1 files changed, 39 insertions, 0 deletions
diff --git a/third_party/rust/cssparser-macros/lib.rs b/third_party/rust/cssparser-macros/lib.rs
new file mode 100644
index 0000000000..971c03048d
--- /dev/null
+++ b/third_party/rust/cssparser-macros/lib.rs
@@ -0,0 +1,39 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+#[proc_macro]
+pub fn _cssparser_internal_max_len(input: TokenStream) -> TokenStream {
+    struct Input {
+        max_length: usize,
+    }
+
+    impl syn::parse::Parse for Input {
+        fn parse(input: syn::parse::ParseStream) -> syn::parse::Result<Self> {
+            let mut max_length = 0;
+            while !input.is_empty() {
+                if input.peek(syn::Token![_]) {
+                    input.parse::<syn::Token![_]>().unwrap();
+                    continue;
+                }
+                let lit: syn::LitStr = input.parse()?;
+                let value = lit.value();
+                if value.to_ascii_lowercase() != value {
+                    return Err(syn::Error::new(lit.span(), "must be ASCII-lowercase"));
+                }
+                max_length = max_length.max(value.len());
+            }
+            Ok(Input { max_length })
+        }
+    }
+
+    let Input { max_length } = syn::parse_macro_input!(input);
+    quote::quote!(
+        pub(super) const MAX_LENGTH: usize = #max_length;
+    )
+    .into()
+}