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use block_cipher_trait::generic_array::GenericArray;
use block_cipher_trait::BlockCipher;
use block_cipher_trait::generic_array::typenum::Unsigned;
use block_cipher_trait::generic_array::ArrayLength;
use core::slice;

#[inline(always)]
pub fn xor(buf: &mut [u8], key: &[u8]) {
    debug_assert_eq!(buf.len(), key.len());
    for (a, b) in buf.iter_mut().zip(key) {
        *a ^= *b;
    }
}

pub(crate) type Key<C> = GenericArray<u8, <C as BlockCipher>::KeySize>;
pub(crate) type Block<C> = GenericArray<u8, <C as BlockCipher>::BlockSize>;
pub(crate) type ParBlocks<C> = GenericArray<Block<C>, <C as BlockCipher>::ParBlocks>;

pub(crate) fn to_blocks<N>(data: &mut [u8]) -> &mut [GenericArray<u8, N>]
    where N: ArrayLength<u8>
{
    let n = N::to_usize();
    debug_assert!(data.len() % n == 0);
    unsafe {
        slice::from_raw_parts_mut(
            data.as_ptr() as *mut GenericArray<u8, N>,
            data.len() / n,
        )
    }
}

pub(crate) fn get_par_blocks<C: BlockCipher>(blocks: &mut [Block<C>])
    -> (&mut [ParBlocks<C>], &mut [Block<C>])
{
    let pb = C::ParBlocks::to_usize();
    let n_par = blocks.len()/pb;

    let (par, single) = blocks.split_at_mut(n_par*pb);
    let par = unsafe {
        slice::from_raw_parts_mut(
            par.as_ptr() as *mut ParBlocks<C>,
            n_par,
        )
    };
    (par, single)
}