# `KiwiCodec.RustlerGenerator.Decoder`
[🔗](https://github.com/open-pencil/kiwi_codec/blob/v0.7.0/codegen/kiwi_codec/rustler_generator/decoder.ex#L2)

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.

# `source`

```elixir
@spec source() :: Path.t()
```

Returns the path of the reference `Decoder` source.

---

*Consult [api-reference.md](api-reference.md) for complete listing*