1 files changed, 113 insertions, 0 deletions
diff --git a/src/Ryujinx.Graphics.Gpu/Shader/HashTable/HashState.cs b/src/Ryujinx.Graphics.Gpu/Shader/HashTable/HashState.cs
new file mode 100644
index 00000000..584eefdc
--- /dev/null
+++ b/src/Ryujinx.Graphics.Gpu/Shader/HashTable/HashState.cs
@@ -0,0 +1,113 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Graphics.Gpu.Shader.HashTable
+{
+    /// <summary>
+    /// State of a hash calculation.
+    /// </summary>
+    struct HashState
+    {
+        // This is using a slightly modified implementation of FastHash64.
+        // Reference: https://github.com/ztanml/fast-hash/blob/master/fasthash.c
+        private const ulong M = 0x880355f21e6d1965UL;
+        private ulong _hash;
+        private int _start;
+
+        /// <summary>
+        /// One shot hash calculation for a given data.
+        /// </summary>
+        /// <param name="data">Data to be hashed</param>
+        /// <returns>Hash of the given data</returns>
+        public static uint CalcHash(ReadOnlySpan<byte> data)
+        {
+            HashState state = new HashState();
+
+            state.Initialize();
+            state.Continue(data);
+            return state.Finalize(data);
+        }
+
+        /// <summary>
+        /// Initializes the hash state.
+        /// </summary>
+        public void Initialize()
+        {
+            _hash = 23;
+        }
+
+        /// <summary>
+        /// Calculates the hash of the given data.
+        /// </summary>
+        /// <remarks>
+        /// The full data must be passed on <paramref name="data"/>.
+        /// If this is not the first time the method is called, then <paramref name="data"/> must start with the data passed on the last call.
+        /// If a smaller slice of the data was already hashed before, only the additional data will be hashed.
+        /// This can be used for additive hashing of data in chuncks.
+        /// </remarks>
+        /// <param name="data">Data to be hashed</param>
+        public void Continue(ReadOnlySpan<byte> data)
+        {
+            ulong h = _hash;
+
+            ReadOnlySpan<ulong> dataAsUlong = MemoryMarshal.Cast<byte, ulong>(data.Slice(_start));
+
+            for (int i = 0; i < dataAsUlong.Length; i++)
+            {
+                ulong value = dataAsUlong[i];
+
+                h ^= Mix(value);
+                h *= M;
+            }
+
+            _hash = h;
+            _start = data.Length & ~7;
+        }
+
+        /// <summary>
+        /// Performs the hash finalization step, and returns the calculated hash.
+        /// </summary>
+        /// <remarks>
+        /// The full data must be passed on <paramref name="data"/>.
+        /// <paramref name="data"/> must start with the data passed on the last call to <see cref="Continue"/>.
+        /// No internal state is changed, so one can still continue hashing data with <see cref="Continue"/>
+        /// after calling this method.
+        /// </remarks>
+        /// <param name="data">Data to be hashed</param>
+        /// <returns>Hash of all the data hashed with this <see cref="HashState"/></returns>
+        public uint Finalize(ReadOnlySpan<byte> data)
+        {
+            ulong h = _hash;
+
+            int remainder = data.Length & 7;
+            if (remainder != 0)
+            {
+                ulong v = 0;
+
+                for (int i = data.Length - remainder; i < data.Length; i++)
+                {
+                    v |= (ulong)data[i] << ((i - remainder) * 8);
+                }
+
+                h ^= Mix(v);
+                h *= M;
+            }
+
+            h = Mix(h);
+            return (uint)(h - (h >> 32));
+        }
+
+        /// <summary>
+        /// Hash mix function.
+        /// </summary>
+        /// <param name="h">Hash to mix</param>
+        /// <returns>Mixed hash</returns>
+        private static ulong Mix(ulong h)
+        {
+            h ^= h >> 23;
+            h *= 0x2127599bf4325c37UL;
+            h ^= h >> 47;
+            return h;
+        }
+    }
+}