Initial commit

.gitignore

@@ -0,0 +1,2 @@
+/target
+/Cargo.lock

Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "order"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[features]
+nightly = []
+
+[dependencies]

src/lib.rs

@@ -0,0 +1,167 @@
+//! Provides traits for types that can be represented as both big and little-endian byte arrays.
+//! Types that have a "canonical" byte array representation are not appropriate implementors of
+//! [`ByteOrdered`].
+
+#![feature(generic_const_exprs)]
+
+mod private {
+    pub trait Sealed {}
+}
+
+/// Order of bits or bytes.
+pub trait Order {
+    fn from_bytes<T: ByteOrdered>(bytes: [u8; T::BYTES]) -> T;
+    fn to_bytes<T: ByteOrdered>(value: T) -> [u8; T::BYTES];
+}
+
+#[derive(Clone, Copy)]
+pub struct Big;
+
+#[derive(Clone, Copy)]
+pub struct Little;
+
+impl Order for Big {
+    #[inline(always)]
+    fn from_bytes<T: ByteOrdered>(bytes: [u8; T::BYTES]) -> T {
+        T::from_be_bytes(bytes)
+    }
+
+    #[inline(always)]
+    fn to_bytes<T: ByteOrdered>(value: T) -> [u8; T::BYTES] {
+        value.to_be_bytes()
+    }
+}
+
+impl Order for Little {
+    #[inline(always)]
+    fn from_bytes<T: ByteOrdered>(bytes: [u8; T::BYTES]) -> T {
+        T::from_le_bytes(bytes)
+    }
+
+    #[inline(always)]
+    fn to_bytes<T: ByteOrdered>(value: T) -> [u8; T::BYTES] {
+        value.to_le_bytes()
+    }
+}
+
+pub trait ByteOrdered: Copy {
+    /// Length of the type in bytes.
+    const BYTES: usize;
+
+    #[inline(always)]
+    fn to_bytes<O: Order>(self) -> [u8; Self::BYTES] {
+        O::to_bytes(self)
+    }
+
+    #[inline(always)]
+    fn from_bytes<O: Order>(bytes: [u8; Self::BYTES]) -> Self {
+        O::from_bytes(bytes)
+    }
+
+    fn to_be_bytes(self) -> [u8; Self::BYTES];
+
+    fn from_be_bytes(bytes: [u8; Self::BYTES]) -> Self;
+
+    fn to_le_bytes(self) -> [u8; Self::BYTES];
+
+    fn from_le_bytes(bytes: [u8; Self::BYTES]) -> Self;
+}
+
+// TODO: file a bug report "Use-sites of this trait as a bound are required to also duplicate the
+// where clause"
+pub trait ByteOrderedA: ByteOrdered
+where
+    [(); <Self as ByteOrdered>::BYTES]:,
+{
+}
+
+impl<T> ByteOrderedA for T
+where
+    T: ByteOrdered,
+    [(); T::BYTES]:,
+{
+}
+
+macro_rules! num_impl {
+    ($ty:ty) => {
+        impl ByteOrdered for $ty {
+            const BYTES: usize = std::mem::size_of::<$ty>();
+
+            #[inline(always)]
+            fn to_be_bytes(self) -> [u8; Self::BYTES] {
+                <$ty>::to_be_bytes(self)
+            }
+
+            #[inline(always)]
+            fn from_be_bytes(bytes: [u8; Self::BYTES]) -> Self {
+                <$ty>::from_be_bytes(bytes)
+            }
+
+            #[inline(always)]
+            fn to_le_bytes(self) -> [u8; Self::BYTES] {
+                <$ty>::to_le_bytes(self)
+            }
+
+            #[inline(always)]
+            fn from_le_bytes(bytes: [u8; Self::BYTES]) -> Self {
+                <$ty>::from_le_bytes(bytes)
+            }
+        }
+    };
+}
+
+num_impl!(u8);
+num_impl!(u16);
+num_impl!(u32);
+num_impl!(u64);
+num_impl!(u128);
+
+num_impl!(i8);
+num_impl!(i16);
+num_impl!(i32);
+num_impl!(i64);
+num_impl!(i128);
+
+num_impl!(f32);
+num_impl!(f64);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn to_be_bytes() {
+        const CASES: &[(u32, [u8; 4])] = &[
+            (0x420, [0x00, 0x00, 0x04, 0x20]),
+            (0x69, [0x00, 0x00, 0x00, 0x69]),
+            (u32::MAX, [0xFF, 0xFF, 0xFF, 0xFF]),
+            (32, [0, 0, 0, 32]),
+        ];
+
+        for (n, bytes) in CASES {
+            assert_eq!(n.to_be_bytes(), *bytes);
+            assert_eq!(n.to_bytes::<Big>(), *bytes);
+            assert_eq!(Big::to_bytes(*n), *bytes);
+
+            assert_eq!(u32::from_be_bytes(*bytes), *n);
+        }
+    }
+
+    #[test]
+    fn to_le_bytes() {
+        const CASES: &[(u32, [u8; 4])] = &[
+            (0x420, [0x20, 0x04, 0x00, 0x00]),
+            (0x69, [0x69, 0x00, 0x00, 0x00]),
+            (u32::MAX, [0xFF, 0xFF, 0xFF, 0xFF]),
+            (32, [32, 0, 0, 0]),
+        ];
+
+        for (n, bytes) in CASES {
+            assert_eq!(n.to_le_bytes(), *bytes);
+            assert_eq!(n.to_bytes::<Little>(), *bytes);
+            assert_eq!(Little::to_bytes(*n), *bytes);
+
+            assert_eq!(u32::from_le_bytes(*bytes), *n);
+        }
+    }
+}