factmch.c

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   /*===========================================*/
   /* Create a new multifield marker and append */
   /* it to the end of the current list.        */
   /*===========================================*/

   newMark = get_struct(theEnv,multifieldMarker);
   newMark->whichField = thePattern->whichField - 1;
   newMark->where.whichSlotNumber = (short) thePattern->whichSlot;
   newMark->startPosition = (thePattern->whichField - 1) + offset;
   newMark->next = NULL;

   if (endMark == NULL)
     {
      markers = newMark;
      FactData(theEnv)->CurrentPatternMarks = markers;
     }
   else
     { endMark->next = newMark; }

   /*============================================*/
   /* Handle a multifield constraint as the last */
   /* constraint of a slot as a special case.    */
   /*============================================*/

   if (thePattern->header.endSlot)
     {
      newMark->endPosition = (long) theSlotValue->multifieldLength -
                                    (thePattern->leaveFields + 1);

      /*=======================================================*/
      /* Make sure the endPosition is never more than less one */
      /* less of the startPosition (a multifield containing no */
      /* values.                                               */
      /*=======================================================*/

      if (newMark->endPosition < newMark->startPosition)
        { newMark->endPosition = newMark->startPosition - 1; }

      /*===========================================*/
      /* Determine if the constraint is satisfied. */
      /*===========================================*/

      if ((thePattern->networkTest == NULL) ?
          TRUE :
          (EvaluatePatternExpression(theEnv,thePattern,thePattern->networkTest,
                                     (int) thePattern->whichField + offset)))
        {
         /*=======================================================*/
         /* If a leaf pattern node has been successfully reached, */
         /* then the pattern has been satisified. Generate an     */
         /* alpha match to store in the pattern node.             */
         /*=======================================================*/

         if (thePattern->header.stopNode)
           { ProcessFactAlphaMatch(theEnv,FactData(theEnv)->CurrentPatternFact,FactData(theEnv)->CurrentPatternMarks,thePattern); }

         /*=============================================*/
         /* Recursively continue pattern matching based */
         /* on the multifield binding just generated.   */
         /*=============================================*/

         FactPatternMatch(theEnv,FactData(theEnv)->CurrentPatternFact,
                          thePattern->nextLevel,0,FactData(theEnv)->CurrentPatternMarks,newMark);
        }

      /*================================================*/
      /* Discard the multifield marker since we've done */
      /* all the pattern matching for this binding of   */
      /* the multifield slot constraint.                */
      /*================================================*/

      rtn_struct(theEnv,multifieldMarker,newMark);
      if (endMark != NULL) endMark->next = NULL;
      FactData(theEnv)->CurrentPatternMarks = oldMark;
      return;
     }

   /*==============================================*/
   /* Perform matching for nodes beneath this one. */
   /*==============================================*/

   for (repeatCount = (long) (theSlotValue->multifieldLength -
                      (newMark->startPosition + thePattern->leaveFields));
        repeatCount >= 0;
        repeatCount--)
     {
      newMark->endPosition = newMark->startPosition + (repeatCount - 1);

      if ((thePattern->networkTest == NULL) ?
          TRUE :
          (EvaluatePatternExpression(theEnv,thePattern,thePattern->networkTest,
                                     (int) thePattern->whichField + offset)))
        {
         FactPatternMatch(theEnv,FactData(theEnv)->CurrentPatternFact,
                          thePattern->nextLevel,offset + repeatCount - 1,
                          FactData(theEnv)->CurrentPatternMarks,newMark);
        }
     }

    /*======================================================*/
    /* Get rid of the marker created for a multifield node. */
    /*======================================================*/

    rtn_struct(theEnv,multifieldMarker,newMark);
    if (endMark != NULL) endMark->next = NULL;
    FactData(theEnv)->CurrentPatternMarks = oldMark;
   }

/******************************************************/
/* GetNextFactPatternNode: Returns the next node in a */
/*   pattern network tree to be traversed. The next   */
/*   node is computed using a depth first traversal.  */
/******************************************************/
static struct factPatternNode *GetNextFactPatternNode(
  void *theEnv,
  int finishedMatching,
  struct factPatternNode *thePattern)
  {
   EvaluationData(theEnv)->EvaluationError = FALSE;

   /*===================================================*/
   /* If pattern matching was successful at the current */
   /* node in the tree and it's possible to go deeper   */
   /* into the tree, then move down to the next level.  */
   /*===================================================*/

   if (finishedMatching == FALSE)
     { if (thePattern->nextLevel != NULL) return(thePattern->nextLevel); }

