eacp_webapp/public/scripts/StreamSaver/examples/zip-stream.js

class Crc32 {
  constructor () {
    this.crc = -1
  }

  append (data) {
    var crc = this.crc | 0; var table = this.table
    for (var offset = 0, len = data.length | 0; offset < len; offset++) {
      crc = (crc >>> 8) ^ table[(crc ^ data[offset]) & 0xFF]
    }
    this.crc = crc
  }

  get () {
    return ~this.crc
  }
}
Crc32.prototype.table = (() => {
  var i; var j; var t; var table = []
  for (i = 0; i < 256; i++) {
    t = i
    for (j = 0; j < 8; j++) {
      t = (t & 1)
        ? (t >>> 1) ^ 0xEDB88320
        : t >>> 1
    }
    table[i] = t
  }
  return table
})()

const getDataHelper = byteLength => {
  var uint8 = new Uint8Array(byteLength)
  return {
    array: uint8,
    view: new DataView(uint8.buffer)
  }
}

const pump = zipObj => zipObj.reader.read().then(chunk => {
  if (chunk.done) return zipObj.writeFooter()
  const outputData = chunk.value
  zipObj.crc.append(outputData)
  zipObj.uncompressedLength += outputData.length
  zipObj.compressedLength += outputData.length
  zipObj.ctrl.enqueue(outputData)
})

/**
 * [createWriter description]
 * @param  {Object} underlyingSource [description]
 * @return {Boolean}                  [description]
 */
function createWriter (underlyingSource) {
  const files = Object.create(null)
  const filenames = []
  const encoder = new TextEncoder()
  let offset = 0
  let activeZipIndex = 0
  let ctrl
  let activeZipObject, closed

  function next () {
    activeZipIndex++
    activeZipObject = files[filenames[activeZipIndex]]
    if (activeZipObject) processNextChunk()
    else if (closed) closeZip()
  }

  var zipWriter = {
    enqueue (fileLike) {
      if (closed) throw new TypeError('Cannot enqueue a chunk into a readable stream that is closed or has been requested to be closed')

      let name = fileLike.name.trim()
      const date = new Date(typeof fileLike.lastModified === 'undefined' ? Date.now() : fileLike.lastModified)

      if (fileLike.directory && !name.endsWith('/')) name += '/'
      if (files[name]) throw new Error('File already exists.')

      const nameBuf = encoder.encode(name)
      filenames.push(name)

      const zipObject = files[name] = {
        level: 0,
        ctrl,
        directory: !!fileLike.directory,
        nameBuf,
        comment: encoder.encode(fileLike.comment || ''),
        compressedLength: 0,
        uncompressedLength: 0,
        writeHeader () {
          var header = getDataHelper(26)
          var data = getDataHelper(30 + nameBuf.length)

          zipObject.offset = offset
          zipObject.header = header
          if (zipObject.level !== 0 && !zipObject.directory) {
            header.view.setUint16(4, 0x0800)
          }
          header.view.setUint32(0, 0x14000808)
          header.view.setUint16(6, (((date.getHours() << 6) | date.getMinutes()) << 5) | date.getSeconds() / 2, true)
          header.view.setUint16(8, ((((date.getFullYear() - 1980) << 4) | (date.getMonth() + 1)) << 5) | date.getDate(), true)
          header.view.setUint16(22, nameBuf.length, true)
          data.view.setUint32(0, 0x504b0304)
          data.array.set(header.array, 4)
          data.array.set(nameBuf, 30)
          offset += data.array.length
          ctrl.enqueue(data.array)
        },
        writeFooter () {
          var footer = getDataHelper(16)
          footer.view.setUint32(0, 0x504b0708)

          if (zipObject.crc) {
            zipObject.header.view.setUint32(10, zipObject.crc.get(), true)
            zipObject.header.view.setUint32(14, zipObject.compressedLength, true)
            zipObject.header.view.setUint32(18, zipObject.uncompressedLength, true)
            footer.view.setUint32(4, zipObject.crc.get(), true)
            footer.view.setUint32(8, zipObject.compressedLength, true)
            footer.view.setUint32(12, zipObject.uncompressedLength, true)
          }

          ctrl.enqueue(footer.array)
          offset += zipObject.compressedLength + 16
          next()
        },
        fileLike
      }

      if (!activeZipObject) {
        activeZipObject = zipObject
        processNextChunk()
      }
    },
    close () {
      if (closed) throw new TypeError('Cannot close a readable stream that has already been requested to be closed')
      if (!activeZipObject) closeZip()
      closed = true
    }
  }

  function closeZip () {
    var length = 0
    var index = 0
    var indexFilename, file
    for (indexFilename = 0; indexFilename < filenames.length; indexFilename++) {
      file = files[filenames[indexFilename]]
      length += 46 + file.nameBuf.length + file.comment.length
    }
    const data = getDataHelper(length + 22)
    for (indexFilename = 0; indexFilename < filenames.length; indexFilename++) {
      file = files[filenames[indexFilename]]
      data.view.setUint32(index, 0x504b0102)
      data.view.setUint16(index + 4, 0x1400)
      data.array.set(file.header.array, index + 6)
      data.view.setUint16(index + 32, file.comment.length, true)
      if (file.directory) {
        data.view.setUint8(index + 38, 0x10)
      }
      data.view.setUint32(index + 42, file.offset, true)
      data.array.set(file.nameBuf, index + 46)
      data.array.set(file.comment, index + 46 + file.nameBuf.length)
      index += 46 + file.nameBuf.length + file.comment.length
    }
    data.view.setUint32(index, 0x504b0506)
    data.view.setUint16(index + 8, filenames.length, true)
    data.view.setUint16(index + 10, filenames.length, true)
    data.view.setUint32(index + 12, length, true)
    data.view.setUint32(index + 16, offset, true)
    ctrl.enqueue(data.array)
    ctrl.close()
  }

  function processNextChunk () {
    if (!activeZipObject) return
    if (activeZipObject.directory) return activeZipObject.writeFooter(activeZipObject.writeHeader())
    if (activeZipObject.reader) return pump(activeZipObject)
    if (activeZipObject.fileLike.stream) {
      activeZipObject.crc = new Crc32()
      activeZipObject.reader = activeZipObject.fileLike.stream().getReader()
      activeZipObject.writeHeader()
    } else next()
  }
  return new ReadableStream({
    start: c => {
      ctrl = c
      underlyingSource.start && Promise.resolve(underlyingSource.start(zipWriter))
    },
    pull () {
      return processNextChunk() || (
        underlyingSource.pull &&
        Promise.resolve(underlyingSource.pull(zipWriter))
      )
    }
  })
}

window.ZIP = createWriter