What does range full operator do in borsh serialize?

Question

I follow hackernoon-solana to see the syntax in non anchor project. this is the function signature

pub fn process_instruction(program_id:&Pubkey,accounts:&[AccountInfo],input:&[u8])->ProgramResult{}

we pass accounts:&[AccountInfo] array as an arg. Args are always byte array

// Iterating accounts is safer then indexing
let accounts_iter = &mut accounts.iter();

Then I get the first account

let account = next_account_info(accounts_iter)?;

then deserialize the passed arg. in rust arguments are an array of bytes

 let mut greeting_account = GreetingAccount::try_from_slice(&account.data.borrow())?;

So far so good. but I did not understand this line:

 greeting_account.serialize(&mut &mut account.data.borrow_mut()[..])?;

We are storing the data inside greeting_account. BUt what is this [..] for? account is a single object, how can we use a range operator on an object?

Answer 1

That's just another way of dereferencing to get the internal data in Rust. &mut account.data.borrow_mut()[..] and *account_info.data.borrow_mut() should get the same result. You could write that line as:

greeting_account.serialize(&mut *account.data.borrow_mut())?;