From c4155aa62265cb152338da7e07b1f57203cd694f Mon Sep 17 00:00:00 2001
From: Daniil Ovchinnikov <daniil.ovchinnikov@jetbrains.com>
Date: Thu, 28 Jun 2018 17:21:46 +0300
Subject: [PATCH] fix SIOOBE in StringUtil#startsWith

---
 .../openapi/util/text/StringUtil.java         |  1 +
 .../intellij/util/text/StringUtilTest.java    | 34 ++++++++++++++++++-
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/platform/util/src/com/intellij/openapi/util/text/StringUtil.java b/platform/util/src/com/intellij/openapi/util/text/StringUtil.java
index f9493ed6238d..83e74f2d1557 100644
--- a/platform/util/src/com/intellij/openapi/util/text/StringUtil.java
+++ b/platform/util/src/com/intellij/openapi/util/text/StringUtil.java
@@ -1835,6 +1835,7 @@ public class StringUtil extends StringUtilRt {
 
   @Contract(pure = true)
   public static boolean startsWith(@NotNull CharSequence text, int startIndex, @NotNull CharSequence prefix) {
+    if (startIndex < 0) return false;
     int l1 = text.length() - startIndex;
     int l2 = prefix.length();
     if (l1 < l2) return false;
diff --git a/platform/util/testSrc/com/intellij/util/text/StringUtilTest.java b/platform/util/testSrc/com/intellij/util/text/StringUtilTest.java
index 84de2cb6ee4a..be5e58c3e2b1 100644
--- a/platform/util/testSrc/com/intellij/util/text/StringUtilTest.java
+++ b/platform/util/testSrc/com/intellij/util/text/StringUtilTest.java
@@ -1,4 +1,4 @@
-// Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package com.intellij.util.text;
 
 import com.intellij.openapi.util.Comparing;
@@ -684,4 +684,36 @@ public class StringUtilTest {
     assertFalse(StringUtil.isShortNameOf("x.y.zzz", "zz"));
     assertFalse(StringUtil.isShortNameOf("x", "a.b.x"));
   }
+
+  @Test
+  public void testStartsWith() {
+    assertTrue(StringUtil.startsWith("abcdefgh", 5, "fgh"));
+    assertTrue(StringUtil.startsWith("abcdefgh", 2, "cde"));
+    assertTrue(StringUtil.startsWith("abcdefgh", 0, "abc"));
+    assertTrue(StringUtil.startsWith("abcdefgh", 0, "abcdefgh"));
+    assertFalse(StringUtil.startsWith("abcdefgh", 5, "cde"));
+
+    assertFalse(StringUtil.startsWith("abcdefgh", -100, ""));
+    assertFalse(StringUtil.startsWith("abcdefgh", -1, ""));
+    assertTrue(StringUtil.startsWith("abcdefgh", 0, ""));
+    assertTrue(StringUtil.startsWith("abcdefgh", 4, ""));
+    assertTrue(StringUtil.startsWith("abcdefgh", 7, ""));
+    assertTrue(StringUtil.startsWith("abcdefgh", 8, ""));
+    assertFalse(StringUtil.startsWith("abcdefgh", 9, ""));
+    assertFalse(StringUtil.startsWith("abcdefgh", 100, ""));
+
+    assertFalse(StringUtil.startsWith("", -100, ""));
+    assertFalse(StringUtil.startsWith("", -1, ""));
+    assertTrue(StringUtil.startsWith("", 0, ""));
+    assertFalse(StringUtil.startsWith("", 1, ""));
+    assertFalse(StringUtil.startsWith("", 100, ""));
+
+    assertFalse(StringUtil.startsWith("ab", -100, "abcdefgh"));
+    assertFalse(StringUtil.startsWith("ab", -1, "abcdefgh"));
+    assertFalse(StringUtil.startsWith("ab", 0, "abcdefgh"));
+    assertFalse(StringUtil.startsWith("ab", 1, "abcdefgh"));
+    assertFalse(StringUtil.startsWith("ab", 2, "abcdefgh"));
+    assertFalse(StringUtil.startsWith("ab", 3, "abcdefgh"));
+    assertFalse(StringUtil.startsWith("ab", 100, "abcdefgh"));
+  }
 }