Improve performance of RegistryKey.GetValue (#66918)

Reduces typical number of syscalls as well as avoids allocation (or uses the ArrayPool otherwise).

Also updates Corelib's copy of RegistryKey to match (with things like perf key support removed).

Author: stephentoub

src/libraries/Common/src/Interop/Windows/Advapi32/Interop.RegQueryValueEx.cs

@@ -22,30 +22,12 @@ internal static partial int RegQueryValueEx(
             ref int lpcbData);
 
         [LibraryImport(Libraries.Advapi32, EntryPoint = "RegQueryValueExW", StringMarshalling = StringMarshalling.Utf16)]
-        internal static partial int RegQueryValueEx(
-            SafeRegistryHandle hKey,
-            string? lpValueName,
-            int[]? lpReserved,
-            ref int lpType,
-            ref int lpData,
-            ref int lpcbData);
-
-        [LibraryImport(Libraries.Advapi32, EntryPoint = "RegQueryValueExW", StringMarshalling = StringMarshalling.Utf16)]
-        internal static partial int RegQueryValueEx(
-            SafeRegistryHandle hKey,
-            string? lpValueName,
-            int[]? lpReserved,
-            ref int lpType,
-            ref long lpData,
-            ref int lpcbData);
-
-        [LibraryImport(Libraries.Advapi32, EntryPoint = "RegQueryValueExW", StringMarshalling = StringMarshalling.Utf16)]
-        internal static partial int RegQueryValueEx(
+        internal static unsafe partial int RegQueryValueEx(
             SafeRegistryHandle hKey,
             string? lpValueName,
-            int[]? lpReserved,
-            ref int lpType,
-            [Out] char[]? lpData,
-            ref int lpcbData);
+            int* lpReserved,
+            int* lpType,
+            byte* lpData,
+            uint* lpcbData);
     }
 }

src/libraries/Microsoft.Win32.Registry/src/Microsoft/Win32/RegistryKey.Windows.cs

@@ -1,4 +1,5 @@
-<root>
+<?xml version="1.0" encoding="utf-8"?>
+<root>
   <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
     <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
     <xsd:element name="root" msdata:IsDataSet="true">
@@ -84,8 +85,8 @@
   <data name="Arg_RegBadKeyKind" xml:space="preserve">
     <value>The specified RegistryValueKind is an invalid value.</value>
   </data>
-  <data name="Arg_RegGetOverflowBug" xml:space="preserve">
-    <value>RegistryKey.GetValue does not allow a String that has a length greater than Int32.MaxValue.</value>
+  <data name="Arg_RegValueTooLarge" xml:space="preserve">
+    <value>RegistryKey.GetValue does not support values with more than Int32.MaxValue bytes.</value>
   </data>
   <data name="Arg_RegSetMismatchedKind" xml:space="preserve">
     <value>The type of the value object did not match the specified RegistryValueKind or the object could not be properly converted.</value>
@@ -135,4 +136,4 @@
   <data name="UnauthorizedAccess_RegistryNoWrite" xml:space="preserve">
     <value>Cannot write to the registry key.</value>
   </data>
-</root>
+</root>

src/libraries/Microsoft.Win32.Registry/src/Resources/Strings.resx

@@ -44,10 +44,13 @@ public void ReadRegMultiSzLackingFinalNullTerminatorCorrectly()
         }
 
         [Theory]
-        [InlineData(RegistryValueKind.String, new byte[] { 6, 5, 6 })]
-        [InlineData(RegistryValueKind.ExpandString, new byte[] { 6, 5, 6 })]
-        [InlineData(RegistryValueKind.MultiString, new byte[] { 6, 5, 6, 0, 0 })]
-        public void RegSzOddByteLength(RegistryValueKind kind, byte[] contents)
+        [InlineData(RegistryValueKind.String, new byte[] { 6, 5, 6 }, "\u0506")]
+        [InlineData(RegistryValueKind.ExpandString, new byte[] { 6, 5, 6 }, "\u0506")]
+        [InlineData(RegistryValueKind.MultiString, new byte[] { 6, 5, 6 }, "\u0506")]
+        [InlineData(RegistryValueKind.String, new byte[] { 6, 5, 6, 0, 0 }, "\u0506\u0006")]
+        [InlineData(RegistryValueKind.ExpandString, new byte[] { 6, 5, 6, 0, 0 }, "\u0506\u0006")]
+        [InlineData(RegistryValueKind.MultiString, new byte[] { 6, 5, 6, 0, 0 }, "\u0506\u0006")]
+        public void RegSzOddByteLength(RegistryValueKind kind, byte[] contents, string expected)
         {
             const string TestValueName = "CorruptData2";
 
@@ -73,9 +76,7 @@ public void RegSzOddByteLength(RegistryValueKind kind, byte[] contents)
                     s = (string)o;
                 }
 
-                Assert.Equal(2, s.Length);
-                Assert.Equal(0x506, s[0]);
-                Assert.Equal(0x6, s[1]);
+                Assert.Equal(expected, s);
             }
             finally
             {

src/libraries/Microsoft.Win32.Registry/tests/RegistryKey/RegistryKey_GetValue_CorruptData.cs

@@ -86,5 +86,12 @@ public void GetStringArrayTest()
             Assert.Equal(expected, (string[])TestRegistryKey.GetValue(valueName));
             TestRegistryKey.DeleteValue(valueName);
         }
+
+        [Fact]
+        public void GetPerformanceKeyValue()
+        {
+            string[] counterNames = (string[])Registry.PerformanceData.GetValue("Counter");
+            Assert.NotEmpty(counterNames);
+        }
     }
 }