Motown in-proc streaming framework used to implement media services.

services/media/framework/packet.h

+// Copyright 2016 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.
+
+#ifndef SERVICES_MEDIA_FRAMEWORK_PACKET_H_
+#define SERVICES_MEDIA_FRAMEWORK_PACKET_H_
+
+#include <memory>
+
+#include "base/logging.h"
+#include "services/media/framework/allocator.h"
+#include "services/media/framework/ptr.h"
+
+namespace mojo {
+namespace media {
+
+class Packet;
+
+// Used for PacketPtr.
+struct PacketDeleter {
+  void operator()(Packet* ptr) const;
+};
+
+// Unique pointer for packets.
+typedef UniquePtr<Packet, PacketDeleter> PacketPtr;
+
+// Media packet abstract base class. Subclasses may be defined as needed.
+// Packet::Create and Packet::CreateEndOfStream use an implementation with
+// no special behavior.
+// TODO(dalesat): Revisit this definition:
+// 1) We probably need an extensible way to add metadata to packets.

[jeffbrown, 2016/02/02 05:35:47]

Worth asking whether the metadata is part of the packet or the stream, or
whether the packet's relationship to a stream should be expressed, and whether
the allocation policy for packets should be located someplace else perhaps on a
stream.

In general it's going to get confusing to have packets floating around with
varying allocation models unless they're anchored in some way, such as by saying
that Packets all come from a stream of some kind which then becomes a natural
place to describe allocation / reuse policies.

[dalesat, 2016/02/02 21:46:39]

Acknowledged.

+// 2) The relationship to the allocator could be clearer.
+class Packet {
+ public:
+  // Creates a packet. If size is 0, payload must be nullptr and vice-versa.
+  // If payload is not nullptr, an allocator must be provided.
+  static PacketPtr Create(
+      int64_t presentation_time,
+      uint64_t duration,
+      bool end_of_stream,
+      uint64_t size,
+      void* payload,
+      Allocator* allocator);
+
+  // Creates a packet. If size is 0, payload must be nullptr and vice-versa.
+  // No allocator is provided, and the payload will not be released when the
+  // packet is released.
+  static PacketPtr CreateNoAllocator(
+      int64_t presentation_time,
+      uint64_t duration,
+      bool end_of_stream,
+      uint64_t size,
+      void* payload);
+
+  // Creates an end-of-stream packet with no payload.
+  static PacketPtr CreateEndOfStream(int64_t presentation_time);
+
+  virtual int64_t presentation_time() const = 0;

[jeffbrown, 2016/02/02 05:35:47]

Virtual methods can't use accessor notation.  So this must be
GetPresentationTime().

That said, perhaps these shouldn't be virtual in the first place...

[dalesat, 2016/02/02 21:46:39]

Acknowledged.

+
+  virtual uint64_t duration() const = 0;
+
+  virtual bool end_of_stream() const = 0;
+
+  virtual uint64_t size() const = 0;
+
+  virtual void* payload() const = 0;
+
+ protected:
+  virtual ~Packet() {}
+
+  virtual void release() = 0;

[jeffbrown, 2016/02/02 05:35:47]

Release()

[dalesat, 2016/02/02 21:46:39]

Done.

+
+  friend PacketDeleter;
+};
+
+inline void PacketDeleter::operator()(Packet* ptr) const {
+  DCHECK(ptr);
+  ptr->release();
+}
+
+}  // namespace media
+}  // namespace mojo
+
+#endif // SERVICES_MEDIA_FRAMEWORK_PACKET_H_