Semaphore.cpp

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 #include "rtos/Semaphore.h"
00023 #include "rtos/Kernel.h"
00024 #include "platform/mbed_assert.h"
00025 
00026 #include <string.h>
00027 
00028 namespace rtos {
00029 
00030 Semaphore::Semaphore(int32_t count) {
00031     constructor(count, 0xffff);
00032 }
00033 
00034 Semaphore::Semaphore(int32_t count, uint16_t max_count) {
00035     constructor(count, max_count);
00036 }
00037 
00038 void Semaphore::constructor(int32_t count, uint16_t max_count) {
00039     memset(&_obj_mem, 0, sizeof(_obj_mem));
00040     osSemaphoreAttr_t attr = { 0 };
00041     attr.cb_mem = &_obj_mem;
00042     attr.cb_size = sizeof(_obj_mem);
00043     _id = osSemaphoreNew(max_count, count, &attr);
00044     MBED_ASSERT(_id != NULL);
00045 }
00046 
00047 int32_t Semaphore::wait(uint32_t millisec) {
00048     osStatus_t stat = osSemaphoreAcquire(_id, millisec);
00049     switch (stat) {
00050         case osOK:
00051             return osSemaphoreGetCount(_id) + 1;
00052         case osErrorTimeout:
00053         case osErrorResource:
00054             return 0;
00055         case osErrorParameter:
00056         default:
00057             return -1;
00058     }
00059 }
00060 
00061 int32_t Semaphore::wait_until(uint64_t millisec) {
00062     uint64_t now = Kernel::get_ms_count();
00063 
00064     if (now >= millisec) {
00065         return wait(0);
00066     } else if (millisec - now >= osWaitForever) {
00067         // API permits early return
00068         return wait(osWaitForever - 1);
00069     } else {
00070         return wait(millisec - now);
00071     }
00072 }
00073 
00074 osStatus Semaphore::release(void) {
00075     return osSemaphoreRelease(_id);
00076 }
00077 
00078 Semaphore::~Semaphore() {
00079     osSemaphoreDelete(_id);
00080 }
00081 
00082 }