util/async.lua

   1 local log = require "util.logger".init("util.async");
   2
   3 local function runner_continue(thread)
   4         -- ASSUMPTION: runner is in 'waiting' state (but we don't have the runner to know for sure)
   5         if coroutine.status(thread) ~= "suspended" then -- This should suffice
   6                 return false;
   7         end
   8         local ok, state, runner = coroutine.resume(thread);
   9         if not ok then
  10                 local level = 0;
  11                 while debug.getinfo(thread, level, "") do level = level + 1; end
  12                 ok, runner = debug.getlocal(thread, level-1, 1);
  13                 local error_handler = runner.watchers.error;
  14                 if error_handler then error_handler(runner, debug.traceback(thread, state)); end
  15         elseif state == "ready" then
  16                 -- If state is 'ready', it is our responsibility to update runner.state from 'waiting'.
  17                 -- We also have to :run(), because the queue might have further items that will not be
  18                 -- processed otherwise. FIXME: It's probably best to do this in a nexttick (0 timer).
  19                 runner.state = "ready";
  20                 runner:run();
  21         end
  22         return true;
  23 end
  24
  25 local function waiter(num)
  26         local thread = coroutine.running();
  27         if not thread then
  28                 error("Not running in an async context, see http://prosody.im/doc/developers/async");
  29         end
  30         num = num or 1;
  31         local waiting;
  32         return function ()
  33                 if num == 0 then return; end -- already done
  34                 waiting = true;
  35                 coroutine.yield("wait");
  36         end, function ()
  37                 num = num - 1;
  38                 if num == 0 and waiting then
  39                         runner_continue(thread);
  40                 end
  41         end;
  42 end
  43
  44 local runner_mt = {};
  45 runner_mt.__index = runner_mt;
  46
  47 local function runner_create_thread(func, self)
  48         local thread = coroutine.create(function (self)
  49                 while true do
  50                         func(coroutine.yield("ready", self));
  51                 end
  52         end);
  53         assert(coroutine.resume(thread, self)); -- Start it up, it will return instantly to wait for the first input
  54         return thread;
  55 end
  56
  57 local empty_watchers = {};
  58 local function runner(func, watchers, data)
  59         return setmetatable({ func = func, thread = false, state = "ready", notified_state = "ready",
  60                 queue = {}, watchers = watchers or empty_watchers, data = data }
  61         , runner_mt);
  62 end
  63
  64 function runner_mt:run(input)
  65         if input ~= nil then
  66                 table.insert(self.queue, input);
  67         end
  68         if self.state ~= "ready" then
  69                 return true, self.state, #self.queue;
  70         end
  71
  72         local q, thread = self.queue, self.thread;
  73         if not thread or coroutine.status(thread) == "dead" then
  74                 thread = runner_create_thread(self.func, self);
  75                 self.thread = thread;
  76         end
  77
  78         local n, state, err = #q, self.state, nil;
  79         self.state = "running";
  80         while n > 0 and state == "ready" do
  81                 local consumed;
  82                 for i = 1,n do
  83                         local input = q[i];
  84                         local ok, new_state = coroutine.resume(thread, input);
  85                         if not ok then
  86                                 consumed, state, err = i, "ready", debug.traceback(thread, new_state);
  87                                 self.thread = nil;
  88                                 break;
  89                         elseif new_state == "wait" then
  90                                 consumed, state = i, "waiting";
  91                                 break;
  92                         end
  93                 end
  94                 if not consumed then consumed = n; end
  95                 if q[n+1] ~= nil then
  96                         n = #q;
  97                 end
  98                 for i = 1, n do
  99                         q[i] = q[consumed+i];
 100                 end
 101                 n = #q;
 102         end
 103         self.state = state;
 104         if state ~= self.notified_state then
 105                 self.notified_state = state;
 106                 local handler = self.watchers[state];
 107                 if handler then handler(self, err); end
 108         end
 109         return true, state, n;
 110 end
 111
 112 function runner_mt:enqueue(input)
 113         table.insert(self.queue, input);
 114 end
 115
 116 return { waiter = waiter, runner = runner };