src/common/ConditionServer.h

/***************************************************************************
 *                                                                         *
 *   LinuxSampler - modular, streaming capable sampler                     *
 *                                                                         *
 *   Copyright (C) 2003 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	schoenebeck	53	/***************************************************************************
2			* *
3			* LinuxSampler - modular, streaming capable sampler *
4			* *
5			* Copyright (C) 2003 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__