Add CollectionsMarshal

apiCount.include.md

@@ -1,28 +1,28 @@
-**API count: 956**
+**API count: 959**
 
 ### Per Target Framework
 
 | Target | APIs |
 | -- | -- |
-| `net461` | 932 |
-| `net462` | 932 |
-| `net47` | 931 |
-| `net471` | 930 |
-| `net472` | 926 |
-| `net48` | 926 |
-| `net481` | 926 |
-| `netstandard2.0` | 928 |
-| `netstandard2.1` | 759 |
-| `netcoreapp2.0` | 852 |
-| `netcoreapp2.1` | 771 |
-| `netcoreapp2.2` | 771 |
-| `netcoreapp3.0` | 717 |
-| `netcoreapp3.1` | 716 |
-| `net5.0` | 588 |
-| `net6.0` | 493 |
-| `net7.0` | 340 |
-| `net8.0` | 222 |
-| `net9.0` | 146 |
-| `net10.0` | 94 |
-| `net11.0` | 57 |
-| `uap10.0` | 918 |
+| `net461` | 933 |
+| `net462` | 933 |
+| `net47` | 932 |
+| `net471` | 931 |
+| `net472` | 927 |
+| `net48` | 927 |
+| `net481` | 927 |
+| `netstandard2.0` | 929 |
+| `netstandard2.1` | 760 |
+| `netcoreapp2.0` | 853 |
+| `netcoreapp2.1` | 772 |
+| `netcoreapp2.2` | 772 |
+| `netcoreapp3.0` | 718 |
+| `netcoreapp3.1` | 717 |
+| `net5.0` | 589 |
+| `net6.0` | 494 |
+| `net7.0` | 341 |
+| `net8.0` | 223 |
+| `net9.0` | 147 |
+| `net10.0` | 95 |
+| `net11.0` | 58 |
+| `uap10.0` | 919 |

api_list.include.md

@@ -1414,6 +1414,14 @@
  * `KeyValuePair<TKey, TValue> Create<TKey, TValue>(TKey, TValue)` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.keyvaluepair.create?view=net-11.0)
 
 
+#### CollectionsMarshal
+
+ * `Span<T> AsSpan<T>(List<T>?)` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.collectionsmarshal.asspan?view=net-11.0)
+   * Note: Reads the list's private backing array via reflection on this target.
+ * `void SetCount<T>(List<T>, int)` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.collectionsmarshal.setcount?view=net-11.0)
+   * Note: When growing, new elements are default(T); the BCL exposes uninitialized data.
+
+
 #### TaskCompletionSource
 
 #### UnreachableException

src/ApiBuilderTests/BuildApiTest.cs

@@ -18,6 +18,7 @@ public Task RunWithRoslyn()
         WriteHelper("Ensure*", writer, ref count);
         WriteHelper("Lock", writer, ref count);
         WriteHelper(nameof(KeyValuePair), writer, ref count);
+        WriteHelper("CollectionsMarshal", writer, ref count);
         WriteType(nameof(TaskCompletionSource), writer, ref count);
         WriteType(nameof(UnreachableException), writer, ref count);
 

src/Consume/Consume.cs

@@ -128,6 +128,12 @@ class Consume
         type = typeof(MatchType);
         type = typeof(MatchCasing);
 
+        var collectionsMarshalList = new List<int> {1, 2, 3};
+        CollectionsMarshal.SetCount(collectionsMarshalList, 5);
+#if FeatureMemory && !WINDOWS_UWP
+        var collectionsMarshalSpan = CollectionsMarshal.AsSpan(collectionsMarshalList);
+#endif
+
         var (key, value) = KeyValuePair.Create("a", "b");
 
