send/app/zip.js

import crc32 from './crc32';

const encoder = new TextEncoder();

function dosDateTime(dateTime = new Date()) {
  const year = (dateTime.getFullYear() - 1980) << 9;
  const month = (dateTime.getMonth() + 1) << 5;
  const day = dateTime.getDate();
  const date = year | month | day;
  const hour = dateTime.getHours() << 11;
  const minute = dateTime.getMinutes() << 5;
  const second = Math.floor(dateTime.getSeconds() / 2);
  const time = hour | minute | second;

  return { date, time };
}

class File {
  constructor(info) {
    this.name = encoder.encode(info.name);
    this.size = info.size;
    this.bytesRead = 0;
    this.crc = null;
    this.dateTime = dosDateTime();
  }

  get header() {
    const h = new ArrayBuffer(30 + this.name.byteLength);
    const v = new DataView(h);
    v.setUint32(0, 0x04034b50, true); // sig
    v.setUint16(4, 20, true); // version
    v.setUint16(6, 8, true); // bit flags (8 = use data descriptor)
    v.setUint16(8, 0, true); // compression
    v.setUint16(10, this.dateTime.time, true); // modified time
    v.setUint16(12, this.dateTime.date, true); // modified date
    v.setUint32(14, 0, true); // crc32 (in descriptor)
    v.setUint32(18, 0, true); // compressed size (in descriptor)
    v.setUint32(22, 0, true); // uncompressed size (in descriptor)
    v.setUint16(26, this.name.byteLength, true); // name length
    v.setUint16(28, 0, true); // extra field length
    for (let i = 0; i < this.name.byteLength; i++) {
      v.setUint8(30 + i, this.name[i]);
    }
    return new Uint8Array(h);
  }

  get dataDescriptor() {
    const dd = new ArrayBuffer(16);
    const v = new DataView(dd);
    v.setUint32(0, 0x08074b50, true); // sig
    v.setUint32(4, this.crc, true); // crc32
    v.setUint32(8, this.size, true); // compressed size
    v.setUint32(12, this.size, true); // uncompressed size
    return new Uint8Array(dd);
  }

  directoryRecord(offset) {
    const dr = new ArrayBuffer(46 + this.name.byteLength);
    const v = new DataView(dr);
    v.setUint32(0, 0x02014b50, true); // sig
    v.setUint16(4, 20, true); // version made
    v.setUint16(6, 20, true); // version required
    v.setUint16(8, 8, true); // bit flags (8 = use data descriptor)
    v.setUint16(10, 0, true); // compression
    v.setUint16(12, this.dateTime.time, true); // modified time
    v.setUint16(14, this.dateTime.date, true); // modified date
    v.setUint32(16, this.crc, true); // crc
    v.setUint32(20, this.size, true); // compressed size
    v.setUint32(24, this.size, true); // uncompressed size
    v.setUint16(28, this.name.byteLength, true); // name length
    v.setUint16(30, 0, true); // extra length
    v.setUint16(32, 0, true); // comment length
    v.setUint16(34, 0, true); // disk number
    v.setUint16(36, 0, true); // internal file attrs
    v.setUint32(38, 0, true); // external file attrs
    v.setUint32(42, offset, true); // file offset
    for (let i = 0; i < this.name.byteLength; i++) {
      v.setUint8(46 + i, this.name[i]);
    }
    return new Uint8Array(dr);
  }

  get byteLength() {
    return this.size + this.name.byteLength + 30 + 16;
  }

  append(data, controller) {
    this.bytesRead += data.byteLength;
    const endIndex = data.byteLength - Math.max(this.bytesRead - this.size, 0);
    const buf = data.slice(0, endIndex);
    this.crc = crc32(buf, this.crc);
    controller.enqueue(buf);
    if (endIndex < data.byteLength) {
      return data.slice(endIndex, data.byteLength);
    }
  }
}

function centralDirectory(files, controller) {
  let directoryOffset = 0;
  let directorySize = 0;
  for (let i = 0; i < files.length; i++) {
    const file = files[i];
    const record = file.directoryRecord(directoryOffset);
    directoryOffset += file.byteLength;
    controller.enqueue(record);
    directorySize += record.byteLength;
  }
  controller.enqueue(eod(files.length, directorySize, directoryOffset));
}

function eod(fileCount, directorySize, directoryOffset) {
  const e = new ArrayBuffer(22);
  const v = new DataView(e);
  v.setUint32(0, 0x06054b50, true); // sig
  v.setUint16(4, 0, true); // disk number
  v.setUint16(6, 0, true); // directory disk
  v.setUint16(8, fileCount, true); // number of records
  v.setUint16(10, fileCount, true); // total records
  v.setUint32(12, directorySize, true); // size of directory
  v.setUint32(16, directoryOffset, true); // offset of directory
  v.setUint16(20, 0, true); // comment length
  return new Uint8Array(e);
}

class ZipStreamController {
  constructor(files, source) {
    this.files = files;
    this.fileIndex = 0;
    this.file = null;
    this.reader = source.getReader();
    this.nextFile();
    this.extra = null;
  }

  nextFile() {
    this.file = this.files[this.fileIndex++];
  }

  async pull(controller) {
    if (!this.file) {
      // end of archive
      centralDirectory(this.files, controller);
      return controller.close();
    }
    if (this.file.bytesRead === 0) {
      // beginning of file
      controller.enqueue(this.file.header);
      if (this.extra) {
        this.extra = this.file.append(this.extra, controller);
      }
    }
    if (this.file.bytesRead >= this.file.size) {
      // end of file
      controller.enqueue(this.file.dataDescriptor);
      this.nextFile();
      return this.pull(controller);
    }
    const data = await this.reader.read();
    if (data.done) {
      this.nextFile();
      return this.pull(controller);
    }
    this.extra = this.file.append(data.value, controller);
  }
}

export default class Zip {
  constructor(manifest, source) {
    this.files = manifest.files.map(info => new File(info));
    this.source = source;
  }

  get stream() {
    return new ReadableStream(new ZipStreamController(this.files, this.source));
  }

  get size() {
    const entries = this.files.reduce(
      (total, file) => total + file.byteLength * 2 - file.size,
      0
    );
    const eod = 22;
    return entries + eod;
  }
}