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

   1: #include "../h/rt.h"
   2: 
   3: /*
   4:  * deref - dereference a descriptor.
   5:  */
   6: deref(d)
   7: struct descrip *d;
   8:    {
   9:    register int i, j;
  10:    register union block *bp;
  11:    struct descrip v, tbl, tref;
  12:    char sbuf[MAXSTRING];
  13:    extern char *alcstr();
  14: 
  15:    if (!QUAL(*d) && VAR(*d)) {
  16:       /*
  17:        * *d is a variable and must be dereferenced.
  18:        */
  19:       if (TVAR(*d)) {
  20:          switch (TYPE(*d)) {
  21:             case T_TVSUBS:
  22:                /*
  23:                 * A substring trapped variable is being dereferenced.  Point
  24:                 *  bp at the trapped variable block and v at the substrung
  25:                 *  string.
  26:                 */
  27:                bp = TVARLOC(*d);
  28:                v = bp->tvsubs.ssvar;
  29:                /*
  30:                 * Convert v into a string.
  31:                 */
  32:                switch (cvstr(&v, sbuf)) {
  33:                   case NULL:
  34:                      runerr(103,&v);
  35:                   case 1:
  36:                      /*
  37:                       * A conversion to string was made.  Allocate the
  38:                       *  converted string and fall through to common code
  39:                       *  for allocated strings.  Note that bp is reassigned
  40:                       *  in case the sneed caused a garbage collection.
  41:                       */
  42:                      sneed(STRLEN(v));
  43:                      STRLOC(v) = alcstr(STRLOC(v), STRLEN(v));
  44:                      bp = TVARLOC(*d);
  45:                   case 2:
  46:                      /*
  47:                       * The substrung string is an allocated string.  Be sure
  48:                       *  that the position is in range.
  49:                       */
  50:                      if (bp->tvsubs.sspos + bp->tvsubs.sslen - 1 > STRLEN(v))
  51:                         runerr(205,NULL);
  52:                      /*
  53:                       * Make a descriptor for the substring by getting the
  54:                       *  length and  pointing into the substrung string.
  55:                       */
  56:                      STRLEN(*d) = bp->tvsubs.sslen;
  57:                      STRLOC(*d) = STRLOC(v) + bp->tvsubs.sspos - 1;
  58:                   }
  59:                break;
  60: 
  61:             case T_TVTBL:
  62:                /*
  63:                 * A table element trapped variable is being dereferenced.
  64:                 *  Point tbl at the table header block,
  65:                 *  tref at the subscripting value,
  66:                 *  bp at the appropriate element chain.  Make d a
  67:                 *  descriptor for the default value in case the value
  68:                 *  referenced by the subscript isn't in the table.
  69:                 */
  70:                if (BLKLOC(*d)->tvtbl.type == T_TELEM) {
  71:                /*
  72:                     * the tvtbl has been converted to a telem and is in the table
  73:                 * just replace d with the value of the element
  74:                       */
  75:                         *d = BLKLOC(*d)->telem.tval;
  76:                         break;
  77:                         }
  78:                tbl = BLKLOC(*d)->tvtbl.tvtable;
  79:                tref = BLKLOC(*d)->tvtbl.tvtref;
  80:                i = BLKLOC(*d)->tvtbl.hashnum;
  81:                *d = BLKLOC(tbl)->table.defvalue;
  82:                bp = BLKLOC(BLKLOC(tbl)->table.buckets[i % NBUCKETS]);
  83:                /*
  84:                 * Look down the element chain for the subscript value.
  85:                 *  If found, replace d with the value of the element.
  86:                 */
  87:                while (bp != NULL) {
  88:                   if (bp->telem.hashnum > i)
  89:                            break;
  90:                      if ((bp->telem.hashnum == i) &&
  91:                        (equiv(&bp->telem.tref, &tref))) {
  92:                                      *d = bp->telem.tval;
  93:                                      break;
  94:                                      }
  95:                   bp = BLKLOC(bp->telem.blink);
  96:                   }
  97:                break;
  98: 
  99:             case T_TVPOS:
 100:                /*
 101:                 * &pos is being dereferenced, make a descriptor for the
 102:                 *  appropriate integer value.
 103:                 */
 104:                d->type = D_INTEGER;
 105:                INTVAL(*d) = k_pos;
 106:                break;
 107: 
 108:             case T_TVRAND:
 109:                /*
 110:                 * &random is being dereferenced, use mkint to make a
 111:                 *  an integer descriptor from the value of k_random.
 112:                 */
 113:                mkint(k_random, d);
 114:                break;
 115: 
 116:             case T_TVTRACE:
 117:                /*
 118:                 * &trace is being dereferenced, make a descriptor for the
 119:                 *  appropriate integer value.
 120:                 */
 121:                d->type = D_INTEGER;
 122:                INTVAL(*d) = k_trace;
 123:                break;
 124: 
 125:             default:
 126:                syserr("deref: illegal trapped variable");
 127:             }
 128:          }
 129:       else
 130:          /*
 131:           * An ordinary variable is being dereferenced, just replace *d
 132:           *  with the the descriptor *d is pointing to.
 133:           */
 134:          *d = *VARLOC(*d);
 135:       }
 136: #ifdef DEBUG
 137:    if (!QUAL(*d) && VAR(*d))
 138:       syserr("deref: didn't get dereferenced");
 139: #endif DEBUG
 140:    return (1);
 141:    }

Defined functions