   /*================================================*/
   /* Keep backing up toward the root of the pattern */
   /* network until a side branch can be taken.      */
   /*================================================*/

   while (thePattern->rightNode == NULL)
     {
      /*========================================*/
      /* Back up to check the next side branch. */
      /*========================================*/

      thePattern = thePattern->lastLevel;

      /*======================================*/
      /* If we branched up from the root, the */
      /* entire tree has been traversed.      */
      /*======================================*/

      if (thePattern == NULL) return(NULL);

      /*===================================================*/
      /* If we branched up to a multifield node, then stop */
      /* since these nodes are handled recursively. The    */
      /* previous call to the pattern matching algorithm   */
      /* on the stack will handle backing up to the nodes  */
      /* above the multifield node in the pattern network. */
      /*===================================================*/

      if (thePattern->header.multifieldNode) return(NULL);
     }

   /*==================================*/
   /* Move on to the next side branch. */
   /*==================================*/

   return(thePattern->rightNode);
  }

/*******************************************************/
/* ProcessFactAlphaMatch: When a fact pattern has been */
/*   satisfied, this routine creates an alpha match to */
/*   store in the pattern network and then sends the   */
/*   new alpha match through the join network.         */
/*******************************************************/
static void ProcessFactAlphaMatch(
  void *theEnv,
  struct fact *theFact,
  struct multifieldMarker *theMarks,
  struct factPatternNode *thePattern)
  {
   struct partialMatch *theMatch;
   struct patternMatch *listOfMatches;
   struct joinNode *listOfJoins;

  /*===========================================*/
  /* Create the partial match for the pattern. */
  /*===========================================*/

  theMatch = CreateAlphaMatch(theEnv,theFact,theMarks,(struct patternNodeHeader *) &thePattern->header);

  /*=======================================================*/
  /* Add the pattern to the list of matches for this fact. */
  /*=======================================================*/

  listOfMatches = (struct patternMatch *) theFact->list;
  theFact->list = (void *) get_struct(theEnv,patternMatch);
  ((struct patternMatch *) theFact->list)->next = listOfMatches;
  ((struct patternMatch *) theFact->list)->matchingPattern = (struct patternNodeHeader *) thePattern;
  ((struct patternMatch *) theFact->list)->theMatch = theMatch;

  /*================================================================*/
  /* Send the partial match to the joins connected to this pattern. */
  /*================================================================*/

  for (listOfJoins = thePattern->header.entryJoin;
       listOfJoins != NULL;
       listOfJoins = listOfJoins->rightMatchNode)
     { NetworkAssert(theEnv,theMatch,listOfJoins,RHS); }
  }

/*****************************************************************/
/* EvaluatePatternExpression: Performs a faster evaluation for   */
/*   fact pattern network expressions than if EvaluateExpression */
/*   were used directly.                                         */
/*****************************************************************/
static int EvaluatePatternExpression(
  void *theEnv,
  struct factPatternNode *patternPtr,
  struct expr *theTest,
  int thePosition)
  {
   DATA_OBJECT theResult;
   struct expr *oldArgument;
   int rv;

   /*=====================================*/
   /* A pattern node without a constraint */
   /* is always satisfied.                */
   /*=====================================*/

   if (theTest == NULL) return(TRUE);

   /*======================================*/
   /* Evaluate pattern network primitives. */
   /*======================================*/

   switch(theTest->type)
     {
      /*==============================================*/
      /* This primitive compares the value stored in  */
      /* a single field slot to a constant for either */
      /* equality or inequality.                      */
      /*==============================================*/

      case FACT_PN_CONSTANT1:
        oldArgument = EvaluationData(theEnv)->CurrentExpression;
        EvaluationData(theEnv)->CurrentExpression = theTest;
        rv = FactPNConstant1(theEnv,theTest->value,&theResult);
        EvaluationData(theEnv)->CurrentExpression = oldArgument;
        return(rv);

      /*=============================================*/
      /* This primitive compares the value stored in */
      /* a multifield slot to a constant for either  */
      /* equality or inequality.                     */
      /*=============================================*/

      case FACT_PN_CONSTANT2:
        oldArgument = EvaluationData(theEnv)->CurrentExpression;
        EvaluationData(theEnv)->CurrentExpression = theTest;
        rv = FactPNConstant2(theEnv,theTest->value,&theResult);
        EvaluationData(theEnv)->CurrentExpression = oldArgument;