Re-add NVDEC project (not integrated)

Ryujinx.Graphics.Nvdec/Vic/StructUnpacker.cs

@@ -0,0 +1,69 @@
+using Ryujinx.Graphics.Gpu.Memory;
+using System;
+
+namespace Ryujinx.Graphics.Vic
+{
+    class StructUnpacker
+    {
+        private MemoryAccessor _vmm;
+
+        private ulong _position;
+
+        private ulong _buffer;
+        private int   _buffPos;
+
+        public StructUnpacker(MemoryAccessor vmm, ulong position)
+        {
+            _vmm      = vmm;
+            _position = position;
+
+            _buffPos = 64;
+        }
+
+        public int Read(int bits)
+        {
+            if ((uint)bits > 32)
+            {
+                throw new ArgumentOutOfRangeException(nameof(bits));
+            }
+
+            int value = 0;
+
+            while (bits > 0)
+            {
+                RefillBufferIfNeeded();
+
+                int readBits = bits;
+
+                int maxReadBits = 64 - _buffPos;
+
+                if (readBits > maxReadBits)
+                {
+                    readBits = maxReadBits;
+                }
+
+                value <<= readBits;
+
+                value |= (int)(_buffer >> _buffPos) & (int)(0xffffffff >> (32 - readBits));
+
+                _buffPos += readBits;
+
+                bits -= readBits;
+            }
+
+            return value;
+        }
+
+        private void RefillBufferIfNeeded()
+        {
+            if (_buffPos >= 64)
+            {
+                _buffer = _vmm.ReadUInt64(_position);
+
+                _position += 8;
+
+                _buffPos = 0;
+            }
+        }
+    }
+}