1 files changed, 141 insertions, 0 deletions
diff --git a/Ryujinx.Memory/PageTable.cs b/Ryujinx.Memory/PageTable.cs
new file mode 100644
index 00000000..71db1e76
--- /dev/null
+++ b/Ryujinx.Memory/PageTable.cs
@@ -0,0 +1,141 @@
+namespace Ryujinx.Memory
+{
+    class PageTable<T> where T : unmanaged
+    {
+        public const int PageBits = 12;
+        public const int PageSize = 1 << PageBits;
+        public const int PageMask = PageSize - 1;
+
+        private const int PtLevelBits = 9; // 9 * 4 + 12 = 48 (max address space size)
+        private const int PtLevelSize = 1 << PtLevelBits;
+        private const int PtLevelMask = PtLevelSize - 1;
+
+        private readonly T[][][][] _pageTable;
+
+        public PageTable()
+        {
+            _pageTable = new T[PtLevelSize][][][];
+        }
+
+        public T Read(ulong va)
+        {
+            int l3 = (int)(va >> PageBits) & PtLevelMask;
+            int l2 = (int)(va >> (PageBits + PtLevelBits)) & PtLevelMask;
+            int l1 = (int)(va >> (PageBits + PtLevelBits * 2)) & PtLevelMask;
+            int l0 = (int)(va >> (PageBits + PtLevelBits * 3)) & PtLevelMask;
+
+            if (_pageTable[l0] == null)
+            {
+                return default;
+            }
+
+            if (_pageTable[l0][l1] == null)
+            {
+                return default;
+            }
+
+            if (_pageTable[l0][l1][l2] == null)
+            {
+                return default;
+            }
+
+            return _pageTable[l0][l1][l2][l3];
+        }
+
+        public void Map(ulong va, T value)
+        {
+            int l3 = (int)(va >> PageBits) & PtLevelMask;
+            int l2 = (int)(va >> (PageBits + PtLevelBits)) & PtLevelMask;
+            int l1 = (int)(va >> (PageBits + PtLevelBits * 2)) & PtLevelMask;
+            int l0 = (int)(va >> (PageBits + PtLevelBits * 3)) & PtLevelMask;
+
+            if (_pageTable[l0] == null)
+            {
+                _pageTable[l0] = new T[PtLevelSize][][];
+            }
+
+            if (_pageTable[l0][l1] == null)
+            {
+                _pageTable[l0][l1] = new T[PtLevelSize][];
+            }
+
+            if (_pageTable[l0][l1][l2] == null)
+            {
+                _pageTable[l0][l1][l2] = new T[PtLevelSize];
+            }
+
+            _pageTable[l0][l1][l2][l3] = value;
+        }
+
+        public void Unmap(ulong va)
+        {
+            int l3 = (int)(va >> PageBits) & PtLevelMask;
+            int l2 = (int)(va >> (PageBits + PtLevelBits)) & PtLevelMask;
+            int l1 = (int)(va >> (PageBits + PtLevelBits * 2)) & PtLevelMask;
+            int l0 = (int)(va >> (PageBits + PtLevelBits * 3)) & PtLevelMask;
+
+            if (_pageTable[l0] == null)
+            {
+                return;
+            }
+
+            if (_pageTable[l0][l1] == null)
+            {
+                return;
+            }
+
+            if (_pageTable[l0][l1][l2] == null)
+            {
+                return;
+            }
+
+            _pageTable[l0][l1][l2][l3] = default;
+
+            bool empty = true;
+
+            for (int i = 0; i < _pageTable[l0][l1][l2].Length; i++)
+            {
+                empty &= _pageTable[l0][l1][l2][i].Equals(default);
+            }
+
+            if (empty)
+            {
+                _pageTable[l0][l1][l2] = null;
+
+                RemoveIfAllNull(l0, l1);
+            }
+        }
+
+        private void RemoveIfAllNull(int l0, int l1)
+        {
+            bool empty = true;
+
+            for (int i = 0; i < _pageTable[l0][l1].Length; i++)
+            {
+                empty &= (_pageTable[l0][l1][i] == null);
+            }
+
+            if (empty)
+            {
+                _pageTable[l0][l1] = null;
+
+                RemoveIfAllNull(l0);
+            }
+        }
+
+        private void RemoveIfAllNull(int l0)
+        {
+            bool empty = true;
+
+            for (int i = 0; i < _pageTable[l0].Length; i++)
+            {
+                empty &= (_pageTable[l0][i] == null);
+            }
+
+            if (empty)
+            {
+                _pageTable[l0] = null;
+            }
+        }
+    }
+}