use static to avoid recreating Finder every time

Author: diana-qing

filtergen/src/utils.rs

@@ -154,8 +154,15 @@ pub(crate) fn binary_to_tokens(
                 }
                 BinOp::Contains => {
                     let val_lit = syn::LitStr::new(text, Span::call_site());
+                    
+                    let finder_name = format!("FINDER{}", statics.len());
+                    let finder_ident = Ident::new(&finder_name, Span::call_site());
+                    let lazy_finder = quote! {
+                        static ref #finder_ident: memchr::memmem::Finder<'static> = memchr::memmem::Finder::new(#val_lit.as_bytes());
+                    };
+                    statics.push(lazy_finder);
                     quote! {
-                        memchr::memmem::Finder::new(#val_lit.as_bytes()).find(#proto.#field().as_bytes()).is_some()
+                        #finder_ident.find(#proto.#field().as_bytes()).is_some()
                     }
                 }
                 _ => panic!("Invalid binary operation `{}` for value: `{}`.", op, value),
@@ -170,8 +177,15 @@ pub(crate) fn binary_to_tokens(
             }
             BinOp::Contains => {
                 let bytes_lit = syn::LitByteStr::new(b, Span::call_site());
+                
+                let finder_name = format!("FINDER{}", statics.len());
+                let finder_ident = Ident::new(&finder_name, Span::call_site());
+                let lazy_finder = quote! {
+                    static ref #finder_ident: memchr::memmem::Finder<'static> = memchr::memmem::Finder::new(#bytes_lit);
+                };
+                statics.push(lazy_finder);
                 quote! {
-                    memchr::memmem::Finder::new(#bytes_lit).find(#proto.#field().as_ref()).is_some()
+                    #finder_ident.find(#proto.#field().as_ref()).is_some()
                 }
             }
             _ => panic!("Invalid binary operation `{}` for value: `{}`.", op, value),