Salieri: shader cache (#1701)

Here come Salieri, my implementation of a disk shader cache!

"I'm sure you know why I named it that."
"It doesn't really mean anything."

This implementation collects shaders at runtime and cache them to be later compiled when starting a game.

Ryujinx.Graphics.Gpu/Shader/Cache/Definition/GuestShaderCacheEntry.cs

@@ -0,0 +1,88 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Graphics.Gpu.Shader.Cache.Definition
+{
+    /// <summary>
+    /// Represent a cached shader entry in a guest shader program.
+    /// </summary>
+    class GuestShaderCacheEntry
+    {
+        /// <summary>
+        /// The header of the cached shader entry.
+        /// </summary>
+        public GuestShaderCacheEntryHeader Header { get; }
+
+        /// <summary>
+        /// The code of this shader.
+        /// </summary>
+        /// <remarks>If a Vertex A is present, this also contains the code 2 section.</remarks>
+        public byte[] Code { get; }
+
+        /// <summary>
+        /// The textures descriptors used for this shader.
+        /// </summary>
+        public Dictionary<int, GuestTextureDescriptor> TextureDescriptors { get; }
+
+        /// <summary>
+        /// Create a new instance of <see cref="GuestShaderCacheEntry"/>.
+        /// </summary>
+        /// <param name="header">The header of the cached shader entry</param>
+        /// <param name="code">The code of this shader</param>
+        private GuestShaderCacheEntry(GuestShaderCacheEntryHeader header, byte[] code)
+        {
+            Header = header;
+            Code = code;
+            TextureDescriptors = new Dictionary<int, GuestTextureDescriptor>();
+        }
+
+        /// <summary>
+        /// Parse a raw cached user shader program into an array of shader cache entry.
+        /// </summary>
+        /// <param name="data">The raw cached user shader program</param>
+        /// <param name="fileHeader">The user shader program header</param>
+        /// <returns>An array of shader cache entry</returns>
+        public static GuestShaderCacheEntry[] Parse(ref ReadOnlySpan<byte> data, out GuestShaderCacheHeader fileHeader)
+        {
+            fileHeader = MemoryMarshal.Read<GuestShaderCacheHeader>(data);
+
+            data = data.Slice(Unsafe.SizeOf<GuestShaderCacheHeader>());
+
+            ReadOnlySpan<GuestShaderCacheEntryHeader> entryHeaders = MemoryMarshal.Cast<byte, GuestShaderCacheEntryHeader>(data.Slice(0, fileHeader.Count * Unsafe.SizeOf<GuestShaderCacheEntryHeader>()));
+
+            data = data.Slice(fileHeader.Count * Unsafe.SizeOf<GuestShaderCacheEntryHeader>());
+
+            GuestShaderCacheEntry[] result = new GuestShaderCacheEntry[fileHeader.Count];
+
+            for (int i = 0; i < result.Length; i++)
+            {
+                GuestShaderCacheEntryHeader header = entryHeaders[i];
+
+                // Ignore empty entries
+                if (header.Size == 0 && header.SizeA == 0)
+                {
+                    continue;
+                }
+
+                byte[] code = data.Slice(0, header.Size + header.SizeA).ToArray();
+
+                data = data.Slice(header.Size + header.SizeA);
+
+                result[i] = new GuestShaderCacheEntry(header, code);
+
+                ReadOnlySpan<GuestTextureDescriptor> textureDescriptors = MemoryMarshal.Cast<byte, GuestTextureDescriptor>(data.Slice(0, header.GpuAccessorHeader.TextureDescriptorCount * Unsafe.SizeOf<GuestTextureDescriptor>()));
+
+                foreach (GuestTextureDescriptor textureDescriptor in textureDescriptors)
+                {
+                    result[i].TextureDescriptors.Add((int)textureDescriptor.Handle, textureDescriptor);
+                }
+
+                data = data.Slice(header.GpuAccessorHeader.TextureDescriptorCount * Unsafe.SizeOf<GuestTextureDescriptor>());
+            }
+
+            return result;
+        }
+    }
+}