nedb/lib/byline.js

// Forked from https://github.com/jahewson/node-byline

// 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.

const stream = require('stream')
const util = require('util')
const timers = require('timers')

// convinience API
module.exports = function (readStream, options) {
  return module.exports.createStream(readStream, options)
}

// basic API
module.exports.createStream = function (readStream, options) {
  if (readStream) {
    return createLineStream(readStream, options)
  } else {
    return new LineStream(options)
  }
}

// deprecated API
module.exports.createLineStream = function (readStream) {
  console.log('WARNING: byline#createLineStream is deprecated and will be removed soon')
  return createLineStream(readStream)
}

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
//

module.exports.LineStream = LineStream

function LineStream (options) {
  stream.Transform.call(this, options)
  options = options || {}

  // use objectMode to stop the output from being buffered
  // which re-concatanates 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
  const self = this
  this.on('pipe', function (src) {
    if (!self.encoding) {
      // but we can't do this for old-style streams
      if (src instanceof stream.Readable) {
        self.encoding = src._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

  // see: http://www.unicode.org/reports/tr18/#Line_Boundaries
  const lines = chunk.split(/\r\n|[\n\v\f\r\x85\u2028\u2029]/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
        timers.setImmediate(() => {
          this._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)
  }
}