initial runs

include/file_writer.hpp

@@ -0,0 +1,23 @@
+#pragma once
+#include "record.hpp"
+#include <fstream>
+#include <span>
+
+class FileWriter {
+private:
+    std::ofstream stream_;
+    std::vector<Record> buffer_;
+    size_t current_pos_;
+    size_t total_writes_;
+
+    void write_buffer();
+
+public:
+    FileWriter(const std::string& filename, size_t buffer_size = 8);
+    ~FileWriter();
+
+    void write(const Record& record);
+    void write_chunk(std::span<const Record>& chunk);
+
+    size_t total_writes() const;
+};