bp3d-os 2.2.3

Operating System tools designed for BlockProject3D
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
139
140
141
142
143

// Copyright (c) 2023, BlockProject 3D
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification,
// are permitted provided that the following conditions are met:
//
//     * Redistributions of source code must retain the above copyright notice,
//       this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above copyright notice,
//       this list of conditions and the following disclaimer in the documentation
//       and/or other materials provided with the distribution.
//     * Neither the name of BlockProject 3D nor the names of its contributors
//       may be used to endorse or promote products derived from this software
//       without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

use std::{cmp::Ordering, fs::File};

use time::{OffsetDateTime, UtcOffset};

use bp3d_util::tzif::{LeapSecondRecord, TZIF};

//Imported from https://github.com/Yuri6037/time-tz/blob/master/src/binary_search.rs
pub fn binary_search<F: Fn(usize) -> Ordering>(start: usize, end: usize, cmp: F) -> Option<usize> {
    if start >= end {
        return None;
    }
    let half = (end - start) / 2;
    let mid = start + half;
    match cmp(mid) {
        Ordering::Greater => binary_search(start, mid, cmp),
        Ordering::Equal => Some(mid),
        Ordering::Less => binary_search(mid + 1, end, cmp),
    }
}

struct Span {
    start: Option<i64>,
    end: Option<i64>,
}

impl Span {
    pub fn new(start: Option<i64>, end: Option<i64>) -> Span {
        Span { start, end }
    }

    pub fn cmp(&self, x: i64) -> Ordering {
        match (self.start, self.end) {
            (Some(a), Some(b)) if a <= x && x < b => Ordering::Equal,
            (Some(a), Some(b)) if a <= x && b <= x => Ordering::Less,
            (Some(_), Some(_)) => Ordering::Greater,
            (Some(a), None) if a <= x => Ordering::Equal,
            (Some(_), None) => Ordering::Greater,
            (None, Some(b)) if b <= x => Ordering::Less,
            (None, Some(_)) => Ordering::Equal,
            (None, None) => Ordering::Equal,
        }
    }
}

impl From<(&[LeapSecondRecord], usize)> for Span {
    fn from((records, i): (&[LeapSecondRecord], usize)) -> Self {
        let start = records[i].occurrence;
        let end = if i >= records.len() {
            None
        } else {
            Some(records[i + 1].occurrence)
        };
        Self::new(Some(start), end)
    }
}

impl From<(&[i64], usize)> for Span {
    fn from((records, i): (&[i64], usize)) -> Self {
        let start = records[i];
        let end = if i >= records.len() {
            None
        } else {
            Some(records[i + 1])
        };
        Self::new(Some(start), end)
    }
}

pub fn local_offset_at(tm: &OffsetDateTime) -> Option<UtcOffset> {
    let mut utc = tm.unix_timestamp();
    let file = File::open("/etc/localtime").ok()?;
    let data = TZIF::read(file).ok()?;
    let block = data
        .block_v2p
        .map(|v| v.data)
        .unwrap_or_else(|| data.block_v1.data);
    //Apply leap second correction if any for the given timestamp
    if let Some(i) = binary_search(0, block.leap_second_records.len(), |i| {
        Span::from((&*block.leap_second_records, i)).cmp(utc)
    }) {
        utc += block.leap_second_records[i].correction as i64;
    }
    let i = binary_search(0, block.transition_times.len(), |i| {
        Span::from((&*block.transition_times, i)).cmp(utc)
    })
    .unwrap_or(0);
    let offset = UtcOffset::from_whole_seconds(
        block
            .local_time_type_records
            .get(*block.transition_types.get(i)? as usize)?
            .utoff,
    )
    .ok()?;
    Some(offset)
}

#[cfg(test)]
mod tests {
    #[test]
    fn test_binary_search() {
        assert_eq!(super::binary_search(0, 8, |x| x.cmp(&6)), Some(6));
        assert_eq!(super::binary_search(0, 5000, |x| x.cmp(&1337)), Some(1337));
        assert_eq!(super::binary_search(0, 5000, |x| x.cmp(&9000)), None);
        assert_eq!(super::binary_search(30, 50, |x| x.cmp(&42)), Some(42));
        assert_eq!(super::binary_search(300, 500, |x| x.cmp(&42)), None);
        assert_eq!(
            super::binary_search(0, 500, |x| if x < 42 {
                super::Ordering::Less
            } else {
                super::Ordering::Greater
            }),
            None
        );
    }
}