iso8601-timestamp 0.4.0

High-performance ISO8601 Timestamp formatting and parsing
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138

use time::{Date, Month};

use super::Timestamp;

#[inline(always)]
#[allow(dead_code)]
const fn is_leap_year(y: i32) -> bool {
    //(y % 4 == 0) & ((y % 25 != 0) | (y % 16 == 0)) // old version

    // ternary compiles to cmov
    y & (if y % 25 == 0 { 15 } else { 3 }) == 0
}

#[inline(always)]
#[cfg(target_feature = "avx2")]
unsafe fn to_calendar_date_avx2(date: Date) -> (i32, Month, u8) {
    import_intrinsics!(x86::{
        _mm256_set1_epi16, _mm256_set_epi16, _mm256_setzero_si256,
        _mm256_cmpeq_epi16, _mm256_movemask_epi8, _mm256_subs_epu16, __m256i
    });

    let year = date.year();

    #[rustfmt::skip]
    let mut days = match is_leap_year(year) {
        true => _mm256_set_epi16(i16::MAX, i16::MAX, i16::MAX, i16::MAX, 335, 305, 274, 244, 213, 182, 152, 121, 91, 60, 31, 0),
        false => _mm256_set_epi16(i16::MAX, i16::MAX, i16::MAX, i16::MAX, 334, 304, 273, 243, 212, 181, 151, 120, 90, 59, 31, 0),
    };

    days = _mm256_subs_epu16(_mm256_set1_epi16(date.ordinal() as i16), days);

    let mask = _mm256_movemask_epi8(_mm256_cmpeq_epi16(days, _mm256_setzero_si256()));
    let month = mask.trailing_zeros() / 2;
    let day = *core::mem::transmute::<__m256i, [u16; 16]>(days).get_unchecked(month as usize - 1);

    (year, core::mem::transmute::<u8, Month>(month as u8), day as u8)
}

#[inline(always)]
#[cfg(target_feature = "sse2")]
unsafe fn to_calendar_date_sse2(date: Date) -> (i32, Month, u8) {
    import_intrinsics!(x86::{
        _mm_cmpeq_epi16, _mm_movemask_epi8, _mm_set1_epi16,
        _mm_set_epi16, _mm_setzero_si128, _mm_subs_epu16, __m128i
    });

    let year = date.year();

    #[rustfmt::skip]
    let (mut hd, mut ld) = match is_leap_year(year) {
        true => (
            _mm_set_epi16(i16::MAX, i16::MAX, i16::MAX, i16::MAX, 335, 305, 274, 244),
            _mm_set_epi16(213, 182, 152, 121, 91, 60, 31, 0)),
        false => (
            _mm_set_epi16(i16::MAX, i16::MAX, i16::MAX, i16::MAX, 334, 304, 273, 243),
            _mm_set_epi16(212, 181, 151, 120, 90, 59, 31, 0))
    };

    let ordinals = _mm_set1_epi16(date.ordinal() as i16);

    hd = _mm_subs_epu16(ordinals, hd);
    ld = _mm_subs_epu16(ordinals, ld);

    let z = _mm_setzero_si128();

    let hm = _mm_movemask_epi8(_mm_cmpeq_epi16(hd, z));
    let lm = _mm_movemask_epi8(_mm_cmpeq_epi16(ld, z));

    let mask = (hm << 16) | lm;
    let month = mask.trailing_zeros() / 2;

    let day = *core::mem::transmute::<[__m128i; 2], [u16; 16]>([ld, hd]).get_unchecked(month as usize - 1);

    (year, core::mem::transmute::<u8, Month>(month as u8), day as u8)
}

#[inline(always)]
#[allow(unreachable_code)]
pub(crate) fn to_calendar_date(date: Date) -> (i32, Month, u8) {
    #[cfg(target_feature = "avx2")]
    // SAFETY: Checked for AVX2 support
    return unsafe { to_calendar_date_avx2(date) };

    #[cfg(target_feature = "sse2")]
    // SAFETY: Checked for SSE2 support
    return unsafe { to_calendar_date_sse2(date) };

    date.to_calendar_date()
}

impl Timestamp {
    /// Get the year, month, and day.
    ///
    /// Like [`PrimitiveDateTime::to_calendar_date`](time::PrimitiveDateTime::to_calendar_date), but optimized for SSE2/AVX2 when available.
    ///
    /// ```rust
    /// # use time::{Month, macros::datetime};
    /// # use iso8601_timestamp::Timestamp;
    /// assert_eq!(
    ///     Timestamp::from(datetime!(2019-01-01 0:00)).to_calendar_date(),
    ///     (2019, Month::January, 1)
    /// );
    /// ```
    #[inline(always)]
    #[must_use]
    pub fn to_calendar_date(&self) -> (i32, Month, u8) {
        to_calendar_date(self.date())
    }
}

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

    #[cfg(target_feature = "avx2")]
    #[test]
    fn test_to_calendar_date() {
        for year in &[2004, 2005, 2006] {
            for ordinal in 0..367 {
                let Ok(date) = Date::from_ordinal_date(*year, ordinal) else {
                    continue;
                };

                // SAFETY: Only tested on x86_64 with AVX2 and SSE2
                let (avx2, sse2, none) = unsafe {
                    (
                        to_calendar_date_avx2(date),
                        to_calendar_date_sse2(date),
                        date.to_calendar_date(),
                    )
                };

                assert_eq!(none, avx2);
                assert_eq!(none, sse2);
            }
        }
    }
}