SQLite

*/
void sqlite3Fts5BufferAppendBlob(
  int *pRc,
  Fts5Buffer *pBuf, 
  int nData, 
  const u8 *pData
){
  assert( nData>=0 );
  assert( *pRc || nData>=0 );
  if( sqlite3Fts5BufferGrow(pRc, pBuf, nData) ) return;
  memcpy(&pBuf->p[pBuf->n], pData, nData);
  pBuf->n += nData;
}

/*
** Append the nul-terminated string zStr to the buffer pBuf. This function

struct Fts5HashEntry {
  Fts5HashEntry *pHashNext;       /* Next hash entry with same hash-key */
  Fts5HashEntry *pScanNext;       /* Next entry in sorted order */
  
  int nAlloc;                     /* Total size of allocation */
  int iSzPoslist;                 /* Offset of space for 4-byte poslist size */
  int nData;                      /* Total bytes of data (incl. structure) */
  u8 bDel;                        /* Set delete-flag @ iSzPoslist */

  int iCol;                       /* Column of last value written */
  int iPos;                       /* Position of last value written */
  i64 iRowid;                     /* Rowid of last value written */
  char zKey[0];                   /* Nul-terminated entry key */
};

  pHash->nSlot = nNew;
  pHash->aSlot = apNew;
  return SQLITE_OK;
}

static void fts5HashAddPoslistSize(Fts5HashEntry *p){
  if( p->iSzPoslist ){
    /* WRITEPOSLISTSIZE */
    u8 *pPtr = (u8*)p;
    int nSz = (p->nData - p->iSzPoslist - 1) * 2;
    int nSz = (p->nData - p->iSzPoslist - 1);         /* Size in bytes */
    int nPos = nSz*2 + p->bDel;                       /* Value of nPos field */

    assert( p->bDel==0 || p->bDel==1 );
    if( nSz<=127 ){
      pPtr[p->iSzPoslist] = nSz;
    if( nPos<=127 ){
      pPtr[p->iSzPoslist] = nPos;
    }else{
      int nByte = sqlite3Fts5GetVarintLen((u32)nSz);
      int nByte = sqlite3Fts5GetVarintLen((u32)nPos);
      /* WRITEPOSLISTSIZE */
      memmove(&pPtr[p->iSzPoslist + nByte], &pPtr[p->iSzPoslist + 1], nSz/2);
      sqlite3PutVarint(&pPtr[p->iSzPoslist], nSz);
      memmove(&pPtr[p->iSzPoslist + nByte], &pPtr[p->iSzPoslist + 1], nSz);
      sqlite3PutVarint(&pPtr[p->iSzPoslist], nPos);
      p->nData += (nByte-1);
    }
    p->bDel = 0;
    p->iSzPoslist = 0;
  }
}

int sqlite3Fts5HashWrite(
  Fts5Hash *pHash,
  i64 iRowid,                     /* Rowid for this entry */

      p->iCol = iCol;
      p->iPos = 0;
    }

    /* Append the new position offset */
    p->nData += sqlite3PutVarint(&pPtr[p->nData], iPos - p->iPos + 2);
    p->iPos = iPos;
  }else{
    /* This is a delete. Set the delete flag. */
    p->bDel = 1;
  }
  nIncr += p->nData;

  *pHash->pnByte += nIncr;
  return SQLITE_OK;
}

** pSeg:
**   The segment to iterate through.
**
** iLeafPgno:
**   Current leaf page number within segment.
**
** iLeafOffset:
**   Byte offset within the current leaf that is one byte past the end of the
**   Byte offset within the current leaf that is the first byte of the 
**   position list data (one byte passed the position-list size field).
**   rowid field of the current entry. Usually this is the size field of the
**   position list data. The exception is if the rowid for the current entry 
**   is the last thing on the leaf page.
**
** pLeaf:
**   Buffer containing current leaf page data. Set to NULL at EOF.
**

**     This flag is only ever set if FTS5_SEGITER_ONETERM is also set. If
**     it is set, iterate through docids in descending order instead of the
**     default ascending order.
**
** iRowidOffset/nRowidOffset/aRowidOffset:
**     These are used if the FTS5_SEGITER_REVERSE flag is set.
**
**     Each time a new page is loaded, the iterator is set to point to the
**     final rowid. Additionally, the aRowidOffset[] array is populated 
**     with the byte offsets of all relevant rowid fields on the page. 
**     For each rowid on the page corresponding to the current term, the
**     corresponding aRowidOffset[] entry is set to the byte offset of the
**     start of the "position-list-size" field within the page.
*/
struct Fts5SegIter {
  Fts5StructureSegment *pSeg;     /* Segment to iterate through */
  int iIdx;                       /* Byte offset within current leaf */
  int flags;                      /* Mask of configuration flags */
  int iLeafPgno;                  /* Current leaf page number */
  Fts5Data *pLeaf;                /* Current leaf data */

  int *aRowidOffset;              /* Array of offset to rowid fields */

  Fts5DlidxIter *pDlidx;          /* If there is a doclist-index */

  /* Variables populated based on current entry. */
  Fts5Buffer term;                /* Current term */
  i64 iRowid;                     /* Current rowid */
  int nPos;                       /* Number of bytes in current position list */
  int bDel;                       /* True if the delete flag is set */
};

#define FTS5_SEGITER_ONETERM 0x01
#define FTS5_SEGITER_REVERSE 0x02


/*

  const u8 *pRight, int nRight    /* Right hand side of comparison */
){
  int nCmp = MIN(pLeft->n, nRight);
  int res = memcmp(pLeft->p, pRight, nCmp);
  return (res==0 ? (pLeft->n - nRight) : res);
}

