Add mmap allocator

include/engine/datafacade/mmap_memory_allocator.hpp

@@ -0,0 +1,45 @@
+#ifndef OSRM_ENGINE_DATAFACADE_MMAP_MEMORY_ALLOCATOR_HPP_
+#define OSRM_ENGINE_DATAFACADE_MMAP_MEMORY_ALLOCATOR_HPP_
+
+#include "engine/datafacade/contiguous_block_allocator.hpp"
+
+#include "storage/storage_config.hpp"
+
+#include "util/vector_view.hpp"
+
+#include <boost/iostreams/device/mapped_file.hpp>
+
+#include <memory>
+
+namespace osrm
+{
+namespace engine
+{
+namespace datafacade
+{
+
+/**
+ * This allocator uses file backed mmap memory block as the data location.
+ */
+class MMapMemoryAllocator : public ContiguousBlockAllocator
+{
+  public:
+    explicit MMapMemoryAllocator(const storage::StorageConfig &config,
+                                 const boost::filesystem::path &memory_file);
+    ~MMapMemoryAllocator() override final;
+
+    // interface to give access to the datafacades
+    storage::DataLayout &GetLayout() override final;
+    char *GetMemory() override final;
+
+  private:
+    storage::DataLayout *data_layout;
+    util::vector_view<char> mapped_memory;
+    boost::iostreams::mapped_file mapped_memory_file;
+};
+
+} // namespace datafacade
+} // namespace engine
+} // namespace osrm
+
+#endif // OSRM_ENGINE_DATAFACADE_SHARED_MEMORY_ALLOCATOR_HPP_