musli 0.2.0

Müsli is a flexible and efficient serialization framework.
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
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172

use core::mem::MaybeUninit;
use core::slice::from_raw_parts_mut;

use super::ArrayBuffer;

mod sealed {
    use core::mem::MaybeUninit;

    use super::super::ArrayBuffer;

    pub trait Sealed {}
    impl Sealed for [MaybeUninit<u8>] {}
    impl Sealed for [MaybeUninit<u16>] {}
    impl Sealed for [MaybeUninit<u32>] {}
    impl Sealed for [MaybeUninit<u64>] {}
    impl Sealed for [MaybeUninit<u128>] {}
    impl<const N: usize> Sealed for [MaybeUninit<u8>; N] {}
    impl<const N: usize> Sealed for [MaybeUninit<u16>; N] {}
    impl<const N: usize> Sealed for [MaybeUninit<u32>; N] {}
    impl<const N: usize> Sealed for [MaybeUninit<u64>; N] {}
    impl<const N: usize> Sealed for [MaybeUninit<u128>; N] {}
    impl<const N: usize> Sealed for ArrayBuffer<N> {}
}

/// The trait over anything that can be treated as a buffer by the [`Slice`]
/// allocator.
///
/// Only buffers of [`MaybeUninit`] and [`ArrayBuffer`] can be used. The
/// allocator writes arbitrary values into the buffer which might leave bytes
/// uninitialized, such as padding, so it would not be sound to read the buffer
/// back as initialized integers after the allocator has been dropped:
///
/// ```compile_fail,E0277
/// use musli::alloc::{Slice, Vec};
///
/// let mut buf = [0u8; 256];
///
/// {
///     let alloc = Slice::new(&mut buf);
///     let mut values = Vec::new_in(&alloc);
///     values.push((1u8, 2u32))?;
/// }
///
/// // Would read uninitialized padding bytes.
/// let sum = buf.iter().map(|&b| b as u32).sum::<u32>();
/// # Ok::<_, musli::alloc::AllocError>(())
/// ```
///
/// [`Slice`]: super::Slice
pub trait SliceBuffer: self::sealed::Sealed {
    #[doc(hidden)]
    fn as_uninit_bytes(&mut self) -> &mut [MaybeUninit<u8>];
}

/// The [`SliceBuffer`] implementation for `[MaybeUninit<u8>]`.
///
/// # Examples
///
/// ```
/// use core::mem::MaybeUninit;
///
/// use musli::alloc::Slice;
///
/// let mut bytes: [MaybeUninit<u8>; 128] = [const { MaybeUninit::uninit() }; 128];
/// let alloc = Slice::new(&mut bytes[..]);
/// ```
impl SliceBuffer for [MaybeUninit<u8>] {
    #[inline]
    fn as_uninit_bytes(&mut self) -> &mut [MaybeUninit<u8>] {
        self
    }
}

/// The [`SliceBuffer`] implementation for `[MaybeUninit<u8>; N]`.
///
/// # Examples
///
/// ```
/// use core::mem::MaybeUninit;
///
/// # use musli::alloc::SliceBuffer as _;
/// use musli::alloc::Slice;
///
/// let mut bytes: [MaybeUninit<u8>; 128] = [const { MaybeUninit::uninit() }; 128];
/// # assert_eq!(bytes.as_uninit_bytes().len(), 128);
/// let alloc = Slice::new(&mut bytes);
/// ```
impl<const N: usize> SliceBuffer for [MaybeUninit<u8>; N] {
    #[inline]
    fn as_uninit_bytes(&mut self) -> &mut [MaybeUninit<u8>] {
        self
    }
}

/// The [`SliceBuffer`] implementation for `ArrayBuffer<N>`.
///
/// # Examples
///
/// ```
/// use core::mem::MaybeUninit;
///
/// use musli::alloc::{ArrayBuffer, Slice};
///
/// let mut buffer = ArrayBuffer::new();
/// let alloc = Slice::new(&mut buffer);
/// ```
impl<const N: usize> SliceBuffer for ArrayBuffer<N> {
    #[inline]
    fn as_uninit_bytes(&mut self) -> &mut [MaybeUninit<u8>] {
        self
    }
}

macro_rules! primitive {
    ($($ty:ty, $len:expr),* $(,)?) => {
        $(
            #[doc = concat!(" The [`SliceBuffer`] implementation for `[MaybeUninit<", stringify!($ty), ">]`.")]
            ///
            /// # Examples
            ///
            /// ```
            /// use core::mem::MaybeUninit;
            ///
            /// use musli::alloc::Slice;
            /// # use musli::alloc::SliceBuffer as _;
            ///
            #[doc = concat!(" let mut bytes: [MaybeUninit<", stringify!($ty), ">; 128] = [const { MaybeUninit::uninit() }; 128];")]
            #[doc = concat!(" # assert_eq!(bytes.as_uninit_bytes().len(), ", stringify!($len), ");")]
            /// let alloc = Slice::new(&mut bytes[..]);
            /// ```
            impl SliceBuffer for [MaybeUninit<$ty>] {
                #[inline]
                fn as_uninit_bytes(&mut self) -> &mut [MaybeUninit<u8>] {
                    // SAFETY: An integer is made up of `BITS / 8` bytes without
                    // padding, so the region can be viewed as uninitialized bytes.
                    unsafe {
                        let len = <[_]>::len(self) * (<$ty>::BITS / 8u32) as usize;
                        from_raw_parts_mut(self.as_mut_ptr().cast(), len)
                    }
                }
            }

            #[doc = concat!(" The [`SliceBuffer`] implementation for `[MaybeUninit<", stringify!($ty), ">; N]`.")]
            ///
            /// # Examples
            ///
            /// ```
            /// use core::mem::MaybeUninit;
            ///
            /// use musli::alloc::Slice;
            /// # use musli::alloc::SliceBuffer as _;
            ///
            #[doc = concat!(" let mut bytes: [MaybeUninit<", stringify!($ty), ">; 128] = [const { MaybeUninit::uninit() }; 128];")]
            #[doc = concat!(" # assert_eq!(bytes.as_uninit_bytes().len(), ", stringify!($len), ");")]
            /// let alloc = Slice::new(&mut bytes);
            /// ```
            impl<const N: usize> SliceBuffer for [MaybeUninit<$ty>; N] {
                #[inline]
                fn as_uninit_bytes(&mut self) -> &mut [MaybeUninit<u8>] {
                    self.as_mut_slice().as_uninit_bytes()
                }
            }
        )*
    }
}

primitive! {
    u16, 128 * 2,
    u32, 128 * 4,
    u64, 128 * 8,
    u128, 128 * 16,
}