Array marshalling (mono#1748)

* Generator: Customization for const char[]

Allow the user to choose whether `const char[]` should be marshalled as
`string` or a normal `char` array in C#.

A new option `MarshalConstCharArrayAsString` is added, and is `true`
by default.

This helps in situations where the original C++ API distinguishes
between C-strings and char arrays using the two different notations.

* CSharpMarshal: Fix unknown length array marshal

For unknown length arrays, also run a conversion loop if the primitive
type encountered needs conversion (e.g. `char` to `sbyte`).

* CSharpTypePrinter: Fix for boolean arrays

Author: trungnt2910

src/Generator/Generators/CLI/CLIMarshal.cs

@@ -61,7 +61,8 @@ public override bool VisitArrayType(ArrayType array, TypeQualifiers quals)
                     break;
                 case ArrayType.ArraySize.Incomplete:
                     // const char* and const char[] are the same so we can use a string
-                    if (array.Type.Desugar().IsPrimitiveType(PrimitiveType.Char) &&
+                    if (Context.Context.Options.MarshalConstCharArrayAsString &&
+                        array.Type.Desugar().IsPrimitiveType(PrimitiveType.Char) &&
                         array.QualifiedType.Qualifiers.IsConst)
                     {
                         var pointer = new PointerType { QualifiedPointee = array.QualifiedType };

src/Generator/Generators/CLI/CLITypePrinter.cs

@@ -35,7 +35,8 @@ public override TypePrinterResult VisitArrayType(ArrayType array,
             TypeQualifiers quals)
         {
             // const char* and const char[] are the same so we can use a string
-            if (array.SizeType == ArrayType.ArraySize.Incomplete &&
+            if (Context.Options.MarshalConstCharArrayAsString &&
+                array.SizeType == ArrayType.ArraySize.Incomplete &&
                 array.Type.Desugar().IsPrimitiveType(PrimitiveType.Char) &&
                 array.QualifiedType.Qualifiers.IsConst)
                 return VisitCILType(new CILType(typeof(string)), quals);

src/Generator/Generators/CSharp/CSharpMarshal.cs

@@ -116,7 +116,8 @@ public override bool VisitArrayType(ArrayType array, TypeQualifiers quals)
                     break;
                 case ArrayType.ArraySize.Incomplete:
                     // const char* and const char[] are the same so we can use a string
-                    if (array.Type.Desugar().IsPrimitiveType(PrimitiveType.Char) &&
+                    if (Context.Context.Options.MarshalConstCharArrayAsString &&
+                        array.Type.Desugar().IsPrimitiveType(PrimitiveType.Char) &&
                         array.QualifiedType.Qualifiers.IsConst)
                     {
                         var pointer = new PointerType { QualifiedPointee = array.QualifiedType };
@@ -874,7 +875,8 @@ private void MarshalArray(ArrayType arrayType)
 
             var elementType = arrayType.Type.Desugar();
 
-            if (elementType.IsPrimitiveType() ||
+            if ((elementType.IsPrimitiveType() &&
+                    !(elementType.IsPrimitiveType(PrimitiveType.Char) && Context.Context.Options.MarshalCharAsManagedChar)) ||
                 elementType.IsPointerToPrimitiveType())
             {
                 if (Context.Context.Options.UseSpan && !elementType.IsConstCharString())
@@ -916,6 +918,10 @@ private void MarshalArray(ArrayType arrayType)
                 Context.Before.WriteLine($@"{intermediateArray}[i] = {
                     element} is null ? {intPtrZero} : {element}.{Helpers.InstanceIdentifier};");
             }
+            else if (elementType.IsPrimitiveType(PrimitiveType.Char) &&
+                        Context.Context.Options.MarshalCharAsManagedChar)
+                Context.Before.WriteLine($@"{intermediateArray}[i] = global::System.Convert.ToSByte({
+                    element});");
             else
                 Context.Before.WriteLine($@"{intermediateArray}[i] = {
                     element} is null ? new {intermediateArrayType}() : *({

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -972,7 +972,7 @@ private string GeneratePointerTo(Variable var)
             string ptr = Generator.GeneratedIdentifier("ptr");
             if (arrayType != null)
             {
-                if (arrayType.Type.IsPrimitiveType(PrimitiveType.Char) && arrayType.SizeType != ArrayType.ArraySize.Constant)
+                if (Context.Options.MarshalConstCharArrayAsString && arrayType.Type.IsPrimitiveType(PrimitiveType.Char) && arrayType.SizeType != ArrayType.ArraySize.Constant)
                     WriteLine($"var {ptr} = {location};");
                 else
                     WriteLine($"var {ptr} = ({arrayType.Type.Visit(TypePrinter)}*){location};");

src/Generator/Generators/CSharp/CSharpTypePrinter.cs

@@ -111,7 +111,8 @@ public override TypePrinterResult VisitArrayType(ArrayType array,
             }
 
             // const char* and const char[] are the same so we can use a string
-            if (array.SizeType == ArrayType.ArraySize.Incomplete &&
+            if (Context.Options.MarshalConstCharArrayAsString &&
+                array.SizeType == ArrayType.ArraySize.Incomplete &&
                 arrayType.IsPrimitiveType(PrimitiveType.Char) &&
                 array.QualifiedType.Qualifiers.IsConst)
                 return "string";
@@ -123,6 +124,13 @@ public override TypePrinterResult VisitArrayType(ArrayType array,
                 return $"{prefix}string[]";
             }
 
+            if (arrayType.IsPrimitiveType(PrimitiveType.Bool))
+            {
+                var prefix = ContextKind == TypePrinterContextKind.Managed ? string.Empty :
+                    "[MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.I1)] ";
+                return $"{prefix}bool[]";
+            }
+
             if (Context.Options.UseSpan && !(array.SizeType != ArrayType.ArraySize.Constant &&
                 MarshalKind == MarshalKind.ReturnVariableArray))
             {

src/Generator/Options.cs

@@ -115,7 +115,7 @@ public bool DoAllModulesHaveLibraries() =>
 
         /// <summary>
         /// Enable this option to enable generation of finalizers. Works in both CLI and
-        /// C# backends. 
+        /// C# backends.
         /// </summary>
         /// <remarks>
         /// Use <see cref="GenerateFinalizersFilter"/> to specify a filter so that
@@ -125,7 +125,7 @@ public bool DoAllModulesHaveLibraries() =>
 
         /// <summary>
         /// A filter that can restrict the classes for which finalizers are generated when
-        /// <see cref="GenerateFinalizers"/> is <c>true</c>. 
+        /// <see cref="GenerateFinalizers"/> is <c>true</c>.
         /// </summary>
         /// <remarks>
         /// The default filter performs no filtering so that whenever <see
@@ -189,6 +189,7 @@ public bool DoAllModulesHaveLibraries() =>
 
         public readonly List<string> DependentNameSpaces = new List<string>();
         public bool MarshalCharAsManagedChar { get; set; }
+        public bool MarshalConstCharArrayAsString { get; set; } = true;
 
         /// <summary>
         /// Use Span Struct instead of Managed Array