From 45c99f8f6b5a379ac304f6dd1c2ea891b4e3fdc6 Mon Sep 17 00:00:00 2001
From: David Majda <david@majda.cz>
Date: Sun, 18 Sep 2011 20:12:26 +0200
Subject: [PATCH] Generate more efficient code for empty literals

Original patch by Wolfgang Kluge:

  https://github.com/WolfgangKluge/pegjs/commit/797173f676805dad80ff96ea733f0d74f93d6664
---
 src/emitter.js |  8 ++++++++
 src/parser.js  | 20 ++------------------
 2 files changed, 10 insertions(+), 18 deletions(-)

diff --git a/src/emitter.js b/src/emitter.js
index 74ef92d..34e3157 100644
--- a/src/emitter.js
+++ b/src/emitter.js
@@ -710,6 +710,14 @@ PEG.compiler.emitter = function(ast) {
 
     literal: function(node, context) {
       var length = node.value.length;
+
+      if (length === 0) {
+        return formatCode(
+          "${resultVar} = '';",
+          { resultVar: resultVar(context.resultIndex) }
+        );
+      }
+
       var testCode = length === 1
         ? formatCode(
             "input.charCodeAt(pos) === ${valueCharCode}",
diff --git a/src/parser.js b/src/parser.js
index d065c46..11a156a 100644
--- a/src/parser.js
+++ b/src/parser.js
@@ -280,15 +280,7 @@ PEG.parser = (function(){
         if (result0 !== null) {
           result1 = parse_literal();
           if (result1 === null) {
-            if (input.substr(pos, 0) === "") {
-              result1 = "";
-              pos += 0;
-            } else {
-              result1 = null;
-              if (reportFailures === 0) {
-                matchFailed("\"\"");
-              }
-            }
+            result1 = '';
             
           }
           if (result1 !== null) {
@@ -837,15 +829,7 @@ PEG.parser = (function(){
           pos3 = pos;
           result1 = parse_literal();
           if (result1 === null) {
-            if (input.substr(pos, 0) === "") {
-              result1 = "";
-              pos += 0;
-            } else {
-              result1 = null;
-              if (reportFailures === 0) {
-                matchFailed("\"\"");
-              }
-            }
+            result1 = '';
             
           }
           if (result1 !== null) {