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

services/media/framework/allocator.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_ALLOCATOR_H_
+#define SERVICES_MEDIA_FRAMEWORK_ALLOCATOR_H_
+
+#include <cstdint>
+
+namespace mojo {
+namespace media {
+
+// Abstract base class for objects that allocate buffers for packets.
+class Allocator {

[jeffbrown, 2016/02/02 05:35:46]

The class name is very generic but its use is more specific.  Odd that this
doesn't refer to the Packet structure or contain PacketPayload in the name.

It's not clear to me how this class would handle scoping.  Say if packets were
allocating from a pool and the pool was being destroyed.  I might advise that
you delete this until you have a use for the polymorphism.

[dalesat, 2016/02/02 21:46:38]

With regard to referencing Packet, my tendency would be to avoid that unless
it's needed. Allocators can be used for purposes other than creating Packet
payloads. The LPCM input/output stuff currently uses Packet, but there's no
reason why it has to (and previous versions have not).

Flushing the graph is part of orderly shutdown. All allocations are released
during flush (not implemented here).

I have multiple implementations of this already. For example, there's a special
one for allocating from a shared buffer for mojo transport.

+ public:

[jeffbrown, 2016/02/02 05:35:46]

missing virtual destructor

[dalesat, 2016/02/02 21:46:38]

Adding this blows up the constexpr stuff:

../../services/media/framework/allocator.cc:17:13: error: constexpr constructor
never produces a constant expression [-Winvalid-constexpr]
  constexpr DefaultAllocator() {}
 

+  // Gets the default allocator, which allocates vanilla memory from the heap.
+  static Allocator* GetDefault();
+
+  // Allocates and returns a buffer of the indicated size or returns nullptr
+  // if the allocation fails.
+  // TODO(dalesat): Use size_t for sizes in units of bytes framework-wide.
+  virtual void* AllocatePayloadBuffer(uint64_t size) = 0;

[jeffbrown, 2016/02/02 05:35:46]

use size_t

[dalesat, 2016/02/02 21:46:38]

John pointed this out. I have this teed up in a future CL.

+
+  // Releases a buffer previously allocated via AllocatePayloadBuffer.
+  virtual void ReleasePayloadBuffer(uint64_t size, void* buffer) = 0;

[jeffbrown, 2016/02/02 05:35:46]

void*, size_t

[dalesat, 2016/02/02 21:46:38]

Acknowledged.

+};
+
+}  // namespace media
+}  // namespace mojo
+
+#endif // SERVICES_MEDIA_FRAMEWORK_ALLOCATOR_H_