byline.ts•4.52 kB
/* eslint-disable @typescript-eslint/no-this-alias */
// Copyright (C) 2011-2015 John Hewson
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.
// @ts-ignore
import stream from 'stream'
import util from 'util'
// convenience API
export default function byline(readStream, options?: any) {
return createStream(readStream, options)
}
// basic API
export function createStream(readStream, options) {
if (readStream) {
return createLineStream(readStream, options)
} else {
return new LineStream(options)
}
}
export function createLineStream(readStream, options) {
if (!readStream) {
throw new Error('expected readStream')
}
if (!readStream.readable) {
throw new Error('readStream must be readable')
}
const ls = new LineStream(options)
readStream.pipe(ls)
return ls
}
//
// using the new node v0.10 "streams2" API
//
export function LineStream(this: any, options) {
stream.Transform.call(this, options)
options = options || {}
// use objectMode to stop the output from being buffered
// which re-concatenates the lines, just without newlines.
this._readableState.objectMode = true
this._lineBuffer = []
this._keepEmptyLines = options.keepEmptyLines || false
this._lastChunkEndedWithCR = false
// take the source's encoding if we don't have one
this.on('pipe', function (this: any, src) {
if (!this.encoding) {
// but we can't do this for old-style streams
if (src instanceof stream.Readable) {
this.encoding = (src as any)._readableState.encoding
}
}
})
}
util.inherits(LineStream, stream.Transform)
LineStream.prototype._transform = function (chunk, encoding, done) {
// decode binary chunks as UTF-8
encoding = encoding || 'utf8'
if (Buffer.isBuffer(chunk)) {
if (encoding == 'buffer') {
chunk = chunk.toString() // utf8
encoding = 'utf8'
} else {
chunk = chunk.toString(encoding)
}
}
this._chunkEncoding = encoding
const lines = chunk.split(/\r\n|\r|\n/g)
// don't split CRLF which spans chunks
if (this._lastChunkEndedWithCR && chunk[0] == '\n') {
lines.shift()
}
if (this._lineBuffer.length > 0) {
this._lineBuffer[this._lineBuffer.length - 1] += lines[0]
lines.shift()
}
this._lastChunkEndedWithCR = chunk[chunk.length - 1] == '\r'
this._lineBuffer = this._lineBuffer.concat(lines)
this._pushBuffer(encoding, 1, done)
}
LineStream.prototype._pushBuffer = function (encoding, keep, done) {
// always buffer the last (possibly partial) line
while (this._lineBuffer.length > keep) {
const line = this._lineBuffer.shift()
// skip empty lines
if (this._keepEmptyLines || line.length > 0) {
if (!this.push(this._reencode(line, encoding))) {
// when the high-water mark is reached, defer pushes until the next tick
const self = this
setImmediate(function () {
self._pushBuffer(encoding, keep, done)
})
return
}
}
}
done()
}
LineStream.prototype._flush = function (done) {
this._pushBuffer(this._chunkEncoding, 0, done)
}
// see Readable::push
LineStream.prototype._reencode = function (line, chunkEncoding) {
if (this.encoding && this.encoding != chunkEncoding) {
return Buffer.from(line, chunkEncoding).toString(this.encoding)
} else if (this.encoding) {
// this should be the most common case, i.e. we're using an encoded source stream
return line
} else {
return Buffer.from(line, chunkEncoding)
}
}