Add output stream interface

inc/f4ll/output_stream.h

@@ -0,0 +1,20 @@
+#pragma once
+#include <cstdint>
+
+namespace f4ll {
+class ioutput_stream
+{
+public:
+    enum class format { dec, hex_padded, hex_trimmed };
+
+    virtual ioutput_stream &operator<<(format fmt) = 0;
+    virtual ioutput_stream &operator<<(char const *str) = 0;
+    virtual ioutput_stream &operator<<(char chr) = 0;
+    virtual ioutput_stream &operator<<(uint8_t byte) = 0;
+    virtual ioutput_stream &operator<<(uint16_t ui16) = 0;
+    virtual ioutput_stream &operator<<(int16_t i16) = 0;
+    virtual ioutput_stream &operator<<(uint32_t ui32) = 0;
+    virtual ioutput_stream &operator<<(int32_t i32) = 0;
+    virtual ~ioutput_stream() = default;
+};
+}