 #if NET6_0_OR_GREATER

src/Polyfill/CollectionsMarshal.cs

@@ -0,0 +1,91 @@
+#pragma warning disable
+
+#if !NET5_0_OR_GREATER
+
+namespace System.Runtime.InteropServices;
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Reflection;
+
+/// <summary>
+/// An unsafe class that provides a set of methods to access the underlying data representations of collections.
+/// </summary>
+[ExcludeFromCodeCoverage]
+[DebuggerNonUserCode]
+#if PolyUseEmbeddedAttribute
+[global::Microsoft.CodeAnalysis.EmbeddedAttribute]
+#endif
+#if PolyPublic
+public
+#endif
+static class CollectionsMarshal
+{
+#if FeatureMemory && !WINDOWS_UWP
+
+    /// <summary>
+    /// Gets a <see cref="Span{T}"/> view over the data in a list. Items should not be added or removed from the <see cref="List{T}"/> while the <see cref="Span{T}"/> is in use.
+    /// </summary>
+    //Link: https://learn.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.collectionsmarshal.asspan?view=net-11.0
+    //Note: Reads the list's private backing array via reflection on this target.
+    public static Span<T> AsSpan<T>(List<T>? list)
+    {
+        if (list == null)
+        {
+            return default;
+        }
+
+        var items = (T[]) ItemsAccessor<T>.Field.GetValue(list)!;
+        return new(items, 0, list.Count);
+    }
+
+    static class ItemsAccessor<T>
+    {
+        public static readonly FieldInfo Field = typeof(List<T>)
+            .GetField("_items", BindingFlags.Instance | BindingFlags.NonPublic)!;
+    }
+
+#endif
+
+    /// <summary>
+    /// Sets the count of the <see cref="List{T}"/> to the specified value.
+    /// </summary>
+    //Link: https://learn.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.collectionsmarshal.setcount?view=net-11.0
+    //Note: When growing, new elements are default(T); the BCL exposes uninitialized data.
+    public static void SetCount<T>(List<T> list, int count)
+    {
+        if (list == null)
+        {
+            throw new ArgumentNullException(nameof(list));
+        }
+
+        if (count < 0)
+        {
+            throw new ArgumentOutOfRangeException(nameof(count));
+        }
+
+        var current = list.Count;
+        if (count < current)
+        {
+            list.RemoveRange(count, current - count);
+        }
+        else if (count > current)
+        {
+            if (list.Capacity < count)
+            {
+                list.Capacity = count;
+            }
+
+            for (var index = current; index < count; index++)
+            {
+                list.Add(default!);
+            }
+        }
+    }
+}
+
+#else
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Runtime.InteropServices.CollectionsMarshal))]
+#endif

src/Polyfill/CollectionsMarshalSetCount.cs

@@ -0,0 +1,57 @@
+#pragma warning disable
+
+// SetCount was added to the BCL CollectionsMarshal in net8.0, but the type itself
+// exists from net5.0. For net5.0-net7.0 the type is present (so it cannot be
+// recreated) and SetCount is added as a static extension member. For earlier
+// targets SetCount lives on the recreated type in CollectionsMarshal.cs.
+#if NET5_0_OR_GREATER && !NET8_0_OR_GREATER
+
+namespace Polyfills;
+
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+
+static partial class Polyfill
+{
+    extension(CollectionsMarshal)
+    {
+        /// <summary>
+        /// Sets the count of the <see cref="List{T}"/> to the specified value.
+        /// </summary>
+        //Link: https://learn.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.collectionsmarshal.setcount?view=net-11.0
+        //Note: When growing, new elements are default(T); the BCL exposes uninitialized data.
+        public static void SetCount<T>(List<T> list, int count)
+        {
+            if (list == null)
+            {
+                throw new ArgumentNullException(nameof(list));
+            }
+
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count));
+            }
+
+            var current = list.Count;
+            if (count < current)
+            {
+                list.RemoveRange(count, current - count);
+            }
+            else if (count > current)
+            {
+                if (list.Capacity < count)
+                {
+                    list.Capacity = count;
+                }
+
+                for (var index = current; index < count; index++)
+                {
+                    list.Add(default!);
+                }
+            }
+        }
+    }
+}
+
+#endif

src/Split/net10.0/TypeForwardeds.cs

@@ -4,6 +4,7 @@
 [assembly: TypeForwardedTo(typeof(System.Buffers.Text.Base64Url))]
 [assembly: TypeForwardedTo(typeof(System.Runtime.CompilerServices.CallerArgumentExpressionAttribute))]
 [assembly: TypeForwardedTo(typeof(System.Runtime.CompilerServices.CollectionBuilderAttribute))]
+[assembly: TypeForwardedTo(typeof(System.Runtime.InteropServices.CollectionsMarshal))]
 [assembly: TypeForwardedTo(typeof(System.Runtime.CompilerServices.CompilerFeatureRequiredAttribute))]
 [assembly: TypeForwardedTo(typeof(System.Threading.Tasks.ConfigureAwaitOptions))]
 [assembly: TypeForwardedTo(typeof(System.Diagnostics.CodeAnalysis.ConstantExpectedAttribute))]

src/Split/net11.0/TypeForwardeds.cs

@@ -4,6 +4,7 @@
 [assembly: TypeForwardedTo(typeof(System.Buffers.Text.Base64Url))]
 [assembly: TypeForwardedTo(typeof(System.Runtime.CompilerServices.CallerArgumentExpressionAttribute))]
 [assembly: TypeForwardedTo(typeof(System.Runtime.CompilerServices.CollectionBuilderAttribute))]
+[assembly: TypeForwardedTo(typeof(System.Runtime.InteropServices.CollectionsMarshal))]
 [assembly: TypeForwardedTo(typeof(System.Runtime.CompilerServices.CompilerFeatureRequiredAttribute))]
 [assembly: TypeForwardedTo(typeof(System.Threading.Tasks.ConfigureAwaitOptions))]
 [assembly: TypeForwardedTo(typeof(System.Diagnostics.CodeAnalysis.ConstantExpectedAttribute))]

