Add an option to generate bitfield-like typesafe enums.

Author: emilio

src/bin/bindgen.rs

@@ -28,6 +28,7 @@ Usage:
         [--whitelist-type=<type>...] \
         [--whitelist-function=<name>...] \
         [--whitelist-var=<name>...] \
+        [--bitfield-enum=<name>...] \
         <input-header> \
         [-- <clang-args>...]
 
@@ -91,6 +92,10 @@ Options:
                                   matching <regex>.  Same behavior on emptyness
                                   than the type whitelisting.
 
+    --bitfield-enum=<regex>       Mark a bitfield as being used as an enum.
+                                  This makes bindgen don't generate a rust enum
+                                  for it, but a bitfield-like wrapper.
+
     --dummy-uses=<path>           For testing purposes, generate a C/C++ file
                                   containing dummy uses of all types defined in
                                   the input header.
@@ -163,6 +168,11 @@ fn parse_args_or_exit(args: Vec<String>) -> (BindgenOptions, Box<io::Write>) {
                     .expect("--whitelist-var expects a pattern");
                 options.whitelisted_vars.insert(&var_pat);
             }
+            "--bitfield-enum" => {
+                let enum_pat = iter.next()
+                    .expect("--bitfield-enum expects a pattern");
+                options.bitfield_enums.insert(&enum_pat);
+            }
             "--" => {
                 while let Some(clang_arg) = iter.next() {
                     options.clang_args.push(clang_arg);

src/codegen/mod.rs

@@ -1224,6 +1224,79 @@ impl MethodCodegen for Method {
     }
 }
 
+enum EnumBuilder<'a> {
+    Rust(aster::item::ItemEnumBuilder<aster::invoke::Identity>),
+    Bitfield {
+        canonical_name: &'a str,
+        aster: P<ast::Item>,
+    },
+}
+
+impl<'a> EnumBuilder<'a> {
+    fn new(aster: aster::item::ItemBuilder<aster::invoke::Identity>,
+           name: &'a str,
+           repr_name: &str,
+           is_rust: bool)
+           -> Self {
+        if is_rust {
+            EnumBuilder::Rust(aster.enum_(name))
+        } else {
+            EnumBuilder::Bitfield {
+                canonical_name: name,
+                aster: aster.tuple_struct(name)
+                    .field()
+                    .pub_()
+                    .ty()
+                    .id(repr_name)
+                    .build(),
+            }
+        }
+    }
+
+    fn with_variant_(self,
+                     ctx: &BindgenContext,
+                     name: &str,
+                     expr: P<ast::Expr>,
+                     rust_ty: P<ast::Ty>,
+                     result: &mut CodegenResult)
+                     -> Self {
+        match self {
+            EnumBuilder::Rust(b) => {
+                EnumBuilder::Rust(b.with_variant_(ast::Variant_ {
+                    name: ctx.rust_ident(name),
+                    attrs: vec![],
+                    data: ast::VariantData::Unit(ast::DUMMY_NODE_ID),
+                    disr_expr: Some(expr),
+                }))
+            }
+            EnumBuilder::Bitfield { canonical_name, .. } => {
+                // FIXME: Probably if unnamed we should be smarter! Easy to
+                // improve.
+                let constant_name = format!("{}_{}", canonical_name, name);
+                let constant = aster::AstBuilder::new()
+                    .item()
+                    .const_(constant_name)
+                    .expr()
+                    .call()
+                    .id(canonical_name)
+                    .arg()
+                    .build(expr)
+                    .build()
+                    .build(rust_ty);
+                result.push(constant);
+                self
+            }
+        }
+    }
+
+    fn build(self) -> P<ast::Item> {
+        match self {
+            EnumBuilder::Rust(b) => b.build(),
+            EnumBuilder::Bitfield { aster, .. } => aster,
+        }
+    }
+}
+
 impl CodeGenerator for Enum {
     type Extra = Item;
 
@@ -1234,7 +1307,8 @@ impl CodeGenerator for Enum {
         use ir::enum_ty::EnumVariantValue;
 
         let name = item.canonical_name(ctx);
-        let layout = item.expect_type().layout(ctx);
+        let enum_ty = item.expect_type();
+        let layout = enum_ty.layout(ctx);
 
         let repr = self.repr().map(|repr| ctx.resolve_type(repr));
         let repr = match repr {
@@ -1270,10 +1344,24 @@ impl CodeGenerator for Enum {
 
         let mut builder = aster::AstBuilder::new().item().pub_();
 
+        let is_bitfield = {
+            ctx.options().bitfield_enums.matches(&name) ||
+            (enum_ty.name().is_none() &&
+             self.variants()
+                .iter()
+                .any(|v| ctx.options().bitfield_enums.matches(&v.name())))
+        };
+
+        let is_rust_enum = !is_bitfield;
+
         // FIXME: Rust forbids repr with empty enums. Remove this condition when
         // this is allowed.
-        if !self.variants().is_empty() {
-            builder = builder.with_attr(attributes::repr(repr_name));
+        if is_rust_enum {
+            if !self.variants().is_empty() {
+                builder = builder.with_attr(attributes::repr(repr_name));
+            }
+        } else {
+            builder = builder.with_attr(attributes::repr("C"));
         }
 
         if let Some(comment) = item.comment() {
@@ -1289,8 +1377,6 @@ impl CodeGenerator for Enum {
 
         builder = builder.with_attr(derives);
 
