From 3526cd29c4c3686eef47665d83c3707b2e1cc620 Mon Sep 17 00:00:00 2001
From: Bazaah <github@luxolus.com>
Date: Wed, 16 Jun 2021 15:24:44 +0000
Subject: [PATCH] scanner/macros: allow advance! to update a var with $amount
 consumed

---
 src/scanner/macros.rs | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/scanner/macros.rs b/src/scanner/macros.rs
index 4a51a91..f65a12e 100644
--- a/src/scanner/macros.rs
+++ b/src/scanner/macros.rs
@@ -1,17 +1,25 @@
 /// Moves head in $buffer $amount forward
 macro_rules! advance {
-    ($buffer:expr, $amount:expr) => {
+    ($buffer:expr, $amount:expr $(, $var:ident )? ) => {
         let (_, rest) = $buffer.split_at($amount);
 
+        $( advance!(@update $var, $amount); )?
+
         $buffer = rest
     };
-    (<- $buffer:expr, $amount:expr) => {{
+    (<- $buffer:expr, $amount:expr $(, $var:ident )? ) => {{
         let (cut, rest) = $buffer.split_at($amount);
 
         $buffer = rest;
 
+        $( advance!(@update $var, $amount) )?
+
         cut
     }};
+
+    (@update $( $var:ident, $amount:expr)? ) => {
+          $({ $var += $amount } )?
+    };
 }
 
 /// New cow pointer from the given expr