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'use strict'
const defaultMaxRunning = 50
const limit = module.exports = function (func, maxRunning) {
const state = {running: 0, queue: []}
if (!maxRunning) maxRunning = defaultMaxRunning
return function limited () {
const args = Array.prototype.slice.call(arguments)
if (state.running >= maxRunning) {
state.queue.push({obj: this, args})
} else {
callFunc(this, args)
}
}
function callNext () {
if (state.queue.length === 0) return
const next = state.queue.shift()
callFunc(next.obj, next.args)
}
function callFunc (obj, args) {
const cb = typeof args[args.length - 1] === 'function' && args.pop()
try {
++state.running
func.apply(obj, args.concat(function () {
--state.running
process.nextTick(callNext)
if (cb) process.nextTick(() => cb.apply(obj, arguments))
}))
} catch (err) {
--state.running
if (cb) process.nextTick(() => cb.call(obj, err))
process.nextTick(callNext)
}
}
}
module.exports.method = function (classOrObj, method, maxRunning) {
if (typeof classOrObj === 'function') {
const func = classOrObj.prototype[method]
classOrObj.prototype[method] = limit(func, maxRunning)
} else {
const func = classOrObj[method]
classOrObj[method] = limit(func, maxRunning)
}
}
module.exports.promise = function (func, maxRunning) {
const state = {running: 0, queue: []}
if (!maxRunning) maxRunning = defaultMaxRunning
return function limited () {
const args = Array.prototype.slice.call(arguments)
if (state.running >= maxRunning) {
return new Promise(resolve => {
state.queue.push({resolve, obj: this, args})
})
} else {
return callFunc(this, args)
}
}
function callNext () {
if (state.queue.length === 0) return
const next = state.queue.shift()
next.resolve(callFunc(next.obj, next.args))
}
function callFunc (obj, args) {
return callFinally(() => {
++state.running
return func.apply(obj, args)
}, () => {
--state.running
process.nextTick(callNext)
})
}
function callFinally (action, fin) {
try {
return Promise.resolve(action()).then(value => {
fin()
return value
}, err => {
fin()
return Promise.reject(err)
})
} catch (err) {
fin()
return Promise.reject(err)
}
}
}
module.exports.promise.method = function (classOrObj, method, maxRunning) {
if (typeof classOrObj === 'function') {
const func = classOrObj.prototype[method]
classOrObj.prototype[method] = limit.promise(func, maxRunning)
} else {
const func = classOrObj[method]
classOrObj[method] = limit.promise(func, maxRunning)
}
}
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