4.3BSD - /usr/src/new/icon/rt/mksubs.c

   1: #include "../h/rt.h"
   2: 
   3: /*
   4:  * mksubs - form a substring.  var is a descriptor for the string from
   5:  *  which the substring is to be formed.  var may be a variable.  val
   6:  *  is a dereferenced version of val.  The descriptor for the resulting
   7:  *  substring is placed in *result.  The substring starts at position
   8:  *  i and extends for j characters.
   9:  */
  10: 
  11: struct descrip mksubs(var, val, i, j, result)
  12: register struct descrip *var, *val, *result;
  13: int i, j;
  14:    {
  15:    extern struct b_tvsubs *alcsubs();
  16: 
  17:    if (QUAL(*var) || !VAR(*var)) {
  18:       /*
  19:        * var isn't a variable, just form a descriptor that points into
  20:        *  the string named by val.
  21:        */
  22:       STRLEN(*result) = j;
  23:       STRLOC(*result) = STRLOC(*val) + i - 1;
  24:       return;
  25:       }
  26: 
  27:    if (TVAR(*var)) {
  28:       /*
  29:        * var is a trapped variable.  If it is a substring trapped variable,
  30:        *  adjust the position and make var the substrung string.  For other
  31:        *  trapped variables, don't do anything.
  32:        */
  33:       switch (TYPE(*var)) {
  34:          case T_TVSUBS:
  35:             i += BLKLOC(*var)->tvsubs.sspos - 1;
  36:             var = &BLKLOC(*var)->tvsubs.ssvar;
  37:             break;
  38: 
  39:          default:
  40:             break;
  41:          }
  42:       }
  43: 
  44:    /*
  45:     * Make a substring trapped variable by passing the buck to alcsubs.
  46:     */
  47:    result->type = D_TVSUBS;
  48:    BLKLOC(*result) = (union block *) alcsubs(j, i, var);
  49:    return;
  50:    }

Defined functions