Add Experimental Initial Span (#1651)

* Fix NotImplementedException

* Add Experimental Span

* Fix Some Problems and Comment

src/Generator/Generators/CSharp/CSharpMarshal.cs

@@ -69,10 +69,18 @@ namespace CppSharp.Generators.CSharp
                     var arrayType = array.Type.Desugar();
 
                     if (CheckIfArrayCanBeCopiedUsingMemoryCopy(array))
+                    {
+                        if (Context.Context.Options.UseSpan)
+                            Context.Return.Write($"new Span<{arrayType}>({Context.ReturnVarName}, {array.Size})");
+                        else
                             Context.Return.Write($"CppSharp.Runtime.MarshalUtil.GetArray<{arrayType}>({Context.ReturnVarName}, {array.Size})");
+                    }                   
                     else if (array.Type.IsPrimitiveType(PrimitiveType.Char) && Context.Context.Options.MarshalCharAsManagedChar)
                         Context.Return.Write($"CppSharp.Runtime.MarshalUtil.GetCharArray({Context.ReturnVarName}, {array.Size})");
                     else if (array.Type.IsPointerToPrimitiveType(PrimitiveType.Void))
+                        if (Context.Context.Options.UseSpan)
+                            Context.Return.Write($"Span<IntPtr>({Context.ReturnVarName}, {array.Size})");
+                        else
                             Context.Return.Write($"CppSharp.Runtime.MarshalUtil.GetIntPtrArray({Context.ReturnVarName}, {array.Size})");
                     else
                     {
@@ -876,16 +884,28 @@ namespace CppSharp.Generators.CSharp
             if (elementType.IsPrimitiveType() ||
                 elementType.IsPointerToPrimitiveType())
             {
+                if (Context.Context.Options.UseSpan && !elementType.IsConstCharString())
+                {
+                    var local = Generator.GeneratedIdentifier($@"{
+                      Context.Parameter.Name}{Context.ParameterIndex}");
+                    Context.Before.WriteLine($@"fixed ({
+                        typePrinter.PrintNative(elementType)}* {local} = &MemoryMarshal.GetReference({Context.Parameter.Name}))");
+                    Context.HasCodeBlock = true;
+                    Context.Before.WriteOpenBraceAndIndent();
+                    Context.Return.Write(local);
+                }
+                else
                     Context.Return.Write(Context.Parameter.Name);
                 return;
             }
 
             var intermediateArray = Generator.GeneratedIdentifier(Context.Parameter.Name);
             var intermediateArrayType = typePrinter.PrintNative(elementType);
-
+            if (Context.Context.Options.UseSpan)
+                Context.Before.WriteLine($"Span<{intermediateArrayType}> {intermediateArray};");
+            else
                 Context.Before.WriteLine($"{intermediateArrayType}[] {intermediateArray};");
-
-            Context.Before.WriteLine($"if ({Context.Parameter.Name} is null)");
+            Context.Before.WriteLine($"if ({Context.Parameter.Name} == null)");
             Context.Before.WriteLineIndent($"{intermediateArray} = null;");
             Context.Before.WriteLine("else");
 
@@ -911,6 +931,17 @@ namespace CppSharp.Generators.CSharp
 
             Context.Before.UnindentAndWriteCloseBrace();
 
+            if (Context.Context.Options.UseSpan)
+            {
+                var local = Generator.GeneratedIdentifier($@"{
+                  intermediateArray}{Context.ParameterIndex}");
+                Context.Before.WriteLine($@"fixed ({
+                    typePrinter.PrintNative(elementType)}* {local} = &MemoryMarshal.GetReference({intermediateArray}))");
+                Context.HasCodeBlock = true;
+                Context.Before.WriteOpenBraceAndIndent();
+                Context.Return.Write(local);
+            }
+            else
                 Context.Return.Write(intermediateArray);
         }
 

src/Generator/Generators/CSharp/CSharpTypePrinter.cs

@@ -123,6 +123,20 @@ namespace CppSharp.Generators.CSharp
                 return $"{prefix}string[]";
             }
 
+            if (Context.Options.UseSpan && !(array.SizeType != ArrayType.ArraySize.Constant &&
+                MarshalKind == MarshalKind.ReturnVariableArray))
+            {
+                if (ContextKind == TypePrinterContextKind.Managed)
+                {
+                    return $"Span<{arrayType.Visit(this)}>";
+                }
+                else
+                {
+                    return $"{arrayType.Visit(this)}*"; ;
+
+                }
+            }
+           
             var arraySuffix = array.SizeType != ArrayType.ArraySize.Constant &&
                 MarshalKind == MarshalKind.ReturnVariableArray ?
                 (ContextKind == TypePrinterContextKind.Managed &&

src/Generator/Options.cs

@@ -184,6 +184,12 @@ namespace CppSharp
         public readonly List<string> DependentNameSpaces = new List<string>();
         public bool MarshalCharAsManagedChar { get; set; }
 
+        /// <summary>
+        /// Use Span Struct instead of Managed Array
+        /// </summary>
+        public bool UseSpan { get; set; }
+
+
         /// <summary>
         /// Generates a single C# file.
         /// </summary>