1 files changed, 37 insertions, 0 deletions
diff --git a/src/line.hh b/src/line.hh
new file mode 100644
index 0000000..a8eeea8
--- /dev/null
+++ b/src/line.hh
@@ -0,0 +1,37 @@
+#ifndef LINE_HH
+#define LINE_HH
+
+#include "io.hh"  // IWYU pragma: export
+
+#include <cstddef>
+#include <expected>
+#include <memory>
+#include <optional>
+#include <string_view>
+
+namespace line {
+
+class Reader {
+ public:
+  virtual ~Reader() = default;
+
+  // Returned view is only valid until next call to read.
+  [[nodiscard]]
+  virtual std::expected<std::string_view, io::ReadError> read() = 0;
+  // Starts at zero. Returns next line.
+  // So, before first read it is zero, after first read it is one.
+  [[nodiscard]] virtual uint64_t number() const = 0;
+
+ protected:
+  Reader() = default;
+
+  Reader(Reader const&) = delete;
+  Reader& operator=(Reader const&) = delete;
+};
+
+[[nodiscard]] std::unique_ptr<Reader> open(std::unique_ptr<io::Reader> reader,
+                                           size_t max_len = 8192);
+
+}  // namespace line
+
+#endif  // LINE_HH