src/common/ConditionServer.h

/***************************************************************************
 *                                                                         *
 *   LinuxSampler - modular, streaming capable sampler                     *
 *                                                                         *
 *   Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the Free Software           *
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston,                 *
 *   MA  02111-1307  USA                                                   *
 ***************************************************************************/

#ifndef __CONDITIONSERVER_H__
#define __CONDITIONSERVER_H__

#include "Mutex.h"
#include "Condition.h"
#include "global.h"

/**
 * Thread safe condition for semi real time operation
 *
 * Sense behind the ConditionServer is to sync a boolean condition between
 * one real time thread (RTT) and n non real time threads (NRTT).
 *
 *   1 Real Time Thread <--> Condition Object <--> n Non Real Time Threads
 *
 * The non real time threads set the condition by calling Push(), this
 * method will immediately return if the current condition already equals
 * the desired condition given with Push(), if it's not equal then Push()
 * will cause a request to change the condition and will block until the
 * condition actually changed, which happens when the RTT calls the Pop()
 * method, which will also return the new condition to the RTT.
 *
 * Advantage of this technique is that the RTT doesn't has to execute system
 * calls whenever it wants to check for a condition change, the RTT only has
 * to execute one system call when the condition changed. Disadvantage on
 * the other hand is that the NRTTs might be blocked for a long time, but
 * this is usually unproblematic for NRTTs.
 */
class ConditionServer {
    public:
        ConditionServer();


        // methods for non realtime threads (0..n NRTTs)

        /**
         * Set condition to \a bCondition. If current condition already
         * equals \a bCondition, then this method will immediately return,
         * if not it will block the calling thread until the condition
         * actually changed to the requested condition (which happens when
         * Pop() is called by the real time thread). If there are multiple
         * non real time threads calling Push() only one by one will be
         * served, all others blocked meanwhile. When the calling thread
         * returns from Push() the Push() method will still be blocked
         * against other NRTTs, so the thread can safely enter a critical
         * section and has to Unlock() right after it left it's critical
         * section, so other NRTTs can pass Push().
         *
         * @param bCondition         - condition to set
         * @param TimeoutSeconds     - optional: max. wait time in seconds
         *                             (default: 0s)
         * @param TimeoutNanoSeconds - optional: max wait time in nano
         *                             seconds (default: 0ns)
         * @returns  bool pointer with condition before Push() call, NULL if
         *           timeout exceeded
         * @see Unlock()
         */
        bool* Push(bool bCondition, long TimeoutSeconds = 0L, long TimeoutNanoSeconds = 0L);

        /**
         * Same as Push(), except that PushAndUnlock() will unlock the
         * ConditionServer right after so that other NRTTs can follow to
         * pass push. You should only call this method if you're sure that
         * no other NRTT will change the condition, otherwise you should
         * call Push() instead, execute the critical section and manually
         * unlock at the end of the critical section.
         *
         * @param bCondition         - condition to set
         * @param TimeoutSeconds     - optional: max. wait time in seconds
         *                             (default: 0s)
         * @param TimeoutNanoSeconds - optional: max wait time in nano
         *                             seconds (default: 0ns)
         * @returns  bool pointer with condition before PushAndUnlock()
         *           call, NULL if timeout exceeded
         */
        bool* PushAndUnlock(bool bCondition, long TimeoutSeconds = 0L, long TimeoutNanoSeconds = 0L);

        /**
         * Should be called by the NRTT after it left it's critical section
         * to unlock the ConditionServer and give other NRTTs the chance to
         * pass Push().
         */
        void Unlock();

        /**
         * Returns unsafely the current condition. This method will not
         * block and should only be used in a not thread critical context.
         *
         * @returns  current condition (unsafe)
         */
        bool GetUnsafe();


        // method for real time thread (1 RTT)

        /**
         * Should frequently be called by the real time thread (RTT) to
         * check for a condition change. If a NRTT requested a condition
         * change by calling Push() ot PushAndUnlock() the NRTT wil be
         * blocked until the RTT calls Pop(), means until the RTT actually
         * knows about the condition change.
         *
         * @returns  current condition
         */
        bool Pop();

    protected:
        bool      bConditionQuick;
        bool      bChangeRequest;
        bool      bOldCondition;
        Condition SyncCondition;
        Mutex     PushMutex;
};

