1 files changed, 53 insertions, 0 deletions
diff --git a/ARMeilleure/Memory/ReservedRegion.cs b/ARMeilleure/Memory/ReservedRegion.cs
new file mode 100644
index 00000000..521019ad
--- /dev/null
+++ b/ARMeilleure/Memory/ReservedRegion.cs
@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace ARMeilleure.Memory
+{
+    class ReservedRegion
+    {
+        private const int DefaultGranularity = 65536; // Mapping granularity in Windows.
+
+        public IntPtr Pointer { get; }
+
+        private ulong _maxSize;
+        private ulong _sizeGranularity;
+        private ulong _currentSize;
+
+        public ReservedRegion(ulong maxSize, ulong granularity = 0)
+        {
+            if (granularity == 0)
+            {
+                granularity = DefaultGranularity;
+            }
+
+            Pointer = MemoryManagement.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.
+                        MemoryManagement.Commit(new IntPtr((long)Pointer + (long)_currentSize), moreToCommit);
+                        _currentSize += moreToCommit;
+                    }
+                }
+            }
+        }
+    }
+}