filepizza/src/zip-stream.ts

// Based on https://github.com/jimmywarting/StreamSaver.js/blob/master/examples/zip-stream.js
//
// Disabling typechecking for now since this was originally JavaScript, should
// find some time to add types later.
//
// eslint-disable-next-line @typescript-eslint/ban-ts-comment
// @ts-nocheck

class Crc32 {
  crc: number

  constructor() {
    this.crc = -1
  }

  table = (() => {
    let i
    let j
    let t
    const 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
  })()

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

  get() {
    return ~this.crc
  }
}

const getDataHelper = (byteLength) => {
  const 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)
  })

export function createZipStream(
  underlyingSource: UnderlyingSource<any>,
): ReadableStream {
  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]]
    // eslint-disable-next-line @typescript-eslint/no-use-before-define
    if (activeZipObject) processNextChunk()
    // eslint-disable-next-line @typescript-eslint/no-use-before-define
    else if (closed) closeZip()
  }

  const 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() {
          const header = getDataHelper(26)
          const 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() {
          const 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
        // eslint-disable-next-line @typescript-eslint/no-use-before-define
        processNextChunk()
      }
    },
    close() {
      if (closed)
        throw new TypeError(
          'Cannot close a readable stream that has already been requested to be closed',
        )
      // eslint-disable-next-line @typescript-eslint/no-use-before-define
      if (!activeZipObject) closeZip()
      closed = true
    },
  }

  function closeZip() {
    let length = 0
    let index = 0
    let 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)))
      )
    },
  })
}