ASTC optimizations (#845)

* ASTC optimizations

* Move code to Ryujinx.Common

* Support 3D textures

* Address feedback

* Remove ASTC logging

* Use stackalloc instead of a Buffer20 struct

* Code style and cleanup

* Respond to feedback

* Rearrange public/private property ordering

1 files changed, 72 insertions, 0 deletions

diff --git a/Ryujinx.Graphics.Texture/Astc/BitStream128.cs b/Ryujinx.Graphics.Texture/Astc/BitStream128.cs
new file mode 100644
index 00000000..3bf9769f
--- /dev/null
+++ b/Ryujinx.Graphics.Texture/Astc/BitStream128.cs
@@ -0,0 +1,72 @@
+using Ryujinx.Common.Utilities;
+using System;
+using System.Diagnostics;
+
+namespace Ryujinx.Graphics.Texture.Astc
+{
+    public struct BitStream128
+    {
+        private Buffer16 _data;
+        public int BitsLeft { get; set; }
+
+        public BitStream128(Buffer16 data)
+        {
+            _data = data;
+            BitsLeft = 128;
+        }
+
+        public int ReadBits(int bitCount)
+        {
+            Debug.Assert(bitCount < 32);
+
+            if (bitCount == 0)
+            {
+                return 0;
+            }
+
+            int mask = (1 << bitCount) - 1;
+            int value = _data.As<int>() & mask;
+
+            Span<ulong> span = _data.AsSpan<ulong>();
+
+            ulong carry = span[1] << (64 - bitCount);
+            span[0] = (span[0] >> bitCount) | carry;
+            span[1] >>= bitCount;
+
+            BitsLeft -= bitCount;
+
+            return value;
+        }
+
+        public void WriteBits(int value, int bitCount)
+        {
+            Debug.Assert(bitCount < 32);
+
+            if (bitCount == 0) return;
+
+            ulong maskedValue = (uint)(value & ((1 << bitCount) - 1));
+
+            Span<ulong> span = _data.AsSpan<ulong>();
+
+            if (BitsLeft < 64)
+            {
+                ulong lowMask = maskedValue << BitsLeft;
+                span[0] |= lowMask;
+            }
+
+            if (BitsLeft + bitCount > 64)
+            {
+                if (BitsLeft > 64)
+                {
+                    span[1] |= maskedValue << (BitsLeft - 64);
+                }
+                else
+                {
+                    span[1] |= maskedValue >> (64 - BitsLeft);
+                }
+            }
+
+            BitsLeft += bitCount;
+        }
+    }
+}
\ No newline at end of file