[#1] Define SDK structure

TODO: Вынести маппинг модель -> grpc в отдельный слой

Signed-off-by: Ivan Pchelintsev <i.pchelintsev@yadro.com>

sdk/src/FrostFS.SDK.Cryptography/ArrayHelper.cs

@@ -0,0 +1,24 @@
+using System.Runtime.CompilerServices;
+
+namespace FrostFS.SDK.Cryptography
+{
+    internal static class ArrayHelper
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static byte[] Concat(params byte[][] buffers)
+        {
+            int length = 0;
+            for (int i = 0; i < buffers.Length; i++)
+                length += buffers[i].Length;
+            byte[] dst = new byte[length];
+            int p = 0;
+            foreach (byte[] src in buffers)
+            {
+                Buffer.BlockCopy(src, 0, dst, p, src.Length);
+                p += src.Length;
+            }
+
+            return dst;
+        }
+    }
+}