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use std::simd::{
cmp::{SimdPartialEq, SimdPartialOrd},
simd_swizzle, u8x16,
};
#[must_use]
pub fn dateparse(s: &str) -> Option<(usize, usize, usize)> {
// inf and sup for indiv. values
const LO: u8x16 = u8x16::from_array([
b'0', b'0', b'/', b'0', b'0', b'/', b'0', b'0', //
0, 0, 0, 0, 0, 0, 0, 0, // load_or_default isnt const
]);
const HI: u8x16 = u8x16::from_array([
b'1', b'9', b'/', b'3', b'9', b'/', b'9', b'9', //
0xFF, 0xFF, 0xFF, 0xFF, //
0xFF, 0xFF, 0xFF, 0xFF, //
]);
const INTMSK: u8x16 = u8x16::from_array([b'0'; 16]);
const SLHMSK: u8x16 = u8x16::from_array([b'/'; 16]);
const NUMMSK: u8x16 = u8x16::from_array([
10, 1, 0, // [m_10, m_1] -> m_10 * 10 + m_1 (0 is slash)
10, 1, 0, // dd ..
10, 1, 0, // yy ..
0, 0, 0, 0, 0, 0, 0,
]);
let b = s.as_bytes();
let v = u8x16::load_or_default(b);
let mut valid = true;
// index 16 for swizzles with INTMSK is b'0'
// index 15 is 0
// this will compile to a shuffle, but a relaxed_laneselect would be cool
let mut v = match (b.len(), v.simd_eq(SLHMSK).to_bitmask()) {
// m/d/yy
(6, 0b1010) => simd_swizzle!(
v,
INTMSK,
[16, 0, 1, 16, 2, 3, 4, 5, 15, 15, 15, 15, 15, 15, 15, 15]
),
// m/dd/yy
(7, 0b10010) => simd_swizzle!(
v,
INTMSK,
[16, 0, 1, 2, 3, 4, 5, 6, 15, 15, 15, 15, 15, 15, 15, 15]
),
// mm/d/yy
(7, 0b10100) => simd_swizzle!(
v,
INTMSK,
[0, 1, 2, 16, 3, 4, 5, 6, 15, 15, 15, 15, 15, 15, 15, 15]
),
// mm/dd/yy
(8, 0b100100) => v,
_ => {
valid = false;
v
}
};
// est-ce numerique?
valid &= (v.simd_ge(LO) & v.simd_le(HI)).all();
// parse
// '0' '3' '/' '3' '1' '/' '2' '6'
// - '0' '0' '0' '0' '0' '0' '0' '0'
// ---------------------------------
// 0 3 . 3 1 . 2 6
// * 10 1 0 10 1 0 10 1
// ---------------------------------
// 0 3 0 30 1 0 20 6
// + 3 0 30 1 0 20 6<<<<
// ---------------------------------
// 3 . . 31 . . 26
v -= INTMSK;
v *= NUMMSK;
v += v.rotate_elements_left::<1>();
let n = v.to_array();
let (m, d, y) = (n[0], n[3], n[6]);
(valid & (1..=12).contains(&m) & (1..=31).contains(&d))
.then(|| (m.into(), d.into(), y.into()))
}
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