| 1 | /* |
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| 2 | * pthread.h - User level <semaphore> library definition. |
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| 3 | * |
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| 4 | * Author Alain Greiner (2016,2017) |
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| 5 | * |
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| 6 | * Copyright (c) UPMC Sorbonne Universites |
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| 7 | * |
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| 8 | * This file is part of ALMOS-MKH. |
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| 9 | * |
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| 10 | * ALMOS-MKH is free software; you can redistribute it and/or modify it |
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| 11 | * under the terms of the GNU General Public License as published by |
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| 12 | * the Free Software Foundation; version 2.0 of the License. |
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| 13 | * |
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| 14 | * ALMOS-MKH is distributed in the hope that it will be useful, but |
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| 15 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 17 | * General Public License for more details. |
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| 18 | * |
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| 19 | * You should have received a copy of the GNU General Public License |
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| 20 | * along with ALMOS-MKH; if not, write to the Free Software Foundation, |
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| 21 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
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| 22 | */ |
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| 23 | |
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| 24 | #ifndef _SEMAPHORE_H_ |
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| 25 | #define _SEMAPHORE_H_ |
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| 26 | |
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| 27 | ////////////////////////////////////////////////////////////////////////////////////////////// |
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| 28 | // POSIX unnamed semaphores related functions |
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| 29 | ////////////////////////////////////////////////////////////////////////////////////////////// |
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| 30 | |
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| 31 | #include <shared_semaphore.h> |
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| 32 | |
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| 33 | /********************************************************************************************* |
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| 34 | * This function initializes an unnamed semaphore. |
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| 35 | * Process shared semaphores are not supported in this implementation. |
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| 36 | * Initializing a semaphore that has already been initialized results in undefined behavior. |
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| 37 | ********************************************************************************************* |
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| 38 | * @ sem : [in] pointer on semaphore. |
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| 39 | * @ pshared : [in] unsupported => must be zero. |
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| 40 | * @ value : [in] initial semaphore value. |
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| 41 | * @ return 0 if success / return -1 if failure. |
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| 42 | ********************************************************************************************/ |
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| 43 | int sem_init( sem_t * sem, |
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| 44 | int pshared, |
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| 45 | unsigned int value ); |
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| 46 | |
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| 47 | /********************************************************************************************* |
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| 48 | * This blocking function locks a semaphore. It decrements the semaphore pointed to by <sem>. |
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| 49 | * If the semaphore's value is greater than zero, then the decrement proceeds, and the |
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| 50 | * function returns immediately. If the semaphore currently has the value zero, then the call |
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| 51 | * blocks until it becomes possible to perform the decrement. |
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| 52 | ********************************************************************************************* |
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| 53 | * @ sem : [in] pointer on semaphore. |
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| 54 | * @ return 0 if success / return -1 if failure. |
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| 55 | ********************************************************************************************/ |
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| 56 | int sem_wait( sem_t * sem ); |
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| 57 | |
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| 58 | /********************************************************************************************* |
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| 59 | * This function unlocks a semaphore. It increments the semaphore pointed to by <sem>. |
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| 60 | * If the semaphore's value consequently becomes greater than zero, then another thread |
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| 61 | * blocked in a sem_wait() call will be woken up and proceed to lock the semaphore. |
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| 62 | ********************************************************************************************* |
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| 63 | * @ sem : [in] pointer on semaphore. |
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| 64 | * @ return 0 if success / return -1 if failure. |
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| 65 | ********************************************************************************************/ |
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| 66 | int sem_post( sem_t * sem ); |
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| 67 | |
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| 68 | /********************************************************************************************* |
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| 69 | * This function destroys the semaphore pointed to by <sem>. |
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| 70 | ********************************************************************************************* |
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| 71 | * @ sem : [in] pointer on semaphore. |
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| 72 | * @ return 0 if success / return -1 if failure. |
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| 73 | ********************************************************************************************/ |
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| 74 | int sem_destroy( sem_t * sem ); |
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| 75 | |
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| 76 | /********************************************************************************************* |
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| 77 | * This function places the current value of the semaphore pointed to by <sem> |
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| 78 | * into the integer pointed to by <sval>. |
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| 79 | ********************************************************************************************* |
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| 80 | * @ sem : [in] pointer on semaphore. |
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| 81 | * @ value : [out] buffer for semaphore current value. |
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| 82 | * @ return 0 if success / return -1 if failure. |
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| 83 | ********************************************************************************************/ |
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| 84 | int sem_getvalue( sem_t * sem, |
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| 85 | int * value ); |
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| 86 | |
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| 87 | |
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| 88 | #endif // _SEMAPHORE_H_ |
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