minix/lib/libc/stdio/fseek.c
2010-08-16 17:06:08 +00:00

52 lines
1.1 KiB
C

/*
* fseek.c - perform an fseek
*/
/* $Header$ */
#include <assert.h>
#include <stdio.h>
#if (SEEK_CUR != 1) || (SEEK_END != 2) || (SEEK_SET != 0)
#error SEEK_* values are wrong
#endif
#include "loc_incl.h"
#include <sys/types.h>
off_t _lseek(int fildes, off_t offset, int whence);
int
fseek(FILE *stream, long int offset, int whence)
{
assert(sizeof(offset) == sizeof(off_t));
return fseeko(stream, (off_t) offset, whence);
}
int
fseeko(FILE *stream, off_t offset, int whence)
{
int adjust = 0;
long pos;
stream->_flags &= ~(_IOEOF | _IOERR);
/* Clear both the end of file and error flags */
if (io_testflag(stream, _IOREADING)) {
if (whence == SEEK_CUR
&& stream->_buf
&& !io_testflag(stream,_IONBF))
adjust = stream->_count;
stream->_count = 0;
} else if (io_testflag(stream,_IOWRITING)) {
fflush(stream);
} else /* neither reading nor writing. The buffer must be empty */
/* EMPTY */ ;
pos = _lseek(fileno(stream), offset - adjust, whence);
if (io_testflag(stream, _IOREAD) && io_testflag(stream, _IOWRITE))
stream->_flags &= ~(_IOREADING | _IOWRITING);
stream->_ptr = stream->_buf;
return ((pos == -1) ? -1 : 0);
}