function amf0decSArray(buf) {
  let a = [];
  let len = 5;
  let ret;
  for (let count = buf.readUInt32BE(1); count; count--) {
    ret = amf0DecodeOne(buf.slice(len));
    a.push(ret.value);
    len += ret.len;
  }
  return { len: len, value: amf0markSArray(a) };
}
AMF0 Decode Strict Array
@param {Buffer} buf
@returns {{len: number, value: Array}}