Trait ScriptArgs

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pub trait ScriptArgs: Sized + Sealed {
    const FIXED_LEN: Option<usize>;

    // Required methods
    fn decode(arg: Word) -> ScriptArgsResult<Self>;
    fn encode(&self) -> EncodedScriptArgs;
}

Expand description

Transaction-script arguments transported through the TX_SCRIPT_ARGS word.

Every type that implements both FromFeltRepr and ToFeltRepr is a ScriptArgs automatically. The felt-repr encoding selects one of two transport modes at compile time:

Word mode (FIXED_LEN of at most 4 felts): the encoding is packed directly into the args word; the unused felts are zero, and decode rejects anything else.
Commitment mode (longer or variable-length encodings): the args word is the Poseidon2 hash of the zero-padded encoding. decode fetches the preimage from the advice provider and the hash is verified in-VM, so the host cannot substitute values.

The mode is a compile-time property of the argument type, so within one type definition the encoder and decoder always agree on the transport mode. The word carries no field layout — host-side mirrors of a guest type must reproduce its felt-repr wire sequence (see the migration guide for how to pin that).

The trait is sealed: the blanket FromFeltRepr + ToFeltRepr implementation is the only one, which is what makes the documented transport guarantees hold for every implementor.

Required Associated Constants§

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const FIXED_LEN: Option<usize>

Total encoded length in felts, when statically known.

Required Methods§

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fn decode(arg: Word) -> ScriptArgsResult<Self>

Decodes the arguments from the TX_SCRIPT_ARGS word.

Returns an error when the encoding is malformed: a felt-repr decode failure, non-zero padding, or a non-canonical commitment preimage. The #[tx_script]-generated entrypoint wrapper panics on the error, failing the transaction. Commitment-mode decoding requires the Miden VM; word-mode decoding is pure.

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