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Strongswan

    1: /*
    2:  * Copyright (C) 2011 Tobias Brunner
    3:  * HSR Hochschule fuer Technik Rapperswil
    4:  *
    5:  * This program is free software; you can redistribute it and/or modify it
    6:  * under the terms of the GNU General Public License as published by the
    7:  * Free Software Foundation; either version 2 of the License, or (at your
    8:  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
    9:  *
   10:  * This program is distributed in the hope that it will be useful, but
   11:  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
   12:  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   13:  * for more details.
   14:  */
   15: 
   16: /**
   17:  * @defgroup semaphore semaphore
   18:  * @{ @ingroup threading
   19:  */
   20: 
   21: #ifndef THREADING_SEMAPHORE_H_
   22: #define THREADING_SEMAPHORE_H_
   23: 
   24: #include <utils/utils.h>
   25: 
   26: typedef struct semaphore_t semaphore_t;
   27: 
   28: /**
   29:  * A semaphore is basically an integer whose value is never allowed to be
   30:  * lower than 0.  Two operations can be performed on it: increment the
   31:  * value by one, and decrement the value by one.  If the value is currently
   32:  * zero, then the decrement operation will block until the value becomes
   33:  * greater than zero.
   34:  */
   35: struct semaphore_t {
   36: 
   37: 	/**
   38: 	 * Decrease the value by one, if it is greater than zero. Otherwise the
   39: 	 * current thread is blocked and it waits until the value increases.
   40: 	 */
   41: 	void (*wait)(semaphore_t *this);
   42: 
   43: 	/**
   44: 	 * Decrease the value by one, if it is greater than zero. Otherwise the
   45: 	 * current thread is blocked and it waits until the value increases, or the
   46: 	 * call times out.
   47: 	 *
   48: 	 * @param timeout		timeout im ms
   49: 	 * @return				TRUE if timed out, FALSE otherwise
   50: 	 */
   51: 	bool (*timed_wait)(semaphore_t *this, u_int timeout);
   52: 
   53: 	/**
   54: 	 * Decrease the value by one, if it is greater than zero. Otherwise the
   55: 	 * current thread is blocked and it waits until the value increases, or the
   56: 	 * call times out.
   57: 	 *
   58: 	 * The passed timeval should be calculated based on the time_monotonic()
   59: 	 * function.
   60: 	 *
   61: 	 * @param tv			absolute time until timeout
   62: 	 * @return				TRUE if timed out, FALSE otherwise
   63: 	 */
   64: 	bool (*timed_wait_abs)(semaphore_t *this, timeval_t tv);
   65: 
   66: 	/**
   67: 	 * Increase the value by one. If the value becomes greater than zero, then
   68: 	 * another thread waiting will be woken up.
   69: 	 */
   70: 	void (*post)(semaphore_t *this);
   71: 
   72: 	/**
   73: 	 * Destroy a semaphore and free its resources.
   74: 	 */
   75: 	void (*destroy)(semaphore_t *this);
   76: };
   77: 
   78: /**
   79:  * Create a semaphore instance.
   80:  *
   81:  * @param value		initial value (typically 0)
   82:  * @return			semaphore instance
   83:  */
   84: semaphore_t *semaphore_create(u_int value);
   85: 
   86: #endif /** THREADING_SEMAPHORE_H_ @} */