Implement the content/renderer and content/browser part of the Device Motion API.

content/renderer/shared_memory_seqlock_reader.h

+// Copyright (c) 2013 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 CONTENT_RENDERER_SHARED_MEMORY_SEQLOCK_READER_H_
+#define CONTENT_RENDERER_SHARED_MEMORY_SEQLOCK_READER_H_
+
+#include "shared_memory_seqlock_reader_base.h"
+
+namespace content {
+

[darin (slow to review), 2013/06/24 23:40:34]

nit: it is common to put the *Base class here inside an internal:: namespace.

[timvolodine, 2013/06/25 03:36:07]

Done.

+// Template argument Data should be a pod-like structure only containing
+// data fields, such that it is copyable by memcpy method.
+template<typename Data>
+class SharedMemorySeqLockReader : private SharedMemorySeqLockReaderBase {

[scottmg, 2013/06/24 23:24:38]

was the intention that this be the generic reader? it seems you need to rewrite
renderer/gamepad_shared_memory_reader in that case, otherwise probably name it
something more device motion specific.

[timvolodine, 2013/06/25 03:36:07]

The new reader class largely implements the original gamepad reader code, except
for the sync IPC and some gamepad specifics like gestures. I think it should not
be too hard to refactor gamepad reader using this more generic reader class by
replacing the common code with calls to this implementation,

+ public:
+  SharedMemorySeqLockReader() : buffer_(0) { }
+  virtual ~SharedMemorySeqLockReader() { }
+
+  bool GetLatestData(Data* data) {
+    DCHECK(buffer_);
+    DCHECK(sizeof(*data) == sizeof(*temp_buffer_));
+    return FetchFromBuffer(data, temp_buffer_.get(), &buffer_->data,
+        sizeof(*temp_buffer_));
+  }
+
+  bool Initialize(base::SharedMemoryHandle shared_memory_handle) {
+    SharedMemorySeqLockBufferBase* memory = InitializeSharedMemory(
+        shared_memory_handle, sizeof(SharedMemorySeqLockBuffer<Data>));
+    if (memory) {
+      buffer_ = static_cast<SharedMemorySeqLockBuffer<Data>*>(memory);
+      temp_buffer_.reset(new Data);
+      return true;
+    }
+    return false;
+  }
+
+ private:
+  SharedMemorySeqLockBuffer<Data>* buffer_;
+  scoped_ptr<Data> temp_buffer_;
+
+  DISALLOW_COPY_AND_ASSIGN(SharedMemorySeqLockReader);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_SHARED_MEMORY_SEQLOCK_READER_H_