Speed and memory usage optimizations.

src/Hashids.net/ArrayExtensions.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace HashidsNet
+{
+    public static class ArrayExtensions
+    {
+        public static T[] Copy<T>(this T[] array)
+        {
+            return SubArray(array, 0, array.Length);
+        }
+
+        public static T[] SubArray<T>(this T[] array, int index)
+        {
+            return SubArray(array, index, array.Length - index);
+        }
+
+        public static T[] SubArray<T>(this T[] array, int index, int length)
+        {
+            var subarray = new T[length];
+            Array.Copy(array, index, subarray, 0, length);
+            return subarray;
+        }
+
+        public static T[] Append<T>(this T[] array, T[] appendArray, int index, int length)
+        {
+            var newArray = new T[array.Length + length - index];
+            Array.Copy(array, 0, newArray, 0, array.Length);
+            Array.Copy(appendArray, index, newArray, array.Length, length - index);
+            return newArray;
+        }
+
+        public static T[] CopyPooled<T>(this T[] array)
+        {
+            return SubArrayPooled(array, 0, array.Length);
+        }
+
+        public static T[] SubArrayPooled<T>(this T[] array, int index, int length)
+        {
+#if NETSTANDARD1_0 || NET40
+            var subarray = new T[length];
+#else
+            var subarray = System.Buffers.ArrayPool<T>.Shared.Rent(length);
+#endif
+            Array.Copy(array, index, subarray, 0, length);
+            return subarray;
+        }
+    }
+}