19. Lua 非抢先式的（non-preemptive）多线程

最新推荐文章于 2025-12-24 18:31:13 发布

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#lua #junit #开发语言

文章介绍了如何使用LuaSocket库通过HTTP协议实现非抢占式的多线程文件下载功能，包括连接服务器、发送请求、接收响应以及处理超时的并发下载策略。

非抢先式的（non-preemptive）多线程

LuaSocket 库

使用HTTP下载远程文件实例

lua socket 实现文件下载

require "socket"                                 -- 加载 LuaSocket
host = "www.w3.org"                              -- 定义主机
file = "/Help/Webmaster.html"                    -- 下载的文件
c = assert(socket.connect(host,80))              -- 链接到该站点的80端口
c:send("GET " .. file .. " HTTP/1.0\r\n\r\n")     -- 发送文件请求
while true do
  local s, status, partial = c:receive(2^10)
  io.write(s or partial )
  if status == "closed" then
  	break
  end
end
c:close()

多线程下载

require "socket"
function download(host , file )
  local c = assert(socket.connect( host , 80))
  local count = 0 -- 记录接收到的字节数
  c:send("GET " .. file .. " HTTP/1.0\r\n\r\n")
  while true do
  	local s,status,partial = receive(c)
  	count = count + #( s or partial)
  	if status == "closed" then
  		break
  	end
  end
  io.write("文件下载完成,大小: " .. count .. "\n" )
end
-- 顺序下载
function receive(connection)
  return connection:receive(2^10)
end
--  并发下载
function receive(connection)
  connection:settimeout(0)                     -- 使用receive调用不会堵塞
  local s , status , partial = connection:receive(2^10)
  if status == "timeout" then
  	coroutine.yield(connection)
  end
  return s or partial , status
end
threads = {}                  -- 用于记录所有正在运行的线程
function get( host , file )
  -- 创建协同程序
  local co = coroutine.create(
  	function()
  		download(host,file)
  	end
  )
  table.insert(threads,co)
end
function dispatch()
  local i = 1
  while true do
  	if threads[i] == nil then  -- 还有线程吗？
  		if threads[1] == nil then   -- 判断列表是否为空
  			break
  		end
  		i = 1
  	end
  	local status , res = coroutine.resume(threads[i])
  	if not res then
  		table.remove(threads,i)
  	else
  		i = i + 1
  	end
  end
end
host = "www.w3.org"                              -- 定义主机
file1 = "/standards/webofservices/"               -- 下载的文件
file2 = "/Help/Webmaster.html"                    -- 下载的文件
file3 = "/participate/"                    -- 下载的文件
get(host , file1)
get(host , file2)
get(host , file3)
dispatch()

实现多线程下载 (假如超时处理逻辑)

 require "socket"
 function download(host , file )
  local c = assert(socket.connect( host , 80))
  local count = 0 -- 记录接收到的字节数
  c:send("GET " .. file .. " HTTP/1.0\r\n\r\n")
  while true do
  	local s,status,partial = receive(c)
  	count = count + #( s or partial)
  	if status == "closed" then
  		break
  	end
  end
  io.write("文件下载完成,大小: " .. count .. "\n" )
end
-- 顺序下载
function receive(connection)
  return connection:receive(2^10)
end
--  并发下载
function receive(connection)
  connection:settimeout(0)                     -- 使用receive调用不会堵塞
  local s , status , partial = connection:receive(2^10)
  if status == "timeout" then
  	coroutine.yield(connection)
  end
  return s or partial , status
end
threads = {}                  -- 用于记录所有正在运行的线程
function get( host , file )
  -- 创建协同程序
  local co = coroutine.create(
  	function()
  		download(host,file)
  	end
  )
  table.insert(threads,co)
end
function dispatch()
  local i = 1
  while true do
  	if threads[i] == nil then  -- 还有线程吗？
  		if threads[1] == nil then   -- 判断列表是否为空
  			break
  		end
  		i = 1    --　重新开始循环
  	end
  	local status , res =   coroutine.resume(threads[i])
  	if not res then
  		table.remove(threads,i)
  	else        -- 超时
  		i = i + 1
  		if connections==nil then
  			connections = {}   -- connections 用来存放当前超时的 线程
  			connections[1] = res
  		else
  			connections[#connections + 1 ] = res
  			if #connections == #threads then    -- 所有线程都堵塞了
  				socket.select(connections)
  			end
  		end
  	end
  end
end
host = "www.w3.org"                              -- 定义主机
file1 = "/standards/webofservices/"               -- 下载的文件
file2 = "/Help/Webmaster.html"                    -- 下载的文件
file3 = "/participate/"                    -- 下载的文?