| /* Copyright (c) 2012 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 QUEUE_H_ |
| #define QUEUE_H_ |
| |
| #include "ppapi/c/pp_var.h" |
| |
| /* This file implements a single-producer/single-consumer queue, using a mutex |
| * and a condition variable. |
| * |
| * There are techniques to implement a queue like this without using memory |
| * barriers or locks on x86, but ARM's memory system is different from x86, so |
| * we cannot make the same assumptions about visibility order of writes. Using a |
| * mutex is slower, but also simpler. |
| * |
| * We make the assumption that messages are only enqueued on the main thread |
| * and consumed on the worker thread. Because we don't want to block the main |
| * thread, EnqueueMessage will return zero if the message could not be enqueued. |
| * |
| * DequeueMessage will block until a message is available using a condition |
| * variable. Again, this may not be as fast as spin-waiting, but will consume |
| * much less CPU (and battery), which is important to consider for ChromeOS |
| * devices. */ |
| |
| void InitializeMessageQueue(); |
| int EnqueueMessage(struct PP_Var message); |
| struct PP_Var DequeueMessage(); |
| |
| #endif /* QUEUE_H_ */ |
