Implement collection marshaller spec (dotnet/runtimelab#1197)

Commit migrated from https://github.com/dotnet/runtimelab/commit/b3a0ead76a03a92af3b87dd5486563728fb5ecf8

2 files changed, 245 insertions, 6 deletions

diff --git a/src/libraries/System.Runtime.InteropServices/tests/Ancillary.Interop/ArrayMarshaller.cs b/src/libraries/System.Runtime.InteropServices/tests/Ancillary.Interop/ArrayMarshaller.cs
new file mode 100644
index 00000000000..370e90efb3d
--- /dev/null
+++ b/src/libraries/System.Runtime.InteropServices/tests/Ancillary.Interop/ArrayMarshaller.cs
@@ -0,0 +1,217 @@
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.GeneratedMarshalling
+{
+    public unsafe ref struct ArrayMarshaller<T>
+    {
+        private T[]? managedArray;
+        private readonly int sizeOfNativeElement;
+        private IntPtr allocatedMemory;
+
+        public ArrayMarshaller(int sizeOfNativeElement)
+            :this()
+        {
+            this.sizeOfNativeElement = sizeOfNativeElement;
+        }
+
+        public ArrayMarshaller(T[]? managed, int sizeOfNativeElement)
+        {
+            allocatedMemory = default;
+            this.sizeOfNativeElement = sizeOfNativeElement;
+            if (managed is null)
+            {
+                managedArray = null;
+                NativeValueStorage = default;
+                return;
+            }
+            managedArray = managed;
+            this.sizeOfNativeElement = sizeOfNativeElement;
+            // Always allocate at least one byte when the array is zero-length.
+            int spaceToAllocate = Math.Max(managed.Length * sizeOfNativeElement, 1);
+            allocatedMemory = Marshal.AllocCoTaskMem(spaceToAllocate);
+            NativeValueStorage = new Span<byte>((void*)allocatedMemory, spaceToAllocate);
+        }
+
+        public ArrayMarshaller(T[]? managed, Span<byte> stackSpace, int sizeOfNativeElement)
+        {
+            allocatedMemory = default;
+            this.sizeOfNativeElement = sizeOfNativeElement;
+            if (managed is null)
+            {
+                managedArray = null;
+                NativeValueStorage = default;
+                return;
+            }
+            managedArray = managed;
+            // Always allocate at least one byte when the array is zero-length.
+            int spaceToAllocate = Math.Max(managed.Length * sizeOfNativeElement, 1);
+            if (spaceToAllocate <= stackSpace.Length)
+            {
+                NativeValueStorage = stackSpace[0..spaceToAllocate];
+            }
+            else
+            {
+                allocatedMemory = Marshal.AllocCoTaskMem(spaceToAllocate);
+                NativeValueStorage = new Span<byte>((void*)allocatedMemory, spaceToAllocate);
+            }
+        }
+
+        /// <summary>
+        /// Stack-alloc threshold set to 256 bytes to enable small arrays to be passed on the stack.
+        /// Number kept small to ensure that P/Invokes with a lot of array parameters doesn't
+        /// blow the stack since this is a new optimization in the code-generated interop.
+        /// </summary>
+        public const int StackBufferSize = 0x200;
+
+        public Span<T> ManagedValues => managedArray;
+
+        public Span<byte> NativeValueStorage { get; private set; }
+
+        public ref byte GetPinnableReference() => ref MemoryMarshal.GetReference(NativeValueStorage);
+
+        public void SetUnmarshalledCollectionLength(int length)
+        {
+            managedArray = new T[length];
+        }
+
+        public byte* Value
+        {
+            get
+            {
+                Debug.Assert(managedArray is null || allocatedMemory != IntPtr.Zero);
+                return (byte*)allocatedMemory;
+            }
+            set
+            {
+                if (value == null)
+                {
+                    managedArray = null;
+                    NativeValueStorage = default;
+                }
+                else
+                {
+                    allocatedMemory = (IntPtr)value;
+                    NativeValueStorage = new Span<byte>(value, (managedArray?.Length ?? 0) * sizeOfNativeElement);
+                }
+            }
+        }
+
+        public T[]? ToManaged() => managedArray;
+
+        public void FreeNative()
+        {
+            if (allocatedMemory != IntPtr.Zero)
+            {
+                Marshal.FreeCoTaskMem(allocatedMemory);
+            }
+        }
+    }
+
+    public unsafe ref struct PtrArrayMarshaller<T> where T : unmanaged
+    {
+        private T*[]? managedArray;
+        private readonly int sizeOfNativeElement;
+        private IntPtr allocatedMemory;
+
+        public PtrArrayMarshaller(int sizeOfNativeElement)
+            : this()
+        {
+            this.sizeOfNativeElement = sizeOfNativeElement;
+        }
+
+        public PtrArrayMarshaller(T*[]? managed, int sizeOfNativeElement)
+        {
+            allocatedMemory = default;
+            this.sizeOfNativeElement = sizeOfNativeElement;
+            if (managed is null)
+            {
+                managedArray = null;
+                NativeValueStorage = default;
+                return;
+            }
+            managedArray = managed;
+            this.sizeOfNativeElement = sizeOfNativeElement;
+            // Always allocate at least one byte when the array is zero-length.
+            int spaceToAllocate = Math.Max(managed.Length * sizeOfNativeElement, 1);
+            allocatedMemory = Marshal.AllocCoTaskMem(spaceToAllocate);
+            NativeValueStorage = new Span<byte>((void*)allocatedMemory, spaceToAllocate);
+        }
+
+        public PtrArrayMarshaller(T*[]? managed, Span<byte> stackSpace, int sizeOfNativeElement)
+        {
+            allocatedMemory = default;
+            this.sizeOfNativeElement = sizeOfNativeElement;
+            if (managed is null)
+            {
+                managedArray = null;
+                NativeValueStorage = default;
+                return;
+            }
+            managedArray = managed;
+            // Always allocate at least one byte when the array is zero-length.
+            int spaceToAllocate = Math.Max(managed.Length * sizeOfNativeElement, 1);
+            if (spaceToAllocate <= stackSpace.Length)
+            {
+                NativeValueStorage = stackSpace[0..spaceToAllocate];
+            }
+            else
+            {
+                allocatedMemory = Marshal.AllocCoTaskMem(spaceToAllocate);
+                NativeValueStorage = new Span<byte>((void*)allocatedMemory, spaceToAllocate);
+            }
+        }
+
+        /// <summary>
+        /// Stack-alloc threshold set to 256 bytes to enable small arrays to be passed on the stack.
+        /// Number kept small to ensure that P/Invokes with a lot of array parameters doesn't
+        /// blow the stack since this is a new optimization in the code-generated interop.
+        /// </summary>
+        public const int StackBufferSize = 0x200;
+
+        public Span<IntPtr> ManagedValues => Unsafe.As<IntPtr[]>(managedArray);
+
+        public Span<byte> NativeValueStorage { get; private set; }
+
+        public ref byte GetPinnableReference() => ref MemoryMarshal.GetReference(NativeValueStorage);
+
+        public void SetUnmarshalledCollectionLength(int length)
+        {
+            managedArray = new T*[length];
+        }
+
+        public byte* Value
+        {
+            get
+            {
+                Debug.Assert(managedArray is null || allocatedMemory != IntPtr.Zero);
+                return (byte*)allocatedMemory;
+            }
+            set
+            {
+                if (value == null)
+                {
+                    managedArray = null;
+                    NativeValueStorage = default;
+                }
+                else
+                {
+                    allocatedMemory = (IntPtr)value;
+                    NativeValueStorage = new Span<byte>(value, (managedArray?.Length ?? 0) * sizeOfNativeElement);
+                }
+
+            }
+        }
+
+        public T*[]? ToManaged() => managedArray;
+
+        public void FreeNative()
+        {
+            if (allocatedMemory != IntPtr.Zero)
+            {
+                Marshal.FreeCoTaskMem(allocatedMemory);
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/libraries/System.Runtime.InteropServices/tests/Ancillary.Interop/GeneratedMarshallingAttribute.cs b/src/libraries/System.Runtime.InteropServices/tests/Ancillary.Interop/GeneratedMarshallingAttribute.cs
index 11e1b29639f..dd605b9e60b 100644
--- a/src/libraries/System.Runtime.InteropServices/tests/Ancillary.Interop/GeneratedMarshallingAttribute.cs
+++ b/src/libraries/System.Runtime.InteropServices/tests/Ancillary.Interop/GeneratedMarshallingAttribute.cs
@@ -2,17 +2,17 @@
 namespace System.Runtime.InteropServices
 {
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct)]
-    class GeneratedMarshallingAttribute : Attribute
+    sealed class GeneratedMarshallingAttribute : Attribute
     {
     }
 
