ref: 02abca68e91999009c0f3ef154fb99f39c212c2c
dir: /src/libc/stdio/fseek.c/
#include <stdio.h>
#include "../syscall.h"
#undef fseek
int
fseek(FILE *fp, long off, int whence)
{
	if (fp->flags & _IOERR)
		return EOF;
	if ((fp->flags & _IOWRITE) && _flsbuf(fp))
		return -1;
	else if (whence == SEEK_CUR && (fp->flags & _IOREAD))
		off -= fp->wp - fp->rp;
	if (_lseek(fp->fd, off, whence) < 0) {
		fp->flags |= _IOERR;
		return EOF;
	}
	if (fp->flags & _IORW)
		fp->flags &= ~(_IOREAD | _IOWRITE);
	fp->flags &= ~_IOEOF;
	return 0;
}