block-id 0.2.1

Library for generating opaque, unique, and short string values from (unsigned) integers
Documentation 
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use crate::transform::InvertableTransform;

#[derive(Clone)]
pub struct BaseConversion {
    radix: u8,
    min_length: u8,
}

impl BaseConversion {
    #[cfg(test)]
    pub fn new(radix: u8) -> Self {
        Self::new_with_min_length(radix, 1)
    }

    pub fn new_with_min_length(radix: u8, min_length: u8) -> Self {
        BaseConversion { radix, min_length }
    }
}

impl InvertableTransform for BaseConversion {
    type Input = u64;
    type Output = Vec<u8>;

    fn forward(&self, mut input: u64) -> Option<Vec<u8>> {
        let base = self.radix;
        let mut result = Vec::new();

        while input > 0 {
            result.push((input % base as u64) as u8);
            input /= base as u64;
        }

        while result.len() < self.min_length as usize {
            result.push(0);
        }

        result.reverse();

        Some(result)
    }

    fn backward(&self, data: Vec<u8>) -> Option<u64> {
        let mut result: u64 = 0;
        let base = self.radix;

        for (i, b) in data.iter().enumerate() {
            if i > 0 {
                result = result.checked_mul(base as u64)?;
            }
            result = result.checked_add(*b as u64)?;
        }

        Some(result)
    }
}

#[cfg(test)]
mod test {
    use crate::transform::test::round_trip;

    use super::*;

    #[test]
    fn test_base_convert() {
        assert_eq!(vec![5], BaseConversion::new(128).forward(5).unwrap());

        assert_eq!(
            vec![1, 0, 1, 0],
            BaseConversion::new(2).forward(10).unwrap()
        );

        assert_eq!(vec![1, 0, 1], BaseConversion::new(3).forward(10).unwrap());
        assert_eq!(vec![1, 0, 2], BaseConversion::new(3).forward(11).unwrap());
        assert_eq!(vec![1, 1, 0], BaseConversion::new(3).forward(12).unwrap());
        assert_eq!(
            vec![1, 0, 0, 0],
            BaseConversion::new(3).forward(27).unwrap()
        );
    }

    #[test]
    fn test_base_invert() {
        assert_eq!(5, BaseConversion::new(128).backward(vec![5]).unwrap());

        assert_eq!(
            10,
            BaseConversion::new(2).backward(vec![1, 0, 1, 0]).unwrap()
        );

        assert_eq!(10, BaseConversion::new(3).backward(vec![1, 0, 1]).unwrap());
        assert_eq!(11, BaseConversion::new(3).backward(vec![1, 0, 2]).unwrap());
        assert_eq!(12, BaseConversion::new(3).backward(vec![1, 1, 0]).unwrap());
        assert_eq!(
            27,
            BaseConversion::new(3).backward(vec![1, 0, 0, 0]).unwrap()
        );
    }

    #[test]
    fn test_grind() {
        for base in 2..125 {
            for num in 88..99 {
                round_trip(&BaseConversion::new(base), num);
            }
        }
    }
}