2.9BSD - /usr/src/lib/libI77/backspace.c

   1: /*
   2: char id_backspace[] = "@(#)backspace.c	1.6";
   3:  *
   4:  * Backspace records
   5:  */
   6: 
   7: #include "fio.h"
   8: 
   9: static char bksp[]  = "backspace";
  10: char    last_char();
  11: 
  12: f_back(a)
  13: alist   *a;
  14: {   unit *b;
  15:     int n,i;
  16:     long x,y;
  17: 
  18:     lfname = NULL;
  19:     elist = NO;
  20:     external = YES;
  21:     errflag = a->aerr;
  22:     lunit = a->aunit;
  23:     if (not_legal(lunit))
  24:         err(errflag, F_ERUNIT, bksp)
  25:     b= &units[lunit];
  26:     if(!b->ufd && (n = fk_open(READ, SEQ, FMT, (ftnint)lunit)) )
  27:         err(errflag, n, bksp)
  28:     lfname = b->ufnm;
  29:     if(b->uend)
  30:     {   b->uend = NO;
  31:         clearerr(b->ufd);
  32:         return(OK);
  33:     }
  34:     if((x = ftell(b->ufd)) == 0)
  35:         return(OK);
  36:     if(!b->useek)
  37:         err(errflag, F_ERNOBKSP, bksp)
  38:     if(b->uwrt && (n = t_runc(b, errflag, bksp)))   /* sets 'reading' */
  39:         return(n);
  40:     if(b->url)      /* direct access, purely academic */
  41:     {   y = x%(long)b->url;
  42:         x -= y?y:b->url;
  43:         fseek(b->ufd,x,0);
  44:         return(OK);
  45:     }
  46:     if(!b->ufmt)        /* unformatted sequential */
  47:     {   fseek(b->ufd,-(long)sizeof(int),1);
  48:         fread((char *)&n,sizeof(int),1,b->ufd);
  49:         fseek(b->ufd,-(long)n-2*sizeof(int),1);
  50:         return(OK);
  51:     }
  52:     if(x == 1)          /* formatted sequential */
  53:     {   rewind(b->ufd);
  54:         return(OK);
  55:     }
  56:     while (last_char(b->ufd) != '\n')   /* slow but simple */
  57:         ;
  58:     return(OK);
  59: }

Defined functions

Defined variables