D编程 并发
并发使程序在多个线程上运行,一个示例是Web服务器同时响应多个客户端,并发通过消息传递很容易,但是它们基于数据共享则很难编写。
启动线程
函数spawn()将指针作为参数,并从该函数启动新线程,该函数执行的任何操作,包括它可能调用的其他函数,都将在新线程上执行。
import std.stdio;
import std.stdio;
import std.concurrency;
import core.thread;
void worker(int a) {
foreach (i; 0 .. 4) {
Thread.sleep(1);
writeln("Worker Thread ",a + i);
}
}
void main() {
foreach (i; 1 .. 4) {
Thread.sleep(2);
writeln("Main Thread ",i);
spawn(≈worker, i * 5);
}
writeln("main is done.");
}
编译并执行上述代码后,它将读取上一部分中创建的文件,并产生以下输出-
Main Thread 1
Worker Thread 5
Main Thread 2
Worker Thread 6
Worker Thread 10
Main Thread 3
main is done.
Worker Thread 7
Worker Thread 11
Worker Thread 15
Worker Thread 8
Worker Thread 12
Worker Thread 16
Worker Thread 13
Worker Thread 17
Worker Thread 18
线程标识符
在模块级别全局可用的 thisTid 变量始终是当前线程的ID,当调用spawn时,您也可以接收threadId。一个如下所示。
import std.stdio;
import std.concurrency;
void printTid(string tag) {
writefln("%s: %s, address: %s", tag, thisTid, &thisTid);
}
void worker() {
printTid("Worker");
}
void main() {
Tid myWorker=spawn(&worker);
printTid("Owner ");
writeln(myWorker);
}
编译并执行上述代码后,它将读取上一部分中创建的文件,并产生以下输出-
Owner : Tid(std.concurrency.MessageBox), address: 10C71A59C
Worker: Tid(std.concurrency.MessageBox), address: 10C71A59C
Tid(std.concurrency.MessageBox)
消息传递
函数send()发送消息,而函数receiveOnly()等待特定类型的消息。还有其他名为prioritySend(),receive()和receiveTimeout()的函数,稍后将进行说明。
以下示例向其工作程序发送int类型的消息,并等待来自double类型的消息,线程继续来回发送消息,直到发送一个负整数。一个如下所示。
import std.stdio;
import std.concurrency;
import core.thread;
import std.conv;
void workerFunc(Tid tid) {
int value=0;
while (value >= 0) {
value=receiveOnly!int();
auto result=to!double(value) * 5; tid.send(result);
}
}
void main() {
Tid worker=spawn(&workerFunc,thisTid);
foreach (value; 5 .. 10) {
worker.send(value);
auto result=receiveOnly!double();
writefln("sent: %s, received: %s", value, result);
}
worker.send(-1);
}
编译并执行上述代码后,它将读取上一部分中创建的文件,并产生以下输出-
sent: 5, received: 25
sent: 6, received: 30
sent: 7, received: 35
sent: 8, received: 40
sent: 9, received: 45
等待传递消息
下面显示了一个带有等待消息传递的简单示例。
import std.stdio;
import std.concurrency;
import core.thread;
import std.conv;
void workerFunc(Tid tid) {
Thread.sleep(dur!("msecs")( 500 ),);
tid.send("hello");
}
void main() {
spawn(&workerFunc,thisTid);
writeln("Waiting for a message");
bool received=false;
while (!received) {
received=receiveTimeout(dur!("msecs")( 100 ), (string message) {
writeln("received: ", message);
});
if (!received) {
writeln("... no message yet");
}
}
}
编译并执行上述代码后,它将读取上一部分中创建的文件,并产生以下输出-
Waiting for a message
... no message yet
... no message yet
... no message yet
... no message yet
received: hello