Bug 1695817 - Part 1: Make nt::GetLeafName accept nsAString r=mhowell

Differential Revision: https://phabricator.services.mozilla.com/D109302

mozglue/misc/NativeNt.h

@@ -471,11 +471,20 @@ inline void GetLeafName(PUNICODE_STRING aDestString,
 
 #if defined(MOZILLA_INTERNAL_API)
 
-inline const nsDependentSubstring GetLeafName(const nsString& aString) {
-  int32_t lastBackslashPos = aString.RFindChar(L'\\');
-  int32_t leafStartPos =
-      (lastBackslashPos == kNotFound) ? 0 : (lastBackslashPos + 1);
-  return Substring(aString, leafStartPos);
+inline const nsDependentSubstring GetLeafName(const nsAString& aString) {
+  auto it = aString.EndReading();
+  size_t pos = aString.Length();
+  while (it > aString.BeginReading()) {
+    if (*(it - 1) == u'\\') {
+      return Substring(aString, pos);
+    }
+
+    MOZ_ASSERT(pos > 0);
+    --pos;
+    --it;
+  }
+
+  return Substring(aString, 0);  // No backslash in the string
 }
 
 #endif  // defined(MOZILLA_INTERNAL_API)

mozglue/tests/gtest/TestNativeNtGTest.cpp

@@ -25,3 +25,39 @@ TEST(TestNativeNtGTest, GenerateDependentModuleSet)
   EXPECT_TRUE(dependentModules.Contains(u"MOZGLUE.dll"_ns));
   EXPECT_FALSE(dependentModules.Contains(u"xxx.dll"_ns));
 }
+
+TEST(TestNativeNtGTest, GetLeafName)
+{
+  nsAutoString str;
+  str = mozilla::nt::GetLeafName(u""_ns);
+  EXPECT_STREQ(str.get(), L"");
+  str = mozilla::nt::GetLeafName(u"\\"_ns);
+  EXPECT_STREQ(str.get(), L"");
+  str = mozilla::nt::GetLeafName(u"\\\\"_ns);
+  EXPECT_STREQ(str.get(), L"");
+  str = mozilla::nt::GetLeafName(u"abc\\def\\ghi"_ns);
+  EXPECT_STREQ(str.get(), L"ghi");
+  str = mozilla::nt::GetLeafName(u"abcdef"_ns);
+  EXPECT_STREQ(str.get(), L"abcdef");
+  str = mozilla::nt::GetLeafName(u"\\abcdef"_ns);
+  EXPECT_STREQ(str.get(), L"abcdef");
+
+  const auto kEntireText =
+      u"\\"_ns
+      u"\\\\abc"_ns
+      u"\\x\\y\\z"_ns
+      u"123\\456\\"_ns
+      u"789"_ns;
+  str = mozilla::nt::GetLeafName(Substring(kEntireText, 0, 0));
+  EXPECT_STREQ(str.get(), L"");
+  str = mozilla::nt::GetLeafName(Substring(kEntireText, 0, 1));
+  EXPECT_STREQ(str.get(), L"");
+  str = mozilla::nt::GetLeafName(Substring(kEntireText, 1, 5));
+  EXPECT_STREQ(str.get(), L"abc");
+  str = mozilla::nt::GetLeafName(Substring(kEntireText, 6, 6));
+  EXPECT_STREQ(str.get(), L"z");
+  str = mozilla::nt::GetLeafName(Substring(kEntireText, 12, 8));
+  EXPECT_STREQ(str.get(), L"");
+  str = mozilla::nt::GetLeafName(Substring(kEntireText, 20));
+  EXPECT_STREQ(str.get(), L"789");
+}