polars_utils/
slice.rs

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1use std::cmp::Ordering;
2use std::mem::MaybeUninit;
3use std::ops::Range;
4
5pub trait SliceAble {
6    /// # Safety
7    /// no bound checks.
8    unsafe fn slice_unchecked(&self, range: Range<usize>) -> Self;
9
10    fn slice(&self, range: Range<usize>) -> Self;
11}
12
13impl<T> SliceAble for &[T] {
14    unsafe fn slice_unchecked(&self, range: Range<usize>) -> Self {
15        unsafe { self.get_unchecked(range) }
16    }
17
18    fn slice(&self, range: Range<usize>) -> Self {
19        self.get(range).unwrap()
20    }
21}
22
23pub trait Extrema<T> {
24    fn min_value(&self) -> Option<&T>;
25    fn max_value(&self) -> Option<&T>;
26}
27
28impl<T: PartialOrd> Extrema<T> for [T] {
29    fn min_value(&self) -> Option<&T> {
30        self.iter()
31            .min_by(|a, b| a.partial_cmp(b).unwrap_or(Ordering::Equal))
32    }
33
34    fn max_value(&self) -> Option<&T> {
35        self.iter()
36            .max_by(|a, b| a.partial_cmp(b).unwrap_or(Ordering::Equal))
37    }
38}
39
40pub trait SortedSlice<T> {
41    fn is_sorted_ascending(&self) -> bool;
42}
43
44impl<T: PartialOrd + Copy> SortedSlice<T> for [T] {
45    fn is_sorted_ascending(&self) -> bool {
46        if self.is_empty() {
47            true
48        } else {
49            let mut previous = self[0];
50            let mut sorted = true;
51
52            // don't early stop or branch
53            // so it autovectorizes
54            for &v in &self[1..] {
55                sorted &= previous <= v;
56                previous = v;
57            }
58            sorted
59        }
60    }
61}
62
63pub trait Slice2Uninit<T> {
64    fn as_uninit(&self) -> &[MaybeUninit<T>];
65}
66
67impl<T> Slice2Uninit<T> for [T] {
68    #[inline]
69    fn as_uninit(&self) -> &[MaybeUninit<T>] {
70        unsafe { std::slice::from_raw_parts(self.as_ptr() as *const MaybeUninit<T>, self.len()) }
71    }
72}
73
74// Loads a u64 from the given byteslice, as if it were padded with zeros.
75#[inline]
76pub fn load_padded_le_u64(bytes: &[u8]) -> u64 {
77    let len = bytes.len();
78    if len >= 8 {
79        return u64::from_le_bytes(bytes[0..8].try_into().unwrap());
80    }
81
82    if len >= 4 {
83        let lo = u32::from_le_bytes(bytes[0..4].try_into().unwrap());
84        let hi = u32::from_le_bytes(bytes[len - 4..len].try_into().unwrap());
85        return (lo as u64) | ((hi as u64) << (8 * (len - 4)));
86    }
87
88    if len == 0 {
89        return 0;
90    }
91
92    let lo = bytes[0] as u64;
93    let mid = (bytes[len / 2] as u64) << (8 * (len / 2));
94    let hi = (bytes[len - 1] as u64) << (8 * (len - 1));
95    lo | mid | hi
96}
polars_utils/slice.rs

polars_utils/
slice.rs
