const Minipass = require('minipass')
|
const EE = require('events')
|
const isStream = s => s && s instanceof EE && (
|
typeof s.pipe === 'function' || // readable
|
(typeof s.write === 'function' && typeof s.end === 'function') // writable
|
)
|
|
const _head = Symbol('_head')
|
const _tail = Symbol('_tail')
|
const _linkStreams = Symbol('_linkStreams')
|
const _setHead = Symbol('_setHead')
|
const _setTail = Symbol('_setTail')
|
const _onError = Symbol('_onError')
|
const _onData = Symbol('_onData')
|
const _onEnd = Symbol('_onEnd')
|
const _onDrain = Symbol('_onDrain')
|
const _streams = Symbol('_streams')
|
class Pipeline extends Minipass {
|
constructor (opts, ...streams) {
|
if (isStream(opts)) {
|
streams.unshift(opts)
|
opts = {}
|
}
|
|
super(opts)
|
this[_streams] = []
|
if (streams.length)
|
this.push(...streams)
|
}
|
|
[_linkStreams] (streams) {
|
// reduce takes (left,right), and we return right to make it the
|
// new left value.
|
return streams.reduce((src, dest) => {
|
src.on('error', er => dest.emit('error', er))
|
src.pipe(dest)
|
return dest
|
})
|
}
|
|
push (...streams) {
|
this[_streams].push(...streams)
|
if (this[_tail])
|
streams.unshift(this[_tail])
|
|
const linkRet = this[_linkStreams](streams)
|
|
this[_setTail](linkRet)
|
if (!this[_head])
|
this[_setHead](streams[0])
|
}
|
|
unshift (...streams) {
|
this[_streams].unshift(...streams)
|
if (this[_head])
|
streams.push(this[_head])
|
|
const linkRet = this[_linkStreams](streams)
|
this[_setHead](streams[0])
|
if (!this[_tail])
|
this[_setTail](linkRet)
|
}
|
|
destroy (er) {
|
// set fire to the whole thing.
|
this[_streams].forEach(s =>
|
typeof s.destroy === 'function' && s.destroy())
|
return super.destroy(er)
|
}
|
|
// readable interface -> tail
|
[_setTail] (stream) {
|
this[_tail] = stream
|
stream.on('error', er => this[_onError](stream, er))
|
stream.on('data', chunk => this[_onData](stream, chunk))
|
stream.on('end', () => this[_onEnd](stream))
|
stream.on('finish', () => this[_onEnd](stream))
|
}
|
|
// errors proxied down the pipeline
|
// they're considered part of the "read" interface
|
[_onError] (stream, er) {
|
if (stream === this[_tail])
|
this.emit('error', er)
|
}
|
[_onData] (stream, chunk) {
|
if (stream === this[_tail])
|
super.write(chunk)
|
}
|
[_onEnd] (stream) {
|
if (stream === this[_tail])
|
super.end()
|
}
|
pause () {
|
super.pause()
|
return this[_tail] && this[_tail].pause && this[_tail].pause()
|
}
|
|
// NB: Minipass calls its internal private [RESUME] method during
|
// pipe drains, to avoid hazards where stream.resume() is overridden.
|
// Thus, we need to listen to the resume *event*, not override the
|
// resume() method, and proxy *that* to the tail.
|
emit (ev, ...args) {
|
if (ev === 'resume' && this[_tail] && this[_tail].resume)
|
this[_tail].resume()
|
return super.emit(ev, ...args)
|
}
|
|
// writable interface -> head
|
[_setHead] (stream) {
|
this[_head] = stream
|
stream.on('drain', () => this[_onDrain](stream))
|
}
|
[_onDrain] (stream) {
|
if (stream === this[_head])
|
this.emit('drain')
|
}
|
write (chunk, enc, cb) {
|
return this[_head].write(chunk, enc, cb) &&
|
(this.flowing || this.buffer.length === 0)
|
}
|
end (chunk, enc, cb) {
|
this[_head].end(chunk, enc, cb)
|
return this
|
}
|
}
|
|
module.exports = Pipeline
|
