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sfpurge.c

/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*          Copyright (c) 1985-2008 AT&T Intellectual Property          *
*                      and is licensed under the                       *
*                  Common Public License, Version 1.0                  *
*                    by AT&T Intellectual Property                     *
*                                                                      *
*                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);
}

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