feat: add Unpack for IBinaryInteger<T>

This introduces an experiment, to add support for generic math in X10D. So far, build and tests remain passing - this is a good sign. There is potential here.

This API is subject to change and may be removed without warning.

X10D/src/Collections/BinaryIntegerExtensions.cs

@@ -0,0 +1,89 @@
+#if NET7_0_OR_GREATER
+using System.Diagnostics.Contracts;
+using System.Numerics;
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics.X86;
+using X10D.CompilerServices;
+
+namespace X10D.Collections;
+
+/// <summary>
+///     Collection-related extension methods for <see cref="IBinaryInteger{T}" />.
+/// </summary>
+public static class BinaryIntegerExtensions
+{
+    /// <summary>
+    ///     Unpacks this integer into a boolean list, treating it as a bit field.
+    /// </summary>
+    /// <param name="value">The value to unpack.</param>
+    /// <returns>An array of <see cref="bool" /> with a length equal to the size of <typeparamref name="TInteger" />.</returns>
+    [Pure]
+    [MethodImpl(CompilerResources.MethodImplOptions)]
+    public static bool[] Unpack<TInteger>(this TInteger value)
+        where TInteger : unmanaged, IBinaryInteger<TInteger>
+    {
+        unsafe
+        {
+            var buffer = new bool[sizeof(TInteger) * 8];
+            value.Unpack(buffer);
+            return buffer;
+        }
+    }
+
+    /// <summary>
+    ///     Unpacks this integer into a boolean list, treating it as a bit field.
+    /// </summary>
+    /// <param name="value">The value to unpack.</param>
+    /// <param name="destination">When this method returns, contains the unpacked booleans from <paramref name="value" />.</param>
+    /// <exception cref="ArgumentException"><paramref name="destination" /> is not large enough to contain the result.</exception>
+    [MethodImpl(CompilerResources.MethodImplOptions)]
+    public static void Unpack<TInteger>(this TInteger value, Span<bool> destination)
+        where TInteger : unmanaged, IBinaryInteger<TInteger>
+    {
+        unsafe
+        {
+            if (destination.Length < sizeof(TInteger) * 8)
+            {
+                throw new ArgumentException(ExceptionMessages.DestinationSpanLengthTooShort, nameof(destination));
+            }
+        }
+
+        switch (value)
+        {
+            case byte valueByte when Sse3.IsSupported:
+                valueByte.UnpackInternal_Ssse3(destination);
+                break;
+
+            case int valueInt32 when Avx2.IsSupported:
+                valueInt32.UnpackInternal_Ssse3(destination);
+                break;
+
+            case int valueInt32 when Sse3.IsSupported:
+                valueInt32.UnpackInternal_Ssse3(destination);
+                break;
+
+            case short valueInt16 when Sse3.IsSupported:
+                valueInt16.UnpackInternal_Ssse3(destination);
+                break;
+
+            default:
+                UnpackInternal_Fallback(value, destination);
+                break;
+        }
+    }
+
+    [MethodImpl(CompilerResources.MethodImplOptions)]
+    internal static void UnpackInternal_Fallback<TInteger>(this TInteger value, Span<bool> destination)
+        where TInteger : unmanaged, IBinaryInteger<TInteger>
+    {
+        unsafe
+        {
+            int bitCount = sizeof(TInteger) * 8;
+            for (var index = 0; index < bitCount; index++)
+            {
+                destination[index] = (value & (TInteger.One << index)) != TInteger.Zero;
+            }
+        }
+    }
+}
+#endif

X10D/src/Collections/ByteExtensions.cs

@@ -1,5 +1,7 @@
-using System.Diagnostics.CodeAnalysis;
+#if !NET7_0_OR_GREATER
+using System.Diagnostics.CodeAnalysis;
 using System.Diagnostics.Contracts;
+#endif
 using System.Runtime.CompilerServices;
 using X10D.CompilerServices;
 
@@ -17,6 +19,7 @@ public static class ByteExtensions
 {
     private const int Size = sizeof(byte) * 8;
 
+#if !NET7_0_OR_GREATER
     /// <summary>
     ///     Unpacks this 8-bit unsigned integer into a boolean list, treating it as a bit field.
     /// </summary>
@@ -56,6 +59,7 @@ public static void Unpack(this byte value, Span<bool> destination)
 
         UnpackInternal_Fallback(value, destination);
     }
+#endif
 
     [MethodImpl(CompilerResources.MethodImplOptions)]
     internal static void UnpackInternal_Fallback(this byte value, Span<bool> destination)

X10D/src/Collections/Int16Extensions.cs

@@ -1,5 +1,7 @@
-using System.Diagnostics.CodeAnalysis;
+#if !NET7_0_OR_GREATER
+using System.Diagnostics.CodeAnalysis;
 using System.Diagnostics.Contracts;
+#endif
 using System.Runtime.CompilerServices;
 using X10D.CompilerServices;
 
@@ -17,6 +19,7 @@ public static class Int16Extensions
 {
     private const int Size = sizeof(short) * 8;
 
+#if !NET7_0_OR_GREATER
     /// <summary>
     ///     Unpacks this 16-bit signed integer into a boolean list, treating it as a bit field.
     /// </summary>
@@ -56,6 +59,7 @@ public static void Unpack(this short value, Span<bool> destination)
 
         UnpackInternal_Fallback(value, destination);
     }
+#endif
 
     [MethodImpl(CompilerResources.MethodImplOptions)]
     internal static void UnpackInternal_Fallback(this short value, Span<bool> destination)

X10D/src/Collections/Int32Extensions.cs

@@ -1,5 +1,7 @@
-using System.Diagnostics.CodeAnalysis;
+#if !NET7_0_OR_GREATER
+using System.Diagnostics.CodeAnalysis;
 using System.Diagnostics.Contracts;
+#endif
 using System.Runtime.CompilerServices;
 using X10D.CompilerServices;
 
@@ -17,6 +19,7 @@ public static class Int32Extensions
 {
     private const int Size = sizeof(int) * 8;
 
+#if !NET7_0_OR_GREATER
     /// <summary>
     ///     Unpacks this 32-bit signed integer into a boolean list, treating it as a bit field.
     /// </summary>
@@ -62,6 +65,7 @@ public static void Unpack(this int value, Span<bool> destination)
 
         UnpackInternal_Fallback(value, destination);
     }
+#endif
 
     [MethodImpl(CompilerResources.MethodImplOptions)]
     internal static void UnpackInternal_Fallback(this int value, Span<bool> destination)

X10D/src/Collections/Int64Extensions.cs

@@ -1,4 +1,5 @@
-using System.Diagnostics.Contracts;
+#if !NET7_0_OR_GREATER
+using System.Diagnostics.Contracts;
 
 namespace X10D.Collections;
 
@@ -41,3 +42,4 @@ public static void Unpack(this long value, Span<bool> destination)
         }
     }
 }
+#endif