Added FeaturesOffsetsTable, which maps feature's index to its offset in a MWM file.

1 files changed, 69 insertions, 0 deletions

diff --git a/indexer/features_offsets_table.hpp b/indexer/features_offsets_table.hpp
new file mode 100644
index 0000000000..c4dbb1c8ea
--- /dev/null
+++ b/indexer/features_offsets_table.hpp
@@ -0,0 +1,69 @@
+#pragma once
+
+#include "../3party/succinct/elias_fano.hpp"
+#include "../3party/succinct/mapper.hpp"
+#include "../coding/file_container.hpp"
+#include "../std/stdint.hpp"
+#include "../std/unique_ptr.hpp"
+#include "../std/vector.hpp"
+
+namespace feature
+{
+  class FeaturesOffsetsTable
+  {
+  public:
+    class Builder
+    {
+    public:
+      Builder();
+
+      ~Builder();
+
+      void PushOffset(uint64_t offset);
+
+      inline uint64_t size() const
+      {
+        return static_cast<uint64_t>(m_offsets.size());
+      }
+
+    private:
+      friend class FeaturesOffsetsTable;
+
+      vector<uint64_t> m_offsets;
+    };
+
+    static unique_ptr<FeaturesOffsetsTable> Build(Builder & builder);
+
+    static unique_ptr<FeaturesOffsetsTable> Load(
+        FilesMappingContainer const & container);
+
+    ~FeaturesOffsetsTable();
+
+    FeaturesOffsetsTable(FeaturesOffsetsTable const &) = delete;
+    FeaturesOffsetsTable const & operator=(FeaturesOffsetsTable const &) =
+        delete;
+
+    void Save(FilesContainerW & container);
+
+    uint64_t GetFeatureOffset(size_t index) const;
+
+    inline uint64_t size() const
+    {
+      return m_table.num_ones();
+    }
+
+    inline uint64_t byte_size()
+    {
+      return succinct::mapper::size_of(m_table);
+    }
+
+  private:
+    FeaturesOffsetsTable(succinct::elias_fano::elias_fano_builder & builder);
+
+    FeaturesOffsetsTable(FilesMappingContainer::Handle && handle);
+
+    succinct::elias_fano m_table;
+
+    FilesMappingContainer::Handle m_handle;
+  };
+}  // namespace feature