overleaf/services/document-updater/app/coffee/sharejs/syncqueue.coffee
2014-02-12 10:40:42 +00:00

42 lines
1.1 KiB
CoffeeScript

# A synchronous processing queue. The queue calls process on the arguments,
# ensuring that process() is only executing once at a time.
#
# process(data, callback) _MUST_ eventually call its callback.
#
# Example:
#
# queue = require 'syncqueue'
#
# fn = queue (data, callback) ->
# asyncthing data, ->
# callback(321)
#
# fn(1)
# fn(2)
# fn(3, (result) -> console.log(result))
#
# ^--- async thing will only be running once at any time.
module.exports = (process) ->
throw new Error('process is not a function') unless typeof process == 'function'
queue = []
enqueue = (data, callback) ->
queue.push [data, callback]
flush()
enqueue.busy = false
flush = ->
return if enqueue.busy or queue.length == 0
enqueue.busy = true
[data, callback] = queue.shift()
process data, (result...) -> # TODO: Make this not use varargs - varargs are really slow.
enqueue.busy = false
# This is called after busy = false so a user can check if enqueue.busy is set in the callback.
callback.apply null, result if callback
flush()
enqueue