let Sys = {
  // ## **`Sys._sbuf(len)`**
  // Helper function to allocate string of at least given length. Note that
  // the resulting string is usually bigger than this, and it is always
  // longer than 5 bytes; that's to guarantee that the string data is stored in
  // a common buffer and not inlined into mjs_val_t, thus the buffer can be
  // used as an "output" buffer: a string can be passed to some function which
  // will alter the contents, and these changes will be visible to the caller.
  _sbuf: function(len) {
    let chunk = '          ', buf = chunk;
    while (buf.length < len) buf += chunk;
    return buf;
  },

  // ## **`Sys.calloc(nmemb, size)`**
  // Allocate a memory region.
  // Note: currently memory allocated this way must be explicitly released with `free()`.
  malloc: ffi('void *malloc(int)'),
  free: ffi('void free(void *)'),

  // ## **`Sys.total_ram()`**
  // Return total available RAM in bytes.
  total_ram: ffi('int mgos_get_heap_size()'),

  // ## **`Sys.free_ram()`**
  // Return free available RAM in bytes.
  free_ram: ffi('int mgos_get_free_heap_size()'),

  // ## **`Sys.reboot(us)`**
  // Reboot the system after `us` microseconds. Return value: none.
  reboot: ffi('void mgos_system_restart(int)'),

  // ## **`Sys.uptime()`**
  // Return number of seconds since last reboot.
  uptime: ffi('double mgos_uptime()'),

  // ## **`Sys.usleep(microseconds)`**
  // Sleep given number of microseconds.
  // Return value: none.
  usleep: ffi('void mgos_usleep(int)'),

  // ## **`Sys.wdt_feed()`**
  // Feed the watchdog timer.
  // Return value: none.
  wdt_feed: ffi('void mgos_wdt_feed()')
};