1 files changed, 191 insertions, 0 deletions
diff --git a/Tools/Hazel-Networking/Hazel/ByteSpan.cs b/Tools/Hazel-Networking/Hazel/ByteSpan.cs
new file mode 100644
index 0000000..7cfa3b5
--- /dev/null
+++ b/Tools/Hazel-Networking/Hazel/ByteSpan.cs
@@ -0,0 +1,191 @@
+using System;
+
+namespace Hazel
+{
+    /// <summary>
+    /// This is a minimal implementation of `System.Span` in .NET 5.0
+    /// </summary>
+    public struct ByteSpan
+    {
+        private readonly byte[] array_;
+
+        /// <summary>
+        /// Createa a new span object containing an entire array
+        /// </summary>
+        public ByteSpan(byte[] array)
+        {
+            if (array == null)
+            {
+                this.array_ = null;
+                this.Offset = 0;
+                this.Length = 0;
+            }
+            else
+            {
+                this.array_ = array;
+                this.Offset = 0;
+                this.Length = array.Length;
+            }
+        }
+
+        /// <summary>
+        /// Creates a new span object containing a subset of an array
+        /// </summary>
+        public ByteSpan(byte[] array, int offset, int length)
+        {
+            if (array == null)
+            {
+                if (offset != 0)
+                {
+                    throw new ArgumentException("Invalid offset", nameof(offset));
+                }
+                if (length != 0)
+                {
+                    throw new ArgumentException("Invalid length", nameof(offset));
+                }
+
+                this.array_ = null;
+                this.Offset = 0;
+                this.Length = 0;
+            }
+            else
+            {
+                if (offset < 0 || offset > array.Length)
+                {
+                    throw new ArgumentException("Invalid offset", nameof(offset));
+                }
+                if (length < 0)
+                {
+                    throw new ArgumentException($"Invalid length: {length}", nameof(length));
+                }
+                if ((offset + length) > array.Length)
+                {
+                    throw new ArgumentException($"Invalid length. Length: {length} Offset: {offset} Array size: {array.Length}", nameof(length));
+                }
+
+                this.array_ = array;
+                this.Offset = offset;
+                this.Length = length;
+            }
+        }
+
+        /// <summary>
+        /// Returns the underlying array.
+        ///
+        /// WARNING: This does not return the span, but the entire underlying storage block
+        /// </summary>
+        public byte[] GetUnderlyingArray()
+        {
+            return this.array_;
+        }
+
+        /// <summary>
+        /// Returns the offset into the underlying array
+        /// </summary>
+        public int Offset { get; }
+
+        /// <summary>
+        /// Returns the length of the current span
+        /// </summary>
+        public int Length { get; }
+
+        /// <summary>
+        /// Gets the span element at the specified index
+        /// </summary>
+        public byte this[int index]
+        {
+            get
+            {
+                if (index < 0 || index >= this.Length)
+                {
+                    throw new IndexOutOfRangeException();
+                }
+
+                return this.array_[this.Offset + index];
+            }
+            set
+            {
+                if (index < 0 || index >= this.Length)
+                {
+                    throw new IndexOutOfRangeException();
+                }
+
+                this.array_[this.Offset + index] = value;
+            }
+        }
+
+        /// <summary>
+        /// Create a new span that is a subset of this span [offset, this.Length-offset)
+        /// </summary>
+        public ByteSpan Slice(int offset)
+        {
+            return Slice(offset, this.Length - offset);
+        }
+
+        /// <summary>
+        /// Create a new span that is a subset of this span [offset, length)
+        /// </summary>
+        public ByteSpan Slice(int offset, int length)
+        {
+            return new ByteSpan(this.array_, this.Offset + offset, length);
+        }
+
+        /// <summary>
+        /// Copies the contents of the span to an array
+        /// </summary>
+        public void CopyTo(byte[] array, int offset)
+        {
+            CopyTo(new ByteSpan(array, offset, array.Length - offset));
+        }
+
+        /// <summary>
+        /// Copies the contents of the span to another span
+        /// </summary>
+        public void CopyTo(ByteSpan destination)
+        {
+            if (destination.Length < this.Length)
+            {
+                throw new ArgumentException("Destination span is shorter than source", nameof(destination));
+            }
+
+            if (Length > 0)
+            {
+                Buffer.BlockCopy(this.array_, this.Offset, destination.array_, destination.Offset, this.Length);
+            }
+        }
+
+        /// <summary>
+        /// Create a new array with the contents of this span
+        /// </summary>
+        public byte[] ToArray()
+        {
+            byte[] result = new byte[Length];
+            CopyTo(result);
+            return result;
+        }
+
+        public override string ToString()
+        {
+            return string.Join(" ", this.ToArray());
+        }
+
+        /// <summary>
+        /// Implicit conversion from byte[] -> ByteSpan
+        /// </summary>
+        public static implicit operator ByteSpan(byte[] array)
+        {
+            return new ByteSpan(array);
+        }
+
+        /// <summary>
+        /// Retuns an empty span object
+        /// </summary>
+        public static ByteSpan Empty
+        {
+            get
+            {
+                return new ByteSpan(null);
+            }
+        }
+    }
+}