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                 elseif num < 0 then
  41                         error("done() called too many times");
  42                 end
  43         end;
  44 end
  45
  46 local runner_mt = {};
  47 runner_mt.__index = runner_mt;
  48
  49 local function runner_create_thread(func, self)
  50         local thread = coroutine.create(function (self)
  51                 while true do
  52                         func(coroutine.yield("ready", self));
  53                 end
  54         end);
  55         assert(coroutine.resume(thread, self)); -- Start it up, it will return instantly to wait for the first input
  56         return thread;
  57 end
  58
  59 local empty_watchers = {};
  60 local function runner(func, watchers, data)
  61         return setmetatable({ func = func, thread = false, state = "ready", notified_state = "ready",
  62                 queue = {}, watchers = watchers or empty_watchers, data = data }
  63         , runner_mt);
  64 end
  65
  66 function runner_mt:run(input)
  67         if input ~= nil then
  68                 table.insert(self.queue, input);
  69         end
  70         if self.state ~= "ready" then
  71                 return true, self.state, #self.queue;
  72         end
  73
  74         local q, thread = self.queue, self.thread;
  75         if not thread or coroutine.status(thread) == "dead" then
  76                 thread = runner_create_thread(self.func, self);
  77                 self.thread = thread;
  78         end
  79
  80         local n, state, err = #q, self.state, nil;
  81         self.state = "running";
  82         while n > 0 and state == "ready" do
  83                 local consumed;
  84                 for i = 1,n do
  85                         local input = q[i];
  86                         local ok, new_state = coroutine.resume(thread, input);
  87                         if not ok then
  88                                 consumed, state, err = i, "ready", debug.traceback(thread, new_state);
  89                                 self.thread = nil;
  90                                 break;
  91                         elseif new_state == "wait" then
  92                                 consumed, state = i, "waiting";
  93                                 break;
  94                         end
  95                 end
  96                 if not consumed then consumed = n; end
  97                 if q[n+1] ~= nil then
  98                         n = #q;
  99                 end
 100                 for i = 1, n do
 101                         q[i] = q[consumed+i];
 102                 end
 103                 n = #q;
 104         end
 105         self.state = state;
 106         if err or state ~= self.notified_state then
 107                 if err then
 108                         state = "error"
 109                 else
 110                         self.notified_state = state;
 111                 end
 112                 local handler = self.watchers[state];
 113                 if handler then handler(self, err); end
 114         end
 115         return true, state, n;
 116 end
 117
 118 function runner_mt:enqueue(input)
 119         table.insert(self.queue, input);
 120 end
 121
 122 return { waiter = waiter, runner = runner };