zerometry 0.3.0

Make some zerocopy operations on serialized geo data
Documentation 
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use core::fmt;

use crate::{Coord, Coords};

/// A segment is a line between two points.
///
/// The segment is represented by two coordinates: the start and end points.
///
/// The coordinates are stored in a `Coords` struct, which is a slice of `f64` values.
/// The first coordinate is the start point, and the second coordinate is the end point.
#[derive(Clone, Copy)]
pub struct Segment<'a> {
    start: &'a Coord,
    end: &'a Coord,
}

impl<'a> Segment<'a> {
    /// # Safety
    /// The data must be aligned on 64bit and contains exactly 4 f64.
    #[inline]
    pub unsafe fn from_bytes(data: &'a [u8]) -> Self {
        unsafe { Self::from_coords(Coords::from_bytes(data)) }
    }

    /// # Safety
    /// The data must contain exactly 4 f64.
    #[inline]
    pub unsafe fn from_slice(data: &'a [f64]) -> Self {
        unsafe { Self::from_coords(Coords::from_slice(data)) }
    }

    /// # Safety
    /// The data must contain exactly 2 coords.
    #[inline]
    pub unsafe fn from_coords(coords: &'a Coords) -> Self {
        debug_assert_eq!(coords.len(), 2, "Segment must have 2 coordinates");
        Self {
            start: &coords[0],
            end: &coords[1],
        }
    }

    /// Create a segment from two coords.
    #[inline]
    pub fn from_coord_pair(start: &'a Coord, end: &'a Coord) -> Self {
        Self { start, end }
    }

    /// Return the coord of the start of the segment.
    #[inline]
    pub fn start(&self) -> &'a Coord {
        self.start
    }

    /// Return the coord of the end of the segment.
    #[inline]
    pub fn end(&self) -> &'a Coord {
        self.end
    }

    /// Returns true if the segment intersects with the other segment.
    #[inline]
    pub fn intersects(&self, other: &Segment) -> bool {
        geo::intersects::Intersects::intersects(
            &geo_types::Line::new(self.start.to_geo(), self.end.to_geo()),
            &geo_types::Line::new(other.start.to_geo(), other.end.to_geo()),
        )
    }
}

impl<'a> fmt::Debug for Segment<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Segment")
            .field("start", &self.start)
            .field("end", &self.end)
            .finish()
    }
}

#[cfg(test)]
mod tests {
    use bytemuck::cast_slice;

    use super::*;

    #[test]
    fn test_segment_from_bytes() {
        let data = [1.0, 2.0, 3.0, 4.0];
        let bb = unsafe { Segment::from_bytes(cast_slice(&data)) };
        insta::assert_debug_snapshot!(bb, @r"
        Segment {
            start: Coord {
                x: 1.0,
                y: 2.0,
            },
            end: Coord {
                x: 3.0,
                y: 4.0,
            },
        }
        ");
    }

    #[test]
    #[should_panic]
    fn test_segment_from_bytes_panic_on_missing_point_bytes() {
        let data = [1.0, 2.0];
        unsafe { Segment::from_bytes(cast_slice(&data)) };
    }

    #[test]
    #[should_panic]
    fn test_segment_from_bytes_panic_on_too_many_point_bytes() {
        let data = [1.0, 2.0, 3.0, 4.0, 5.0, 6.0];
        unsafe { Segment::from_bytes(cast_slice(&data)) };
    }

    #[test]
    #[should_panic]
    fn test_segment_from_bytes_panic_on_too_long_bytes() {
        let data = [1.0, 2.0, 3.0, 4.0, 5.0];
        unsafe { Segment::from_bytes(cast_slice(&data)) };
    }

    #[test]
    #[should_panic]
    fn test_segment_from_bytes_panic_on_unaligned_bytes() {
        let data = [1.0, 2.0, 3.0, 4.0, 5.0];
        unsafe { Segment::from_bytes(&cast_slice(&data)[1..]) };
    }

