async build(appOutDir: string, arch: Arch): Promise<any> {
    const packager = this.packager

    // avoid spaces in the file name
    const image = path.join(this.outDir, packager.generateName("AppImage", arch, true))
    const appInfo = packager.appInfo
    await unlinkIfExists(image)

    const appImagePath = await appImagePathPromise
    const args = [
      "-joliet", "on",
      "-volid", "AppImage",
      "-dev", image,
      "-padding", "0",
      "-map", appOutDir, "/usr/bin",
      "-map", path.join(__dirname, "..", "..", "templates", "linux", "AppRun.sh"), `/AppRun`,
      "-map", await this.desktopEntry, `/${appInfo.name}.desktop`,
      "-move", `/usr/bin/${appInfo.productFilename}`, `/usr/bin/${appInfo.name}`,
    ]
    for (let [from, to] of (await this.helper.icons)) {
      args.push("-map", from, `/usr/share/icons/default/${to}`)
    }

    // must be after this.helper.icons call
    if (this.helper.maxIconPath == null) {
      throw new Error("Icon is not provided")
    }
    args.push("-map", this.helper.maxIconPath, "/.DirIcon")

    args.push("-chown_r", "0", "/", "--")
    args.push("-zisofs", `level=${packager.devMetadata.build.compression === "store" ? "0" : "9"}:block_size=128k:by_magic=off`)
    args.push("set_filter_r", "--zisofs", "/")

    await exec(process.env.USE_SYSTEM_FPM === "true" || process.arch !== "x64" ? "xorriso" : path.join(appImagePath, "xorriso"), args)

    await new BluebirdPromise((resolve, reject) => {
      const rd = createReadStream(path.join(appImagePath, arch === Arch.ia32 ? "32" : "64", "runtime"))
      rd.on("error", reject)
      const wr = createWriteStream(image, {flags: "r+"})
      wr.on("error", reject)
      wr.on("finish", resolve)
      rd.pipe(wr)
    })

    const fd = await open(image, "r+")
    try {
      const magicData = new Buffer([0x41, 0x49, 0x01])
      await write(fd, magicData, 0, magicData.length, 8)
    }
    finally {
      await close(fd)
    }

    await chmod(image, "0755")

    packager.dispatchArtifactCreated(image, packager.generateName("AppImage", arch, true))
  }

async function readEmbeddedBlockMapData(file: string): Promise<BlockMap> {
  const fd = await open(file, "r")
  try {
    const fileSize = (await fstat(fd)).size
    const sizeBuffer = Buffer.allocUnsafe(4)
    await read(fd, sizeBuffer, 0, sizeBuffer.length, fileSize - sizeBuffer.length)

    const dataBuffer = Buffer.allocUnsafe(sizeBuffer.readUInt32BE(0))
    await read(fd, dataBuffer, 0, dataBuffer.length, fileSize - sizeBuffer.length - dataBuffer.length)
    await close(fd)

    return readBlockMap(dataBuffer)
  }
  catch (e) {
    await close(fd)
    throw e
  }
}

export async function readEmbeddedBlockMapData(file: string) {
  const fd = await open(file, "r")
  try {
    const fileSize = (await fstat(fd)).size
    const sizeBuffer = Buffer.allocUnsafe(4)
    await read(fd, sizeBuffer, 0, sizeBuffer.length, fileSize - sizeBuffer.length)

    const dataBuffer = Buffer.allocUnsafe(sizeBuffer.readUInt32BE(0))
    await read(fd, dataBuffer, 0, dataBuffer.length, fileSize - sizeBuffer.length - dataBuffer.length)
    await close(fd)

    const inflateRaw: any = BluebirdPromise.promisify(require("zlib").inflateRaw)
    return (await inflateRaw(dataBuffer)).toString()
  }
  catch (e) {
    await close(fd)
    throw e
  }
}

async function checkIcon(file: string): Promise<void> {
  const fd = await open(file, "r")
  const buffer = new Buffer(512)
  try {
    await read(fd, buffer, 0, buffer.length, 0)
  }
  finally {
    await close(fd)
  }

  const sizes = parseIco(buffer)
  for (let size of sizes) {
    if (size.w >= 256 && size.h >= 256) {
      return
    }
  }

