SQLite

** The number of rowset entries per allocation chunk.
*/
#define ROWSET_ENTRY_PER_CHUNK  \
                       ((ROWSET_ALLOCATION_SIZE-8)/sizeof(struct RowSetEntry))

/*
** Each entry in a RowSet is an instance of the following object.
**
** This same object is reused to store a linked list of trees of RowSetEntry
** objects.  In that alternative use, pRight points to the next entry
** in the list, pLeft points to the tree, and v is unused.  The
** RowSet.pForest value points to the head of this forest list.
*/
struct RowSetEntry {            
  i64 v;                        /* ROWID value for this entry */
  struct RowSetEntry *pRight;   /* Right subtree (larger entries) or list */
  struct RowSetEntry *pLeft;    /* Left subtree (smaller entries) */
};

*/
struct RowSet {
  struct RowSetChunk *pChunk;    /* List of all chunk allocations */
  sqlite3 *db;                   /* The database connection */
  struct RowSetEntry *pEntry;    /* List of entries using pRight */
  struct RowSetEntry *pLast;     /* Last entry on the pEntry list */
  struct RowSetEntry *pFresh;    /* Source of new entry objects */
  struct RowSetEntry *pForest;   /* List of binary trees of entries */
  u16 nFresh;                    /* Number of objects on pFresh */
  u8 rsFlags;                    /* Various flags */
  u8 iBatch;                     /* Current insert batch */
};

/*
** Allowed values for RowSet.rsFlags
*/
#define ROWSET_SORTED  0x01   /* True if RowSet.pEntry is sorted */
#define ROWSET_NEXT    0x02   /* True if sqlite3RowSetNext() has been called */

/*
** Turn bulk memory into a RowSet object.  N bytes of memory
** are available at pSpace.  The db pointer is used as a memory context
** for any subsequent allocations that need to occur.
** Return a pointer to the new RowSet object.
**
** It must be the case that N is sufficient to make a Rowset.  If not
** an assertion fault occurs.
** 
** If N is larger than the minimum, use the surplus as an initial
** allocation of entries available to be filled.
*/
RowSet *sqlite3RowSetInit(sqlite3 *db, void *pSpace, unsigned int N){
  RowSet *p;
  assert( N >= ROUND8(sizeof(*p)) );
  p = pSpace;
  p->pChunk = 0;
  p->db = db;
  p->pEntry = 0;
  p->pLast = 0;
  p->pForest = 0;
  p->pFresh = (struct RowSetEntry*)(ROUND8(sizeof(*p)) + (char*)p);
  p->nFresh = (u16)((N - ROUND8(sizeof(*p)))/sizeof(struct RowSetEntry));
  p->rsFlags = ROWSET_SORTED;
  p->iBatch = 0;
  return p;
}

/*
** Deallocate all chunks from a RowSet.  This frees all memory that
** the RowSet has allocated over its lifetime.  This routine is
** the destructor for the RowSet.
*/
void sqlite3RowSetClear(RowSet *p){
  struct RowSetChunk *pChunk, *pNextChunk;
  for(pChunk=p->pChunk; pChunk; pChunk = pNextChunk){
    pNextChunk = pChunk->pNextChunk;
    sqlite3DbFree(p->db, pChunk);
  }
  p->pChunk = 0;
  p->nFresh = 0;
  p->pEntry = 0;
  p->pLast = 0;
  p->pForest = 0;
  p->rsFlags = ROWSET_SORTED;
}

/*
** Allocate a new RowSetEntry object that is associated with the
** given RowSet.  Return a pointer to the new and completely uninitialized
** objected.
**
** In an OOM situation, the RowSet.db->mallocFailed flag is set and this
** routine returns NULL.
*/
static struct RowSetEntry *rowSetEntryAlloc(RowSet *p){
  assert( p!=0 );
  if( p->nFresh==0 ){
    struct RowSetChunk *pNew;
    pNew = sqlite3DbMallocRaw(p->db, sizeof(*pNew));
    if( pNew==0 ){
      return 0;
    }
    pNew->pNextChunk = p->pChunk;
    p->pChunk = pNew;
    p->pFresh = pNew->aEntry;
    p->nFresh = ROWSET_ENTRY_PER_CHUNK;
  }
  p->nFresh--;
  return p->pFresh++;
}

