introducing FakeBuffer<T> workaround

src/ImageSharp.Drawing/Processors/FillRegionProcessor.cs

@@ -99,8 +99,8 @@ namespace SixLabors.ImageSharp.Drawing.Processors
             using (BrushApplicator<TPixel> applicator = this.Brush.CreateApplicator(source, rect, this.Options))
             {
                 int scanlineWidth = maxX - minX;
-                using (var buffer = source.MemoryManager.Allocate<float>(maxIntersections))
-                using (var scanline = source.MemoryManager.Allocate<float>(scanlineWidth))
+                using (FakeBuffer<float> buffer = source.MemoryManager.AllocateFake<float>(maxIntersections))
+                using (FakeBuffer<float> scanline = source.MemoryManager.AllocateFake<float>(scanlineWidth))
                 {
                     bool scanlineDirty = true;
                     for (int y = minY; y < maxY; y++)

src/ImageSharp/Memory/ArrayPoolMemoryManager.cs

@@ -38,13 +38,13 @@ namespace SixLabors.ImageSharp.Memory
         }
 
         /// <inheritdoc />
-        internal override Buffer<T> Allocate<T>(int itemCount, bool clear)
+        internal override Buffer<T> Allocate<T>(int length, bool clear)
         {
             int itemSizeBytes = Unsafe.SizeOf<T>();
-            int bufferSizeInBytes = itemCount * itemSizeBytes;
+            int bufferSizeInBytes = length * itemSizeBytes;
 
             byte[] byteBuffer = this.pool.Rent(bufferSizeInBytes);
-            var buffer = new Buffer<T>(Unsafe.As<T[]>(byteBuffer), itemCount, this);
+            var buffer = new Buffer<T>(Unsafe.As<T[]>(byteBuffer), length, this);
             if (clear)
             {
                 buffer.Clear();

src/ImageSharp/Memory/FakeBuffer.cs

@@ -0,0 +1,64 @@
+using System;
+using System.Runtime.CompilerServices;
+
+namespace SixLabors.ImageSharp.Memory
+{
+    /// <summary>
+    /// Temporal workaround providing a "Buffer" based on a generic array without the 'Unsafe.As()' hackery.
+    /// </summary>
+    internal class FakeBuffer<T> : IBuffer<T>
+        where T : struct
+    {
+        public FakeBuffer(T[] array)
+        {
+            this.Array = array;
+        }
+
+        public T[] Array { get; }
+
+        public Span<T> Span => this.Array;
+
+        public int Length => this.Array.Length;
+
+        /// <summary>
+        /// Returns a reference to specified element of the buffer.
+        /// </summary>
+        /// <param name="index">The index</param>
+        /// <returns>The reference to the specified element</returns>
+        public ref T this[int index]
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                DebugGuard.MustBeLessThan(index, this.Length, nameof(index));
+
+                Span<T> span = this.Span;
+                return ref span[index];
+            }
+        }
+
+        /// <summary>
+        /// Converts <see cref="Buffer{T}"/> to an <see cref="ReadOnlySpan{T}"/>.
+        /// </summary>
+        /// <param name="buffer">The <see cref="Buffer{T}"/> to convert.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static implicit operator ReadOnlySpan<T>(FakeBuffer<T> buffer)
+        {
+            return new ReadOnlySpan<T>(buffer.Array, 0, buffer.Length);
+        }
+
+        /// <summary>
+        /// Converts <see cref="Buffer{T}"/> to an <see cref="Span{T}"/>.
+        /// </summary>
+        /// <param name="buffer">The <see cref="Buffer{T}"/> to convert.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static implicit operator Span<T>(FakeBuffer<T> buffer)
+        {
+            return new Span<T>(buffer.Array, 0, buffer.Length);
+        }
+
+        public void Dispose()
+        {
+        }
+    }
+}

src/ImageSharp/Memory/MemoryManager.cs

@@ -12,14 +12,14 @@ namespace SixLabors.ImageSharp.Memory
     public abstract class MemoryManager
     {
         /// <summary>
-        /// Allocates a <see cref="Buffer{T}"/> of size <paramref name="size"/>, optionally
+        /// Allocates a <see cref="Buffer{T}"/> of size <paramref name="length"/>, optionally
         /// clearing the buffer before it gets returned.
         /// </summary>
         /// <typeparam name="T">Type of the data stored in the buffer</typeparam>
-        /// <param name="size">Size of the buffer to allocate</param>
+        /// <param name="length">Size of the buffer to allocate</param>
         /// <param name="clear">True to clear the backing memory of the buffer</param>
         /// <returns>A buffer of values of type <typeparamref name="T"/>.</returns>
-        internal abstract Buffer<T> Allocate<T>(int size, bool clear)
+        internal abstract Buffer<T> Allocate<T>(int length, bool clear)
             where T : struct;
 
         /// <summary>
@@ -30,5 +30,15 @@ namespace SixLabors.ImageSharp.Memory
         /// <param name="buffer">The buffer to release</param>
         internal abstract void Release<T>(Buffer<T> buffer)
             where T : struct;
+
+        /// <summary>
+        /// Temporal workaround. A method providing a "Buffer" based on a generic array without the 'Unsafe.As()' hackery.
+        /// Should be replaced with 'Allocate()' as soon as SixLabors.Shapes has Span-based API-s!
+        /// </summary>
+        internal FakeBuffer<T> AllocateFake<T>(int length)
+            where T : struct
+        {
+            return new FakeBuffer<T>(new T[length]);
+        }
     }
 }

src/ImageSharp/Memory/SimpleManagedMemoryManager.cs

@@ -6,9 +6,9 @@
     public class SimpleManagedMemoryManager : MemoryManager
     {
         /// <inheritdoc />
-        internal override Buffer<T> Allocate<T>(int size, bool clear)
+        internal override Buffer<T> Allocate<T>(int length, bool clear)
         {
-            return new Buffer<T>(new T[size], size);
+            return new Buffer<T>(new T[length], length);
         }
 
         /// <inheritdoc />