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/*! multistream. MIT License. Feross Aboukhadijeh <https://feross.org/opensource> */
const stream = require('readable-stream')
const once = require('once')
function toStreams2Obj (s) {
return toStreams2(s, { objectMode: true, highWaterMark: 16 })
}
function toStreams2Buf (s) {
return toStreams2(s)
}
function toStreams2 (s, opts) {
if (!s || typeof s === 'function' || s._readableState) return s
const wrap = new stream.Readable(opts).wrap(s)
if (s.destroy) {
wrap.destroy = s.destroy.bind(s)
}
return wrap
}
class MultiStream extends stream.Readable {
constructor (streams, opts) {
super({ ...opts, autoDestroy: true })
this._drained = false
this._forwarding = false
this._current = null
this._toStreams2 = (opts && opts.objectMode) ? toStreams2Obj : toStreams2Buf
if (typeof streams === 'function') {
this._queue = streams
} else {
this._queue = streams.map(this._toStreams2)
this._queue.forEach(stream => {
if (typeof stream !== 'function') this._attachErrorListener(stream)
})
}
this._next()
}
_read () {
this._drained = true
this._forward()
}
_forward () {
if (this._forwarding || !this._drained || !this._current) return
this._forwarding = true
let chunk
while (this._drained && (chunk = this._current.read()) !== null) {
this._drained = this.push(chunk)
}
this._forwarding = false
}
_destroy (err, cb) {
let streams = []
if (this._current) streams.push(this._current)
if (typeof this._queue !== 'function') streams = streams.concat(this._queue)
if (streams.length === 0) {
cb(err)
} else {
let counter = streams.length
let er = err
streams.forEach(stream => {
destroy(stream, err, err => {
er = er || err
if (--counter === 0) {
cb(er)
}
})
})
}
}
_next () {
this._current = null
if (typeof this._queue === 'function') {
this._queue((err, stream) => {
if (err) return this.destroy(err)
stream = this._toStreams2(stream)
this._attachErrorListener(stream)
this._gotNextStream(stream)
})
} else {
let stream = this._queue.shift()
if (typeof stream === 'function') {
stream = this._toStreams2(stream())
this._attachErrorListener(stream)
}
this._gotNextStream(stream)
}
}
_gotNextStream (stream) {
if (!stream) {
this.push(null)
return
}
this._current = stream
this._forward()
const onReadable = () => {
this._forward()
}
const onClose = () => {
if (!stream._readableState.ended && !stream.destroyed) {
const err = new Error('ERR_STREAM_PREMATURE_CLOSE')
err.code = 'ERR_STREAM_PREMATURE_CLOSE'
this.destroy(err)
}
}
const onEnd = () => {
this._current = null
stream.removeListener('readable', onReadable)
stream.removeListener('end', onEnd)
stream.removeListener('close', onClose)
stream.destroy()
this._next()
}
stream.on('readable', onReadable)
stream.once('end', onEnd)
stream.once('close', onClose)
}
_attachErrorListener (stream) {
if (!stream) return
const onError = (err) => {
stream.removeListener('error', onError)
this.destroy(err)
}
stream.once('error', onError)
}
}
MultiStream.obj = streams => (
new MultiStream(streams, { objectMode: true, highWaterMark: 16 })
)
module.exports = MultiStream
// Normalize stream destroy w/ callback.
function destroy (stream, err, cb) {
if (!stream.destroy || stream.destroyed) {
cb(err)
} else {
const callback = once(er => cb(er || err))
stream
.on('error', callback)
.on('close', () => callback())
.destroy(err, callback)
}
}
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