Support zerocopy derives

.github/workflows/rust.yml

@@ -49,7 +49,7 @@ jobs:
       run: cargo install cargo-hack
 
     - name: Powerset
-      run: cargo hack test --feature-powerset --lib --optional-deps "std serde" --depth 3 --skip rustc-dep-of-std
+      run: cargo hack test --feature-powerset --lib --optional-deps "std serde zerocopy_0_6" --depth 3 --skip rustc-dep-of-std
 
     - name: Docs
       run: cargo doc --features example_generated

Cargo.toml

@@ -23,6 +23,7 @@ exclude = ["tests", ".github"]
 serde = { version = "1.0", optional = true, default-features = false }
 core = { version = "1.0.0", optional = true, package = "rustc-std-workspace-core" }
 compiler_builtins = { version = "0.1.2", optional = true }
+zerocopy = { version = "0.6.1", optional = true, default-features = false }
 
 [dev-dependencies]
 trybuild = "1.0"
@@ -35,6 +36,7 @@ serde_test = "1.0"
 std = []
 example_generated = []
 rustc-dep-of-std = ["core", "compiler_builtins"]
+zerocopy_0_6 = ["zerocopy"]
 
 [package.metadata.docs.rs]
 features = ["example_generated"]

examples/zerocopy.rs

@@ -0,0 +1,28 @@
+#[cfg(feature = "zerocopy_0_6")]
+fn main() {
+    use bitflags::bitflags;
+    use zerocopy::{AsBytes, FromBytes};
+
+    bitflags! {
+        #[derive(AsBytes, Debug, Eq, FromBytes, PartialEq)]
+        #[repr(transparent)]
+        pub struct Flags: u32 {
+            const A = 1;
+            const B = 2;
+            const C = 4;
+            const D = 8;
+        }
+    }
+
+    let flags = Flags::A | Flags::B;
+    let bytes = flags.as_bytes();
+    println!("{:?} -> {:?}", flags, bytes);
+
+    let flags_from_bytes = Flags::read_from(bytes).unwrap();
+    println!("{:?} -> {:?}", bytes, flags_from_bytes);
+
+    assert_eq!(flags, flags_from_bytes);
+}
+
+#[cfg(not(feature = "zerocopy_0_6"))]
+fn main() {}

src/internal.rs

@@ -14,6 +14,12 @@ macro_rules! __declare_internal_bitflags {
         $iter_vis:vis struct $Iter:ident;
         $iter_names_vis:vis struct $IterNames:ident;
     ) => {
+        #[cfg(feature = "zerocopy_0_6")]
+        use $crate::__private::zerocopy;
+        #[cfg(feature = "zerocopy_0_6")]
+        use ::core::marker::Sized;
+
+        #[cfg_attr(feature = "zerocopy_0_6", derive($crate::__private::zerocopy::AsBytes, $crate::__private::zerocopy::FromBytes))]
         #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
         #[repr(transparent)]
         $vis struct $InternalBitFlags {

src/lib.rs

@@ -361,6 +361,8 @@ pub mod __private {
 
     #[cfg(feature = "serde")]
     pub use serde;
+    #[cfg(feature = "zerocopy_0_6")]
+    pub use zerocopy;
 }
 
 /*

src/public.rs

@@ -14,7 +14,7 @@ macro_rules! __declare_public_bitflags {
         $vis:vis struct $BitFlags:ident;
     ) => {
         $(#[$outer])*
-        $vis struct $BitFlags(<Self as $crate::__private::PublicFlags>::Internal);
+        $vis struct $BitFlags(<$BitFlags as $crate::__private::PublicFlags>::Internal);
     };
 }