having trouble to encode a u64 as data for CPI

Question

I have a u64 which is an amount of lamports. I need to send it to another program with a CPI. So i'm trying to encode it in the data, but can't figure out how to do it.

Here is what i tried:

let mut instruction_discriminator: Vec<u8> = vec![38, 29, ...];
let mut instruction_data: Vec<u8> = price_in_lamports.to_be_bytes().to_vec();
instruction_discriminator.append(&mut instruction_data);

but then in the programm called thru the CPI, when i log the amount received, it's totally different (wayyyy bigger), so i guess i'm doing something wrong here. Anyone can help ?

Answer 1

I don't know your programs but potentially you just need to use little-endian instead of big-endian.

Try with to_le_bytes and see if that works. Most programs (including the system program) encode their instraction parameters as le.