Add first structure and start work on format specifier parser

include/simple-printf/simple-printf.h

@@ -0,0 +1,30 @@
+#ifndef _SIMPLE_PRINTF_H_
+#define _SIMPLE_PRINTF_H_
+
+#include <stddef.h>
+
+#ifndef SIMPLE_PRINTF_ATTR_FORMAT
+#   if ((__GNUC__ > 3) || ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 3)))
+#       define SIMPLE_PRINTF_ATTR_FORMAT(fmt, args) __attribute__((__format__(__printf__, fmt, args)))
+#   else
+#       define SIMPLE_PRINTF_ATTR_FORMAT(fmt, args)
+#   endif
+#else
+#   define SIMPLE_PRINTF_ATTR_FORMAT(fmt, args)
+#endif
+
+/**
+ * @brief Simple implementation of snprintf
+ * 
+ * Supports the following format specifiers:
+ * %d, %i, %s, %u, %z, %c, %x, %X
+ * @param[out] dest Buffer to write result to
+ * @param dest_size Size of @p dest in bytes
+ * @param[in] fmt Format string
+ * @return Number of written bytes. Not including the null terminator.
+ * @return negative in case of an error
+ * @note The resulting output in @p dest will always be null terminated.
+ */
+int simple_snprintf(char *dest, size_t dest_size, const char *fmt, ...) SIMPLE_PRINTF_ATTR_FORMAT(3, 4);
+
+#endif /* _SIMPLE_PRINTF_H_ */