Lua编程示例（八）：生产者-消费者问题

admin Lua

2023-12-05 0 280

这个问题是比较经典的啦，基本所有语言的多线程都会涉及到，但是没想到Lua的这个这么复杂抓狂
看了好长时间才算看明白，先上个逻辑图：

开始时调用消费者，当消费者需要值时，再调用生产者生产值，生产者生产值后停止，直到消费者再次请求。设计为消费者驱动的设计。
图画的不太好，可以先将Filter遮住，它是过滤器对两个程序之间传递的信息进行处理。去掉Filter逻辑就更清晰些了，就是两个“线程”（其实是两个协同程序）互相调用。resume回到yield处开始，支持嵌套，返回到栈顶的yield位置。yield是非阻塞的“线程同步”。这到有点像linux里的管道通信。

function receive(prod)
print(\”receive is called\”)
local status,value = coroutine.resume(prod)
return value
end

function send(x,prod)
print(\”send is called\”)
return coroutine.yield(x)
end

function producer()
return coroutine.create(function ()
print(\”producer is called\”)
while true do
print(\”producer run again\”)
local x = io.read()
send(x)
end
end)
end

function filter(prod)
return coroutine.create(function ()
for line = 1,1000 do
print(\”enter fliter \”..line)
local x = receive(prod)
print(\”receive in filter finished\”)
x= string.format(\”%5d %s\”,line,x)
send(x,prod)
end
end)
end

function consumer(prod)
print(\”consumer is called\”)
while true do
print(\”consumer run again\”)
local x = receive(prod)
print(\”retrun customer\”)
io.write(x,\”\\n\”)
end
end

p = producer()
f=filter(p)
consumer(f)

运行结果：

consumer is called
consumer run again
receive is called
enter fliter 1
receive is called
producer is called
producer run again
fsy
send is called
receive in filter finished
send is called
retrun customer
1 fsy
consumer run again
receive is called
enter fliter 2
receive is called
producer run again
gaga
send is called
receive in filter finished
send is called
retrun customer
2 gaga
consumer run again
receive is called
enter fliter 3
receive is called
producer run again
……