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ccm 0.4.2

Generic implementation of the Counter with CBC-MAC (CCM) mode
Documentation 
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mod private {
    use aead::{consts, generic_array::typenum::Unsigned};

    // Sealed traits stop other crates from implementing any traits that use it.
    pub trait SealedTag: Unsigned {
        fn get_m_tick() -> u8 {
            (Self::to_u8() - 2) / 2
        }
    }
    pub trait SealedNonce: Unsigned {
        fn get_l() -> u8 {
            15 - Self::to_u8()
        }

        fn get_max_len() -> usize {
            // a somewhat ugly code to prevent overlfow.
            // compiler should be able to completely optimize it out
            let l = Self::get_l() as u128;
            let v = (1 << (8 * l)) - 1;
            core::cmp::min(v, core::usize::MAX as u128) as usize
        }
    }

    impl SealedTag for consts::U4 {}
    impl SealedTag for consts::U6 {}
    impl SealedTag for consts::U8 {}
    impl SealedTag for consts::U10 {}
    impl SealedTag for consts::U12 {}
    impl SealedTag for consts::U14 {}
    impl SealedTag for consts::U16 {}

    impl SealedNonce for consts::U7 {}
    impl SealedNonce for consts::U8 {}
    impl SealedNonce for consts::U9 {}
    impl SealedNonce for consts::U10 {}
    impl SealedNonce for consts::U11 {}
    impl SealedNonce for consts::U12 {}
    impl SealedNonce for consts::U13 {}
}

/// Trait implemented for valid tag sizes, i.e. [`U4`], [`U6`], [`U8`],
/// [`U10`], [`U12`], [`U14`], and [`U12`].
pub trait TagSize: private::SealedTag {}

impl<T: private::SealedTag> TagSize for T {}

/// Trait implemented for valid nonce sizes, i.e. [`U7`], [`U8`], [`U9`],
/// [`U10`], [`U11`], [`U12`], and [`U13`].
pub trait NonceSize: private::SealedNonce {}

impl<T: private::SealedNonce> NonceSize for T {}