Jack2: JackAtomicArrayState.h Source File

Jack2 1.9.12

JackAtomicArrayState.h
1 /*
2 Copyright (C) 2004-2008 Grame
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU Lesser General Public License as published by
6 the Free Software Foundation; either version 2.1 of the License, or
7 (at your option) any later version.
8
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17
18 */
19
20 #ifndef __JackAtomicArrayState__
21 #define __JackAtomicArrayState__
22
23 #include "JackAtomic.h"
24 #include "JackCompilerDeps.h"
25 #include <string.h> // for memcpy
26
27 namespace Jack
28 {
29
33 PRE_PACKED_STRUCTURE
34 struct AtomicArrayCounter
35 {
36 union {
37 struct {
38 unsigned char fByteVal[4];
39 }
40 scounter;
41 UInt32 fLongVal;
42 }info;
43
44 AtomicArrayCounter()
45 {
46 info.fLongVal = 0;
47 }
48
49 AtomicArrayCounter(volatile const AtomicArrayCounter& obj)
50 {
51 info.fLongVal = obj.info.fLongVal;
52 }
53
54 AtomicArrayCounter(volatile AtomicArrayCounter& obj)
55 {
56 info.fLongVal = obj.info.fLongVal;
57 }
58
59 AtomicArrayCounter& operator=(volatile AtomicArrayCounter& obj)
60 {
61 info.fLongVal = obj.info.fLongVal;
62 return *this;
63 }
64
65 AtomicArrayCounter& operator=(AtomicArrayCounter& obj)
66 {
67 info.fLongVal = obj.info.fLongVal;
68 return *this;
69 }
70
71 } POST_PACKED_STRUCTURE;
72
73 #define Counter1(e) (e).info.fLongVal
74 #define GetIndex1(e, state) ((e).info.scounter.fByteVal[state])
75 #define SetIndex1(e, state, val) ((e).info.scounter.fByteVal[state] = val)
76 #define IncIndex1(e, state) ((e).info.scounter.fByteVal[state]++)
77 #define SwapIndex1(e, state) (((e).info.scounter.fByteVal[0] == state) ? 0 : state)
78
110 // CHECK livelock
111
112 PRE_PACKED_STRUCTURE
113 template <class T>
114 class JackAtomicArrayState
115 {
116
117 protected:
118
119 // fState[0] ==> current
120 // fState[1] ==> pending
121 // fState[2] ==> request
122
123 T fState[3];
124 volatile AtomicArrayCounter fCounter;
125
126 UInt32 WriteNextStateStartAux(int state, bool* result)
127 {
128 AtomicArrayCounter old_val;
129 AtomicArrayCounter new_val;
130 UInt32 cur_index;
131 UInt32 next_index;
132 bool need_copy;
133 do {
134 old_val = fCounter;
135 new_val = old_val;
136 *result = GetIndex1(new_val, state);
137 cur_index = GetIndex1(new_val, 0);
138 next_index = SwapIndex1(fCounter, state);
139 need_copy = (GetIndex1(new_val, state) == 0); // Written = false, switch just occured
140 SetIndex1(new_val, state, 0); // Written = false, invalidate state
141 } while (!CAS(Counter1(old_val), Counter1(new_val), (UInt32*)&fCounter));
142 if (need_copy)
143 memcpy(&fState[next_index], &fState[cur_index], sizeof(T));
144 return next_index;
145 }
146
147 void WriteNextStateStopAux(int state)
148 {
149 AtomicArrayCounter old_val;
150 AtomicArrayCounter new_val;
151 do {
152 old_val = fCounter;
153 new_val = old_val;
154 SetIndex1(new_val, state, 1); // Written = true, state becomes "switchable"
155 } while (!CAS(Counter1(old_val), Counter1(new_val), (UInt32*)&fCounter));
156 }
157
158 public:
159
160 JackAtomicArrayState()
161 {
162 Counter1(fCounter) = 0;
163 }
164
165 ~JackAtomicArrayState() // Not virtual ??
