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//! Utility macros.

/// Implement [`digest::Digest`][1] for a struct implementing [`hash::Hasher`][2].
///
/// [1]: https://docs.rs/digest/trait.Digest.html
/// [2]: https://doc.rust-lang.org/core/hash/trait.Hasher.html
#[allow(unused)]
macro_rules! implement_digest {

    ($Hasher:ident, $BlockSize:ident, $OutputSize:ident) => (

        #[cfg(feature = "generic")]
        impl digest::BlockInput for $Hasher {
            type BlockSize = generic_array::typenum::$BlockSize;
        }

        #[cfg(feature = "generic")]
        impl digest::Input for $Hasher {
            #[inline]
            fn process(&mut self, input: &[u8]) {
                self.write(input)
            }
        }

        #[cfg(feature = "generic")]
        impl digest::FixedOutput for $Hasher {
            type OutputSize = generic_array::typenum::$OutputSize;
            #[inline]
            fn fixed_result(self) -> generic_array::GenericArray<u8, Self::OutputSize> {
                use generic_array::typenum::Unsigned;
                let mut array = generic_array::GenericArray::default();
                let mut out = self.finish();
                let size = Self::OutputSize::to_usize();
                for i in 0..size {
                    array[size-i-1] = (out & u8::max_value() as u64) as u8;
                    out >>= 8;
                }
                array
            }
        }

    )

}