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