static int fts3MatchinfoLcs(Fts3Cursor *pCsr, MatchInfo *pInfo){
  LcsIterator *aIter;
  int i;
  int iCol;
  int nToken = 0;

  /* Allocate and populate the array of LcsIterator objects. The array
  ** contains one element for each matchable phrase in the query.
  **/
  aIter = sqlite3_malloc(sizeof(LcsIterator) * pCsr->nPhrase);
  if( !aIter ) return SQLITE_NOMEM;
  memset(aIter, 0, sizeof(LcsIterator) * pCsr->nPhrase);
  (void)fts3ExprIterate(pCsr->pExpr, fts3MatchinfoLcsCb, (void*)aIter);

  for(i=0; i<pInfo->nPhrase; i++){
    LcsIterator *pIter = &aIter[i];
    nToken -= pIter->pExpr->pPhrase->nToken;
    pIter->iPosOffset = nToken;
  }

  for(iCol=0; iCol<pInfo->nCol; iCol++){
    int nLcs = 0;                 /* LCS value for this column */
    int nLive = 0;                /* Number of iterators in aIter not at EOF */

    for(i=0; i<pInfo->nPhrase; i++){
      int rc;
      LcsIterator *pIt = &aIter[i];
      rc = sqlite3Fts3EvalPhrasePoslist(pCsr, pIt->pExpr, iCol, &pIt->pRead);
      if( rc!=SQLITE_OK ) return rc;
      if( pIt->pRead ){
        pIt->iPos = pIt->iPosOffset;
        fts3LcsIteratorAdvance(&aIter[i]);
        nLive++;
      }
    }

    while( nLive>0 ){
      LcsIterator *pAdv = 0;      /* The iterator to advance by one position */
      int nThisLcs = 0;           /* LCS for the current iterator positions */

      for(i=0; i<pInfo->nPhrase; i++){
        LcsIterator *pIter = &aIter[i];
        if( pIter->pRead==0 ){
          /* This iterator is already at EOF for this column. */
          nThisLcs = 0;
        }else{
          if( pAdv==0 || pIter->iPos<pAdv->iPos ){
            pAdv = pIter;
          }
          if( nThisLcs==0 || pIter->iPos==pIter[-1].iPos ){
            nThisLcs++;
          }else{
            nThisLcs = 1;
          }
          if( nThisLcs>nLcs ) nLcs = nThisLcs;
        }
      }
      if( fts3LcsIteratorAdvance(pAdv) ) nLive--;
    }

    pInfo->aMatchinfo[iCol] = nLcs;
  }

  sqlite3_free(aIter);
  return SQLITE_OK;
}
Unknown