The Decoder<'a> generated decoders read Kiwi data with.

The native crate provides it, imported from crate::runtime::Decoder unless the generator's :decoder option names another path. decoder.rs, beside this module, is a complete implementation to copy or start from; the tests build every generator feature against it. It names the runtime schema type crate::RuntimeSchema, which a crate using unknown_fields: :runtime_schema defines as pub use KiwiRuntimeSchema as RuntimeSchema;, and any other crate as an empty pub enum RuntimeSchema {}.

Every feature uses new(&'a [u8]), finish(&self) -> NifResult<()>, and the primitive readers, each returning NifResult: read_bool, read_byte, read_var_uint, read_var_uint64, read_var_int, read_var_int64, read_var_float_value, read_var_float(env), read_string(env), read_byte_array(env), skip_string, skip_byte_array, and read_repeated(read).

• Records also need read_byte_array_value, read_string_str, and remaining.
• unknown_fields: :runtime_schema also needs runtime_schema(&self) -> Option<&'a KiwiRuntimeSchema>, returning None to keep the :error behavior, and read_string_value.

The generator reads the method signatures from decoder.rs to know which calls return a NifResult, so a crate's own Decoder keeps them.