Renumber nodes after running osrm-partition

The new numbering uses the partition information
to sort border nodes first to compactify storages
that need access indexed by border node ID.

We also get an optimized cache performance for free
sincr we can also recursively sort the nodes by cell ID.

This implements issue #3779.

include/util/mmap_file.hpp

@@ -0,0 +1,54 @@
+#ifndef OSRM_UTIL_MMAP_FILE_HPP
+#define OSRM_UTIL_MMAP_FILE_HPP
+
+#include "util/exception.hpp"
+#include "util/exception_utils.hpp"
+#include "util/vector_view.hpp"
+
+#include <boost/filesystem/path.hpp>
+#include <boost/iostreams/device/mapped_file.hpp>
+
+namespace osrm
+{
+namespace util
+{
+
+namespace detail
+{
+template <typename T, typename RegionT>
+util::vector_view<T> mmapFile(const boost::filesystem::path &file, RegionT &region)
+{
+    try
+    {
+        region.open(file);
+        std::size_t num_objects = region.size() / sizeof(T);
+        auto data_ptr = region.data();
+        BOOST_ASSERT(reinterpret_cast<uintptr_t>(data_ptr) % alignof(T) == 0);
+        return util::vector_view<T>(reinterpret_cast<T *>(data_ptr), num_objects);
+    }
+    catch (const std::exception &exc)
+    {
+        throw exception(
+            boost::str(boost::format("File %1% mapping failed: %2%") % file % exc.what()) +
+            SOURCE_REF);
+    }
+}
+}
+
+template <typename T>
+util::vector_view<const T> mmapFile(const boost::filesystem::path &file,
+                                    boost::iostreams::mapped_file_source &region)
+{
+    return detail::mmapFile<const T>(file, region);
+}
+
+template <typename T>
+util::vector_view<T> mmapFile(const boost::filesystem::path &file,
+                              boost::iostreams::mapped_file &region)
+{
+    return detail::mmapFile<T>(file, region);
+}
+}
+}
+
+#endif