-/* Writing out unwritten buffers of a specific stream. A NULL parameter (as is
- possible with standard fflush()) is not supported.
- Return 0 if successful, EOF if error occured. Set error flag of stream and
- errno as appropriate in case of error.
+/* 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 );
+
+/* Closing all streams on program exit */
+void _PDCLIB_closeall( void );
+
+/* -------------------------------------------------------------------------- */
+/* errno */
+/* -------------------------------------------------------------------------- */
+
+/* If PDCLib would call its error number "errno" directly, there would be no way
+ to catch its value from underlying system calls that also use it (i.e., POSIX
+ operating systems). That is why we use an internal name, providing a means to
+ access it through <errno.h>.
+*/
+extern int _PDCLIB_errno;
+
+/* A mechanism for delayed evaluation. (Not sure if this is really necessary, so
+ no detailed documentation on the "why".)