'use strict'
module.exports = (mode, isDir, portable) => {
  mode &= 0o7777

  // in portable mode, use the minimum reasonable umask
  // if this system creates files with 0o664 by default
  // (as some linux distros do), then we'll write the
  // archive with 0o644 instead.  Also, don't ever create
  // a file that is not readable/writable by the owner.
  if (portable) {
    mode = (mode | 0o600) &~0o22
  }

  // if dirs are readable, then they should be listable
  if (isDir) {
    if (mode & 0o400)
      mode |= 0o100
    if (mode & 0o40)
      mode |= 0o10
    if (mode & 0o4)
      mode |= 0o1
  }
  return mode
}