Function encode_from_cdr 

pub fn encode_from_cdr<S: SchemaSink + ?Sized>(
    reader: &mut CdrReader<'_>,
    type_name: &str,
    schema: &'static [Field],
    sink: &mut S,
) -> Result<(), SchemaError>

Walk schema, reading CDR and pushing each value into sink.

reader must be positioned at the start of the struct’s members (past the encapsulation header). The DHEADER handling mirrors a generated serialize exactly: one per struct, top-level AND nested, a no-op under XCDR1 — the same rule crate::size was written against.