genode/repos/libports/include/format/snprintf.h

/*
 * \brief  Facility to write format string into character buffer
 * \author Norman Feske
 * \date   2006-07-17
 */

/*
 * Copyright (C) 2006-2017 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__FORMAT__SNPRINTF_H_
#define _INCLUDE__FORMAT__SNPRINTF_H_

#include <format/console.h>

namespace Format {

	class String_console;

	using size_t = __SIZE_TYPE__;

	/**
	 * Print format string into character buffer
	 *
	 * \param dst      destination buffer
	 * \param dst_len  size of 'dst' in bytes
	 * \param format   format string followed by the list of arguments
	 *
	 * \return  number of characters written to destination buffer
	 */
	inline size_t snprintf(char *dst, size_t dst_size, const char *format, ...)
	                       __attribute__((format(printf, 3, 4)));
}


class Format::String_console : public Console
{
	private:

		char   *_dst;
		size_t  _dst_len;
		size_t  _w_offset { 0 };

		/*
		 * Noncopyable
		 */
		String_console &operator = (String_console const &);
		String_console(String_console const &);

	public:

		/**
		 * Constructor
		 *
		 * \param dst      destination character buffer
		 * \param dst_len  size of 'dst'
		 */
		String_console(char *dst, size_t dst_len)
		: _dst(dst), _dst_len(dst_len)
		{ _dst[0] = 0; }

		/**
		 * Return number of characters in destination buffer
		 */
		size_t len() { return _w_offset; }


		/***********************
		 ** Console interface **
		 ***********************/

		void _out_char(char c) override
		{
			/* ensure to leave space for null-termination */
			if (_w_offset + 2 > _dst_len)
				return;

			_dst[_w_offset++] = c;
			_dst[_w_offset] = 0;
		}
};


inline Format::size_t Format::snprintf(char *dst, size_t dst_len, const char *format, ...)
{
	va_list list;
	va_start(list, format);

	String_console sc(dst, dst_len);
	sc.vprintf(format, list);

	va_end(list);
	return sc.len();
}

#endif /* _INCLUDE__FORMAT__SNPRINTF_H_ */