Removal of unsafe and check if PTR is correctly aligning, checking in virtual query instead of memory

LightlessSync/PlayerData/Factories/PlayerDataFactory.cs

@@ -1,6 +1,5 @@
 using Dalamud.Utility;
-using FFXIVClientStructs.FFXIV.Client.Game.Character;
+using FFXIVClientStructs.FFXIV.Client.Game.Object;
-using LightlessSync.API.Data.Enum;
 using LightlessSync.FileCache;
 using LightlessSync.Interop.Ipc;
 using LightlessSync.LightlessConfiguration;
@@ -14,6 +13,7 @@ using Microsoft.Extensions.Logging;
 using System.Collections.Concurrent;
 using System.Diagnostics;
 using System.Runtime.InteropServices;
+using ObjectKind = LightlessSync.API.Data.Enum.ObjectKind;
 
 namespace LightlessSync.PlayerData.Factories;
 
@@ -119,39 +119,48 @@ public class PlayerDataFactory
         return null;
     }
 
+    private static readonly int _drawObjectOffset =
+        (int)Marshal.OffsetOf<GameObject>(nameof(GameObject.DrawObject));
+
     private async Task<bool> CheckForNullDrawObject(IntPtr playerPointer)
-        => await _dalamudUtil.RunOnFrameworkThread(() => CheckForNullDrawObjectUnsafe(playerPointer)).ConfigureAwait(false);
+        => await _dalamudUtil.RunOnFrameworkThread(() =>
+        {
+            nint basePtr = playerPointer;
 
-    private unsafe static bool CheckForNullDrawObjectUnsafe(IntPtr playerPointer)
+            if (!LooksLikeUserPtr(basePtr))
+                return true;
+
+            nint drawObjAddr = basePtr + _drawObjectOffset;
+
+            if (!TryReadIntPtr(drawObjAddr, out var drawObj))
+                return true;
+
+            return drawObj == 0;
+        }).ConfigureAwait(false);
+
+    private static bool LooksLikeUserPtr(nint p)
     {
-        if (playerPointer == IntPtr.Zero)
+        if (p == 0) return false;
-            return true;
 
-        if (!IsPointerValid(playerPointer))
+        ulong u = (ulong)p;
-            return true;
 
-        var character = (Character*)playerPointer;
+        if (u < 0x0000_0001_0000UL) return false;
-        if (character == null)
+        if (u > 0x0000_7FFF_FFFF_FFFFUL) return false;
-            return true;
+        if ((u & 0x7UL) != 0) return false;
 
-        var gameObject = &character->GameObject;
+        return true;
-        if (gameObject == null)
-            return true;
-
-        if (!IsPointerValid((IntPtr)gameObject))
-            return true;
-
-        return gameObject->DrawObject == null;
     }
 
-    private static bool IsPointerValid(IntPtr ptr)
+    private static bool TryReadIntPtr(nint addr, out nint value)
     {
-        if (ptr == IntPtr.Zero)
+        value = 0;
+
+        if (!VirtualReadable(addr))
             return false;
 
         try
         {
-            _ = Marshal.ReadByte(ptr);
+            value = Marshal.ReadIntPtr(addr);
             return true;
         }
         catch
@@ -160,6 +169,38 @@ public class PlayerDataFactory
         }
     }
 
+    private static bool VirtualReadable(nint addr)
+    {
+        if (VirtualQuery(addr, out var mbi, (nuint)Marshal.SizeOf<MEMORY_BASIC_INFORMATION>()) == 0)
+            return false;
+
+        const uint MEM_COMMIT = 0x1000;
+        const uint PAGE_NOACCESS = 0x01;
+        const uint PAGE_GUARD = 0x100;
+
+        if (mbi.State != MEM_COMMIT) return false;
+        if ((mbi.Protect & PAGE_GUARD) != 0) return false;
+        if (mbi.Protect == PAGE_NOACCESS) return false;
+
+        return true;
+    }
+
+    [DllImport("kernel32.dll", SetLastError = true)]
+    private static extern nuint VirtualQuery(nint lpAddress, out MEMORY_BASIC_INFORMATION lpBuffer, nuint dwLength);
+
+
+    [StructLayout(LayoutKind.Sequential)]
+    private struct MEMORY_BASIC_INFORMATION
+    {
+        public nint BaseAddress;
+        public nint AllocationBase;
+        public uint AllocationProtect;
+        public nuint RegionSize;
+        public uint State;
+        public uint Protect;
+        public uint Type;
+    }
+
     private static bool IsCacheFresh(CacheEntry entry)
         => (DateTime.UtcNow - entry.CreatedUtc) <= _characterCacheTtl;