1 files changed, 252 insertions, 0 deletions
diff --git a/src/ARMeilleure/Common/AddressTable.cs b/src/ARMeilleure/Common/AddressTable.cs
new file mode 100644
index 00000000..9db2d00d
--- /dev/null
+++ b/src/ARMeilleure/Common/AddressTable.cs
@@ -0,0 +1,252 @@
+using ARMeilleure.Diagnostics;
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+
+namespace ARMeilleure.Common
+{
+    /// <summary>
+    /// Represents a table of guest address to a value.
+    /// </summary>
+    /// <typeparam name="TEntry">Type of the value</typeparam>
+    unsafe class AddressTable<TEntry> : IDisposable where TEntry : unmanaged
+    {
+        /// <summary>
+        /// Represents a level in an <see cref="AddressTable{TEntry}"/>.
+        /// </summary>
+        public readonly struct Level
+        {
+            /// <summary>
+            /// Gets the index of the <see cref="Level"/> in the guest address.
+            /// </summary>
+            public int Index { get; }
+
+            /// <summary>
+            /// Gets the length of the <see cref="Level"/> in the guest address.
+            /// </summary>
+            public int Length { get; }
+
+            /// <summary>
+            /// Gets the mask which masks the bits used by the <see cref="Level"/>.
+            /// </summary>
+            public ulong Mask => ((1ul << Length) - 1) << Index;
+
+            /// <summary>
+            /// Initializes a new instance of the <see cref="Level"/> structure with the specified
+            /// <paramref name="index"/> and <paramref name="length"/>.
+            /// </summary>
+            /// <param name="index">Index of the <see cref="Level"/></param>
+            /// <param name="length">Length of the <see cref="Level"/></param>
+            public Level(int index, int length)
+            {
+                (Index, Length) = (index, length);
+            }
+
+            /// <summary>
+            /// Gets the value of the <see cref="Level"/> from the specified guest <paramref name="address"/>.
+            /// </summary>
+            /// <param name="address">Guest address</param>
+            /// <returns>Value of the <see cref="Level"/> from the specified guest <paramref name="address"/></returns>
+            public int GetValue(ulong address)
+            {
+                return (int)((address & Mask) >> Index);
+            }
+        }
+
+        private bool _disposed;
+        private TEntry** _table;
+        private readonly List<IntPtr> _pages;
+
+        /// <summary>
+        /// Gets the bits used by the <see cref="Levels"/> of the <see cref="AddressTable{TEntry}"/> instance.
+        /// </summary>
+        public ulong Mask { get; }
+
+        /// <summary>
+        /// Gets the <see cref="Level"/>s used by the <see cref="AddressTable{TEntry}"/> instance.
+        /// </summary>
+        public Level[] Levels { get; }
+
+        /// <summary>
+        /// Gets or sets the default fill value of newly created leaf pages.
+        /// </summary>
+        public TEntry Fill { get; set; }
+
+        /// <summary>
+        /// Gets the base address of the <see cref="EntryTable{TEntry}"/>.
+        /// </summary>
+        /// <exception cref="ObjectDisposedException"><see cref="EntryTable{TEntry}"/> instance was disposed</exception>
+        public IntPtr Base
+        {
+            get
+            {
+                ObjectDisposedException.ThrowIf(_disposed, this);
+
+                lock (_pages)
+                {
+                    return (IntPtr)GetRootPage();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Constructs a new instance of the <see cref="AddressTable{TEntry}"/> class with the specified list of
+        /// <see cref="Level"/>.
+        /// </summary>
+        /// <exception cref="ArgumentNullException"><paramref name="levels"/> is null</exception>
+        /// <exception cref="ArgumentException">Length of <paramref name="levels"/> is less than 2</exception>
+        public AddressTable(Level[] levels)
+        {
+            ArgumentNullException.ThrowIfNull(levels);
+
+            if (levels.Length < 2)
+            {
+                throw new ArgumentException("Table must be at least 2 levels deep.", nameof(levels));
+            }
+
+            _pages = new List<IntPtr>(capacity: 16);
+
+            Levels = levels;
+            Mask = 0;
+
+            foreach (var level in Levels)
+            {
+                Mask |= level.Mask;
+            }
+        }
+
+        /// <summary>
+        /// Determines if the specified <paramref name="address"/> is in the range of the
+        /// <see cref="AddressTable{TEntry}"/>.
