Add Arena Allocator

- Adding files that were not staged

include/arena.h

@@ -0,0 +1,59 @@
+//
+//  arena.h
+//  Kraken Engine / Mimir
+//
+//  Copyright 2026 Kearwood Gilbert. All rights reserved.
+//
+//  Redistribution and use in source and binary forms, with or without modification, are
+//  permitted provided that the following conditions are met:
+//
+//  1. Redistributions of source code must retain the above copyright notice, this list of
+//  conditions and the following disclaimer.
+//
+//  2. Redistributions in binary form must reproduce the above copyright notice, this list
+//  of conditions and the following disclaimer in the documentation and/or other materials
+//  provided with the distribution.
+//
+//  THIS SOFTWARE IS PROVIDED BY KEARWOOD GILBERT ''AS IS'' AND ANY EXPRESS OR IMPLIED
+//  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+//  FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL KEARWOOD GILBERT OR
+//  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+//  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+//  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+//  ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+//  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+//  ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+//  The views and conclusions contained in the software and documentation are those of the
+//  authors and should not be interpreted as representing official policies, either expressed
+//  or implied, of Kearwood Gilbert.
+//
+
+#pragma once
+
+#include <string>
+#include <cstddef>
+
+namespace mimir {
+class Arena
+{
+public:
+  Arena(size_t minSize = 1ULL << 24, size_t maxSize = 1ULL << 32);
+  ~Arena();
+
+  std::byte* alloc(size_t size);
+  std::byte* allocA16(size_t size);
+  std::byte* allocA64(size_t size);
+  void reset();
+private:
+  std::byte* m_data;
+  size_t m_minSize;
+  size_t m_maxSize;
+  size_t m_committedSize;
+  size_t m_usedSize;
+
+  static const size_t kWatermarkLen = 8;
+  size_t m_watermark[kWatermarkLen];
+}; // class Arena
+
+} // namespace mimir