From 25fc1191fdc62a43dede30c87edc5c3eb5d5cae7 Mon Sep 17 00:00:00 2001
From: franz1981 <nigro.fra@gmail.com>
Date: Wed, 13 Mar 2024 15:40:39 -0400
Subject: [PATCH] Reduce allocations and batch appends on
 StringUtil::replaceNonAlphanumericByUnderscores

---
 .../config/common/utils/StringUtil.java       | 26 +++++++++++++++----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/common/src/main/java/io/smallrye/config/common/utils/StringUtil.java b/common/src/main/java/io/smallrye/config/common/utils/StringUtil.java
index 6faefd8f3..9c15f7594 100644
--- a/common/src/main/java/io/smallrye/config/common/utils/StringUtil.java
+++ b/common/src/main/java/io/smallrye/config/common/utils/StringUtil.java
@@ -94,21 +94,37 @@ public static boolean isAsciiLetterOrDigit(char c) {
     }
 
     public static String replaceNonAlphanumericByUnderscores(final String name) {
-        return replaceNonAlphanumericByUnderscores(name, new StringBuilder(name.length()));
+        return replaceNonAlphanumericByUnderscores(name, null);
     }
 
-    public static String replaceNonAlphanumericByUnderscores(final String name, final StringBuilder sb) {
+    public static String replaceNonAlphanumericByUnderscores(final String name, StringBuilder sb) {
         int length = name.length();
+        int copyIndex = -1;
         for (int i = 0; i < length; i++) {
             char c = name.charAt(i);
-            if (isAsciiLetterOrDigit(c)) {
-                sb.append(c);
-            } else {
+            if (!isAsciiLetterOrDigit(c)) {
+                if (sb == null) {
+                    sb = new StringBuilder(name.length());
+                }
+                if (copyIndex != -1) {
+                    sb.append(name, copyIndex, i);
+                    copyIndex = -1;
+                }
                 sb.append('_');
                 if (c == '"' && i + 1 == length) {
                     sb.append('_');
                 }
+            } else {
+                if (copyIndex == -1) {
+                    copyIndex = i;
+                }
+            }
+        }
+        if (copyIndex != -1) {
+            if (sb == null) {
+                return name;
             }
+            sb.append(name, copyIndex, length);
         }
         return sb.toString();
     }