setInt64 method Null safety
Sets the eight bytes starting at the specified
byteOffset in this
object to the two's complement binary representation of the specified
value, which must fit in eight bytes.
In other words,
value must lie
between -263 and 263 - 1, inclusive.
byteOffset must be non-negative, and
byteOffset + 8 must be less than or equal to the length of this object.
void setInt64(int byteOffset, int value, [Endian endian = Endian.big]);