function bodyLength (body) {
  if (body == null) {
    return 0
  } else if (isStream(body)) {
    const state = body._readableState
    return state && state.objectMode === false && state.ended === true && Number.isFinite(state.length)
      ? state.length
      : null
  } else if (isBlobLike(body)) {
    return body.size != null ? body.size : null
  } else if (isBuffer(body)) {
    return body.byteLength
  }

  return null
}
@param {Blob|Buffer|import ('stream').Stream} body
@returns {number|null}