  throw new Error("Windows icon image size must be at least 256x256")
}

      packed: async context => {
        const outDir = context.outDir
        outDirs.push(outDir)
        const targetOutDir = path.join(outDir, "nsis-web")
        const updateInfoFile = path.join(targetOutDir, "latest.yml")

        const updateInfo: UpdateInfo = safeLoad(await readFile(updateInfoFile, "utf-8"))
        const fd = await open(path.join(targetOutDir, `TestApp-${version}-x64.nsis.7z`), "r")
        try {
          const packageInfo = updateInfo.packages!!.x64
          const buffer = Buffer.allocUnsafe(packageInfo.blockMapSize!!)
          await read(fd, buffer, 0, buffer.length, packageInfo.size - buffer.length)
          const inflateRaw: any = BluebirdPromise.promisify(require("zlib").inflateRaw)
          const blockMapData = (await inflateRaw(buffer)).toString()
          await writeFile(path.join(outDir, "win-unpacked", BLOCK_MAP_FILE_NAME), blockMapData)
        }
        finally {
          await close(fd)
        }
      }

async function checkIcon(file: string): Promise<void> {
  const fd = await open(file, "r")
  const buffer = new Buffer(512)
  try {
    await read(fd, buffer, 0, buffer.length, 0)
  }
  finally {
    await close(fd)
  }

  if (!isIco(buffer)) {
    throw new Error(`Windows icon is not valid ico file, please fix "${file}"`)
  }

  const sizes = parseIco(buffer)
  for (let size of sizes) {
    if (size!.w >= 256 && size!.h >= 256) {
      return
    }
  }

  throw new Error(`Windows icon size must be at least 256x256, please fix "${file}"`)
}

 .then(() => close(oldFileFd))

  async build(appOutDir: string, arch: Arch): Promise<any> {
    const packager = this.packager

    const image = path.join(this.outDir, packager.generateName(null, arch, true))
    const appInfo = packager.appInfo
    await unlinkIfExists(image)

    const appImagePath = await appImagePathPromise
    const args = [
      "-joliet", "on",
      "-volid", "AppImage",
      "-dev", image,
      "-padding", "0",
      "-map", appOutDir, "/usr/bin",
      "-map", path.join(__dirname, "..", "..", "templates", "linux", "AppRun.sh"), `/AppRun`,
      "-map", await this.desktopEntry, `/${appInfo.name}.desktop`,
      "-move", `/usr/bin/${appInfo.productFilename}`, "/usr/bin/app",
    ]
    for (let [from, to] of (await this.helper.icons)) {
      args.push("-map", from, `/usr/share/icons/default/${to}`)
    }

    // must be after this.helper.icons call
    if (this.helper.maxIconPath == null) {
      throw new Error("Icon is not provided")
    }
    args.push("-map", this.helper.maxIconPath, "/.DirIcon")

    // args.push("-zisofs", `level=0:block_size=128k:by_magic=off`, "-chown_r", "0")
    // args.push("/", "--", "set_filter_r", "--zisofs", "/")

    await exec(process.platform === "darwin" ? path.join(appImagePath, "xorriso") : "xorriso", args)

    await new BluebirdPromise((resolve, reject) => {
      const rd = createReadStream(path.join(appImagePath, arch === Arch.ia32 ? "32" : "64", "runtime"))
      rd.on("error", reject)
      const wr = createWriteStream(image)
      wr.on("error", reject)
      wr.on("finish", resolve)
      rd.pipe(wr)
    })

    const fd = await open(image, "r+")
    try {
      const magicData = new Buffer([0x41, 0x49, 0x01])
      await write(fd, magicData, 0, magicData.length, 8)
    }
    finally {
      await close(fd)
    }

    await chmod(image, "0755")
    // we archive because you cannot distribute exe as is - e.g. Ubuntu clear exec flag and user cannot just click on AppImage to run
    // also, LZMA compression - 29MB vs zip 42MB
    // we use slow xz instead of 7za because 7za doesn't preserve exec file permissions for xz
    await spawn("xz", ["--x86", "--lzma2", "--compress", "--force", packager.devMetadata.build.compression === "store" ? "-0" : "-9e", image], {
      cwd: path.dirname(image),
      stdio: ["ignore", debug.enabled ? "inherit" : "ignore", "inherit"],
    })

    packager.dispatchArtifactCreated(image)
  }

 .finally(() => close(oldFileFd))