166 {}
167
172 T* ReadCurrentState()
173 {
174 return &fState[GetIndex1(fCounter, 0)];
175 }
176
181 UInt16 GetCurrentIndex()
182 {
183 return GetIndex1(fCounter, 3);
184 }
185
190 T* TrySwitchState(int state)
191 {
192 AtomicArrayCounter old_val;
193 AtomicArrayCounter new_val;
194 do {
195 old_val = fCounter;
196 new_val = old_val;
197 if (GetIndex1(new_val, state)) { // If state has been written
198 SetIndex1(new_val, 0, SwapIndex1(new_val, state)); // Prepare switch
199 SetIndex1(new_val, state, 0); // Invalidate the state "state"
200 IncIndex1(new_val, 3); // Inc switch
201 }
202 } while (!CAS(Counter1(old_val), Counter1(new_val), (UInt32*)&fCounter));
203 return &fState[GetIndex1(fCounter, 0)]; // Read the counter again
204 }
205
210 T* TrySwitchState(int state, bool* result)
211 {
212 AtomicArrayCounter old_val;
213 AtomicArrayCounter new_val;
214 do {
215 old_val = fCounter;
216 new_val = old_val;
217 if ((*result = GetIndex1(new_val, state))) { // If state has been written
218 SetIndex1(new_val, 0, SwapIndex1(new_val, state)); // Prepare switch
219 SetIndex1(new_val, state, 0); // Invalidate the state "state"
220 IncIndex1(new_val, 3); // Inc switch
221 }
222 } while (!CAS(Counter1(old_val), Counter1(new_val), (UInt32*)&fCounter));
223 return &fState[GetIndex1(fCounter, 0)]; // Read the counter again
224 }
225
230 T* WriteNextStateStart(int state)
231 {
232 bool tmp;
233 UInt32 index = WriteNextStateStartAux(state, &tmp);
234 return &fState[index];
235 }
236
237 T* WriteNextStateStart(int state, bool* result)
238 {
239 UInt32 index = WriteNextStateStartAux(state, result);
240 return &fState[index];
241 }
242
247 void WriteNextStateStop(int state)
248 {
249 WriteNextStateStopAux(state);
250 }
251
252 } POST_PACKED_STRUCTURE;
253
254 } // end of namespace
255
256
257 #endif
258
Jack::JackAtomicArrayState
A class to handle several states in a lock-free manner.
Definition: JackAtomicArrayState.h:114
Jack::JackAtomicArrayState::WriteNextStateStop
void WriteNextStateStop(int state)
Stop write operation : make the next state ready to be used by the RT thread.
Definition: JackAtomicArrayState.h:247
Jack::JackAtomicArrayState::WriteNextStateStart
T * WriteNextStateStart(int state)
Start write operation : setup and returns the next state to update, check for recursive write calls.
Definition: JackAtomicArrayState.h:230
Jack::JackAtomicArrayState::ReadCurrentState
T * ReadCurrentState()
Returns the current state : only valid in the RT reader thread.
Definition: JackAtomicArrayState.h:172
Jack::JackAtomicArrayState::TrySwitchState
T * TrySwitchState(int state, bool *result)
Tries to switch to the next state and returns the new current state (either the same as before if cas...
Definition: JackAtomicArrayState.h:210
Jack::JackAtomicArrayState::GetCurrentIndex
UInt16 GetCurrentIndex()
Returns the current switch counter.
Definition: JackAtomicArrayState.h:181
Jack::JackAtomicArrayState::TrySwitchState
T * TrySwitchState(int state)
Tries to switch to the next state and returns the new current state (either the same as before if cas...
Definition: JackAtomicArrayState.h:190
Jack::AtomicArrayCounter
Counter for CAS.
Definition: JackAtomicArrayState.h:34