     [AttributeUsage(AttributeTargets.Struct)]
-    public class BlittableTypeAttribute : Attribute
+    public sealed class BlittableTypeAttribute : Attribute
     {
     }
 
     [AttributeUsage(AttributeTargets.Struct | AttributeTargets.Class)]
-    public class NativeMarshallingAttribute : Attribute
+    public sealed class NativeMarshallingAttribute : Attribute
     {
         public NativeMarshallingAttribute(Type nativeType)
         {
@@ -22,14 +22,36 @@ namespace System.Runtime.InteropServices
         public Type NativeType { get; }
     }
 
-    [AttributeUsage(AttributeTargets.Parameter | AttributeTargets.ReturnValue | AttributeTargets.Field)]
-    public class MarshalUsingAttribute : Attribute
+    [AttributeUsage(AttributeTargets.Parameter | AttributeTargets.ReturnValue | AttributeTargets.Field, AllowMultiple = true)]
+    public sealed class MarshalUsingAttribute : Attribute
     {
+        public MarshalUsingAttribute()
+        {
+            CountElementName = string.Empty;
+        }
+
         public MarshalUsingAttribute(Type nativeType)
+            :this()
         {
             NativeType = nativeType;
         }
 
-        public Type NativeType { get; }
+        public Type? NativeType { get; }
+
+        public string CountElementName { get; set; }
+
+        public int ConstantElementCount { get; set; }
+
+        public int ElementIndirectionLevel { get; set; }
+
+        public const string ReturnsCountValue = "return-value";
+    }
+
+    [AttributeUsage(AttributeTargets.Struct | AttributeTargets.Class)]
+    public sealed class GenericContiguousCollectionMarshallerAttribute : Attribute
+    {
+        public GenericContiguousCollectionMarshallerAttribute()
+        {
+        }
     }
 }
\ No newline at end of file