seloperator.nc

用于传感器网络的节点操作系统 TinyOS 结构设计非常有意思

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/*
 * Authors:	Sam Madden
 *              Design by Sam Madden, Wei Hong, and Joe Hellerstein
 * Date last modified:  6/26/02
 *
 *
 */


module SelOperator {
  provides {
    interface Operator;
  }

  uses {
    interface TupleIntf;
    interface ExprEval;
  }
}

implementation
{
  ParsedQuery *mQs;
  Tuple *mT;
  Expr *mE;

  task void doFilter();

  /* Process a tuple produced locally 
     qs: The query the tuple belongs to
     t: The tuple
     e: The expression to apply to the tuple
    */
  command TinyDBError Operator.processTuple(ParsedQueryPtr qs, TuplePtr t, ExprPtr e) {
    mQs = qs;
    mT = t;
    mE = e;

    post doFilter();

    return err_NoError;
  }



  task void doFilter() {
    ParsedQuery *qs = mQs;
    Tuple *t = mT;
    Expr *e = mE;
    
    OpValExpr ex = e->ex.opval;
    short size = call TupleIntf.fieldSize(qs, (char)ex.field);
    char *fieldBytes = call TupleIntf.getFieldPtr(qs, t, (char)ex.field);
    short fieldVal = 0;
    short i;
    bool result = FALSE;
    

    for (i = 0; i < size; i++) {
      unsigned char b = (*fieldBytes++);
      fieldVal += ((unsigned short)b)<<(i * 8);    
    }
    
    fieldVal = call ExprEval.evaluate(e, fieldVal);

    switch (ex.op) {
    case EQ:
      result = (fieldVal == ex.value);
      break;
    case NEQ:
      result = (fieldVal != ex.value);
      break;
    case GT:
      result = (fieldVal > ex.value);
      break;
    case GE:
      result = (fieldVal >= ex.value);
      break;
    case LT:
      result = (fieldVal < ex.value);
      break;
    case LE:
      result = (fieldVal <= ex.value);
      break;
    }

    signal Operator.processedTuple(t,qs,e,result);
  }

    /* Return the next result for this expression
       qr (input):  The index of the result to return
       qr (output):  The value of the result
       qs: The query whose results we are fetching
       e: The expressions whose results we are fetching
       
       Note that stateless operators (e.g. filters) may not return any results
    */
  command TinyDBError Operator.nextResult(QueryResultPtr qr, ParsedQueryPtr qs, ExprPtr e) {
    return err_NoMoreResults;
  }

  
  //not implemented
  command TinyDBError Operator.processPartialResult(QueryResultPtr qr, ParsedQueryPtr qs, ExprPtr e) {
    return err_NoError;
  }

    /* Not Implemented
    */ 
  command result_t Operator.endOfEpoch(ParsedQueryPtr q, ExprPtr e) {
    return SUCCESS;
  }

  command bool Operator.resultIsForExpr(QueryResultPtr qr, ExprPtr e) {
    if (qr->qrType != kNOT_AGG) return FALSE;
    return TRUE;
  }


}