1 files changed, 98 insertions, 0 deletions
diff --git a/Ryujinx.HLE/Loaders/Mods/MemPatch.cs b/Ryujinx.HLE/Loaders/Mods/MemPatch.cs
new file mode 100644
index 00000000..0fc19159
--- /dev/null
+++ b/Ryujinx.HLE/Loaders/Mods/MemPatch.cs
@@ -0,0 +1,98 @@
+using Ryujinx.Cpu;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+using Ryujinx.Common.Logging;
+
+namespace Ryujinx.HLE.Loaders.Mods
+{
+    public class MemPatch
+    {
+        readonly Dictionary<uint, byte[]> _patches = new Dictionary<uint, byte[]>();
+
+        /// <summary>
+        /// Adds a patch to specified offset. Overwrites if already present. 
+        /// </summary>
+        /// <param name="offset">Memory offset</param>
+        /// <param name="patch">The patch to add</param>
+        public void Add(uint offset, byte[] patch)
+        {
+            _patches[offset] = patch;
+        }
+
+        /// <summary>
+        /// Adds a patch in the form of an RLE (Fill mode).
+        /// </summary>
+        /// <param name="offset">Memory offset</param>
+        /// <param name="length"The fill length</param>
+        /// <param name="filler">The byte to fill</param>
+        public void AddFill(uint offset, int length, byte filler)
+        {
+            // TODO: Can be made space efficient by changing `_patches`
+            // Should suffice for now
+            byte[] patch = new byte[length];
+            patch.AsSpan().Fill(filler);
+
+            _patches[offset] = patch;
+        }
+
+        /// <summary>
+        /// Adds all patches from an existing MemPatch
+        /// </summary>
+        /// <param name="patches">The patches to add</param>
+        public void AddFrom(MemPatch patches)
+        {
+            if (patches == null)
+            {
+                return;
+            }
+
+            foreach (var (patchOffset, patch) in patches._patches)
+            {
+                _patches[patchOffset] = patch;
+            }
+        }
+
+        /// <summary>
+        /// Applies all the patches added to this instance.
+        /// </summary>
+        /// <remarks>
+        /// Patches are applied in ascending order of offsets to guarantee
+        /// overlapping patches always apply the same way.
+        /// </remarks>
+        /// <param name="memory">The span of bytes to patch</param>
+        /// <param name="maxSize">The maximum size of the slice of patchable memory</param>
+        /// <param name="protectedOffset">A secondary offset used in special cases (NSO header)</param>
+        /// <returns>Successful patches count</returns>
+        public int Patch(Span<byte> memory, int protectedOffset = 0)
+        {
+            int count = 0;
+            foreach (var (offset, patch) in _patches.OrderBy(item => item.Key))
+            {
+                int patchOffset = (int)offset;
+                int patchSize = patch.Length;
+
+                if (patchOffset < protectedOffset || patchOffset > memory.Length)
+                {
+                    continue; // Add warning?
+                }
+
+                patchOffset -= protectedOffset;
+
+                if (patchOffset + patchSize > memory.Length)
+                {
+                    patchSize = memory.Length - (int)patchOffset; // Add warning?
+                }
+
+                Logger.PrintInfo(LogClass.ModLoader, $"Patching address offset {patchOffset:x} <= {BitConverter.ToString(patch).Replace('-', ' ')} len={patchSize}");
+
+                patch.AsSpan().Slice(0, patchSize).CopyTo(memory.Slice(patchOffset, patchSize));
+
+                count++;
+            }
+
+            return count;
+        }
+    }
+}
+\ No newline at end of file