var wrappy = require('wrappy')
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var reqs = Object.create(null)
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var once = require('once')
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module.exports = wrappy(inflight)
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function inflight (key, cb) {
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if (reqs[key]) {
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reqs[key].push(cb)
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return null
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} else {
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reqs[key] = [cb]
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return makeres(key)
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}
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}
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function makeres (key) {
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return once(function RES () {
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var cbs = reqs[key]
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var len = cbs.length
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var args = slice(arguments)
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// XXX It's somewhat ambiguous whether a new callback added in this
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// pass should be queued for later execution if something in the
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// list of callbacks throws, or if it should just be discarded.
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// However, it's such an edge case that it hardly matters, and either
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// choice is likely as surprising as the other.
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// As it happens, we do go ahead and schedule it for later execution.
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try {
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for (var i = 0; i < len; i++) {
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cbs[i].apply(null, args)
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}
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} finally {
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if (cbs.length > len) {
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// added more in the interim.
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// de-zalgo, just in case, but don't call again.
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cbs.splice(0, len)
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process.nextTick(function () {
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RES.apply(null, args)
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})
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} else {
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delete reqs[key]
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}
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}
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})
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}
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function slice (args) {
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var length = args.length
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var array = []
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for (var i = 0; i < length; i++) array[i] = args[i]
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return array
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}
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