sys/stdio: factor out STDIO abstraction

sys/include/stdio_base.h

+/*
+ * Copyright (C) 2015 Kaspar Schleiser <kaspar@schleiser.de>
+ *               2018 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup    sys_stdio STDIO abstraction
+ * @ingroup     sys
+ *
+ * @brief       Simple standard input/output (STDIO) abstraction for RIOT
+ *
+ * @{
+ * @file
+ *
+ * @author      Kaspar Schleiser <kaspar@schleiser.de>
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ */
+
+#ifndef STDIO_BASE_H
+#define STDIO_BASE_H
+
+#include <unistd.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief initialize the module
+ */
+void stdio_init(void);
+
+/**
+ * @brief read @p len bytes from stdio uart into @p buffer
+ *
+ * @param[out]  buffer  buffer to read into
+ * @param[in]   max_len nr of bytes to read
+ *
+ * @return nr of bytes read
+ * @return <0 on error
+ */
+ssize_t stdio_read(void* buffer, size_t max_len);
+
+/**
+ * @brief write @p len bytes from @p buffer into uart
+ *
+ * @param[in]   buffer  buffer to read from
+ * @param[in]   len     nr of bytes to write
+ *
+ * @return nr of bytes written
+ * @return <0 on error
+ */
+ssize_t stdio_write(const void* buffer, size_t len);
+
+#ifdef __cplusplus
+}
+#endif
+/** @} */
+#endif /* STDIO_BASE_H */