  NOTREACHED();
+  return false;
+}
+
+}  // namespace mojo