Generate NullSafeHandle.NullHandle helper field

jnm2 · Feb 16, 2021 · b34a12d · b34a12d
1 parent 89267f2
commit b34a12d
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Showing 2 changed files with 38 additions and 1 deletion.
diff --git a/src/Microsoft.Windows.CsWin32/Generator.cs b/src/Microsoft.Windows.CsWin32/Generator.cs
@@ -255,6 +255,8 @@ public class Generator : IDisposable
         private readonly CSharpCompilation? compilation;
         private readonly CSharpParseOptions? parseOptions;
 
+        private bool nullSafeHandleGenerated;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Generator"/> class.
         /// </summary>
@@ -820,6 +822,8 @@ internal void GenerateConstant(FieldDefinitionHandle fieldDefHandle)
 
         internal TypeSyntax? GenerateSafeHandle(string releaseMethod)
         {
+            this.GenerateNullSafeHandleHelper();
+
             if (this.releaseMethodsWithSafeHandleTypesGenerating.TryGetValue(releaseMethod, out TypeSyntax? safeHandleType))
             {
                 return safeHandleType;
@@ -1413,6 +1417,39 @@ private static bool IsAnsiFunction(string methodName)
             return false;
         }
 
+        private void GenerateNullSafeHandleHelper()
+        {
+            if (this.nullSafeHandleGenerated)
+            {
+                return;
+            }
+
+            this.nullSafeHandleGenerated = true;
+
+            const string className = "NullSafeHandle";
+            string fullName = $"{this.Namespace}.{className}";
+            if (this.FindSymbolIfAlreadyAvailable(fullName) is object)
+            {
+                return;
+            }
+
+            // static readonly SafeHandle NullHandle = new SafeFileHandle(IntPtr.Zero, ownsHandle: false);
+            FieldDeclarationSyntax nullHandle = FieldDeclaration(
+                VariableDeclaration(SafeHandleTypeSyntax)
+                    .AddVariables(VariableDeclarator("NullHandle").WithInitializer(EqualsValueClause(
+                        ObjectCreationExpression(ParseTypeName("Microsoft.Win32.SafeHandles.SafeFileHandle")).AddArgumentListArguments(
+                                Argument(DefaultExpression(IntPtrTypeSyntax)),
+                                Argument(LiteralExpression(SyntaxKind.FalseLiteralExpression)))))))
+                .AddModifiers(Token(this.Visibility), Token(SyntaxKind.StaticKeyword), Token(SyntaxKind.ReadOnlyKeyword));
+
+            // static class NullSafeHandle { ... }
+            ClassDeclarationSyntax helper = ClassDeclaration(className)
+                .AddModifiers(Token(this.Visibility), Token(SyntaxKind.StaticKeyword))
+                .AddMembers(nullHandle);
+
+            this.safeHandleTypes.Add(helper);
+        }
+
         private FunctionPointerTypeSyntax FunctionPointer(CallingConvention callingConvention, MethodSignature<TypeSyntax> signature, string delegateName)
             => FunctionPointerType(
                 FunctionPointerCallingConvention(Token(SyntaxKind.UnmanagedKeyword), FunctionPointerUnmanagedCallingConventionList(SingletonSeparatedList(ToUnmanagedCallingConventionSyntax(callingConvention)))),

diff --git a/test/GenerationSandbox.Tests/BasicTests.cs b/test/GenerationSandbox.Tests/BasicTests.cs
@@ -128,7 +128,7 @@ public void CreateFile()
             lpSecurityAttributes: null,
             FILE_CREATE_FLAGS.CREATE_NEW,
             FILE_FLAGS_AND_ATTRIBUTES.FILE_ATTRIBUTE_TEMPORARY | (FILE_FLAGS_AND_ATTRIBUTES)FILE_FLAG_DELETE_ON_CLOSE,
-            hTemplateFile: CloseHandleSafeHandle.Null);
+            hTemplateFile: NullSafeHandle.NullHandle);
         Assert.True(File.Exists(path));
         fileHandle.Dispose();
         Assert.False(File.Exists(path));