我正在使用 libevent 的 PHP Event 类包装器来读取串行端口。我正在使用它来避免缓冲区溢出 - 想法是使用 Event 定期检查端口，这样就不会丢失数据。
我希望事件在设置时会触发，但得出的结论是事件仅在调用EventBase::loop(). 在这种情况下，当我调用loop(). 最终控制流返回到我的代码在调用循环之后的位置。
我从这种行为中假设我本质上是在调度事件的调度，并且应该定期调用 loop() 以避免我的事件被 CPU 耗尽。
但是在这种情况下，我不应该loop()在之前的loop()调用运行时调用，因为根据上面的解释，控制流要么在我的代码中，要么在 libevent 中，并且不能同时在两者中。
loop()所以我通过我的代码（总共四个 - 我正在摸索）发出调用，其中两个产生 libevent 重入警告。
我显然不明白这一点。任何人都可以帮忙吗？
干杯保罗
<?php
// serial comms defines
define("PORT", "/dev/serial0");
const PORTSETTINGS = array(
'baud' => 9600,
'bits' => 8,
'stop' => 1,
'parity' => 0
);
define("SYN", 170);
define("MSB", 127);
const POLL = 0.1;
/*
** Class Scanner
**
** Manages low level serial comms with the vbus master
**
*/
class Scanner {
private $fd;
private $pkt;
private $state;
private $base;
private $timer;
/*
** __construct()
**
** setup the serial port for reading using dio
** setup a timer to read anything on the serial port frequently
**
*/
function __construct() {
// set up port and state machine
$this->fd = dio_open(PORT, O_RDONLY | O_NOCTTY | O_NONBLOCK);
dio_tcsetattr($this->fd, PORTSETTINGS);
$this->pkt = array();
$this->state = "discard";
// set up timer handler
$this->base = new EventBase();
$this->timer = new Event($this->base, -1, Event::TIMEOUT | Event::PERSIST, array($this, "Tickle"));
$this->timer->addTimer(POLL);
$this->base->loop(EventBase::LOOP_NONBLOCK);
}
function PrintPkt($pkt) {
echo "\n\n".date("H:i:s");
foreach($pkt as $i)
echo " ".dechex($i);
}
/*
** Tickle()
**
** read the serial port, if MSB set discard the packet, else save the packet and then pass for processing
** called by the event timer on a regular basis ie POLL seconds
*/
function Tickle() {
do {
// read the next one and convert to int
$ch = dio_read($this->fd, 1);
$i = ord($ch);
// check for MSB, if set discard to the next packet
if (($i > MSB) && ($i != SYN))
$state="discard";
// if there is nothing on the port it returns 0x0 ie null/false
if ($i) {
if ($i == SYN) {
// we are at the start of a new packet
if (count($this->pkt) > 0) {
if ($this->state === "save")
// this is where we would save the packet but for now we are printing it.
$this->PrintPkt($this->pkt);
// reset for the next packet
$this->pkt = array();
$this->state = "save";
}
}
// save this number
$this->pkt[] = $i;
}
} while ($ch);
// restart the timer
$this->timer->addTimer(POLL);
}
/*
** spin()
**
** call the base loop so that the timer event is serviced
*/
function spin() {
$this->base->loop(EventBase::LOOP_NONBLOCK);
}
}
$c = new Scanner();
echo "setup";
while(1);
// $c->spin();
?>