sfpurge.c revision da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968
/***********************************************************************
* *
* This software is part of the ast package *
* Copyright (c) 1985-2007 AT&T Knowledge Ventures *
* and is licensed under the *
* Common Public License, Version 1.0 *
* by AT&T Knowledge Ventures *
* *
* A copy of the License is available at *
* http://www.opensource.org/licenses/cpl1.0.txt *
* (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9) *
* *
* Information and Software Systems Research *
* AT&T Research *
* Florham Park NJ *
* *
* Glenn Fowler <gsf@research.att.com> *
* David Korn <dgk@research.att.com> *
* Phong Vo <kpv@research.att.com> *
* *
***********************************************************************/
#include "sfhdr.h"
/* Delete all pending data in the buffer
**
** Written by Kiem-Phong Vo.
*/
#if __STD_C
int sfpurge(reg Sfio_t* f)
#else
int sfpurge(f)
reg Sfio_t* f;
#endif
{
reg int mode;
SFMTXSTART(f,-1);
if((mode = f->mode&SF_RDWR) != (int)f->mode && _sfmode(f,mode|SF_SYNCED,0) < 0)
SFMTXRETURN(f, -1);
if((f->flags&SF_IOCHECK) && f->disc && f->disc->exceptf)
(void)(*f->disc->exceptf)(f,SF_PURGE,(Void_t*)((int)1),f->disc);
if(f->disc == _Sfudisc)
(void)sfclose((*_Sfstack)(f,NIL(Sfio_t*)));
/* cannot purge read string streams */
if((f->flags&SF_STRING) && (f->mode&SF_READ) )
goto done;
SFLOCK(f,0);
/* if memory map must be a read stream, pretend data is gone */
#ifdef MAP_TYPE
if(f->bits&SF_MMAP)
{ f->here -= f->endb - f->next;
if(f->data)
{ SFMUNMAP(f,f->data,f->endb-f->data);
SFSK(f,f->here,SEEK_SET,f->disc);
}
SFOPEN(f,0);
SFMTXRETURN(f, 0);
}
#endif
switch(f->mode&~SF_LOCK)
{
default :
SFOPEN(f,0);
SFMTXRETURN(f, -1);
case SF_WRITE :
f->next = f->data;
if(!f->proc || !(f->flags&SF_READ) || !(f->mode&SF_WRITE) )
break;
/* 2-way pipe, must clear read buffer */
(void)_sfmode(f,SF_READ,1);
/* fall through */
case SF_READ:
if(f->extent >= 0 && f->endb > f->next)
{ f->here -= f->endb-f->next;
SFSK(f,f->here,SEEK_SET,f->disc);
}
f->endb = f->next = f->data;
break;
}
SFOPEN(f,0);
done:
if((f->flags&SF_IOCHECK) && f->disc && f->disc->exceptf)
(void)(*f->disc->exceptf)(f,SF_PURGE,(Void_t*)((int)0),f->disc);
SFMTXRETURN(f, 0);
}