armdb 0.2.0

sharded bitcask key-value storage optimized for NVMe
Documentation 
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/// Position of an entry's value on disk.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[repr(C)]
pub struct DiskLoc {
    pub offset: u32,
    pub len: u32,
    pub file_id: u32,
    pub shard_id: u8,
    _pad: [u8; 3],
}

impl DiskLoc {
    #[inline]
    pub fn new(shard_id: u8, file_id: u32, offset: u32, len: u32) -> Self {
        Self {
            offset,
            len,
            file_id,
            shard_id,
            _pad: [0; 3],
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::mem::{align_of, size_of};

    #[test]
    fn disk_loc_size_is_16() {
        assert_eq!(size_of::<DiskLoc>(), 16);
    }

    #[test]
    fn disk_loc_alignment_is_4() {
        assert_eq!(align_of::<DiskLoc>(), 4);
    }

    #[test]
    fn disk_loc_new_zeroes_padding() {
        let loc = DiskLoc::new(1, 0xDEAD_BEEF, 0x1234_5678, 0x9ABC_DEF0);
        // SAFETY: DiskLoc is repr(C) plain-old-data with no niches.
        let bytes: [u8; 16] = unsafe { std::mem::transmute(loc) };
        assert_eq!(&bytes[13..16], &[0u8, 0u8, 0u8]);
    }

    #[test]
    fn disk_loc_roundtrip_large_file_id() {
        for &fid in &[0u32, 1, 65535, 65536, 65537, 1_000_000, u32::MAX] {
            let loc = DiskLoc::new(7, fid, 4096, 1024);
            assert_eq!(loc.file_id, fid);
            assert_eq!(loc.shard_id, 7);
            assert_eq!(loc.offset, 4096);
            assert_eq!(loc.len, 1024);
        }
    }
}