Function crypto_generichash_init 

pub fn crypto_generichash_init(
    key: Option<&[u8]>,
    outlen: usize,
) -> Result<GenericHashState, Error>

Initializes the state for the generic hash function using outlen for the expected hash output length, and optional key, returning it upon success.

Parameter	Typical length	Recommended minimum	Accepted lengths
outlen	CRYPTO_GENERICHASH_BYTES	CRYPTO_GENERICHASH_BYTES_MIN	1 to CRYPTO_GENERICHASH_BYTES_MAX
key	CRYPTO_GENERICHASH_KEYBYTES	CRYPTO_GENERICHASH_KEYBYTES_MIN	0 to CRYPTO_GENERICHASH_KEYBYTES_MAX

As in libsodium, the *_MIN constants are recommendations rather than limits, and an empty key (Some(&[])) is the same as None.

Equivalent to libsodium’s crypto_generichash_init.

Errors

Returns an error if outlen or the key length is outside the accepted range.