Add tar file mmaping

include/util/mmap_tar.hpp

@@ -0,0 +1,44 @@
+#ifndef OSRM_UTIL_MMAP_TAR_HPP
+#define OSRM_UTIL_MMAP_TAR_HPP
+
+#include "storage/tar.hpp"
+
+#include "util/mmap_file.hpp"
+
+#include <boost/iostreams/device/mapped_file.hpp>
+
+#include <tuple>
+#include <unordered_map>
+
+namespace osrm
+{
+namespace util
+{
+using DataRange = std::pair<const char *, const char *>;
+using DataMap = std::unordered_map<std::string, DataRange>;
+
+inline DataMap mmapTarFile(const boost::filesystem::path &path,
+                           boost::iostreams::mapped_file_source &region)
+{
+    DataMap map;
+
+    storage::tar::FileReader reader{path, storage::tar::FileReader::VerifyFingerprint};
+
+    std::vector<storage::tar::FileReader::FileEntry> entries;
+    reader.List(std::back_inserter(entries));
+
+    auto raw_file = mmapFile<char>(path, region);
+
+    for (const auto &entry : entries)
+    {
+        auto begin = raw_file.data() + entry.offset;
+        auto end = begin + entry.size;
+        map[entry.name] = DataRange{begin, end};
+    }
+
+    return map;
+}
+}
+}
+
+#endif