+        /// </summary>
+        /// <param name="address">Guest address</param>
+        /// <returns><see langword="true"/> if is valid; otherwise <see langword="false"/></returns>
+        public bool IsValid(ulong address)
+        {
+            return (address & ~Mask) == 0;
+        }
+
+        /// <summary>
+        /// Gets a reference to the value at the specified guest <paramref name="address"/>.
+        /// </summary>
+        /// <param name="address">Guest address</param>
+        /// <returns>Reference to the value at the specified guest <paramref name="address"/></returns>
+        /// <exception cref="ObjectDisposedException"><see cref="EntryTable{TEntry}"/> instance was disposed</exception>
+        /// <exception cref="ArgumentException"><paramref name="address"/> is not mapped</exception>
+        public ref TEntry GetValue(ulong address)
+        {
+            ObjectDisposedException.ThrowIf(_disposed, this);
+
+            if (!IsValid(address))
+            {
+                throw new ArgumentException($"Address 0x{address:X} is not mapped onto the table.", nameof(address));
+            }
+
+            lock (_pages)
+            {
+                return ref GetPage(address)[Levels[^1].GetValue(address)];
+            }
+        }
+
+        /// <summary>
+        /// Gets the leaf page for the specified guest <paramref name="address"/>.
+        /// </summary>
+        /// <param name="address">Guest address</param>
+        /// <returns>Leaf page for the specified guest <paramref name="address"/></returns>
+        private TEntry* GetPage(ulong address)
+        {
+            TEntry** page = GetRootPage();
+
+            for (int i = 0; i < Levels.Length - 1; i++)
+            {
+                ref Level level = ref Levels[i];
+                ref TEntry* nextPage = ref page[level.GetValue(address)];
+
+                if (nextPage == null)
+                {
+                    ref Level nextLevel = ref Levels[i + 1];
+
+                    nextPage = i == Levels.Length - 2 ?
+                        (TEntry*)Allocate(1 << nextLevel.Length, Fill, leaf: true) :
+                        (TEntry*)Allocate(1 << nextLevel.Length, IntPtr.Zero, leaf: false);
+                }
+
+                page = (TEntry**)nextPage;
+            }
+
+            return (TEntry*)page;
+        }
+
+        /// <summary>
+        /// Lazily initialize and get the root page of the <see cref="AddressTable{TEntry}"/>.
+        /// </summary>
+        /// <returns>Root page of the <see cref="AddressTable{TEntry}"/></returns>
+        private TEntry** GetRootPage()
+        {
+            if (_table == null)
+            {
+                _table = (TEntry**)Allocate(1 << Levels[0].Length, fill: IntPtr.Zero, leaf: false);
+            }
+
+            return _table;
+        }
+
+        /// <summary>
+        /// Allocates a block of memory of the specified type and length.
+        /// </summary>
+        /// <typeparam name="T">Type of elements</typeparam>
+        /// <param name="length">Number of elements</param>
+        /// <param name="fill">Fill value</param>
+        /// <param name="leaf"><see langword="true"/> if leaf; otherwise <see langword="false"/></param>
+        /// <returns>Allocated block</returns>
+        private IntPtr Allocate<T>(int length, T fill, bool leaf) where T : unmanaged
+        {
+            var size = sizeof(T) * length;
+            var page = (IntPtr)NativeAllocator.Instance.Allocate((uint)size);
+            var span = new Span<T>((void*)page, length);
+
+            span.Fill(fill);
+
+            _pages.Add(page);
+
+            TranslatorEventSource.Log.AddressTableAllocated(size, leaf);
+
+            return page;
+        }
+
+        /// <summary>
+        /// Releases all resources used by the <see cref="AddressTable{TEntry}"/> instance.
+        /// </summary>
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Releases all unmanaged and optionally managed resources used by the <see cref="AddressTable{TEntry}"/>
+        /// instance.
+        /// </summary>
+        /// <param name="disposing"><see langword="true"/> to dispose managed resources also; otherwise just unmanaged resouces</param>
+        protected virtual void Dispose(bool disposing)
+        {
+            if (!_disposed)
+            {
+                foreach (var page in _pages)
+                {
+                    Marshal.FreeHGlobal(page);
+                }
+
+                _disposed = true;
+            }
+        }
+
+        /// <summary>
+        /// Frees resources used by the <see cref="AddressTable{TEntry}"/> instance.
+        /// </summary>
+        ~AddressTable()
+        {
+            Dispose(false);
+        }
+    }
+}