Add byte conversions

bilge-impl/src/bitsize_internal.rs

@@ -231,5 +231,29 @@ fn generate_common(ir: ItemIr, arb_int: &TokenStream) -> TokenStream {
             const BITS: usize = <Self::ArbitraryInt as Bitsized>::BITS;
             const MAX: Self::ArbitraryInt = <Self::ArbitraryInt as Bitsized>::MAX;
         }
+        impl #name {
+            pub fn to_ne_bytes(&self) -> [u8; (<Self as Bitsized>::BITS + 7) / 8] {
+                // u40 = u64 = 8 bytes
+                const ARB_INT_BYTES: usize = core::mem::size_of::<#name>();
+                // u40 = (40 + 7) / 8 = 5 bytes
+                const MIN_BYTES: usize = (<#name as Bitsized>::BITS + 7) / 8;
+
+                // u40, as 8 bytes
+                let mut full = unsafe { core::mem::transmute_copy::<Self, [u8; ARB_INT_BYTES]>(self) };
+                // u40, as 5 bytes
+                #[cfg(target_endian = "big")]
+                {
+                    // = 3
+                    let size_difference = ARB_INT_BYTES - MIN_BYTES;
+                    // 0 0 0 [1 1 1 1 1]
+                    return full[size_difference..].try_into().unwrap()
+                }
+                #[cfg(target_endian = "little")]
+                {
+                    // [1 1 1 1 1] 0 0 0
+                    return full[..MIN_BYTES].try_into().unwrap();
+                }
+            }
+        }
     }
 }

examples/nested_tuples_and_arrays.rs

@@ -3,13 +3,13 @@
 // you can use the "Expand glob import" command on
 // use bilge::prelude::*;
 // but still need to add Bitsized, Number yourself
-use bilge::prelude::{bitsize, u1, u18, u2, u39, Bitsized, DebugBits, DefaultBits, FromBits, Number, TryFromBits};
+use bilge::prelude::{bitsize, u1, u18, u2, u39, BinaryBits, Bitsized, DebugBits, DefaultBits, FromBits, Number, TryFromBits};
 
 // This file basically just informs you that yes, combinations of different nestings work.
 // also see `tests/struct.rs`
 
 #[bitsize(39)]
-#[derive(FromBits, DebugBits, PartialEq)]
+#[derive(FromBits, DebugBits, PartialEq, BinaryBits)]
 struct Mess {
     field1: (u1, (u2, u8), u1),
     array: [[InnerTupleStruct; 2]; 2],
@@ -123,4 +123,23 @@ fn main() {
 
     let default = UnfilledEnumMess::default();
     println!("{default:?}");
+
+    println!("{:b}", mess);
+    println!("{:?}", mess.to_ne_bytes());
+    println!(
+        "{:?} == {:?} == {:?}",
+        core::mem::size_of::<Mess>(),
+        core::mem::size_of::<[u8; (<Mess as Bitsized>::BITS + 7) / 8]>(),
+        core::mem::size_of::<[u8; (<<Mess as Bitsized>::ArbitraryInt as Number>::UnderlyingType::BITS as usize + 7) / 8]>()
+    );
+    // 1u8.to_ne_bytes() -> unsafe { mem::transmute(self) }
+    const SIZE: usize = core::mem::size_of::<Mess>();
+    let mut full = unsafe { core::mem::transmute_copy::<Mess, [u8; SIZE]>(&mess) };
+    println!("{:?}", full);
+    full.rotate_left(3);
+    println!("{:?}", full);
+    let part: [u8; (<Mess as Bitsized>::BITS + 7) / 8] = full[0..((<Mess as Bitsized>::BITS + 7) / 8)].try_into().unwrap();
+    println!("{:?}", part);
+
+    println!("{:?}", default.to_ne_bytes());
 }

examples/readme.rs

@@ -48,6 +48,7 @@ struct InterruptSetEnables([bool; 32]);
 
 #[bitsize(32)]
 #[derive(FromBits, Debug, PartialEq)]
+#[repr(u32)]
 enum Subclass {
     Mouse,
     Keyboard,
@@ -84,6 +85,8 @@ fn main() {
     assert_eq!(3, num);
     assert_ne!(42, num);
 
+    println!("{:?}", Subclass::from(42).to_ne_bytes());
+
     assert_eq!(Subclass2::Reserved(3), Subclass2::from(3));
     assert_eq!(Subclass2::Reserved(42), Subclass2::from(42));
     let num = u32::from(Subclass2::from(42));