Repo created

libs/coding/var_record_reader.hpp

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+#pragma once
+
+#include "coding/reader.hpp"
+#include "coding/varint.hpp"
+
+#include <string>
+#include <vector>
+
+// Reads records, encoded as [VarUint size] [Data] .. [VarUint size] [Data].
+template <class ReaderT>
+class VarRecordReader
+{
+public:
+  explicit VarRecordReader(ReaderT const & reader) : m_reader(reader) {}
+
+  std::vector<uint8_t> ReadRecord(uint64_t const pos) const
+  {
+    ReaderSource source(m_reader);
+    ASSERT_LESS(pos, source.Size(), ());
+    source.Skip(pos);
+    uint32_t const recordSize = ReadVarUint<uint32_t>(source);
+    std::vector<uint8_t> buffer(recordSize);
+    source.Read(buffer.data(), recordSize);
+    return buffer;
+  }
+
+  template <class FnT>
+  void ForEachRecord(FnT && fn) const
+  {
+    ReaderSource source(m_reader);
+    while (source.Size() > 0)
+    {
+      auto const pos = source.Pos();
+      uint32_t const recordSize = ReadVarUint<uint32_t>(source);
+      std::vector<uint8_t> buffer(recordSize);
+      source.Read(buffer.data(), recordSize);
+      fn(static_cast<uint32_t>(pos), std::move(buffer));
+    }
+  }
+
+private:
+  ReaderT m_reader;
+};