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pub trait FromU8{
    fn from_u8(data: &[u8]) -> Self;
}


macro_rules! impl_from_u8_for_int {
    ($T: ty, $N: expr) => {
     impl FromU8 for $T {
         fn from_u8(data: &[u8]) -> $T {
             assert_eq!(data.len(), $N);

             let mut value: $T = 0;

             for i in 0..$N {
                 value |= (data[i] as $T) << 8 * ($N - i - 1);
             }

             value
         }
     }
    };
}

impl_from_u8_for_int!(u8, 1);
impl_from_u8_for_int!(i8, 1);
impl_from_u8_for_int!(u16, 2);
impl_from_u8_for_int!(i16, 2);
impl_from_u8_for_int!(u32, 4);
impl_from_u8_for_int!(i32, 4);
impl_from_u8_for_int!(u64, 8);
impl_from_u8_for_int!(i64, 8);
impl_from_u8_for_int!(u128, 16);
impl_from_u8_for_int!(i128, 16);