oracle_write.rs

impl Instructions {

    #[inline(always)]
    pub fn write_instruction_0_data(data: &[u8], dst: &mut [u8]) -> u16 {
        unsafe {
            let base = data.as_ptr();
            let p = base.add((base.add(2) as *const u16).read_unaligned() as usize);
            let _ = 1u8 / (*p | *p.add(1) == 0) as u8; // trap if non-zero (ensures no accounts are passed to the ed25519 verify ix)
            let len = min_branchless((p.add(34) as *const u16).read_unaligned(), dst.len() as u16);
            solana_define_syscall::definitions::sol_memcpy_(dst.as_mut_ptr(), p.add(36), len as u64);
            len
        }
    }
}

#[inline(always)]
fn min_branchless(a: u16, b: u16) -> u16 {
    // mask = 0xFFFF if a < b, else 0x0000
    let mask = ((a < b) as u16).wrapping_neg();
    (a & mask) | (b & !mask)
}