dope-kqueue 0.2.3

use super::token::{Token, TokenEpoch, TokenSlot};

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub(crate) struct Udata(u64);

impl Udata {
    const EPOCH_MASK: u64 = 0x00FF_FFFF;
    const SLOT_SHIFT: u32 = 24;
    const SLOT_MASK: u64 = 0xFFFF;
    const TAG_SHIFT: u32 = 40;
    const TAG_MASK: u64 = 0xFF;

    pub(crate) fn pack(tag: u8, slot: u16, epoch: u32) -> Self {
        let raw = (epoch as u64 & Self::EPOCH_MASK)
            | ((slot as u64 & Self::SLOT_MASK) << Self::SLOT_SHIFT)
            | ((tag as u64 & Self::TAG_MASK) << Self::TAG_SHIFT);
        Self(raw)
    }

    pub(crate) fn unpack(self) -> (u8, u16, u32) {
        let epoch = (self.0 & Self::EPOCH_MASK) as u32;
        let slot = ((self.0 >> Self::SLOT_SHIFT) & Self::SLOT_MASK) as u16;
        let tag = ((self.0 >> Self::TAG_SHIFT) & Self::TAG_MASK) as u8;
        (tag, slot, epoch)
    }

    pub(crate) fn from_kevent(p: *mut libc::c_void) -> Self {
        Self(p as usize as u64)
    }

    pub(crate) fn into_kevent(self) -> *mut libc::c_void {
        self.0 as usize as *mut libc::c_void
    }

    pub(crate) fn into_token(self) -> Token {
        let (_, slot, epoch) = self.unpack();
        Token::new(TokenSlot::from_raw(slot), TokenEpoch::from_raw(epoch))
    }

    pub(crate) fn from_token(token: Token, tag: u8) -> Self {
        Self::pack(tag, token.slot_raw(), token.epoch_raw())
    }
}