new function for file input. rewind the filedescriptor to the current

new function for file input. rewind the filedescriptor to the current

Tue Oct 27 07:25:53 1998  Tim Janik  <timj@gtk.org>

        * glib.h:
        * gscanner.c:
        (g_scanner_sync_file_offset): new function for file input.
        rewind the filedescriptor to the current buffer position and blow
        the file read ahead buffer. usefull for third party uses of our
        filedescriptor, which hooks onto the current scanning position.
        (this became neccessary with the implementation of buffered
        reads).
        (g_scanner_input_file):
        (g_scanner_input_text): automatically blow the read ahead buffer.
        (g_scanner_get_char): blow the read ahead buffer when the end of
        input is reached, i.e. a '\000' char is read.