/*
** Insert a new value into a RowSet.
**
** The mallocFailed flag of the database connection is set if a
** memory allocation fails.
*/
void sqlite3RowSetInsert(RowSet *p, i64 rowid){
  struct RowSetEntry *pEntry;  /* The new entry */
  struct RowSetEntry *pLast;   /* The last prior entry */










  /* This routine is never called after sqlite3RowSetNext() */
  assert( p!=0 && (p->rsFlags & ROWSET_NEXT)==0 );

  pEntry = rowSetEntryAlloc(p);
  if( pEntry==0 ) return;
  pEntry->v = rowid;
  pEntry->pRight = 0;
  pLast = p->pLast;
  if( pLast ){
    if( (p->rsFlags & ROWSET_SORTED)!=0 && rowid<=pLast->v ){
      p->rsFlags &= ~ROWSET_SORTED;
    }
    pLast->pRight = pEntry;
  }else{

    p->pEntry = pEntry;
  }
  p->pLast = pEntry;
}

/*
** Merge two lists of RowSetEntry objects.  Remove duplicates.
**
** The input lists are connected via pRight pointers and are 
** assumed to each already be in sorted order.
*/
static struct RowSetEntry *rowSetEntryMerge(
  struct RowSetEntry *pA,    /* First sorted list to be merged */
  struct RowSetEntry *pB     /* Second sorted list to be merged */
){
  struct RowSetEntry head;
  struct RowSetEntry *pTail;

  pTail = &head;

    assert( pB==0 || pB->pRight==0 || pB->v<=pB->pRight->v );
    pTail->pRight = pB;
  }
  return head.pRight;
}

/*
** Sort all elements on the list of RowSetEntry objects into order of
** increasing v.
*/ 
static struct RowSetEntry *rowSetEntrySort(struct RowSetEntry *pIn){
  unsigned int i;
  struct RowSetEntry *pNext, *aBucket[40];



  memset(aBucket, 0, sizeof(aBucket));
  while( pIn ){

    pNext = pIn->pRight;
    pIn->pRight = 0;
    for(i=0; aBucket[i]; i++){
      pIn = rowSetEntryMerge(aBucket[i], pIn);
      aBucket[i] = 0;
    }
    aBucket[i] = pIn;
    pIn = pNext;
  }
  pIn = 0;
  for(i=0; i<sizeof(aBucket)/sizeof(aBucket[0]); i++){
    pIn = rowSetEntryMerge(pIn, aBucket[i]);
  }
  return pIn;


}


/*
** The input, pIn, is a binary tree (or subtree) of RowSetEntry objects.
** Convert this tree into a linked list connected by the pRight pointers
** and return pointers to the first and last elements of the new list.

    p->pLeft = pLeft;
    p->pRight = rowSetNDeepTree(&pList, iDepth);
  }
  return p;
}

/*
** Take all the entries on p->pEntry and on the trees in p->pForest and
** sort them all together into one big ordered list on p->pEntry.
**
** This routine should only be called once in the life of a RowSet.
*/
static void rowSetToList(RowSet *p){

  /* This routine is called only once */
  assert( p!=0 && (p->rsFlags & ROWSET_NEXT)==0 );

  if( (p->rsFlags & ROWSET_SORTED)==0 ){
    p->pEntry = rowSetEntrySort(p->pEntry);
  }

