pi_vec_remain 0.2.1

vec remain range
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

//! 保留vec中指定范围的数据，其余部分释放

// #![feature(test)]
// extern crate test;

use std::{
    ops::{Bound, RangeBounds},
    ptr,
};

pub trait VecRemain<R: RangeBounds<usize>> {
    fn remain(&mut self, range: R) -> usize;
    fn remain_to(&mut self, range: R, other: &mut Self) -> usize;
}

impl<T, R: RangeBounds<usize>> VecRemain<R> for Vec<T> {
    fn remain(&mut self, range: R) -> usize {
        let end = end(self, range.end_bound());
        let start = match range.start_bound() {
            Bound::Included(&start) => {
                if start == 0 {
                    return end;
                }
                if start >= end {
                    self.clear();
                    return 0;
                }
                start
            }
            Bound::Excluded(&start) => {
                if start.saturating_add(1) >= end {
                    self.clear();
                    return 0;
                }
                start.saturating_add(1)
            }
            Bound::Unbounded => {
                return end;
            }
        };
        let ptr = self.as_mut_ptr();
        unsafe {
            // 释放start之前的内存
            let s = ptr::slice_from_raw_parts_mut(ptr, start);
            ptr::drop_in_place(s);
            self.set_len(self.len() - start);
            ptr.add(start).copy_to(ptr, self.len());
        }
        end - start
    }
    fn remain_to(&mut self, range: R, other: &mut Self) -> usize {
        let end = end(self, range.end_bound());
        let start = match range.start_bound() {
            Bound::Included(&start) => {
                if start >= end {
                    self.clear();
                    return 0;
                }
                start
            }
            Bound::Excluded(&start) => {
                if start.saturating_add(1) >= end {
                    self.clear();
                    return 0;
                }
                start.saturating_add(1)
            }
            Bound::Unbounded => 0,
        };
        let count = end - start;
        let ptr = self.as_mut_ptr();
        unsafe {
            // 释放start之前的内存
            let s = ptr::slice_from_raw_parts_mut(ptr, start);
            ptr::drop_in_place(s);

            other.reserve(count);
            ptr.add(start)
                .copy_to_nonoverlapping(other.as_mut_ptr().add(other.len()), count);
            other.set_len(other.len() + count);
            self.set_len(0);
        }
        count
    }
}
fn end<T>(vec: &mut Vec<T>, bound: Bound<&usize>) -> usize {
    match bound {
        Bound::Included(end) => {
            let end = end.saturating_add(1);
            if end < vec.len() {
                vec.truncate(end);
                end
            } else {
                vec.len()
            }
        }
        Bound::Excluded(end) => {
            if *end < vec.len() {
                vec.truncate(*end);
                *end
            } else {
                vec.len()
            }
        }
        Bound::Unbounded => vec.len(),
    }
}
#[test]
fn test_vec_remain() {
    let mut vec = vec![1, 2, 3, 4, 5];
    vec.remain(1..);
    assert_eq!(vec, &[2, 3, 4, 5]);
    let mut vec = vec![1, 2, 3, 4, 5];
    vec.remain(1..3);
    assert_eq!(vec, &[2, 3]);
    let mut vec = vec![1, 2, 3, 4, 5];
    vec.remain(1..=3);
    assert_eq!(vec, &[2, 3, 4]);
    let mut vec = vec![1, 2, 3, 4, 5];
    vec.remain(..=3);
    assert_eq!(vec, &[1, 2, 3, 4]);
    let mut vec = vec![1, 2, 3, 4, 5];
    vec.remain_to(..=3, &mut vec![6, 7, 8, 9]);
    assert_eq!(vec, &[]);
    let mut vec = vec![1, 2, 3, 4, 5];
    let mut other = vec![6, 7, 8, 9];
    vec.remain_to(1..=3, &mut other);
    assert_eq!(other, &[6, 7, 8, 9, 2, 3, 4]);
    assert_eq!(vec, &[]);
}