mirror of https://github.com/ARMmbed/mbed-os.git
93 lines
2.7 KiB
C++
93 lines
2.7 KiB
C++
/* mbed Microcontroller Library
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* Copyright (c) 2017 ARM Limited
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "mbed_poll.h"
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#include "FileHandle.h"
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#if MBED_CONF_RTOS_PRESENT
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#include "rtos/Kernel.h"
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#include "rtos/Thread.h"
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using namespace rtos;
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#else
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#include "Timer.h"
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#include "LowPowerTimer.h"
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#endif
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namespace mbed {
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// timeout -1 forever, or milliseconds
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int poll(pollfh fhs[], unsigned nfhs, int timeout)
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{
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/**
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* TODO Proper wake-up mechanism.
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* In order to correctly detect availability of read/write a FileHandle, we needed
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* a select or poll mechanisms. We opted for poll as POSIX defines in
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* http://pubs.opengroup.org/onlinepubs/009695399/functions/poll.html Currently,
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* mbed::poll() just spins and scans filehandles looking for any events we are
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* interested in. In future, his spinning behaviour will be replaced with
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* condition variables.
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*/
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#if MBED_CONF_RTOS_PRESENT
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uint64_t start_time = 0;
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if (timeout > 0) {
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start_time = Kernel::get_ms_count();
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}
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#define TIME_ELAPSED() int64_t(Kernel::get_ms_count() - start_time)
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#else
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#if MBED_CONF_PLATFORM_POLL_USE_LOWPOWER_TIMER
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LowPowerTimer timer;
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#else
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Timer timer;
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#endif
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if (timeout > 0) {
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timer.start();
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}
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#define TIME_ELAPSED() timer.read_ms()
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#endif // MBED_CONF_RTOS_PRESENT
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int count = 0;
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for (;;) {
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/* Scan the file handles */
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for (unsigned n = 0; n < nfhs; n++) {
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FileHandle *fh = fhs[n].fh;
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short mask = fhs[n].events | POLLERR | POLLHUP | POLLNVAL;
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if (fh) {
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fhs[n].revents = fh->poll(mask) & mask;
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} else {
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fhs[n].revents = POLLNVAL;
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}
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if (fhs[n].revents) {
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count++;
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}
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}
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if (count) {
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break;
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}
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/* Nothing selected - this is where timeout handling would be needed */
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if (timeout == 0 || (timeout > 0 && TIME_ELAPSED() > timeout)) {
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break;
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}
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#ifdef MBED_CONF_RTOS_PRESENT
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// TODO - proper blocking
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// wait for condition variable, wait queue whatever here
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rtos::Thread::wait(1);
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#endif
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}
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return count;
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}
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} // namespace mbed
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