uninit 0.6.2

A collection of tools for a safer usage of uninitialized memory
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 super::*;

#[cfg(feature = "specialization")]
#[doc(cfg(feature = "specialization"))]
default unsafe impl<R: Read> ReadIntoUninit for R {
    #[inline]
    default fn read_into_uninit<'buf>(
        self: &'_ mut Self,
        buf: Out<'buf, [u8]>,
    ) -> io::Result<&'buf mut [u8]> {
        let buf = buf.fill_with_iter(::core::iter::repeat(0));
        self.read(buf).map(move |n| &mut buf[..n])
    }

    #[inline]
    default fn read_into_uninit_exact<'buf>(
        self: &'_ mut Self,
        buf: Out<'buf, [u8]>,
    ) -> io::Result<&'buf mut [u8]> {
        let buf = buf.fill_with_iter(::core::iter::repeat(0));
        self.read_exact(buf).map(|()| buf)
    }
}

// # Safety:
//
//   - basic delegation
//
//   - `read_into_uninit_exact` is not overriden
unsafe impl<R: ReadIntoUninit + ?Sized> ReadIntoUninit for &'_ mut R {
    #[inline]
    fn read_into_uninit<'buf>(
        self: &'_ mut Self,
        buf: Out<'buf, [u8]>,
    ) -> io::Result<&'buf mut [u8]> {
        (**self).read_into_uninit(buf)
    }
}

// # Safety
//
//   - `read_into_uninit` does return a prefix slice on success;
//
//   - `read_into_uninit_exact` is not overriden
unsafe impl ReadIntoUninit for &'_ [u8] {
    #[inline]
    fn read_into_uninit<'buf>(
        self: &'_ mut Self,
        buf: Out<'buf, [u8]>,
    ) -> io::Result<&'buf mut [u8]> {
        let count = ::std::cmp::min(buf.len(), self.len());
        let (to_copy, remaining) = self.split_at(count);
        *self = remaining;

        // Taken from stdlib:
        // "First check if the amount of bytes we want to read is small:
        // `copy_from_slice` will generally expand to a call to `memcpy`, and
        // for a single byte the overhead is significant."
        if count == 1 {
            Ok(slice::from_mut(buf.get_out(0).unwrap().write(to_copy[0])))
        } else {
            Ok(buf.get_out(..count).unwrap().copy_from_slice(to_copy))
        }
    }
}

macro_rules! impl_ReadIntoUninit_for_impl_BufRead {(
    $(
        for [$($generics:tt)*]
            $T:ty
        $(where {
            $($wc:tt)*
        })? ;
    )*
) => (
    $(
        // # Safety:
        //
        //   - delegates to `<&'_ [u8] as ReadIntoUninit>::read_into_uninit`
        //
        //   - `read_into_uninit_exact` is not overriden
        unsafe
        impl<$($generics)*> ReadIntoUninit
            for $T
        $(where
            $($wc)*
        )?
        {
            #[inline]
            fn read_into_uninit<'buf> (
                self: &'_ mut Self,
                buf: Out<'buf, [u8]>,
            ) -> io::Result<&'buf mut [u8]>
            {
                let buf = {
                    let mut read_buf: &[u8] = io::BufRead::fill_buf(self)?;
                    read_buf.read_into_uninit(buf)?
                };
                io::BufRead::consume(self, buf.len());
                Ok(buf)
            }

        }
    )*
)}

impl_ReadIntoUninit_for_impl_BufRead! {
    for [R : io::Read]
        io::BufReader<R>
    ;
    for [T : AsRef<[u8]>]
        io::Cursor<T>
    ;
    for []
        io::Empty
    ;
    for []
        io::StdinLock<'_>
    ;
    for [T : io::BufRead]
        io::Take<T>
    ;
}

// # Safety:
//
//   - basic delegation
//
//   - `read_into_uninit_exact` is not overriden
unsafe impl<R: ReadIntoUninit + ?Sized> ReadIntoUninit for Box<R> {
    #[inline]
    fn read_into_uninit<'buf>(
        self: &'_ mut Self,
        buf: Out<'buf, [u8]>,
    ) -> io::Result<&'buf mut [u8]> {
        (**self).read_into_uninit(buf)
    }
}