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'use strict'
var reusify = require('reusify')
function fastqueue (context, worker, concurrency) {
if (typeof context === 'function') {
concurrency = worker
worker = context
context = null
}
var cache = reusify(Task)
var queueHead = null
var queueTail = null
var _running = 0
var errorHandler = null
var self = {
push: push,
drain: noop,
saturated: noop,
pause: pause,
paused: false,
concurrency: concurrency,
running: running,
resume: resume,
idle: idle,
length: length,
getQueue: getQueue,
unshift: unshift,
empty: noop,
kill: kill,
killAndDrain: killAndDrain,
error: error
}
return self
function running () {
return _running
}
function pause () {
self.paused = true
}
function length () {
var current = queueHead
var counter = 0
while (current) {
current = current.next
counter++
}
return counter
}
function getQueue () {
var current = queueHead
var tasks = []
while (current) {
tasks.push(current.value)
current = current.next
}
return tasks
}
function resume () {
if (!self.paused) return
self.paused = false
for (var i = 0; i < self.concurrency; i++) {
_running++
release()
}
}
function idle () {
return _running === 0 && self.length() === 0
}
function push (value, done) {
var current = cache.get()
current.context = context
current.release = release
current.value = value
current.callback = done || noop
current.errorHandler = errorHandler
if (_running === self.concurrency || self.paused) {
if (queueTail) {
queueTail.next = current
queueTail = current
} else {
queueHead = current
queueTail = current
self.saturated()
}
} else {
_running++
worker.call(context, current.value, current.worked)
}
}
function unshift (value, done) {
var current = cache.get()
current.context = context
current.release = release
current.value = value
current.callback = done || noop
if (_running === self.concurrency || self.paused) {
if (queueHead) {
current.next = queueHead
queueHead = current
} else {
queueHead = current
queueTail = current
self.saturated()
}
} else {
_running++
worker.call(context, current.value, current.worked)
}
}
function release (holder) {
if (holder) {
cache.release(holder)
}
var next = queueHead
if (next) {
if (!self.paused) {
if (queueTail === queueHead) {
queueTail = null
}
queueHead = next.next
next.next = null
worker.call(context, next.value, next.worked)
if (queueTail === null) {
self.empty()
}
} else {
_running--
}
} else if (--_running === 0) {
self.drain()
}
}
function kill () {
queueHead = null
queueTail = null
self.drain = noop
}
function killAndDrain () {
queueHead = null
queueTail = null
self.drain()
self.drain = noop
}
function error (handler) {
errorHandler = handler
}
}
function noop () {}
function Task () {
this.value = null
this.callback = noop
this.next = null
this.release = noop
this.context = null
this.errorHandler = null
var self = this
this.worked = function worked (err, result) {
var callback = self.callback
var errorHandler = self.errorHandler
var val = self.value
self.value = null
self.callback = noop
if (self.errorHandler) {
errorHandler(err, val)
}
callback.call(self.context, err, result)
self.release(self)
}
}
module.exports = fastqueue
|
