Module account 

Compressed account abstraction similar to anchor Account.

Light Account

LightAccount is a wrapper around a compressed account similar to anchor Account. LightAccount abstracts hashing of compressed account data, and wraps the compressed account data so that it is easy to use.

Data structs used with LightAccount must implement the traits:

• DataHasher
• LightDiscriminator
• BorshSerialize, BorshDeserialize
• Debug, Default, Clone

Account Data Hashing

The LightHasher derives a hashing scheme from the compressed account layout. Alternatively, DataHasher can be implemented manually.

Constraints:

• Poseidon hashes can only take up to 12 inputs -> use nested structs for structs with more than 12 fields.
• Poseidon hashes inputs must be less than bn254 field size (254 bits). hash_to_field_size methods in light hasher can be used to hash data longer than 253 bits. -> use the #[hash] attribute for fields with data types greater than 31 bytes eg Pubkeys.

Compressed account with LightHasher and LightDiscriminator

use light_sdk::{LightHasher, LightDiscriminator};
use solana_pubkey::Pubkey;
#[derive(Clone, Debug, Default, LightHasher, LightDiscriminator)]
pub struct CounterAccount {
    #[hash]
    pub owner: Pubkey,
    pub counter: u64,
}

Create compressed account

let mut my_compressed_account = LightAccount::<'_, CounterAccount>::new_init(
    &crate::ID,
    // Address
    Some(address),
    output_tree_index,
);
// Set data:
my_compressed_account.owner = ctx.accounts.signer.key();

Update compressed account

let mut my_compressed_account = LightAccount::<'_, CounterAccount>::new_mut(
    &crate::ID,
    &account_meta,
    my_compressed_account,
);
// Increment counter.
my_compressed_account.counter += 1;

Close compressed account

let mut my_compressed_account = LightAccount::<'_, CounterAccount>::new_close(
    &crate::ID,
    &account_meta_close,
    my_compressed_account,
);

Structs

LightAccount