Semaphore.h

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2006-2012 ARM Limited
00003  *
00004  * Permission is hereby granted, free of charge, to any person obtaining a copy
00005  * of this software and associated documentation files (the "Software"), to deal
00006  * in the Software without restriction, including without limitation the rights
00007  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
00008  * copies of the Software, and to permit persons to whom the Software is
00009  * furnished to do so, subject to the following conditions:
00010  *
00011  * The above copyright notice and this permission notice shall be included in
00012  * all copies or substantial portions of the Software.
00013  *
00014  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
00015  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
00016  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
00017  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
00018  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
00019  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
00020  * SOFTWARE.
00021  */
00022 #ifndef SEMAPHORE_H
00023 #define SEMAPHORE_H
00024 
00025 #include <stdint.h>
00026 #include "cmsis_os2.h"
00027 #include "mbed_rtos1_types.h"
00028 #include "mbed_rtos_storage.h"
00029 #include "platform/NonCopyable.h"
00030 
00031 namespace rtos {
00032 /** \addtogroup rtos */
00033 /** @{*/
00034 /**
00035  * \defgroup rtos_Semaphore Semaphore class
00036  * @{
00037  */
00038 
00039 /** The Semaphore class is used to manage and protect access to a set of shared resources.
00040  *
00041  * @note
00042  * Memory considerations: The semaphore control structures will be created on current thread's stack, both for the mbed OS
00043  * and underlying RTOS objects (static or dynamic RTOS memory pools are not being used).
00044  */
00045 class Semaphore : private mbed::NonCopyable<Semaphore> {
00046 public:
00047     /** Create and Initialize a Semaphore object used for managing resources.
00048       @param count      number of available resources; maximum index value is (count-1). (default: 0).
00049 
00050       @note You cannot call this function from ISR context.
00051     */
00052     Semaphore(int32_t count=0);
00053 
00054     /** Create and Initialize a Semaphore object used for managing resources.
00055       @param  count     number of available resources
00056       @param  max_count maximum number of available resources
00057 
00058       @note You cannot call this function from ISR context.
00059     */
00060     Semaphore(int32_t count, uint16_t max_count);
00061 
00062     /** Wait until a Semaphore resource becomes available.
00063       @param   millisec  timeout value or 0 in case of no time-out. (default: osWaitForever).
00064       @return  number of available tokens, before taking one; or -1 in case of incorrect parameters
00065 
00066       @note You may call this function from ISR context if the millisec parameter is set to 0.
00067     */
00068     int32_t wait(uint32_t millisec=osWaitForever);
00069 
00070     /** Wait until a Semaphore resource becomes available.
00071       @param   millisec  absolute timeout time, referenced to Kernel::get_ms_count()
00072       @return  number of available tokens, before taking one; or -1 in case of incorrect parameters
00073       @note the underlying RTOS may have a limit to the maximum wait time
00074             due to internal 32-bit computations, but this is guaranteed to work if the
00075             wait is <= 0x7fffffff milliseconds (~24 days). If the limit is exceeded,
00076             the acquire attempt will time out earlier than specified.
00077 
00078       @note You cannot call this function from ISR context.
00079     */
00080     int32_t wait_until(uint64_t millisec);
00081 
00082     /** Release a Semaphore resource that was obtain with Semaphore::wait.
00083       @return status code that indicates the execution status of the function:
00084               @a osOK the token has been correctly released.
00085               @a osErrorResource the maximum token count has been reached.
00086               @a osErrorParameter internal error.
00087 
00088       @note You may call this function from ISR context.
00089     */
00090     osStatus release(void);
00091 
00092     /** Semaphore destructor
00093      *
00094      * @note You cannot call this function from ISR context.
00095      */
00096     ~Semaphore();
00097 
00098 private:
00099     void constructor(int32_t count, uint16_t max_count);
00100 
00101     osSemaphoreId_t               _id;
00102     mbed_rtos_storage_semaphore_t _obj_mem;
00103 };
00104 /** @}*/
00105 /** @}*/
00106 }
00107 #endif
00108 
00109