Simplify resource path validation

Author: trask

javaagent-bootstrap/src/main/java/io/opentelemetry/javaagent/bootstrap/AgentClassLoader.java

@@ -288,9 +288,18 @@ private static boolean isNormalizedResourcePath(String resourceName) {
       return false;
     }
 
-    for (String segment : resourceName.split("/", -1)) {
-      if (segment.isEmpty() || segment.equals(".") || segment.equals("..")) {
-        return false;
+    int segmentStart = 0;
+    for (int i = 0; i <= resourceName.length(); i++) {
+      if (i == resourceName.length() || resourceName.charAt(i) == '/') {
+        int length = i - segmentStart;
+        if (length == 0
+            || (length == 1 && resourceName.charAt(segmentStart) == '.')
+            || (length == 2
+                && resourceName.charAt(segmentStart) == '.'
+                && resourceName.charAt(segmentStart + 1) == '.')) {
+          return false;
+        }
+        segmentStart = i + 1;
       }
     }
 

muzzle/src/main/java/io/opentelemetry/javaagent/tooling/muzzle/ReferenceCollector.java

@@ -134,9 +134,18 @@ private static boolean isNormalizedResourcePath(String resourceName) {
       return false;
     }
 
-    for (String segment : resourceName.split("/", -1)) {
-      if (segment.isEmpty() || segment.equals(".") || segment.equals("..")) {
-        return false;
+    int segmentStart = 0;
+    for (int i = 0; i <= resourceName.length(); i++) {
+      if (i == resourceName.length() || resourceName.charAt(i) == '/') {
+        int length = i - segmentStart;
+        if (length == 0
+            || (length == 1 && resourceName.charAt(segmentStart) == '.')
+            || (length == 2
+                && resourceName.charAt(segmentStart) == '.'
+                && resourceName.charAt(segmentStart + 1) == '.')) {
+          return false;
+        }
+        segmentStart = i + 1;
       }
     }