libos: Let users change the buffering mode of a File

libos/include/os/File.h

@@ -143,6 +143,19 @@ namespace os
          */
         Result<void> read(Buffer& buf, usize size);
 
+        /**
+         * @brief Read an object from this File.
+         *
+         * @tparam T The type of the object to read.
+         * @param object A reference to the object in question.
+         * @return Result<void> Whether the operation succeeded.
+         */
+        template <typename T> Result<void> read_typed(T& object)
+        {
+            TRY(raw_read((u8*)&object, sizeof(T)));
+            return {};
+        }
+
         /**
          * @brief Read the entire File's contents.
          *
@@ -178,6 +191,20 @@ namespace os
          */
         void rewind();
 
+        enum BufferingMode
+        {
+            NotBuffered = _IONBF,
+            LineBuffered = _IOLBF,
+            FullyBuffered = _IOFBF,
+        };
+
+        /**
+         * @brief Change the buffering mode of this File.
+         *
+         * @param mode The buffering mode.
+         */
+        void set_buffer(BufferingMode mode);
+
         File(Badge<File>);
         ~File();
 

libos/src/File.cpp

@@ -226,6 +226,11 @@ namespace os
         fflush(m_file);
     }
 
+    void File::set_buffer(BufferingMode mode)
+    {
+        setvbuf(m_file, NULL, mode, 0);
+    }
+
     // FIXME: Do not allocate memory for printing.
     Result<void> print_impl(SharedPtr<File> f, StringView fmt, va_list ap)
     {