Ultrix-3.1/src/libc/stdio/fseek.c

/**********************************************************************
 *   Copyright (c) Digital Equipment Corporation 1984, 1985, 1986.    *
 *   All Rights Reserved. 					      *
 *   Reference "/usr/src/COPYRIGHT" for applicable restrictions.      *
 **********************************************************************/

/*
 * SCCSID: @(#)fseek.c	3.0	4/22/86
 */
/*	(System 5)  fseek.c	1.3	*/
/*	3.0 SID #	1.2	*/

/*LINTLIBRARY*/
/*
 * Seek for standard library.  Coordinates with buffering.
 */
#include <stdio.h>

extern long lseek();
extern int fflush();

int
fseek(iop, offset, ptrname)
register FILE *iop;
long	offset;
int	ptrname;
{
	register int c;
	long	p;

	iop->_flag &= ~_IOEOF;
	if(iop->_flag & _IOREAD) {
		if(ptrname < 2 && iop->_base && !(iop->_flag&_IONBF)) {
			c = iop->_cnt;
			p = offset;
			if(ptrname == 0)
				p += (long)c-lseek(fileno(iop), 0L, 1);
			else
				offset -= (long)c;
			if(!(iop->_flag&_IORW) && c > 0 && p <= c &&
					p >= iop->_base - iop->_ptr) {
				iop->_ptr += (int)p;
				iop->_cnt -= (int)p;
				return(0);
			}
		}
		if(iop->_flag & _IORW) {
			iop->_ptr = iop->_base;
			iop->_flag &= ~_IOREAD;
		}
		p = lseek(fileno(iop), offset, ptrname);
		iop->_cnt = 0;
	} else if(iop->_flag & (_IOWRT | _IORW)) {
		(void) fflush(iop);
		iop->_cnt = 0;
		if(iop->_flag & _IORW) {
			iop->_flag &= ~_IOWRT;
			iop->_ptr = iop->_base;
		}
		p = lseek(fileno(iop), offset, ptrname);
	}
	return((p == -1)? -1: 0);
}