core/portable-simd/crates/core_simd/src/
to_bytes.rs

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
use crate::simd::{
    num::{SimdFloat, SimdInt, SimdUint},
    LaneCount, Simd, SimdElement, SupportedLaneCount,
};

mod sealed {
    use super::*;
    pub trait Sealed {}
    impl<T: SimdElement, const N: usize> Sealed for Simd<T, N> where LaneCount<N>: SupportedLaneCount {}
}
use sealed::Sealed;

/// Converts SIMD vectors to vectors of bytes
pub trait ToBytes: Sealed {
    /// This type, reinterpreted as bytes.
    type Bytes: Copy
        + Unpin
        + Send
        + Sync
        + AsRef<[u8]>
        + AsMut<[u8]>
        + SimdUint<Scalar = u8>
        + 'static;

    /// Returns the memory representation of this integer as a byte array in native byte
    /// order.
    fn to_ne_bytes(self) -> Self::Bytes;

    /// Returns the memory representation of this integer as a byte array in big-endian
    /// (network) byte order.
    fn to_be_bytes(self) -> Self::Bytes;

    /// Returns the memory representation of this integer as a byte array in little-endian
    /// byte order.
    fn to_le_bytes(self) -> Self::Bytes;

    /// Creates a native endian integer value from its memory representation as a byte array
    /// in native endianness.
    fn from_ne_bytes(bytes: Self::Bytes) -> Self;

    /// Creates an integer value from its representation as a byte array in big endian.
    fn from_be_bytes(bytes: Self::Bytes) -> Self;

    /// Creates an integer value from its representation as a byte array in little endian.
    fn from_le_bytes(bytes: Self::Bytes) -> Self;
}

macro_rules! swap_bytes {
    { f32, $x:expr } => { Simd::from_bits($x.to_bits().swap_bytes()) };
    { f64, $x:expr } => { Simd::from_bits($x.to_bits().swap_bytes()) };
    { $ty:ty, $x:expr } => { $x.swap_bytes() }
}

macro_rules! impl_to_bytes {
    { $ty:tt, 1  } => { impl_to_bytes! { $ty, 1  * [1, 2, 4, 8, 16, 32, 64] } };
    { $ty:tt, 2  } => { impl_to_bytes! { $ty, 2  * [1, 2, 4, 8, 16, 32] } };
    { $ty:tt, 4  } => { impl_to_bytes! { $ty, 4  * [1, 2, 4, 8, 16] } };
    { $ty:tt, 8  } => { impl_to_bytes! { $ty, 8  * [1, 2, 4, 8] } };
    { $ty:tt, 16 } => { impl_to_bytes! { $ty, 16 * [1, 2, 4] } };
    { $ty:tt, 32 } => { impl_to_bytes! { $ty, 32 * [1, 2] } };
    { $ty:tt, 64 } => { impl_to_bytes! { $ty, 64 * [1] } };

    { $ty:tt, $size:literal * [$($elems:literal),*] } => {
        $(
        impl ToBytes for Simd<$ty, $elems> {
            type Bytes = Simd<u8, { $size * $elems }>;

            #[inline]
            fn to_ne_bytes(self) -> Self::Bytes {
                // Safety: transmuting between vectors is safe
                unsafe {
                    #![allow(clippy::useless_transmute)]
                    core::mem::transmute(self)
                }
            }

            #[inline]
            fn to_be_bytes(mut self) -> Self::Bytes {
                if !cfg!(target_endian = "big") {
                    self = swap_bytes!($ty, self);
                }
                self.to_ne_bytes()
            }

            #[inline]
            fn to_le_bytes(mut self) -> Self::Bytes {
                if !cfg!(target_endian = "little") {
                    self = swap_bytes!($ty, self);
                }
                self.to_ne_bytes()
            }

            #[inline]
            fn from_ne_bytes(bytes: Self::Bytes) -> Self {
                // Safety: transmuting between vectors is safe
                unsafe {
                    #![allow(clippy::useless_transmute)]
                    core::mem::transmute(bytes)
                }
            }

            #[inline]
            fn from_be_bytes(bytes: Self::Bytes) -> Self {
                let ret = Self::from_ne_bytes(bytes);
                if cfg!(target_endian = "big") {
                    ret
                } else {
                    swap_bytes!($ty, ret)
                }
            }

            #[inline]
            fn from_le_bytes(bytes: Self::Bytes) -> Self {
                let ret = Self::from_ne_bytes(bytes);
                if cfg!(target_endian = "little") {
                    ret
                } else {
                    swap_bytes!($ty, ret)
                }
            }
        }
        )*
    }
}

impl_to_bytes! { u8, 1 }
impl_to_bytes! { u16, 2 }
impl_to_bytes! { u32, 4 }
impl_to_bytes! { u64, 8 }
#[cfg(target_pointer_width = "32")]
impl_to_bytes! { usize, 4 }
#[cfg(target_pointer_width = "64")]
impl_to_bytes! { usize, 8 }

impl_to_bytes! { i8, 1 }
impl_to_bytes! { i16, 2 }
impl_to_bytes! { i32, 4 }
impl_to_bytes! { i64, 8 }
#[cfg(target_pointer_width = "32")]
impl_to_bytes! { isize, 4 }
#[cfg(target_pointer_width = "64")]
impl_to_bytes! { isize, 8 }

impl_to_bytes! { f32, 4 }
impl_to_bytes! { f64, 8 }