feat: add streamed_io.

src/data_format/io/streamed_io.cpp

@@ -0,0 +1,17 @@
+#include "data_format/io/streamed_io.h"
+
+namespace di {
+
+void StreamedIO::read(const fs::path& path) {
+    m_file_stream.open(path, std::ios::binary);
+    if (!m_file_stream) {
+        throw std::runtime_error("Failed to open file!");
+    }
+}
+
+void StreamedIO::write(const fs::path& path) const {
+    std::fstream ofs(path, std::ios::binary);
+    ofs << m_file_stream.rdbuf();
+}
+
+} // namespace di

src/data_format/io/streamed_io.h

@@ -0,0 +1,43 @@
+#pragma once
+
+#include "data_format/io/io_base.h"
+
+namespace di {
+
+class StreamedIO : public IOBase {
+public:
+    void read(const fs::path& path) override;
+    void write(const fs::path& path) const override;
+
+    constexpr auto next() { return m_file_stream.peek(); }
+
+    // Avoid confusion with the function that opens a file, so use eat
+    // instead of read. Maybe come up with another name for write as well.
+    //
+    // TODO: write<T>() method.
+
+    template <typename T>
+    constexpr T eat() {
+        T value;
+        m_file_stream.read((char*)&value, sizeof(T));
+        return value;
+    }
+
+    template <std::unsigned_integral T>
+    constexpr T eat_varint() {
+        T   res   = 0;
+        int shift = 0;
+        while (true) {
+            auto byte  = m_file_stream.get();
+            res       |= static_cast<T>(byte & 0x7F) << shift;
+            if ((byte & 0x80) == 0) break;
+            shift += 7;
+        }
+        return res;
+    }
+
+private:
+    std::ifstream m_file_stream;
+};
+
+} // namespace di