  /* While this module could theoretically support it, sqlite3RowSetNext()
  ** is never called after sqlite3RowSetText() for the same RowSet.  So
  ** there is never a forest to deal with.  Should this change, simply
  ** remove the assert() and the #if 0. */
  assert( p->pForest==0 );
#if 0
  while( p->pForest ){
    struct RowSetEntry *pTree = p->pForest->pLeft;
    if( pTree ){
      struct RowSetEntry *pHead, *pTail;
      rowSetTreeToList(pTree, &pHead, &pTail);

      p->pEntry = rowSetEntryMerge(p->pEntry, pHead);
    }
    p->pForest = p->pForest->pRight;
  }
#endif
  p->rsFlags |= ROWSET_NEXT;  /* Verify this routine is never called again */
}

/*
** Extract the smallest element from the RowSet.
** Write the element into *pRowid.  Return 1 on success.  Return
** 0 if the RowSet is already empty.
**
** After this routine has been called, the sqlite3RowSetInsert()
** routine may not be called again.  
*/
int sqlite3RowSetNext(RowSet *p, i64 *pRowid){
  assert( p!=0 );

  /* Merge the forest into a single sorted list on first call */
  if( (p->rsFlags & ROWSET_NEXT)==0 ) rowSetToList(p);

  /* Return the next entry on the list */
  if( p->pEntry ){
    *pRowid = p->pEntry->v;
    p->pEntry = p->pEntry->pRight;
    if( p->pEntry==0 ){
      sqlite3RowSetClear(p);
    }
    return 1;
  }else{
    return 0;
  }
}

/*
** Check to see if element iRowid was inserted into the the rowset as
** part of any insert batch prior to iBatch.  Return 1 or 0.
**
** If this is the first test of a new batch and if there exist entires
** on pRowSet->pEntry, then sort those entires into the forest at
** pRowSet->pForest so that they can be tested.
*/
int sqlite3RowSetTest(RowSet *pRowSet, u8 iBatch, sqlite3_int64 iRowid){
  struct RowSetEntry *p, *pTree;

  /* This routine is never called after sqlite3RowSetNext() */
  assert( pRowSet!=0 && (pRowSet->rsFlags & ROWSET_NEXT)==0 );

  /* Sort entries into the forest on the first test of a new batch 
  */
  if( iBatch!=pRowSet->iBatch ){
    p = pRowSet->pEntry;
    if( p ){
      struct RowSetEntry **ppPrevTree = &pRowSet->pForest;
      if( (pRowSet->rsFlags & ROWSET_SORTED)==0 ){
        p = rowSetEntrySort(p);
      }
      for(pTree = pRowSet->pForest; pTree; pTree=pTree->pRight){
        ppPrevTree = &pTree->pRight;
        if( pTree->pLeft==0 ){
          pTree->pLeft = rowSetListToTree(p);
          break;
        }else{
          struct RowSetEntry *pAux, *pTail;
          rowSetTreeToList(pTree->pLeft, &pAux, &pTail);
          pTree->pLeft = 0;
          p = rowSetEntryMerge(pAux, p);
        }
      }
      if( pTree==0 ){
        *ppPrevTree = pTree = rowSetEntryAlloc(pRowSet);
        if( pTree ){
          pTree->v = 0;
          pTree->pRight = 0;
          pTree->pLeft = rowSetListToTree(p);
        }
      }
      pRowSet->pEntry = 0;
      pRowSet->pLast = 0;
      pRowSet->rsFlags |= ROWSET_SORTED;
    }
    pRowSet->iBatch = iBatch;
  }

  /* Test to see if the iRowid value appears anywhere in the forest.
  ** Return 1 if it does and 0 if not.
  */
  for(pTree = pRowSet->pForest; pTree; pTree=pTree->pRight){
    p = pTree->pLeft;
    while( p ){
      if( p->v<iRowid ){
        p = p->pRight;
      }else if( p->v>iRowid ){
        p = p->pLeft;
      }else{
        return 1;
      }
    }
  }
  return 0;
}