无涯教程-D语言 - 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);
});
  </span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(!</span><span class="pln">received</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln"> 
     writeln</span><span class="pun">(</span><span class="str">"... no message yet"</span><span class="pun">);</span><span class="pln"> 
  </span><span class="pun">}</span><span class="pln">

}
}

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 

参考链接

www.learnfk.com/d-programmi…