probe-image-size/stream.js

Get image size without full download (JPG, GIF, PNG, WebP, BMP, TIFF, PSD)

'use strict'


var ProbeError = require('./lib/common').ProbeError
var parsers = require('./lib/parsers_stream')
var PassThrough = require('stream').PassThrough
var pipeline = require('stream').pipeline


module.exports = function probeStream (src, keepOpen) {
  var proxy = new PassThrough()

  // increase max number of listeners to stop memory leak warning
  proxy.setMaxListeners(Object.keys(parsers).length + 10)

  var result = new Promise(function (resolve, reject) {
    src.on('error', reject)
    proxy.on('error', reject)

    var alive_parsers = []
    var last_error

    function parserEnd (err) {
      var idx = alive_parsers.indexOf[this]

      /* istanbul ignore if */
      if (idx < 0) return

      /* istanbul ignore if */
      if (err) last_error = err

      proxy.unpipe(this)
      this.removeAllListeners()
      alive_parsers.splice(idx, 1)

      if (alive_parsers.length) return

      // if all parsers finished without success -> fail.
      reject(last_error || new ProbeError('unrecognized file format', 'ECONTENT'))
    }

    Object.keys(parsers).forEach(function (type) {
      var pStream = parsers[type]()

      alive_parsers.push(pStream)

      pStream.once('data', function (data) {
        if (data.width > 0 && data.height > 0) {
          resolve(data)
          return
        }

        // Manually finish parser to get standars "unrecognized" error.
        parserEnd.call(pStream)
      })
      pStream.once('end', parserEnd)
      // User does not need to know that something wrong in parser
      // Process error the same was unrecognized format (end without data)
      pStream.on('error', parserEnd)

      proxy.pipe(pStream)
    })
  })

  function cleanup () {
    // request stream doesn't have unpipe, https://github.com/request/request/issues/874
    if (keepOpen && typeof src.unpipe === 'function') src.unpipe(proxy)
    proxy.destroy()
  }

  result.then(cleanup).catch(cleanup)

  if (keepOpen) src.pipe(proxy)
  else pipeline(src, proxy, function () {})

  return result
}


module.exports.parsers = parsers