[B@rmaley.e><e]

А что там сложного-то?

function (fd, buffer, offset, length, position, callback) {
*!*
  if (!Buffer.isBuffer(buffer)) {
    // legacy string interface (fd, data, position, encoding, callback)
    callback = arguments[4];
    position = arguments[2];

    buffer = new Buffer('' + arguments[1], arguments[3]);
    offset = 0;
    length = buffer.length;
  }
*/!*

  if (!length) {
    if (typeof callback == 'function') {
      process.nextTick(function() {
        callback(undefined, 0);
      });
    }
    return;
  }

  function wrapper(err, written) {
    // Retain a reference to buffer so that it can't be GC'ed too soon.
    callback && callback(err, written || 0, buffer);
  }

  binding.write(fd, buffer, offset, length, position, wrapper);
}

Очевидно, строка — не буфер.