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1 #ifndef _DESEMAPHORE_HPP
2 #define _DESEMAPHORE_HPP
3 /*-------------------------------------------------------------------------
4  * drawElements C++ Base Library
5  * -----------------------------
6  *
7  * Copyright 2014 The Android Open Source Project
8  *
9  * Licensed under the Apache License, Version 2.0 (the "License");
10  * you may not use this file except in compliance with the License.
11  * You may obtain a copy of the License at
12  *
13  *      http://www.apache.org/licenses/LICENSE-2.0
14  *
15  * Unless required by applicable law or agreed to in writing, software
16  * distributed under the License is distributed on an "AS IS" BASIS,
17  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
18  * See the License for the specific language governing permissions and
19  * limitations under the License.
20  *
21  *//*!
22  * \file
23  * \brief deSemaphore C++ wrapper.
24  *//*--------------------------------------------------------------------*/
25 
26 #include "deDefs.hpp"
27 #include "deSemaphore.h"
28 
29 namespace de
30 {
31 
32 /*--------------------------------------------------------------------*//*!
33  * \brief Semaphore
34  *
35  * Semaphore provides standard semaphore functionality.
36  *
37  * Semaphore is thread-safe counter that can be used to control access
38  * to a set of resources. The count can be incremented and decremented.
39  * When decrementing causes counter to reach negative value, it will
40  * block until increment has been called from an another thread.
41  *//*--------------------------------------------------------------------*/
42 class Semaphore
43 {
44 public:
45 					Semaphore		(int initialValue, deUint32 flags = 0);
46 					~Semaphore		(void);
47 
48 	void			increment		(void) throw();
49 	void			decrement		(void) throw();
50 	bool			tryDecrement	(void) throw();
51 
52 private:
53 					Semaphore		(const Semaphore& other); // Not allowed!
54 	Semaphore&		operator=		(const Semaphore& other); // Not allowed!
55 
56 	deSemaphore		m_semaphore;
57 };
58 
59 // Inline implementations.
60 
61 /*--------------------------------------------------------------------*//*!
62  * \brief Increment semaphore count.
63  *
64  * Incremeting increases semaphore value by 1. If a value is currently
65  * negative (there is a thread waiting in decrement) the waiting thread
66  * will be resumed.
67  *
68  * Incrementing semaphore will never block.
69  *//*--------------------------------------------------------------------*/
increment(void)70 inline void Semaphore::increment (void) throw()
71 {
72 	deSemaphore_increment(m_semaphore);
73 }
74 
75 /*--------------------------------------------------------------------*//*!
76  * \brief Decrement semaphore count.
77  *
78  * Decrementing decreases semaphore value by 1. If resulting value is negative
79  * (only -1 is possible) decrement() will block until the value is again 0
80  * (increment() has been called).
81  *
82  * If there is an another thread waiting in decrement(), the current thread
83  * will block until other thread(s) have been resumed.
84  *//*--------------------------------------------------------------------*/
decrement(void)85 inline void Semaphore::decrement (void) throw()
86 {
87 	deSemaphore_decrement(m_semaphore);
88 }
89 
90 /*--------------------------------------------------------------------*//*!
91  * \brief Try to decrement semaphore value.
92  * \return true if decrementing was successful without blocking, false
93  *		   otherwise
94  *
95  * This function will never block, i.e. it will return false if decrementing
96  * semaphore counter would result in negative value or there is already
97  * one or more threads waiting for this semaphore.
98  *//*--------------------------------------------------------------------*/
tryDecrement(void)99 inline bool Semaphore::tryDecrement (void) throw()
100 {
101 	return deSemaphore_tryDecrement(m_semaphore) == DE_TRUE;
102 }
103 
104 } // de
105 
106 #endif // _DESEMAPHORE_HPP
107