1 files changed, 53 insertions, 0 deletions
diff --git a/third_party/rust/zerocopy-derive/src/ext.rs b/third_party/rust/zerocopy-derive/src/ext.rs
new file mode 100644
index 0000000000..87cf838f88
--- /dev/null
+++ b/third_party/rust/zerocopy-derive/src/ext.rs
@@ -0,0 +1,53 @@
+// Copyright 2019 The Fuchsia Authors
+//
+// Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
+// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
+// license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
+// This file may not be copied, modified, or distributed except according to
+// those terms.
+
+use syn::{Data, DataEnum, DataStruct, DataUnion, Type};
+
+pub trait DataExt {
+    /// Extract the types of all fields. For enums, extract the types of fields
+    /// from each variant.
+    fn field_types(&self) -> Vec<&Type>;
+}
+
+impl DataExt for Data {
+    fn field_types(&self) -> Vec<&Type> {
+        match self {
+            Data::Struct(strc) => strc.field_types(),
+            Data::Enum(enm) => enm.field_types(),
+            Data::Union(un) => un.field_types(),
+        }
+    }
+}
+
+impl DataExt for DataStruct {
+    fn field_types(&self) -> Vec<&Type> {
+        self.fields.iter().map(|f| &f.ty).collect()
+    }
+}
+
+impl DataExt for DataEnum {
+    fn field_types(&self) -> Vec<&Type> {
+        self.variants.iter().flat_map(|var| &var.fields).map(|f| &f.ty).collect()
+    }
+}
+
+impl DataExt for DataUnion {
+    fn field_types(&self) -> Vec<&Type> {
+        self.fields.named.iter().map(|f| &f.ty).collect()
+    }
+}
+
+pub trait EnumExt {
+    fn is_c_like(&self) -> bool;
+}
+
+impl EnumExt for DataEnum {
+    fn is_c_like(&self) -> bool {
+        self.field_types().is_empty()
+    }
+}