From 42deff2c7a2fb749a4e509deea339632f3048770 Mon Sep 17 00:00:00 2001
From: Alexey Kudravtsev <cdr@intellij.com>
Date: Thu, 4 Mar 2021 23:49:19 +0100
Subject: [PATCH] a bit of performance: reduce allocation

GitOrigin-RevId: e686767e0d5fe6182499491a72e7c241ace23b94
---
 .../src/com/intellij/openapi/vfs/VfsUtilCore.java | 15 +++++++--------
 .../com/intellij/openapi/vfs/VfsUtilTest.java     | 15 +++++++--------
 .../src/com/intellij/util/text/CharArrayUtil.java | 12 ++++++++++++
 3 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/platform/core-api/src/com/intellij/openapi/vfs/VfsUtilCore.java b/platform/core-api/src/com/intellij/openapi/vfs/VfsUtilCore.java
index 4791e1b16c5f..16911b51bf15 100644
--- a/platform/core-api/src/com/intellij/openapi/vfs/VfsUtilCore.java
+++ b/platform/core-api/src/com/intellij/openapi/vfs/VfsUtilCore.java
@@ -20,6 +20,7 @@ import com.intellij.util.Processor;
 import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.containers.DistinctRootsCollection;
 import com.intellij.util.io.URLUtil;
+import com.intellij.util.text.CharArrayUtil;
 import org.jetbrains.annotations.*;
 
 import java.io.*;
@@ -731,19 +732,17 @@ public class VfsUtilCore {
     path = FileUtil.toCanonicalPath(path);
     int li = path.length();
     while (file != null && li != -1) {
-      int i = path.lastIndexOf('/', li - 1);
+      int sepIndex = path.lastIndexOf('/', li - 1);
       CharSequence fileName = file.getNameSequence();
-      if (i == 6 && StringUtil.startsWith(fileName, "//wsl$")) {
-        i = -1;
+      int fileNameEnd = fileName.length() + (StringUtil.endsWithChar(fileName, '/') ? -1 : 0);
+      if (sepIndex == 6 && StringUtil.startsWith(fileName, "//wsl$")) {
+        sepIndex = -1;
       }
-      if (StringUtil.endsWithChar(fileName, '/')) {
-        fileName = fileName.subSequence(0, fileName.length() - 1);
-      }
-      if (!StringUtilRt.equal(fileName, path.substring(i + 1, li), file.isCaseSensitive())) {
+      if (!CharArrayUtil.regionMatches(fileName, 0, fileNameEnd, path, sepIndex + 1, li, file.isCaseSensitive())) {
         return false;
       }
       file = file.getParent();
-      li = i;
+      li = sepIndex;
     }
     return li == -1 && file == null;
   }
diff --git a/platform/platform-tests/testSrc/com/intellij/openapi/vfs/VfsUtilTest.java b/platform/platform-tests/testSrc/com/intellij/openapi/vfs/VfsUtilTest.java
index 50d228e2b1cc..4d43533cac57 100644
--- a/platform/platform-tests/testSrc/com/intellij/openapi/vfs/VfsUtilTest.java
+++ b/platform/platform-tests/testSrc/com/intellij/openapi/vfs/VfsUtilTest.java
@@ -58,7 +58,6 @@ import java.util.stream.Stream;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.*;
-import static org.junit.Assume.assumeFalse;
 import static org.junit.Assume.assumeTrue;
 
 public class VfsUtilTest extends BareTestFixtureTestCase {
@@ -555,12 +554,12 @@ public class VfsUtilTest extends BareTestFixtureTestCase {
     assumeTrue("No WSL distributions found", !distributions.isEmpty());
 
     String wslName = distributions.get(0);
-
-    VirtualFile file = LocalFileSystem.getInstance().findFileByIoFile(new File("\\\\wsl$\\" + wslName + "\\usr\\bin\\"));
-    assertTrue(VfsUtilCore.pathEqualsTo(file, "\\\\wsl$\\" + wslName + "\\usr\\bin\\"));
-    assertTrue(VfsUtilCore.pathEqualsTo(file, "//wsl$/" + wslName + "/usr/bin"));
-    assertTrue(VfsUtilCore.pathEqualsTo(file, "//wsl$/" + wslName + "/usr/bin/"));
-    assertFalse(VfsUtilCore.pathEqualsTo(file, "//xxx$/" + wslName + "/usr/bin/"));
-    assertFalse(VfsUtilCore.pathEqualsTo(file, "//wsl$/xxx/usr/bin/"));
+    VirtualFile usrBin = LocalFileSystem.getInstance().findFileByIoFile(new File("\\\\wsl$\\" + wslName + "\\usr\\bin\\"));
+    assertTrue(VfsUtilCore.pathEqualsTo(usrBin, "\\\\wsl$\\" + wslName + "\\usr\\bin\\"));
+    assertTrue(VfsUtilCore.pathEqualsTo(usrBin, "//wsl$/" + wslName + "/usr/bin"));
+    assertTrue(VfsUtilCore.pathEqualsTo(usrBin, "//wsl$/" + wslName + "/usr/bin/"));
+    assertFalse(VfsUtilCore.pathEqualsTo(usrBin, "//xxx$/" + wslName + "/usr/bin/"));
+    assertFalse(VfsUtilCore.pathEqualsTo(usrBin, "//wsl$/xxx/usr/bin/"));
+    assertFalse(VfsUtilCore.pathEqualsTo(usrBin.getParent(), "//wsl$/xxx/usr"));
   }
 }
\ No newline at end of file
diff --git a/platform/util/strings/src/com/intellij/util/text/CharArrayUtil.java b/platform/util/strings/src/com/intellij/util/text/CharArrayUtil.java
index 2cc855d28e27..45ce572bf9cc 100644
--- a/platform/util/strings/src/com/intellij/util/text/CharArrayUtil.java
+++ b/platform/util/strings/src/com/intellij/util/text/CharArrayUtil.java
@@ -2,6 +2,7 @@
 package com.intellij.util.text;
 
 import com.intellij.openapi.util.TextRange;
+import com.intellij.openapi.util.text.StringUtilRt;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -296,6 +297,17 @@ public final class CharArrayUtil {
     }
     return true;
   }
+  public static boolean regionMatches(@NotNull CharSequence s1, int start1, int end1, @NotNull CharSequence s2, int start2, int end2, boolean caseSensitive) {
+    if (caseSensitive) {
+      return regionMatches(s1, start1, end1, s2, start2, end2);
+    }
+    if (end1-start1 != end2-start2) return false;
+
+    for (int i = start1,j=start2; i < end1; i++,j++) {
+      if (!StringUtilRt.charsEqualIgnoreCase(s1.charAt(i), s2.charAt(j))) return false;
+    }
+    return true;
+  }
 
   public static boolean regionMatches(@NotNull CharSequence buffer, int offset, @NotNull CharSequence s) {
     if (offset + s.length() > buffer.length()) return false;