wedb_embed 0.1.0

Embedded Kvrocks-compatible storage engine for WeDb
Documentation 
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const SIGN_MASK: u64 = 1 << 63;

/// IEEE 754 浮点数大端序保序编码（对标 Kvrocks/RocksDB Score Encoding）
#[inline(always)]
pub const fn encode_sortable_f64(val: f64) -> [u8; 8] {
    let bits = val.to_bits();
    let sortable = if bits & SIGN_MASK != 0 {
        !bits
    } else {
        bits ^ SIGN_MASK
    };
    sortable.to_be_bytes()
}

/// IEEE 754 浮点数大端序保序解码
#[inline(always)]
pub const fn decode_sortable_f64(bytes: [u8; 8]) -> f64 {
    let bits = u64::from_be_bytes(bytes);
    let orig = if bits & SIGN_MASK != 0 {
        bits ^ SIGN_MASK
    } else {
        !bits
    };
    f64::from_bits(orig)
}

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

    #[test]
    fn test_sortable_f64_special_cases() {
        let neg_zero: f64 = -0.0;
        let pos_zero: f64 = 0.0;
        let neg_inf = f64::NEG_INFINITY;
        let pos_inf = f64::INFINITY;

        let enc_neg_inf = encode_sortable_f64(neg_inf);
        let enc_neg_zero = encode_sortable_f64(neg_zero);
        let enc_pos_zero = encode_sortable_f64(pos_zero);
        let enc_pos_inf = encode_sortable_f64(pos_inf);

        assert!(enc_neg_inf < enc_neg_zero);
        assert!(enc_neg_zero < enc_pos_zero);
        assert!(enc_pos_zero < enc_pos_inf);

        assert_eq!(decode_sortable_f64(enc_neg_inf), neg_inf);
        assert_eq!(decode_sortable_f64(enc_pos_inf), pos_inf);
        assert_eq!(
            decode_sortable_f64(enc_neg_zero).to_bits(),
            neg_zero.to_bits()
        );
        assert_eq!(
            decode_sortable_f64(enc_pos_zero).to_bits(),
            pos_zero.to_bits()
        );
    }
}