lua同步调用C异步函数

Question

c call lua with the following code

if ( lua_pcallk(L, 0, LUA_MULTRET, 0, ctx, pcallk_continue) != 0 ) 
{}

the lua code is

local coroutine = coroutine
co = coroutine.create( function (...) 
c.call(...)
    -- [run here]
end )

c.call() is an asynchronous c function(it call lua_yieldk() at the end of the function, util the network recv the data and call lua_resume() )

return lua_yieldk(L, 0, 0, yield_continue);

it run to yield_continue function, but not run to the line of "[run here]" , why?

the reference URL: http://www.lua.org/manual/5.2/manual.html#4.7

Answer 1

This is main idea with dispatcher.

Worker thread start async operation and switch to dispatcher thread. Dispatcher thread polls async operations and when they done switch to worker thread.

-- basic async operation queue
local ASYNC_RECV = {}

-- Put operation to queue and wait
local function recv()
  local co = coroutine.running()

  -- here we start async operation
  ASYNC_RECV[co] = true
  -- here we switch to dispatcher
  return coroutine.yield()
end

coroutine.wrap(function()
  for i = 1, 10 do print(recv()) end
end)()


-- main Loop
-- here we poll all async operation and 
-- resume according coroutines

while true do
  -- we have no async operation
  if not next(ASYNC_RECV) then break end

  for co in pairs(ASYNC_RECV) do
    ASYNC_RECV[co] = nil -- mark operation is done
    coroutine.resume(co, "some string") -- send result to coroutine
  end
end

And here work example with libuv as dispatcher

local uv = require "lluv"

local function sleep(timeout)
  local co = coroutine.running()

  -- here we start async operation
  uv.timer():start(timeout, function(timer)
    timer:close() -- just close unused timer.

    -- dispatcher(libuv) call this callback and
    -- callback switch to coroutine
    coroutine.resume(co)
  end)

  coroutine.yield()
end

coroutine.wrap(function()
  for i = 1, 10 do
    print("Tick")
    sleep(1000)
  end
end)()

uv.run()