pool.rs

// in `state.rs`
use borsh::{BorshDeserialize, BorshSerialize};
use solana_program::pubkey::Pubkey;
#[derive(BorshSerialize, BorshDeserialize, Debug, Clone)]
pub struct Pool {
    pub mint_a: Pubkey,
    pub mint_b: Pubkey,
    pub mint: Pubkey,
    pub fee: u64,
    pub fee_decimals: u64,
}
// code inside of `process_instruction`
// pool_account is of type `AccountInfo` retrieved previously
let pool = Pool::try_from_slice(&pool_account.try_borrow_data()?)?;
msg!("pool fee: {}", pool.fee);