cc: Added inline to Tile::IsReadyToDraw
[chromium-blink-merge.git] / gpu / command_buffer / common / command_buffer_shared.h
blobfafe767bdb19b9a7fff102bbb3e4608a365b05bc
1 // Copyright (c) 2012 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.
5 #ifndef GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_SHARED_H_
6 #define GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_SHARED_H_
8 #include "command_buffer.h"
9 #include "base/atomicops.h"
11 namespace gpu {
13 // This is a standard 4-slot asynchronous communication mechanism, used to
14 // ensure that the reader gets a consistent copy of what the writer wrote.
15 template<typename T>
16 class SharedState {
17 T states_[2][2];
18 base::subtle::Atomic32 reading_;
19 base::subtle::Atomic32 latest_;
20 base::subtle::Atomic32 slots_[2];
22 public:
24 void Initialize() {
25 for (int i = 0; i < 2; ++i) {
26 for (int j = 0; j < 2; ++j) {
27 states_[i][j] = T();
30 base::subtle::NoBarrier_Store(&reading_, 0);
31 base::subtle::NoBarrier_Store(&latest_, 0);
32 base::subtle::NoBarrier_Store(&slots_[0], 0);
33 base::subtle::Release_Store(&slots_[1], 0);
34 base::subtle::MemoryBarrier();
37 void Write(const T& state) {
38 int towrite = !base::subtle::Acquire_Load(&reading_);
39 int index = !base::subtle::Acquire_Load(&slots_[towrite]);
40 states_[towrite][index] = state;
41 base::subtle::Release_Store(&slots_[towrite], index);
42 base::subtle::Release_Store(&latest_, towrite);
43 base::subtle::MemoryBarrier();
46 // Attempt to update the state, updating only if the generation counter is
47 // newer.
48 void Read(T* state) {
49 base::subtle::MemoryBarrier();
50 int toread = !!base::subtle::Acquire_Load(&latest_);
51 base::subtle::Release_Store(&reading_, toread);
52 base::subtle::MemoryBarrier();
53 int index = !!base::subtle::Acquire_Load(&slots_[toread]);
54 if (states_[toread][index].generation - state->generation < 0x80000000U)
55 *state = states_[toread][index];
59 typedef SharedState<CommandBuffer::State> CommandBufferSharedState;
61 } // namespace gpu
63 #endif // GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_SHARED_H_