1 files changed, 58 insertions, 0 deletions
diff --git a/src/ARMeilleure/Memory/ReservedRegion.cs b/src/ARMeilleure/Memory/ReservedRegion.cs
new file mode 100644
index 00000000..2197afad
--- /dev/null
+++ b/src/ARMeilleure/Memory/ReservedRegion.cs
@@ -0,0 +1,58 @@
+using System;
+
+namespace ARMeilleure.Memory
+{
+    class ReservedRegion
+    {
+        public const int DefaultGranularity = 65536; // Mapping granularity in Windows.
+
+        public IJitMemoryBlock Block { get; }
+
+        public IntPtr Pointer => Block.Pointer;
+
+        private readonly ulong _maxSize;
+        private readonly ulong _sizeGranularity;
+        private ulong _currentSize;
+
+        public ReservedRegion(IJitMemoryAllocator allocator, ulong maxSize, ulong granularity = 0)
+        {
+            if (granularity == 0)
+            {
+                granularity = DefaultGranularity;
+            }
+
+            Block = allocator.Reserve(maxSize);
+            _maxSize = maxSize;
+            _sizeGranularity = granularity;
+            _currentSize = 0;
+        }
+
+        public void ExpandIfNeeded(ulong desiredSize)
+        {
+            if (desiredSize > _maxSize)
+            {
+                throw new OutOfMemoryException();
+            }
+
+            if (desiredSize > _currentSize)
+            {
+                // Lock, and then check again. We only want to commit once.
+                lock (this)
+                {
+                    if (desiredSize >= _currentSize)
+                    {
+                        ulong overflowBytes = desiredSize - _currentSize;
+                        ulong moreToCommit = (((_sizeGranularity - 1) + overflowBytes) / _sizeGranularity) * _sizeGranularity; // Round up.
+                        Block.Commit(_currentSize, moreToCommit);
+                        _currentSize += moreToCommit;
+                    }
+                }
+            }
+        }
+
+        public void Dispose()
+        {
+            Block.Dispose();
+        }
+    }
+}