src/Split/net461/CollectionsMarshal.cs

@@ -0,0 +1,72 @@
+// <auto-generated />
+#pragma warning disable
+#pragma warning disable
+namespace System.Runtime.InteropServices;
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Reflection;
+/// <summary>
+/// An unsafe class that provides a set of methods to access the underlying data representations of collections.
+/// </summary>
+[ExcludeFromCodeCoverage]
+[DebuggerNonUserCode]
+#if PolyUseEmbeddedAttribute
+[global::Microsoft.CodeAnalysis.EmbeddedAttribute]
+#endif
+#if PolyPublic
+public
+#endif
+static class CollectionsMarshal
+{
+#if FeatureMemory
+	/// <summary>
+	/// Gets a <see cref="Span{T}"/> view over the data in a list. Items should not be added or removed from the <see cref="List{T}"/> while the <see cref="Span{T}"/> is in use.
+	/// </summary>
+	public static Span<T> AsSpan<T>(List<T>? list)
+	{
+		if (list == null)
+		{
+			return default;
+		}
+		var items = (T[]) ItemsAccessor<T>.Field.GetValue(list)!;
+		return new(items, 0, list.Count);
+	}
+	static class ItemsAccessor<T>
+	{
+		public static readonly FieldInfo Field = typeof(List<T>)
+			.GetField("_items", BindingFlags.Instance | BindingFlags.NonPublic)!;
+	}
+#endif
+	/// <summary>
+	/// Sets the count of the <see cref="List{T}"/> to the specified value.
+	/// </summary>
+	public static void SetCount<T>(List<T> list, int count)
+	{
+		if (list == null)
+		{
+			throw new ArgumentNullException(nameof(list));
+		}
+		if (count < 0)
+		{
+			throw new ArgumentOutOfRangeException(nameof(count));
+		}
+		var current = list.Count;
+		if (count < current)
+		{
+			list.RemoveRange(count, current - count);
+		}
+		else if (count > current)
+		{
+			if (list.Capacity < count)
+			{
+				list.Capacity = count;
+			}
+			for (var index = current; index < count; index++)
+			{
+				list.Add(default!);
+			}
+		}
+	}
+}

src/Split/net462/CollectionsMarshal.cs

@@ -0,0 +1,72 @@
+// <auto-generated />
+#pragma warning disable
+#pragma warning disable
+namespace System.Runtime.InteropServices;
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Reflection;
+/// <summary>
+/// An unsafe class that provides a set of methods to access the underlying data representations of collections.
+/// </summary>
+[ExcludeFromCodeCoverage]
+[DebuggerNonUserCode]
+#if PolyUseEmbeddedAttribute
+[global::Microsoft.CodeAnalysis.EmbeddedAttribute]
+#endif
+#if PolyPublic
+public
+#endif
+static class CollectionsMarshal
+{
+#if FeatureMemory
+	/// <summary>
+	/// Gets a <see cref="Span{T}"/> view over the data in a list. Items should not be added or removed from the <see cref="List{T}"/> while the <see cref="Span{T}"/> is in use.
+	/// </summary>
+	public static Span<T> AsSpan<T>(List<T>? list)
+	{
+		if (list == null)
+		{
+			return default;
+		}
+		var items = (T[]) ItemsAccessor<T>.Field.GetValue(list)!;
+		return new(items, 0, list.Count);
+	}
+	static class ItemsAccessor<T>
+	{
+		public static readonly FieldInfo Field = typeof(List<T>)
+			.GetField("_items", BindingFlags.Instance | BindingFlags.NonPublic)!;
+	}
+#endif
+	/// <summary>
+	/// Sets the count of the <see cref="List{T}"/> to the specified value.
+	/// </summary>
+	public static void SetCount<T>(List<T> list, int count)
+	{
+		if (list == null)
+		{
+			throw new ArgumentNullException(nameof(list));
+		}
+		if (count < 0)
+		{
+			throw new ArgumentOutOfRangeException(nameof(count));
+		}
+		var current = list.Count;
+		if (count < current)
+		{
+			list.RemoveRange(count, current - count);
+		}
+		else if (count > current)
+		{
+			if (list.Capacity < count)
+			{
+				list.Capacity = count;
+			}
+			for (var index = current; index < count; index++)
+			{
+				list.Add(default!);
+			}
+		}
+	}
+}