+
+/* The worker for all scanf() type of functions. The pointer spec should point
+ to the introducing '%' of a conversion specifier. The status structure is to
+ be that of the current scanf() function, of which the member stream will be
+ preserved, n, i, and s will be updated; and all others will be trashed by the
+ function.
+ Returns a pointer to the first character not parsed as conversion specifier.
+*/
+const char * _PDCLIB_scan( const char * spec, struct _PDCLIB_status_t * status );
+
+/* Parsing any fopen() style filemode string into a number of flags. */
+unsigned int _PDCLIB_filemode( const char * mode );
+
+/* Sanity checking and preparing of read buffer, should be called first thing
+ by any stdio read-data function.
+ Returns 0 on success, EOF on error.
+ On error, EOF / error flags and errno are set appropriately.
+*/
+int _PDCLIB_prepread( struct _PDCLIB_file_t * stream );
+
+/* Sanity checking, should be called first thing by any stdio write-data
+ function.
+ Returns 0 on success, EOF on error.
+ On error, error flags and errno are set appropriately.
+*/
+int _PDCLIB_prepwrite( struct _PDCLIB_file_t * stream );
+
+/* -------------------------------------------------------------------------- */
+/* errno */
+/* -------------------------------------------------------------------------- */
+
+extern int _PDCLIB_errno;
+int * _PDCLIB_errno_func( void );
+
+/* ERANGE and EDOM are specified by the standard. */
+#define _PDCLIB_ERANGE 1
+#define _PDCLIB_EDOM 2
+/* Used in the example implementation for any kind of I/O error. */
+#define _PDCLIB_EIO 3
+/* Used in the example implementation for "unknown error". */
+#define _PDCLIB_EUNKNOWN 4
+/* Used in the example implementation for "invalid parameter value". */
+#define _PDCLIB_EINVAL 5
+/* Used in the example implementation for "I/O retries exceeded". */
+#define _PDCLIB_ERETRY 6
+