'use strict'
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/*
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* merge2
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* https://github.com/teambition/merge2
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*
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* Copyright (c) 2014-2020 Teambition
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* Licensed under the MIT license.
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*/
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const Stream = require('stream')
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const PassThrough = Stream.PassThrough
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const slice = Array.prototype.slice
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module.exports = merge2
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function merge2 () {
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const streamsQueue = []
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const args = slice.call(arguments)
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let merging = false
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let options = args[args.length - 1]
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if (options && !Array.isArray(options) && options.pipe == null) {
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args.pop()
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} else {
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options = {}
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}
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const doEnd = options.end !== false
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const doPipeError = options.pipeError === true
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if (options.objectMode == null) {
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options.objectMode = true
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}
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if (options.highWaterMark == null) {
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options.highWaterMark = 64 * 1024
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}
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const mergedStream = PassThrough(options)
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function addStream () {
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for (let i = 0, len = arguments.length; i < len; i++) {
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streamsQueue.push(pauseStreams(arguments[i], options))
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}
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mergeStream()
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return this
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}
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function mergeStream () {
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if (merging) {
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return
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}
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merging = true
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let streams = streamsQueue.shift()
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if (!streams) {
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process.nextTick(endStream)
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return
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}
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if (!Array.isArray(streams)) {
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streams = [streams]
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}
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let pipesCount = streams.length + 1
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function next () {
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if (--pipesCount > 0) {
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return
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}
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merging = false
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mergeStream()
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}
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function pipe (stream) {
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function onend () {
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stream.removeListener('merge2UnpipeEnd', onend)
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stream.removeListener('end', onend)
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if (doPipeError) {
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stream.removeListener('error', onerror)
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}
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next()
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}
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function onerror (err) {
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mergedStream.emit('error', err)
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}
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// skip ended stream
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if (stream._readableState.endEmitted) {
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return next()
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}
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stream.on('merge2UnpipeEnd', onend)
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stream.on('end', onend)
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if (doPipeError) {
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stream.on('error', onerror)
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}
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stream.pipe(mergedStream, { end: false })
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// compatible for old stream
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stream.resume()
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}
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for (let i = 0; i < streams.length; i++) {
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pipe(streams[i])
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}
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next()
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}
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function endStream () {
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merging = false
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// emit 'queueDrain' when all streams merged.
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mergedStream.emit('queueDrain')
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if (doEnd) {
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mergedStream.end()
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}
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}
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mergedStream.setMaxListeners(0)
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mergedStream.add = addStream
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mergedStream.on('unpipe', function (stream) {
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stream.emit('merge2UnpipeEnd')
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})
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if (args.length) {
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addStream.apply(null, args)
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}
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return mergedStream
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}
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// check and pause streams for pipe.
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function pauseStreams (streams, options) {
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if (!Array.isArray(streams)) {
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// Backwards-compat with old-style streams
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if (!streams._readableState && streams.pipe) {
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streams = streams.pipe(PassThrough(options))
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}
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if (!streams._readableState || !streams.pause || !streams.pipe) {
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throw new Error('Only readable stream can be merged.')
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}
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streams.pause()
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} else {
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for (let i = 0, len = streams.length; i < len; i++) {
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streams[i] = pauseStreams(streams[i], options)
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}
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}
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return streams
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}
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