Add byte conversions

Author: calebzulawski

crates/core_simd/src/lib.rs

@@ -17,6 +17,9 @@ mod reduction;
 mod select;
 pub use select::Select;
 
+mod to_bytes;
+pub use to_bytes::ToBytes;
+
 mod comparisons;
 mod fmt;
 mod intrinsics;

crates/core_simd/src/to_bytes.rs

@@ -0,0 +1,68 @@
+mod sealed {
+    pub trait Sealed {}
+}
+use sealed::Sealed;
+
+/// Supporting trait for byte conversion functions.
+pub trait ToBytes: Sealed {
+    /// The bytes representation of this type.
+    type Bytes;
+
+    #[doc(hidden)]
+    fn to_bytes_impl(self) -> Self::Bytes;
+
+    #[doc(hidden)]
+    fn from_bytes_impl(bytes: Self::Bytes) -> Self;
+}
+
+macro_rules! impl_to_bytes {
+    { $name:ident, $($int_width:literal -> $byte_width:literal),* } => {
+        $(
+        impl Sealed for crate::$name<$int_width> where Self: crate::LanesAtMost32 {}
+        impl ToBytes for crate::$name<$int_width>
+        where
+            Self: crate::LanesAtMost32,
+            crate::SimdU8<$byte_width>: crate::LanesAtMost32,
+        {
+            type Bytes = crate::SimdU8<$byte_width>;
+            fn to_bytes_impl(self) -> Self::Bytes {
+                unsafe { core::mem::transmute(self) }
+            }
+            fn from_bytes_impl(bytes: Self::Bytes) -> Self {
+                unsafe { core::mem::transmute(bytes) }
+            }
+        }
+        )*
+
+        impl<const LANES: usize> crate::$name<LANES>
+        where
+            Self: ToBytes + crate::LanesAtMost32,
+        {
+            /// Return the memory representation of this integer as a byte array in native byte
+            /// order.
+            pub fn to_ne_bytes(self) -> <Self as ToBytes>::Bytes { self.to_bytes_impl() }
+
+            /// Create a native endian integer value from its memory representation as a byte array
+            /// in native endianness.
+            pub fn from_ne_bytes(bytes: <Self as ToBytes>::Bytes) -> Self { Self::from_bytes_impl(bytes) }
+        }
+    }
+}
+
+impl_to_bytes! { SimdU8, 1 -> 1, 2 -> 2, 4 -> 4, 8 -> 8, 16 -> 16, 32 -> 32 }
+impl_to_bytes! { SimdU16, 1 -> 2, 2 -> 4, 4 -> 8, 8 -> 16, 16 -> 32 }
+impl_to_bytes! { SimdU32, 1 -> 4, 2 -> 8, 4 -> 16, 8 -> 32 }
+impl_to_bytes! { SimdU64, 1 -> 8, 2 -> 16, 4 -> 32 }
+#[cfg(target_pointer_width = "32")]
+impl_to_bytes! { SimdUsize, 1 -> 4, 2 -> 8, 4 -> 16, 8 -> 32 }
+#[cfg(target_pointer_width = "64")]
+impl_to_bytes! { SimdUsize, 1 -> 8, 2 -> 16, 4 -> 32 }
+
+impl_to_bytes! { SimdI8, 1 -> 1, 2 -> 2, 4 -> 4, 8 -> 8, 16 -> 16, 32 -> 32 }
+impl_to_bytes! { SimdI16, 1 -> 2, 2 -> 4, 4 -> 8, 8 -> 16, 16 -> 32 }
+impl_to_bytes! { SimdI32, 1 -> 4, 2 -> 8, 4 -> 16, 8 -> 32 }
+impl_to_bytes! { SimdI64, 1 -> 8, 2 -> 16, 4 -> 32 }
+#[cfg(target_pointer_width = "32")]
+impl_to_bytes! { SimdIsize, 1 -> 4, 2 -> 8, 4 -> 16, 8 -> 32 }
+#[cfg(target_pointer_width = "64")]
+impl_to_bytes! { SimdIsize, 1 -> 8, 2 -> 16, 4 -> 32 }

crates/core_simd/tests/to_bytes.rs

@@ -0,0 +1,10 @@
+use core_simd::SimdU32;
+
+#[test]
+fn byte_convert() {
+    let int = SimdU32::from_array([0xdeadbeef, 0x8badf00d]);
+    let bytes = int.to_ne_bytes();
+    assert_eq!(int[0].to_ne_bytes(), bytes[..4]); 
+    assert_eq!(int[1].to_ne_bytes(), bytes[4..]);
+    assert_eq!(SimdU32::from_ne_bytes(bytes), int);
+}