Avoid using Pattern and Streams in UnionPath init

Speeds up creation of UnionPath significantly. Reduces time spend in testJarFileExists from 7585 to 2777, other tests like testCommonPathUtilities see improvements as well

Author: ichttt

src/main/java/cpw/mods/niofs/union/UnionPath.java

@@ -9,26 +9,16 @@
 import java.nio.file.WatchKey;
 import java.nio.file.WatchService;
 import java.util.ArrayDeque;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Deque;
+import java.util.List;
 import java.util.Objects;
+import java.util.StringJoiner;
 import java.util.function.IntBinaryOperator;
-import java.util.regex.Pattern;
-import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
 public class UnionPath implements Path {
-    private static final Pattern SEPARATOR_BEGIN_END;
-    private static final Pattern SEPARATOR_DUPLICATES;
-
-    private static final Pattern SEPARATOR_SPLIT;
-
-    static {
-        var sep = "(?:"+ Pattern.quote(UnionFileSystem.SEP_STRING) + ")";
-        SEPARATOR_BEGIN_END = Pattern.compile("^" + sep + "*|" + sep + "*$");
-        SEPARATOR_DUPLICATES = Pattern.compile(sep + "(?=" + sep + ")");
-        SEPARATOR_SPLIT = Pattern.compile(sep);
-    }
     private final UnionFileSystem fileSystem;
     private final boolean absolute;
     private final String[] pathParts;
@@ -42,9 +32,13 @@ public class UnionPath implements Path {
             this.absolute = false;
             this.pathParts = new String[0];
         } else {
-            final var longstring = Arrays.stream(pathParts)
-                    .filter(part -> !part.isEmpty())
-                    .collect(Collectors.joining(UnionFileSystem.SEP_STRING));
+            StringJoiner joiner = new StringJoiner(UnionFileSystem.SEP_STRING);
+            for (String element : pathParts) {
+                if (!element.isEmpty()) {
+                    joiner.add(element);
+                }
+            }
+            final var longstring = joiner.toString();
             this.absolute = longstring.startsWith(UnionFileSystem.SEP_STRING);
             this.pathParts = getPathParts(longstring);
         }
@@ -67,13 +61,22 @@ private UnionPath(final UnionFileSystem fileSystem, boolean absolute, boolean is
     }
 
     private String[] getPathParts(final String longstring) {
-        var clean = longstring.replace("\\", UnionFileSystem.SEP_STRING);
-        clean = SEPARATOR_BEGIN_END.matcher(clean).replaceAll("");
-        clean = SEPARATOR_DUPLICATES.matcher(clean).replaceAll("");
-        if (clean.isEmpty())
-            return new String[0];
-        else
-            return SEPARATOR_SPLIT.split(clean);
+        var clean = longstring.replace('\\', '/');
+        int startIndex = 0;
+        List<String> parts = new ArrayList<>();
+        while (startIndex != longstring.length()) {
+            int index = clean.indexOf('/', startIndex);
+            if (index == -1) {
+                parts.add(clean.substring(startIndex));
+                break;
+            }
+            // Skips double slash and slash and start/end
+            if (index != startIndex) {
+                parts.add(clean.substring(startIndex, index));
+            }
+            startIndex = (index + 1);
+        }
+        return parts.toArray(String[]::new);
     }
 
     @Override

src/test/java/cpw/mods/niofs/union/TestUnionPath.java

@@ -40,9 +40,11 @@ void testUnionPath() {
         var abs123 = fs.getPath("/one/two/three");
         var abs1223 = fs.getPath("/one/two/./three");
         var abs12up3 = fs.getPath("/one/two/../three");
+        var abs12up3otherslash = fs.getPath("/one/two/..\\three");
         var abs13 = fs.getPath("/one/three");
         var abs13slash = fs.getPath("/one/three/");
         var abs1slash3 = fs.getPath("/one//three");
+        var abs1otherslash3 = fs.getPath("/one\\/three");
         var absUpUp1 = fs.getPath("/../../one");
         var absUpUp123 = fs.getPath("/../../one/two/three");
 
@@ -51,6 +53,8 @@ void testUnionPath() {
         assertEquals(rel13, rel1slash3);
         assertEquals(abs13, abs13slash);
         assertEquals(abs13, abs1slash3);
+        assertEquals(abs13, abs1otherslash3);
+        assertEquals(abs12up3, abs12up3otherslash);
         // Not filtering out empty elements for joining will cause this to fail
         assertFalse(fs.getPath("", "one", "two").isAbsolute());