#endif // __CONDITIONSERVER_H__
1	/***************************************************************************
2	* *
3	* LinuxSampler - modular, streaming capable sampler *
4	* *
5	* Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck *
6	* *
7	* This program is free software; you can redistribute it and/or modify *
8	* it under the terms of the GNU General Public License as published by *
9	* the Free Software Foundation; either version 2 of the License, or *
10	* (at your option) any later version. *
11	* *
12	* This program is distributed in the hope that it will be useful, *
13	* but WITHOUT ANY WARRANTY; without even the implied warranty of *
14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
15	* GNU General Public License for more details. *
16	* *
17	* You should have received a copy of the GNU General Public License *
18	* along with this program; if not, write to the Free Software *
19	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, *
20	* MA 02111-1307 USA *
21	***************************************************************************/
22
23	#ifndef __CONDITIONSERVER_H__
24	#define __CONDITIONSERVER_H__
25
26	#include "Mutex.h"
27	#include "Condition.h"
28	#include "global.h"
29
30	/**
31	* Thread safe condition for semi real time operation
32	*
33	* Sense behind the ConditionServer is to sync a boolean condition between
34	* one real time thread (RTT) and n non real time threads (NRTT).
35	*
36	* 1 Real Time Thread <--> Condition Object <--> n Non Real Time Threads
37	*
38	* The non real time threads set the condition by calling Push(), this
39	* method will immediately return if the current condition already equals
40	* the desired condition given with Push(), if it's not equal then Push()
41	* will cause a request to change the condition and will block until the
42	* condition actually changed, which happens when the RTT calls the Pop()
43	* method, which will also return the new condition to the RTT.
44	*
45	* Advantage of this technique is that the RTT doesn't has to execute system
46	* calls whenever it wants to check for a condition change, the RTT only has
47	* to execute one system call when the condition changed. Disadvantage on
48	* the other hand is that the NRTTs might be blocked for a long time, but
49	* this is usually unproblematic for NRTTs.
50	*/
51	class ConditionServer {
52	public:
53	ConditionServer();
54
55
56	// methods for non realtime threads (0..n NRTTs)
57
58	/**
59	* Set condition to \a bCondition. If current condition already
60	* equals \a bCondition, then this method will immediately return,
61	* if not it will block the calling thread until the condition
62	* actually changed to the requested condition (which happens when
63	* Pop() is called by the real time thread). If there are multiple
64	* non real time threads calling Push() only one by one will be
65	* served, all others blocked meanwhile. When the calling thread
66	* returns from Push() the Push() method will still be blocked
67	* against other NRTTs, so the thread can safely enter a critical
68	* section and has to Unlock() right after it left it's critical
69	* section, so other NRTTs can pass Push().
70	*
71	* @param bCondition - condition to set
72	* @param TimeoutSeconds - optional: max. wait time in seconds
73	* (default: 0s)
74	* @param TimeoutNanoSeconds - optional: max wait time in nano
75	* seconds (default: 0ns)
76	* @returns bool pointer with condition before Push() call, NULL if
77	* timeout exceeded
78	* @see Unlock()
79	*/
80	bool* Push(bool bCondition, long TimeoutSeconds = 0L, long TimeoutNanoSeconds = 0L);
81
82	/**
83	* Same as Push(), except that PushAndUnlock() will unlock the
84	* ConditionServer right after so that other NRTTs can follow to
85	* pass push. You should only call this method if you're sure that
86	* no other NRTT will change the condition, otherwise you should
87	* call Push() instead, execute the critical section and manually
88	* unlock at the end of the critical section.
89	*
90	* @param bCondition - condition to set
91	* @param TimeoutSeconds - optional: max. wait time in seconds
92	* (default: 0s)
93	* @param TimeoutNanoSeconds - optional: max wait time in nano
94	* seconds (default: 0ns)
95	* @returns bool pointer with condition before PushAndUnlock()
96	* call, NULL if timeout exceeded
97	*/
98	bool* PushAndUnlock(bool bCondition, long TimeoutSeconds = 0L, long TimeoutNanoSeconds = 0L);
99
100	/**
101	* Should be called by the NRTT after it left it's critical section
102	* to unlock the ConditionServer and give other NRTTs the chance to
103	* pass Push().
104	*/
105	void Unlock();
106
107	/**
108	* Returns unsafely the current condition. This method will not
109	* block and should only be used in a not thread critical context.
110	*
111	* @returns current condition (unsafe)
112	*/
113	bool GetUnsafe();
114
115
116
117	// method for real time thread (1 RTT)
118
119	/**
120	* Should frequently be called by the real time thread (RTT) to
121	* check for a condition change. If a NRTT requested a condition
122	* change by calling Push() ot PushAndUnlock() the NRTT wil be
123	* blocked until the RTT calls Pop(), means until the RTT actually
124	* knows about the condition change.
125	*
126	* @returns current condition
127	*/
128	bool Pop();
129
130	protected:
131	bool bConditionQuick;
132	bool bChangeRequest;
133	bool bOldCondition;
134	Condition SyncCondition;
135	Mutex PushMutex;
136	};
137
138	#endif // __CONDITIONSERVER_H__