usr/src/lib/libcmd/common/revlib.c

   1 /***********************************************************************
   2 *                                                                      *
   3 *               This software is part of the ast package               *
   4 *          Copyright (c) 1992-2010 AT&T Intellectual Property          *
   5 *                      and is licensed under the                       *
   6 *                  Common Public License, Version 1.0                  *
   7 *                    by AT&T Intellectual Property                     *
   8 *                                                                      *
   9 *                A copy of the License is available at                 *
  10 *            http://www.opensource.org/licenses/cpl1.0.txt             *
  11 *         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
  12 *                                                                      *
  13 *              Information and Software Systems Research               *
  14 *                            AT&T Research                             *
  15 *                           Florham Park NJ                            *
  16 *                                                                      *
  17 *                 Glenn Fowler <gsf@research.att.com>                  *
  18 *                  David Korn <dgk@research.att.com>                   *
  19 *                                                                      *
  20 ***********************************************************************/
  21 #pragma prototyped
  22 /*
  23  * common support for tail and rev
  24  */
  25
  26 #include        <cmd.h>
  27 #include        <rev.h>
  28
  29 #define BUFSIZE                 SF_BUFSIZE
  30 #define rounddown(n,size)       (((n)-1)&~((size)-1))
  31
  32 /*
  33  * copy the lines starting at offset <start> from in <in> to <out>
  34  * in reverse order
  35  */
  36 int rev_line(Sfio_t *in, Sfio_t *out, off_t start)
  37 {
  38         register char *cp, *cpold;
  39         register int n, nleft=0;
  40         char buff[BUFSIZE];
  41         off_t offset;
  42         if(sfseek(in,(off_t)0,SEEK_CUR) < 0)
  43         {
  44                 Sfio_t *tmp = sftmp(4*SF_BUFSIZE);
  45                 if(!tmp)
  46                         return(-1);
  47                 if(start>0 && sfmove(in, (Sfio_t*)0, start, -1) != start)
  48                         return(-1);
  49                 if(sfmove(in, tmp, SF_UNBOUND, -1) < 0 || !sfeof(in) || sferror(tmp))
  50                         return(-1);
  51                 in = tmp;
  52                 start=0;
  53         }
  54         if((offset = sfseek(in,(off_t)0,SEEK_END)) <= start)
  55                 return(0);
  56         offset = rounddown(offset,BUFSIZE);
  57         while(1)
  58         {
  59                 n = BUFSIZE;
  60                 if(offset < start)
  61                 {
  62                         n -= (start-offset);
  63                         offset = start;
  64                 }
  65                 sfseek(in, offset, SEEK_SET);
  66                 if((n=sfread(in, buff, n)) <=0)
  67                         break;
  68                 cp = buff+n;
  69                 n = *buff;
  70                 *buff = '\n';
  71                 while(1)
  72                 {
  73                         cpold = cp;
  74                         if(nleft==0)
  75                                 cp--;
  76                         if(cp==buff)
  77                         {
  78                                 nleft= 1;
  79                                 break;
  80                         }
  81                         while(*--cp != '\n');
  82                         if(cp==buff && n!='\n')
  83                         {
  84                                 *cp = n;
  85                                 nleft += cpold-cp;
  86                                 break;
  87                         }
  88                         else
  89                                 cp++;
  90                         if(sfwrite(out,cp,cpold-cp) < 0)
  91                                 return(-1);
  92                         if(nleft)
  93                         {
  94                                 if(nleft==1)
  95                                         sfputc(out,'\n');
  96                                 else if(sfmove(in,out,nleft,-1) != nleft)
  97                                         return(-1);
  98                                 nleft = 0;
  99                         }
 100                 }
 101                 if(offset <= start)
 102                         break;
 103                 offset -= BUFSIZE;
 104         }
 105         if(nleft)
 106         {
 107                 sfseek(in, start, SEEK_SET);
 108                 if(sfmove(in,out,nleft,-1) != nleft)
 109                         return(-1);
 110         }
 111         return(0);
 112 }