    #[test]
    fn test_segment_from_slice() {
        let data = [1.0, 2.0, 3.0, 4.0];
        let bb = unsafe { Segment::from_slice(&data) };
        insta::assert_debug_snapshot!(bb, @r"
        Segment {
            start: Coord {
                x: 1.0,
                y: 2.0,
            },
            end: Coord {
                x: 3.0,
                y: 4.0,
            },
        }
        ");
    }

    #[test]
    #[should_panic]
    fn test_segment_from_slice_panic_on_missing_point_slice() {
        let data = [1.0, 2.0];
        unsafe { Segment::from_slice(&data) };
    }

    #[test]
    #[should_panic]
    fn test_segment_from_slice_panic_on_too_many_point_slice() {
        let data = [1.0, 2.0, 3.0, 4.0, 5.0, 6.0];
        unsafe { Segment::from_slice(&data) };
    }

    #[test]
    fn test_segment_intersects() {
        let segment1 = unsafe { Segment::from_slice(&[0.0, 0.0, 1.0, 1.0]) };
        let segment2 = unsafe { Segment::from_slice(&[1.0, 0.0, 0.0, 1.0]) };
        assert!(segment1.intersects(&segment2));
        let segment1 = unsafe { Segment::from_slice(&[0.0, 0.0, 1.0, 1.0]) };
        let segment2 = unsafe { Segment::from_slice(&[0.0, 1.0, 1.0, 0.0]) };
        assert!(segment1.intersects(&segment2));
    }

    #[test]
    fn test_segment_intersects_parallel() {
        let segment1 = unsafe { Segment::from_slice(&[0.0, 0.0, 1.0, 1.0]) };
        let segment2 = unsafe { Segment::from_slice(&[0.0, 1.0, 1.0, 2.0]) };
        assert!(!segment1.intersects(&segment2));
        let segment1 = unsafe { Segment::from_slice(&[0.0, 0.0, 1.0, 1.0]) };
        let segment2 = unsafe { Segment::from_slice(&[1.0, 0.0, 2.0, 1.0]) };
        assert!(!segment1.intersects(&segment2));
    }

    #[test]
    fn test_segment_overlaps() {
        let segment1 = unsafe { Segment::from_slice(&[0.0, 0.0, 1.0, 1.0]) };
        let segment2 = unsafe { Segment::from_slice(&[0.0, 0.0, 1.0, 1.0]) };
        assert!(segment1.intersects(&segment2));
        let segment1 = unsafe { Segment::from_slice(&[0.0, 0.0, 1.0, 1.0]) };
        let segment2 = unsafe { Segment::from_slice(&[0.5, 0.5, 1.5, 1.5]) };
        assert!(segment1.intersects(&segment2));
        let segment1 = unsafe { Segment::from_slice(&[0.0, 0.0, 1.0, 1.0]) };
        let segment2 = unsafe { Segment::from_slice(&[0.5, 0.5, -1.0, -1.0]) };
        assert!(segment1.intersects(&segment2));
    }

    #[test]
    fn bug_missing_intersection() {
        // ray: Segment { start: Coord { x: -6.436337296790293, y: 49.63676497357687 }, end: Coord { x: 6.0197316417968105, y: 49.63676497357687 } }
        // segment: Segment { start: Coord { x: 1.188509553443464, y: 49.47027919866874 }, end: Coord { x: 3.6300086390995316, y: 50.610463312569514 } }
        let ray = unsafe {
            Segment::from_slice(&[
                -6.436337296790293,
                49.63676497357687,
                6.0197316417968105,
                49.63676497357687,
            ])
        };
        let segment = unsafe {
            Segment::from_slice(&[
                1.188509553443464,
                49.47027919866874,
                3.6300086390995316,
                50.610463312569514,
            ])
        };
        assert!(segment.intersects(&ray));
    }
}