-        let mut builder = builder.enum_(&name);
-
         fn add_constant(enum_: &Type,
                         // Only to avoid recomputing every time.
                         enum_canonical_name: &str,
@@ -1321,21 +1407,38 @@ impl CodeGenerator for Enum {
         // Used to mangle the constants we generate in the unnamed-enum case.
         let mut parent_canonical_name = None;
 
+        let mut builder =
+            EnumBuilder::new(builder, &name, repr_name, is_rust_enum);
+
         // A map where we keep a value -> variant relation.
         let mut seen_values = HashMap::<_, String>::new();
-        let enum_ty = item.expect_type();
         let enum_rust_ty = item.to_rust_ty(ctx);
         for variant in self.variants().iter() {
             match seen_values.entry(variant.val()) {
                 Entry::Occupied(ref entry) => {
-                    let existing_variant_name = entry.get();
-                    let variant_name = ctx.rust_mangle(variant.name());
-                    add_constant(enum_ty,
-                                 &name,
-                                 &*variant_name,
-                                 existing_variant_name,
-                                 enum_rust_ty.clone(),
-                                 result);
+                    if is_rust_enum {
+                        let existing_variant_name = entry.get();
+                        let variant_name = ctx.rust_mangle(variant.name());
+                        add_constant(enum_ty,
+                                     &name,
+                                     &*variant_name,
+                                     existing_variant_name,
+                                     enum_rust_ty.clone(),
+                                     result);
+                    } else {
+                        // FIXME: Don't repeat this block below.
+                        let expr = aster::AstBuilder::new().expr();
+                        let expr = match variant.val() {
+                            EnumVariantValue::Signed(val) => expr.int(val),
+                            EnumVariantValue::Unsigned(val) => expr.uint(val),
+                        };
+                        let variant_name = ctx.rust_mangle(variant.name());
+                        builder = builder.with_variant_(ctx,
+                                                        &*variant_name,
+                                                        expr,
+                                                        enum_rust_ty.clone(),
+                                                        result);
+                    }
                 }
                 Entry::Vacant(entry) => {
                     let expr = aster::AstBuilder::new().expr();
@@ -1344,16 +1447,15 @@ impl CodeGenerator for Enum {
                         EnumVariantValue::Unsigned(val) => expr.uint(val),
                     };
                     let variant_name = ctx.rust_mangle(variant.name());
-                    builder = builder.with_variant_(ast::Variant_ {
-                        name: ctx.rust_ident(&*variant_name),
-                        attrs: vec![],
-                        data: ast::VariantData::Unit(ast::DUMMY_NODE_ID),
-                        disr_expr: Some(expr),
-                    });
+                    builder = builder.with_variant_(ctx,
+                                                    &*variant_name,
+                                                    expr,
+                                                    enum_rust_ty.clone(),
+                                                    result);
 
                     // If it's an unnamed enum, we also generate a constant so
                     // it can be properly accessed.
-                    if enum_ty.name().is_none() {
+                    if is_rust_enum && enum_ty.name().is_none() {
                         // NB: if we want to do this for other kind of nested
                         // enums we can probably mangle the name.
                         let mangled_name = if item.is_toplevel(ctx) {
@@ -1384,7 +1486,6 @@ impl CodeGenerator for Enum {
             }
         }
 
-
         result.push(builder.build());
     }
 }

src/lib.rs

@@ -169,6 +169,15 @@ impl Builder {
         self
     }
 
+    /// Mark the given enum (or set of enums, if using a pattern) as being
+    /// bitfield-like.
+    ///
+    /// This makes bindgen to generate a type for it that isn't a rust `enum`.
+    pub fn bitfield_enum<T: Borrow<str>>(mut self, arg: T) -> Builder {
+        self.options.bitfield_enums.insert(&arg);
+        self
+    }
+
     /// Add a string to prepend to the generated bindings. The string is passed
     /// through without any modification.
     pub fn raw_line<T: Into<String>>(mut self, arg: T) -> Builder {
@@ -272,6 +281,9 @@ pub struct BindgenOptions {
     /// Whitelisted variables. See docs for `whitelisted_types` for more.
     pub whitelisted_vars: RegexSet,
 
+    /// The enum patterns to mark an enum as bitfield.
+    pub bitfield_enums: RegexSet,
+
     /// Whether we should generate builtins or not.
     pub builtins: bool,
 
@@ -343,6 +355,7 @@ impl Default for BindgenOptions {
             whitelisted_types: Default::default(),
             whitelisted_functions: Default::default(),
             whitelisted_vars: Default::default(),
+            bitfield_enums: Default::default(),
             builtins: false,
             links: vec![],
             emit_ast: false,