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mbed_poll.cpp
00001 /* mbed Microcontroller Library 00002 * Copyright (c) 2017 ARM Limited 00003 * 00004 * Licensed under the Apache License, Version 2.0 (the "License"); 00005 * you may not use this file except in compliance with the License. 00006 * You may obtain a copy of the License at 00007 * 00008 * http://www.apache.org/licenses/LICENSE-2.0 00009 * 00010 * Unless required by applicable law or agreed to in writing, software 00011 * distributed under the License is distributed on an "AS IS" BASIS, 00012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 00013 * See the License for the specific language governing permissions and 00014 * limitations under the License. 00015 */ 00016 #include "mbed_poll.h" 00017 #include "FileHandle.h" 00018 #include "Timer.h" 00019 #ifdef MBED_CONF_RTOS_PRESENT 00020 #include "rtos/Thread.h" 00021 #endif 00022 00023 namespace mbed { 00024 00025 // timeout -1 forever, or milliseconds 00026 int poll(pollfh fhs[], unsigned nfhs, int timeout) 00027 { 00028 /** 00029 * TODO Proper wake-up mechanism. 00030 * In order to correctly detect availability of read/write a FileHandle, we needed 00031 * a select or poll mechanisms. We opted for poll as POSIX defines in 00032 * http://pubs.opengroup.org/onlinepubs/009695399/functions/poll.html Currently, 00033 * mbed::poll() just spins and scans filehandles looking for any events we are 00034 * interested in. In future, his spinning behaviour will be replaced with 00035 * condition variables. 00036 */ 00037 Timer timer; 00038 if (timeout > 0) { 00039 timer.start(); 00040 } 00041 00042 int count = 0; 00043 for (;;) { 00044 /* Scan the file handles */ 00045 for (unsigned n = 0; n < nfhs; n++) { 00046 FileHandle *fh = fhs[n].fh; 00047 short mask = fhs[n].events | POLLERR | POLLHUP | POLLNVAL; 00048 if (fh) { 00049 fhs[n].revents = fh->poll(mask) & mask; 00050 } else { 00051 fhs[n].revents = POLLNVAL; 00052 } 00053 if (fhs[n].revents) { 00054 count++; 00055 } 00056 } 00057 00058 if (count) { 00059 break; 00060 } 00061 00062 /* Nothing selected - this is where timeout handling would be needed */ 00063 if (timeout == 0 || (timeout > 0 && timer.read_ms() > timeout)) { 00064 break; 00065 } 00066 #ifdef MBED_CONF_RTOS_PRESENT 00067 // TODO - proper blocking 00068 // wait for condition variable, wait queue whatever here 00069 rtos::Thread::yield(); 00070 #endif 00071 } 00072 return count; 00073 } 00074 00075 } // namespace mbed
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