1 files changed, 143 insertions, 0 deletions
diff --git a/xpcom/rust/malloc_size_of_derive/lib.rs b/xpcom/rust/malloc_size_of_derive/lib.rs
new file mode 100644
index 0000000000..9179c93391
--- /dev/null
+++ b/xpcom/rust/malloc_size_of_derive/lib.rs
@@ -0,0 +1,143 @@
+// Copyright 2016-2017 The Servo Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! A crate for deriving the MallocSizeOf trait.
+
+extern crate proc_macro2;
+#[macro_use]
+extern crate syn;
+#[macro_use]
+extern crate synstructure;
+
+#[cfg(not(test))]
+decl_derive!([MallocSizeOf, attributes(ignore_malloc_size_of, conditional_malloc_size_of)] => malloc_size_of_derive);
+
+fn malloc_size_of_derive(s: synstructure::Structure) -> proc_macro2::TokenStream {
+    let match_body = s.each(|binding| {
+        let mut ignore = false;
+        let mut conditional = false;
+        for attr in binding.ast().attrs.iter() {
+            match attr.meta {
+                syn::Meta::Path(ref path) | syn::Meta::List(syn::MetaList { ref path, .. }) => {
+                    assert!(
+                        !path.is_ident("ignore_malloc_size_of"),
+                        "#[ignore_malloc_size_of] should have an explanation, \
+                         e.g. #[ignore_malloc_size_of = \"because reasons\"]"
+                    );
+                    if path.is_ident("conditional_malloc_size_of") {
+                        conditional = true;
+                    }
+                }
+                syn::Meta::NameValue(syn::MetaNameValue { ref path, .. }) => {
+                    if path.is_ident("ignore_malloc_size_of") {
+                        ignore = true;
+                    }
+                    if path.is_ident("conditional_malloc_size_of") {
+                        conditional = true;
+                    }
+                }
+            }
+        }
+
+        assert!(
+            !ignore || !conditional,
+            "ignore_malloc_size_of and conditional_malloc_size_of are incompatible"
+        );
+
+        if ignore {
+            return None;
+        }
+
+        let path = if conditional {
+            quote! { ::malloc_size_of::MallocConditionalSizeOf::conditional_size_of }
+        } else {
+            quote! { ::malloc_size_of::MallocSizeOf::size_of }
+        };
+
+        if let syn::Type::Array(..) = binding.ast().ty {
+            Some(quote! {
+                for item in #binding.iter() {
+                    sum += #path(item, ops);
+                }
+            })
+        } else {
+            Some(quote! {
+                sum += #path(#binding, ops);
+            })
+        }
+    });
+
+    let ast = s.ast();
+    let name = &ast.ident;
+    let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
+    let mut where_clause = where_clause.unwrap_or(&parse_quote!(where)).clone();
+    for param in ast.generics.type_params() {
+        let ident = &param.ident;
+        where_clause
+            .predicates
+            .push(parse_quote!(#ident: ::malloc_size_of::MallocSizeOf));
+    }
+
+    let tokens = quote! {
+        impl #impl_generics ::malloc_size_of::MallocSizeOf for #name #ty_generics #where_clause {
+            #[inline]
+            #[allow(unused_variables, unused_mut, unreachable_code)]
+            fn size_of(&self, ops: &mut ::malloc_size_of::MallocSizeOfOps) -> usize {
+                let mut sum = 0;
+                match *self {
+                    #match_body
+                }
+                sum
+            }
+        }
+    };
+
+    tokens
+}
+
+#[test]
+fn test_struct() {
+    let source = syn::parse_str(
+        "struct Foo<T> { bar: Bar, baz: T, #[ignore_malloc_size_of = \"\"] z: Arc<T> }",
+    )
+    .unwrap();
+    let source = synstructure::Structure::new(&source);
+
+    let expanded = malloc_size_of_derive(source).to_string();
+    let mut no_space = expanded.replace(" ", "");
+    macro_rules! match_count {
+        ($e: expr, $count: expr) => {
+            assert_eq!(
+                no_space.matches(&$e.replace(" ", "")).count(),
+                $count,
+                "counting occurences of {:?} in {:?} (whitespace-insensitive)",
+                $e,
+                expanded
+            )
+        };
+    }
+    match_count!("struct", 0);
+    match_count!("ignore_malloc_size_of", 0);
+    match_count!("impl<T> ::malloc_size_of::MallocSizeOf for Foo<T> where T: ::malloc_size_of::MallocSizeOf {", 1);
+    match_count!("sum += ::malloc_size_of::MallocSizeOf::size_of(", 2);
+
+    let source = syn::parse_str("struct Bar([Baz; 3]);").unwrap();
+    let source = synstructure::Structure::new(&source);
+    let expanded = malloc_size_of_derive(source).to_string();
+    no_space = expanded.replace(" ", "");
+    match_count!("for item in", 1);
+}
+
+#[should_panic(expected = "should have an explanation")]
+#[test]
+fn test_no_reason() {
+    let input = syn::parse_str("struct A { #[ignore_malloc_size_of] b: C }").unwrap();
+    malloc_size_of_derive(synstructure::Structure::new(&input));
+}