sectorize 0.1.0

A small library for writing arbitrarily-aligned data to sectored mediums
Documentation 
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#![no_std]

#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct SectorMap {
    pub input_start: usize,
    pub input_end: usize,
    pub sector_start: usize,
    pub sector_end: usize,
    pub sector_index: usize,
}

pub struct SectorizeIter {
    sector_size: usize,
    input_start: usize,
    input_len: usize,
    s: usize,
}

impl SectorizeIter {
    pub fn new(sector_size: usize, input_start: usize, input_len: usize) -> Self {
        Self {
            sector_size,
            input_start,
            input_len,
            s: input_start / sector_size,
        }
    }
}

impl Iterator for SectorizeIter {
    type Item = SectorMap;

    fn next(&mut self) -> Option<Self::Item> {
        let idx = self.s;
        let sector_start = self.s * self.sector_size;
        self.s += 1;
        let sector_end = self.s * self.sector_size;

        let overlap_start = sector_start.max(self.input_start);
        let overlap_end = sector_end.min(self.input_start + self.input_len);

        if overlap_start >= overlap_end {
            return None;
        }

        Some(SectorMap {
            input_start: overlap_start - self.input_start,
            input_end: overlap_end - self.input_start,
            sector_start: overlap_start - sector_start,
            sector_end: overlap_end - sector_start,
            sector_index: idx,
        })
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn basic_case() {
        let mut iter = SectorizeIter::new(4, 3, 10);
        assert_eq!(
            SectorMap {
                input_start: 0,
                input_end: 1,
                sector_start: 3,
                sector_end: 4,
                sector_index: 0
            },
            iter.next().unwrap()
        );
        assert_eq!(
            SectorMap {
                input_start: 1,
                input_end: 5,
                sector_start: 0,
                sector_end: 4,
                sector_index: 1
            },
            iter.next().unwrap()
        );
        assert_eq!(
            SectorMap {
                input_start: 5,
                input_end: 9,
                sector_start: 0,
                sector_end: 4,
                sector_index: 2
            },
            iter.next().unwrap()
        );
        assert_eq!(
            SectorMap {
                input_start: 9,
                input_end: 10,
                sector_start: 0,
                sector_end: 1,
                sector_index: 3
            },
            iter.next().unwrap()
        );
        assert_eq!(None, iter.next());
    }

    #[test]
    fn matching_perfectly() {
        let mut iter = SectorizeIter::new(4, 0, 12);
        assert_eq!(
            SectorMap {
                input_start: 0,
                input_end: 4,
                sector_start: 0,
                sector_end: 4,
                sector_index: 0
            },
            iter.next().unwrap()
        );
        assert_eq!(
            SectorMap {
                input_start: 4,
                input_end: 8,
                sector_start: 0,
                sector_end: 4,
                sector_index: 1
            },
            iter.next().unwrap()
        );
        assert_eq!(
            SectorMap {
                input_start: 8,
                input_end: 12,
                sector_start: 0,
                sector_end: 4,
                sector_index: 2
            },
            iter.next().unwrap()
        );
        assert_eq!(None, iter.next());
    }

    #[test]
    fn start_higher_sector() {
        let mut iter = SectorizeIter::new(4, 11, 10);
        assert_eq!(
            SectorMap {
                input_start: 0,
                input_end: 1,
                sector_start: 3,
                sector_end: 4,
                sector_index: 2
            },
            iter.next().unwrap()
        );
        assert_eq!(
            SectorMap {
                input_start: 1,
                input_end: 5,
                sector_start: 0,
                sector_end: 4,
                sector_index: 3
            },
            iter.next().unwrap()
        );
        assert_eq!(
            SectorMap {
                input_start: 5,
                input_end: 9,
                sector_start: 0,
                sector_end: 4,
                sector_index: 4
            },
            iter.next().unwrap()
        );
        assert_eq!(
            SectorMap {
                input_start: 9,
                input_end: 10,
                sector_start: 0,
                sector_end: 1,
                sector_index: 5
            },
            iter.next().unwrap()
        );
        assert_eq!(None, iter.next());
    }
}