external/bsd/pcc/dist/pcc-libs/libI77/backspace.c

   1 /*      $Id: backspace.c,v 1.1.1.1 2008/08/24 05:34:47 gmcgarry Exp $   */
   2 /*
   3  * Copyright(C) Caldera International Inc. 2001-2002. All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * Redistributions of source code and documentation must retain the above
  10  * copyright notice, this list of conditions and the following disclaimer.
  11  * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditionsand the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  * All advertising materials mentioning features or use of this software
  15  * must display the following acknowledgement:
  16  *      This product includes software developed or owned by Caldera
  17  *      International, Inc.
  18  * Neither the name of Caldera International, Inc. nor the names of other
  19  * contributors may be used to endorse or promote products derived from
  20  * this software without specific prior written permission.
  21  *
  22  * USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA
  23  * INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
  24  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  25  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  26  * DISCLAIMED.  IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OFLIABILITY, WHETHER IN CONTRACT,
  31  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  32  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  33  * POSSIBILITY OF SUCH DAMAGE.
  34  */
  35 #include "fio.h"
  36
  37 int
  38 f_back(alist *a)
  39 {
  40         unit *b;
  41         int n,i;
  42         long x;
  43         char buf[32];
  44
  45         if(a->aunit >= MXUNIT || a->aunit < 0)
  46                 err(a->aerr,101,"backspace")
  47         b= &units[a->aunit];
  48         if(b->useek==0) err(a->aerr,106,"backspace")
  49         if(b->ufd==NULL) err(a->aerr,114,"backspace")
  50         if(b->uend==1)
  51         {       b->uend=0;
  52                 return(0);
  53         }
  54         if(b->uwrt)
  55         {       t_runc(b);
  56                 nowreading(b);
  57         }
  58         if(b->url>0)
  59         {
  60                 x=ftell(b->ufd);
  61                 x /= b->url;
  62                 x *= b->url;
  63                 fseek(b->ufd,x,0);
  64                 return(0);
  65         }
  66         if(b->ufmt==0)
  67         {       fseek(b->ufd,-(long)sizeof(int),1);
  68                 fread((char *)&n,sizeof(int),1,b->ufd);
  69                 fseek(b->ufd,-(long)n-2*sizeof(int),1);
  70                 return(0);
  71         }
  72         for(;;)
  73         {
  74                 x=ftell(b->ufd);
  75                 if(x<sizeof(buf)) x=0;
  76                 else x -= sizeof(buf);
  77                 fseek(b->ufd,x,0);
  78                 n=fread(buf,1,sizeof(buf),b->ufd);
  79                 for(i=n-1;i>=0;i--)
  80                 {
  81                         if(buf[i]!='\n') continue;
  82                         fseek(b->ufd,(long)(i-n),1);
  83                         return(0);
  84                 }
  85                 if(x==0) return(0);
  86                 else if(n==0) err(a->aerr,(EOF),"backspace")
  87                 else err(a->aerr,errno,"backspace");
  88         }
  89 }