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1 // Copyright (c) 2013 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #include "device_motion_shared_memory_reader.h" | |
6 | |
7 #include "base/debug/trace_event.h" | |
8 #include "base/metrics/histogram.h" | |
9 #include "content/common/device_motion_hardware_buffer.h" | |
10 #include "third_party/WebKit/public/platform/WebDeviceMotionData.h" | |
11 | |
12 namespace content { | |
13 | |
14 bool DeviceMotionSharedMemoryReader::GetLatestDeviceMotionData( | |
15 WebKit::WebDeviceMotionData& data) { | |
16 | |
17 WebKit::WebDeviceMotionData read_into; | |
18 TRACE_EVENT0("DEVICEMOTION", "lastDeviceMotionData"); | |
19 | |
20 if (!base::SharedMemory::IsHandleValid(renderer_shared_memory_handle_)) | |
21 return false; | |
22 | |
23 // Only try to read this many times before failing to avoid waiting here | |
darin (slow to review)
2013/06/17 05:27:46
it looks like you mostly just copy-pasted code fro
timvolodine
2013/06/17 20:10:55
yes, here the code is mostly the same as for gamep
| |
24 // very long in case of contention with the writer. | |
25 bool is_ready_for_read = false; | |
26 const int kMaximumContentionCount = 10; | |
27 int contention_count = -1; | |
28 base::subtle::Atomic32 version; | |
29 do { | |
30 version = device_motion_hardware_buffer_->sequence.ReadBegin(); | |
31 is_ready_for_read = device_motion_hardware_buffer_->is_ready_for_read; | |
32 memcpy(&read_into, &device_motion_hardware_buffer_->buffer, | |
33 sizeof(read_into)); | |
34 ++contention_count; | |
35 if (contention_count == kMaximumContentionCount) | |
36 break; | |
37 } while (device_motion_hardware_buffer_->sequence.ReadRetry(version)); | |
38 UMA_HISTOGRAM_COUNTS("DeviceMotion.ReadContentionCount", contention_count); | |
39 | |
40 LOG(INFO) << "PUMP CONTENTION = " << contention_count; | |
darin (slow to review)
2013/06/17 05:27:46
nit: indentation... also, is this really needed in
timvolodine
2013/06/17 20:10:55
Done.
| |
41 | |
42 if (contention_count >= kMaximumContentionCount) { | |
43 // We failed to successfully read, presumably because the hardware | |
44 // thread was taking unusually long. Don't copy the data to the output | |
45 // buffer, and simply leave what was there before. | |
46 return false; | |
47 } | |
48 | |
49 // New data was read successfully, copy it into the output buffer. | |
50 memcpy(&data, &read_into, sizeof(data)); | |
51 | |
52 return is_ready_for_read; | |
53 } | |
54 | |
55 DeviceMotionSharedMemoryReader::DeviceMotionSharedMemoryReader() | |
56 : device_motion_hardware_buffer_(NULL) { | |
57 } | |
58 | |
59 bool DeviceMotionSharedMemoryReader::Initialize( | |
60 base::SharedMemoryHandle shared_memory_handle) { | |
61 renderer_shared_memory_handle_ = shared_memory_handle; | |
62 if (!base::SharedMemory::IsHandleValid(renderer_shared_memory_handle_)) | |
63 return false; | |
64 renderer_shared_memory_.reset(new base::SharedMemory( | |
65 renderer_shared_memory_handle_, true)); | |
66 | |
67 if (renderer_shared_memory_->Map(sizeof(DeviceMotionHardwareBuffer))) { | |
68 if (void *memory = renderer_shared_memory_->memory()) { | |
darin (slow to review)
2013/06/17 05:27:46
nit: indentation
timvolodine
2013/06/17 20:10:55
Done.
| |
69 device_motion_hardware_buffer_ = | |
70 static_cast<DeviceMotionHardwareBuffer*>(memory); | |
71 return true; | |
72 } | |
73 } | |
74 return false; | |
75 } | |
76 | |
77 } // namespace content | |
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