sftell.c

su 的源代码库

/* Copyright (c) Colorado School of Mines, 2006.*/
/* All rights reserved.                       */

#include	"sfhdr.h"

/*	Tell the current location in a given stream
**
**	Written by Kiem-Phong Vo.
*/

#if __STD_C
Sfoff_t sftell(reg Sfio_t* f)
#else
Sfoff_t sftell(f)
reg Sfio_t	*f;
#endif
{	
	reg int	mode;
	Sfoff_t	p;

	SFMTXSTART(f, (Sfoff_t)(-1));

	/* set the stream to the right mode */
	if((mode = f->mode&SF_RDWR) != (int)f->mode && _sfmode(f,mode,0) < 0)
		SFMTXRETURN(f, (Sfoff_t)(-1));

	/* throw away ungetc data */
	if(f->disc == _Sfudisc)
		(void)sfclose((*_Sfstack)(f,NIL(Sfio_t*)));

	if(f->flags&SF_STRING)
		SFMTXRETURN(f, (Sfoff_t)(f->next-f->data));

	/* let sfseek() handle the hard case */
	if(f->extent >= 0 && (f->flags&(SF_SHARE|SF_APPENDWR)) )
		p = sfseek(f,(Sfoff_t)0,1);
	else	p = f->here + ((f->mode&SF_WRITE) ? f->next-f->data : f->next-f->endb);

	SFMTXRETURN(f,p);
}