[Zion] Move Memory Mappings to a dedicated tree impl.

zion/lib/memory_mapping_tree.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include <glacier/container/binary_tree.h>
+
+#include "object/memory_object.h"
+
+/* AddressRangeTree stores memory objects referred to by
+ * ranges and ensures those ranges do not overlap.
+ */
+class MemoryMappingTree {
+ public:
+  MemoryMappingTree() = default;
+
+  MemoryMappingTree(const MemoryMappingTree&) = delete;
+  MemoryMappingTree(MemoryMappingTree&&) = delete;
+
+  glcr::ErrorCode AddInMemoryObject(uint64_t vaddr,
+                                    const glcr::RefPtr<MemoryObject>& object);
+
+  glcr::ErrorCode FreeMemoryRange(uint64_t vaddr_base, uint64_t vaddr_limit);
+
+  glcr::ErrorOr<uint64_t> GetPhysicalPageAtVaddr(uint64_t vaddr);
+
+ private:
+  struct MemoryMapping {
+    uint64_t vaddr_base;
+    uint64_t vaddr_limit;
+    glcr::RefPtr<MemoryObject> mem_object;
+  };
+
+  // TODO: Consider adding a red-black tree implementation here.
+  // As is this tree functions about as well as a linked list
+  // because mappings are likely to be added in near-perfect ascedning order.
+  // Also worth considering creating a special tree implementation for
+  // just this purpose, or maybe a BinaryTree implementation that accepts
+  // ranges rather than a single key.
+  glcr::BinaryTree<uint64_t, MemoryMapping> mapping_tree_;
+
+  glcr::Optional<glcr::Ref<MemoryMapping>> GetMemoryMappingForAddr(
+      uint64_t vaddr);
+};