jgd 0.3.0

Transform geodetic datums used in Japan
Documentation 
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use std::{mem, slice};

use crate::{grid::Dot, Grid};

#[cfg(feature = "tky2jgd")]
pub const TKY2JGD: Bin<4707876> = Bin(*include_bytes!("../par/TKY2JGD.in"));

#[cfg(feature = "patchjgd")]
pub const TOUHOKUTAIHEIYOUOKI2011: Bin<1932636> =
    Bin(*include_bytes!("../par/touhokutaiheiyouoki2011.in"));

// wrap bytes to align
#[repr(align(4))]
pub struct Bin<const N: usize>([u8; N]);
impl<const N: usize> Bin<N> {
    pub const fn to_grid(&self) -> Grid {
        assert!(isize::MAX as usize > N);
        let data = self.0.as_ptr() as *const Dot;
        let len = self.0.len() / mem::size_of::<Dot>();

        #[cfg(not(target_endian = "little"))]
        compile_error!("compile target must be little endian");
        // SAFETY:
        // `data` is single allocated and aligned as same as return type.
        // `len * element size` is within the length of `data` and is smaller than `isize::MAX`.
        // Returned value is immutable. Its lifetime is same as `data`.
        let dots = unsafe { slice::from_raw_parts(data, len) };

        Grid::new(dots)
    }
}