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-- ErrorQueue isa WaitQueue with the added feature that a producer can push an
-- error through the queue. Once that error is dequeued, every consumer will
-- raise that error.
local WaitQueue = require('WaitQueue')
-- local dbg = require('printf')
local function dbg(...) end
local ErrorQueue = WaitQueue:new()
function ErrorQueue:Error(message)
-- Setting Error() is a marker, like closing the queue. Once we reach the
-- error, every subsequent Dequeue() call will raise the same error.
dbg('Setting self._closed to %q', message)
self._closed = message
self:_wake_waiters()
end
function ErrorQueue:Dequeue()
local value = WaitQueue.Dequeue(self)
dbg('ErrorQueue:Dequeue: base Dequeue() got %s', value)
if value ~= nil then
-- queue not yet closed, show caller
return value
end
if self._closed == true then
-- WaitQueue:close() sets true: queue has only been closed, tell caller
return nil
end
-- self._closed is a message set by Error()
error(self._closed)
end
return ErrorQueue
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