ftell.c

来自「操作系统SunOS 4.1.3版本的源码」· C语言 代码 · 共 37 行

#if !defined(lint) && defined(SCCSIDS)
static	char sccsid[] = "@(#)ftell.c 1.1 92/07/30 SMI"; /* from S5R2 1.2 */
#endif

/*LINTLIBRARY*/
/*
 * Return file offset.
 * Coordinates with buffering.
 */
#include <stdio.h>

extern long lseek();

long
ftell(iop)
register FILE *iop;
{
	register long tres;
	register int adjust;

	if(iop->_cnt < 0)
		iop->_cnt = 0;
	if(iop->_flag & _IOREAD)
		adjust = - iop->_cnt;
	else if(iop->_flag & (_IOWRT | _IORW)) {
		adjust = 0;
		if(iop->_flag & _IOWRT && iop->_base &&
					(iop->_flag & _IONBF) == 0)
			adjust = iop->_ptr - iop->_base;
	} else
		return(-1);
	tres = lseek(fileno(iop), 0L, 1);
	if(tres >= 0)
		tres += (long)adjust;
	return(tres);
}