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Issue 14678012: Implement the content/renderer and content/browser part of the Device Motion API. (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: fix compilation: peer_handle -> PeerHandle() Created 7 years, 5 months ago
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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be 2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file. 3 // found in the LICENSE file.
4 4
5 #include "content/common/gamepad_seqlock.h" 5 #include "content/common/one_writer_seqlock.h"
6 6
7 namespace content { 7 namespace content {
8 8
9 GamepadSeqLock::GamepadSeqLock() 9 OneWriterSeqLock::OneWriterSeqLock()
10 : sequence_(0) { 10 : sequence_(0) {
11 } 11 }
12 12
13 base::subtle::Atomic32 GamepadSeqLock::ReadBegin() { 13 base::subtle::Atomic32 OneWriterSeqLock::ReadBegin() {
14 base::subtle::Atomic32 version; 14 base::subtle::Atomic32 version;
15 for (;;) { 15 for (;;) {
16 version = base::subtle::NoBarrier_Load(&sequence_); 16 version = base::subtle::NoBarrier_Load(&sequence_);
17 17
18 // If the counter is even, then the associated data might be in a 18 // If the counter is even, then the associated data might be in a
19 // consistent state, so we can try to read. 19 // consistent state, so we can try to read.
20 if ((version & 1) == 0) 20 if ((version & 1) == 0)
21 break; 21 break;
22 22
23 // Otherwise, the writer is in the middle of an update. Retry the read. 23 // Otherwise, the writer is in the middle of an update. Retry the read.
24 base::PlatformThread::YieldCurrentThread(); 24 base::PlatformThread::YieldCurrentThread();
25 } 25 }
26 return version; 26 return version;
27 } 27 }
28 28
29 bool GamepadSeqLock::ReadRetry(base::subtle::Atomic32 version) { 29 bool OneWriterSeqLock::ReadRetry(base::subtle::Atomic32 version) {
30 // If the sequence number was updated then a read should be re-attempted. 30 // If the sequence number was updated then a read should be re-attempted.
31 // -- Load fence, read membarrier 31 // -- Load fence, read membarrier
32 return base::subtle::Release_Load(&sequence_) != version; 32 return base::subtle::Release_Load(&sequence_) != version;
33 } 33 }
34 34
35 void GamepadSeqLock::WriteBegin() { 35 void OneWriterSeqLock::WriteBegin() {
36 // Increment the sequence number to odd to indicate the beginning of a write 36 // Increment the sequence number to odd to indicate the beginning of a write
37 // update. 37 // update.
38 base::subtle::Barrier_AtomicIncrement(&sequence_, 1); 38 base::subtle::Barrier_AtomicIncrement(&sequence_, 1);
39 // -- Store fence, write membarrier 39 // -- Store fence, write membarrier
40 } 40 }
41 41
42 void GamepadSeqLock::WriteEnd() { 42 void OneWriterSeqLock::WriteEnd() {
43 // Increment the sequence to an even number to indicate the completion of 43 // Increment the sequence to an even number to indicate the completion of
44 // a write update. 44 // a write update.
45 // -- Store fence, write membarrier 45 // -- Store fence, write membarrier
46 base::subtle::Barrier_AtomicIncrement(&sequence_, 1); 46 base::subtle::Barrier_AtomicIncrement(&sequence_, 1);
47 } 47 }
48 48
49 } // namespace content 49 } // namespace content
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