base: move 'Buffered_output' class into public header

Fixes #3128

repos/base/include/base/buffered_output.h

@@ -0,0 +1,68 @@
+/*
+ * \brief  Implementation of the output interface that buffers characters
+ * \author Norman Feske
+ * \date   2016-05-03
+ */
+
+/*
+ * Copyright (C) 2016-2019 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#ifndef _INCLUDE__BASE__BUFFERED_OUTPUT_H_
+#define _INCLUDE__BASE__BUFFERED_OUTPUT_H_
+
+#include <base/output.h>
+
+namespace Genode { template <size_t, typename> class Buffered_output; }
+
+
+/**
+ * Implementation of the output interface that buffers characters
+ *
+ * \param BUF_SIZE  maximum number of characters to buffer before writing
+ * \param WRITE_FN  functor called to writing the buffered characters to a
+ *                  backend.
+ *
+ * The 'WRITE_FN' functor is called with a null-terminated 'char const *'
+ * as argument.
+ */
+template <Genode::size_t BUF_SIZE, typename BACKEND_WRITE_FN>
+class Genode::Buffered_output : public Output
+{
+	private:
+
+		BACKEND_WRITE_FN _write_fn;
+		char             _buf[BUF_SIZE];
+		unsigned         _num_chars = 0;
+
+		void _flush()
+		{
+			/* null-terminate string */
+			_buf[_num_chars] = 0;
+			_write_fn(_buf);
+
+			/* restart with empty buffer */
+			_num_chars = 0;
+		}
+
+	public:
+
+		Buffered_output(BACKEND_WRITE_FN const &write_fn) : _write_fn(write_fn) { }
+
+		void out_char(char c) override
+		{
+			/* ensure enough buffer space for complete escape sequence */
+			if ((c == 27) && (_num_chars + 8 > BUF_SIZE)) _flush();
+
+			_buf[_num_chars++] = c;
+
+			/* flush immediately on line break */
+			if (c == '\n' || _num_chars >= sizeof(_buf) - 1)
+				_flush();
+		}
+};
+
+#endif /* _INCLUDE__BASE__BUFFERED_OUTPUT_H_ */