union

A Union is a dynamic byteclass created using the @union decorator.

@union
class MyUnion:
    """My Union Byteclass."""

    var1: UInt64
    var2: UInt32

Similar to a C union, each member of a byteclass union has an offset of 0 and overlay onto the same underlying data.

The length of a Union byteclass is determined when the class is created based on its members.

A Union byteclass can contain both byteclass primitives and other byteclass collections.

Each Union member has its own byte_order. However, the union decorator accepts a byte_order parameter which is used for any members that rely on a factory for instantiation.

@union(byte_order=b"@")
class Union1:
    """A union byteclass with one member using default factory."""

    a: UInt64 = member(factory=UInt64)

@union
class Union2:
    """A union byteclass with one member using default factory."""

    a: UInt64

The Union1 and Union2 defined above are functionally equivalent.