minivec 0.5.0

A version of Vec that's only the size of a single pointer
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

use crate::MiniVec;

#[cfg(not(feature = "minivec_nightly"))]
impl<T> core::iter::FromIterator<T> for MiniVec<T> {
  fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
    struct DropGuard<'a, T> {
      v: &'a mut MiniVec<T>,
      len: usize,
    }

    impl<'a, T> Drop for DropGuard<'a, T> {
      fn drop(&mut self) {
        unsafe { self.v.set_len(self.len) };
      }
    }

    let iter = iter.into_iter();
    let (lower_bound, _) = iter.size_hint();
    let mut v = MiniVec::<T>::with_capacity(lower_bound.saturating_add(1));

    let mut guard = DropGuard { v: &mut v, len: 0 };

    let mut capacity = guard.v.capacity();

    iter.for_each(|item| {
      if guard.len >= capacity {
        guard.v.grow(crate::next_capacity::<T>(capacity)).unwrap();
        capacity = guard.v.capacity();
      }

      unsafe { core::ptr::write(guard.v.as_mut_ptr().add(guard.len), item) };
      guard.len += 1;
    });

    unsafe { guard.v.set_len(guard.len) };
    core::mem::forget(guard);

    v
  }
}

#[cfg(feature = "minivec_nightly")]
trait MiniVecFromIter<T, I>
where
  I: Iterator<Item = T>,
{
  fn from_iter(iter: I) -> MiniVec<T>;
}

#[cfg(feature = "minivec_nightly")]
impl<T, I: Iterator<Item = T>> MiniVecFromIter<T, I> for MiniVec<T> {
  default fn from_iter(iter: I) -> MiniVec<T> {
    struct DropGuard<'a, T> {
      v: &'a mut MiniVec<T>,
      len: usize,
    }

    impl<'a, T> Drop for DropGuard<'a, T> {
      fn drop(&mut self) {
        unsafe { self.v.set_len(self.len) };
      }
    }

    let (lower_bound, _) = iter.size_hint();
    let mut v = MiniVec::<T>::with_capacity(lower_bound.saturating_add(1));

    let mut guard = DropGuard { v: &mut v, len: 0 };

    let mut capacity = guard.v.capacity();

    iter.for_each(|item| {
      if guard.len >= capacity {
        guard.v.grow(crate::next_capacity::<T>(capacity)).unwrap();
        capacity = guard.v.capacity();
      }

      unsafe { core::ptr::write(guard.v.as_mut_ptr().add(guard.len), item) };
      guard.len += 1;
    });

    unsafe { guard.v.set_len(guard.len) };
    core::mem::forget(guard);

    v
  }
}

#[cfg(feature = "minivec_nightly")]
impl<T, I: core::iter::TrustedLen<Item = T>> MiniVecFromIter<T, I> for MiniVec<T> {
  fn from_iter(iter: I) -> MiniVec<T> {
    let (lower_bound, _) = iter.size_hint();
    let mut v = MiniVec::<T>::with_capacity(lower_bound);

    iter.enumerate().for_each(|(idx, item)| {
      unsafe { core::ptr::write(v.as_mut_ptr().add(idx), item) };
    });

    unsafe { v.set_len(lower_bound) };

    v
  }
}

#[cfg(feature = "minivec_nightly")]
impl<T> MiniVecFromIter<T, IntoIter<T>> for MiniVec<T> {
  fn from_iter(mut iter: IntoIter<T>) -> MiniVec<T> {
    let pos = iter.pos;
    let ptr = iter.v.as_mut_ptr();

    if pos != ptr {
      let src = pos;
      let dst = ptr;
      let count = iter.v.len();

      unsafe { core::ptr::copy(src, dst, count) };
    }

    core::mem::forget(iter);

    unsafe { MiniVec::from_raw_part(ptr) }
  }
}

#[cfg(feature = "minivec_nightly")]
impl<T> core::iter::FromIterator<T> for MiniVec<T> {
  fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
    let iter = iter.into_iter();
    <MiniVec<T> as MiniVecFromIter<T, I::IntoIter>>::from_iter(iter)
  }
}