Decoding

Be sure to read the prerequisites to decoding.

Decoding is done via the ABIDecoder:

        use fuels::{
            core::{
                codec::ABIDecoder,
                traits::{Parameterize, Tokenizable},
            },
            macros::{Parameterize, Tokenizable},
            types::Token,
        };

        #[derive(Parameterize, Tokenizable)]
        struct MyStruct {
            field: u64,
        }

        let bytes: &[u8] = &[0, 0, 0, 0, 0, 0, 0, 101];

        let token: Token = ABIDecoder::default().decode(&MyStruct::param_type(), bytes)?;

        let _: MyStruct = MyStruct::from_token(token)?;

First into a Token, then via the Tokenizable trait, into the desired type.

If the type came from abigen! (or uses the ::fuels::macros::TryFrom derivation) then you can also use try_into to convert bytes into a type that implements both Parameterize and Tokenizable:

        use fuels::macros::{Parameterize, Tokenizable, TryFrom};

        #[derive(Parameterize, Tokenizable, TryFrom)]
        struct MyStruct {
            field: u64,
        }

        let bytes: &[u8] = &[0, 0, 0, 0, 0, 0, 0, 101];

        let _: MyStruct = bytes.try_into()?;

Under the hood, try_from_bytes is being called, which does what the preceding example did.

Configuring the decoder

The decoder can be configured to limit its resource expenditure:

        use fuels::core::codec::ABIDecoder;

        ABIDecoder::new(DecoderConfig {
            max_depth: 5,
            max_tokens: 100,
        });

For an explanation of each configuration value visit the DecoderConfig.

The default values for the DecoderConfig are:

impl Default for DecoderConfig {
    fn default() -> Self {
        Self {
            max_depth: 45,
            max_tokens: 10_000,
        }
    }
}

Configuring the decoder for contract/script calls

You can also configure the decoder used to decode the return value of the contract method:

        let _ = contract_instance
            .methods()
            .initialize_counter(42)
            .with_decoder_config(DecoderConfig {
                max_depth: 10,
                max_tokens: 20_00,
            })
            .call()
            .await?;

The same method is available for script calls.