#if 0
static int fts5CompareBlob(
  const u8 *pLeft, int nLeft,
  const u8 *pRight, int nRight
){
  int nCmp = MIN(nLeft, nRight);
  int res = memcmp(pLeft, pRight, nCmp);
  return (res==0 ? (nLeft - nRight) : res);
}
#endif

/*
** Compare the contents of the two buffers using memcmp(). If one buffer
** is a prefix of the other, it is considered the lesser.
**
** Return -ve if pLeft is smaller than pRight, 0 if they are equal or
** +ve if pRight is smaller than pLeft. In other words:
**

    pIter->pLeaf = fts5DataRead(p, 
        FTS5_SEGMENT_ROWID(pIter->iIdx, pSeg->iSegid, 0, pIter->iLeafPgno)
    );
  }else{
    pIter->pLeaf = 0;
  }
}

/*
** Argument p points to a buffer containing a varint to be interpreted as a
** position list size field. Read the varint and return the number of bytes
** read. Before returning, set *pnSz to the number of bytes in the position
** list, and *pbDel to true if the delete flag is set, or false otherwise.
*/
static int fts5GetPoslistSize(const u8 *p, int *pnSz, int *pbDel){
  int nSz;
  int n = fts5GetVarint32(p, nSz);
  *pnSz = nSz/2;
  *pbDel = nSz & 0x0001;
  return n;
}

/*
** Fts5SegIter.iLeafOffset currently points to the first byte of a
** position-list size field. Read the value of the field and store it
** in the following variables:
**
**   Fts5SegIter.nPos
**   Fts5SegIter.bDel
**
** Leave Fts5SegIter.iLeafOffset pointing to the first byte of the 
** position list content (if any).
*/
static void fts5SegIterLoadNPos(Fts5Index *p, Fts5SegIter *pIter){
  if( p->rc==SQLITE_OK ){
    int iOff = pIter->iLeafOffset;  /* Offset to read at */
    if( iOff>=pIter->pLeaf->n ){
      assert( 0 );
      fts5SegIterNextPage(p, pIter);
      if( pIter->pLeaf==0 ){
        if( p->rc==SQLITE_OK ) p->rc = FTS5_CORRUPT;
        return;
      }
      iOff = 4;
    }
    iOff += fts5GetPoslistSize(pIter->pLeaf->p+iOff, &pIter->nPos,&pIter->bDel);
    pIter->iLeafOffset = iOff;
  }
}

/*
** Fts5SegIter.iLeafOffset currently points to the first byte of the 
** "nSuffix" field of a term. Function parameter nKeep contains the value
** of the "nPrefix" field (if there was one - it is passed 0 if this is
** the first term in the segment).
**
** This function populates (Fts5SegIter.term) and (Fts5SegIter.iRowid)
** accordingly and leaves (Fts5SegIter.iLeafOffset) set to the offset to 
** the size field of the first position list. The position list belonging 
** to document (Fts5SegIter.iRowid).
** This function populates:
**
**   Fts5SegIter.term
**   Fts5SegIter.rowid
**   Fts5SegIter.nPos
**   Fts5SegIter.bDel
**
** accordingly and leaves (Fts5SegIter.iLeafOffset) set to the content of
** the first position list. The position list belonging to document 
** (Fts5SegIter.iRowid).
*/
static void fts5SegIterLoadTerm(Fts5Index *p, Fts5SegIter *pIter, int nKeep){
  u8 *a = pIter->pLeaf->p;        /* Buffer to read data from */
  int iOff = pIter->iLeafOffset;  /* Offset to read at */
  int nNew;                       /* Bytes of new data */

  iOff += fts5GetVarint32(&a[iOff], nNew);

    fts5SegIterNextPage(p, pIter);
  }

  if( p->rc==SQLITE_OK ){
    u8 *a = pIter->pLeaf->p;
    pIter->iLeafOffset = fts5GetU16(&a[2]);
    fts5SegIterLoadTerm(p, pIter, 0);
    fts5SegIterLoadNPos(p, pIter);
  }
}

/*
** This function is only ever called on iterators created by calls to
** Fts5IndexQuery() with the FTS5INDEX_QUERY_DESC flag set.
**
** When this function is called, iterator pIter points to the first rowid
** on the current leaf associated with the term being queried. This function
** advances it to point to the last such rowid and, if necessary, initializes
** the aRowidOffset[] and iRowidOffset variables.
** The iterator is in an unusual state when this function is called: the
** Fts5SegIter.iLeafOffset variable is set to the offset of the start of
** the position-list size field for the first relevant rowid on the page.
** Fts5SegIter.rowid is set, but nPos and bDel are not.
**
** This function advances the iterator so that it points to the last 
** relevant rowid on the page and, if necessary, initializes the 
** aRowidOffset[] and iRowidOffset variables. At this point the iterator
** is in its regular state - Fts5SegIter.iLeafOffset points to the first
** byte of the position list content associated with said rowid.
*/
static void fts5SegIterReverseInitPage(Fts5Index *p, Fts5SegIter *pIter){
  int n = pIter->pLeaf->n;
  int i = pIter->iLeafOffset;
  u8 *a = pIter->pLeaf->p;
  int iRowidOffset = 0;

  while( p->rc==SQLITE_OK && i<n ){
    i64 iDelta = 0;
    int nPos;
    int bDummy;

    /* READPOSLISTSIZE */
    i += fts5GetVarint32(&a[i], nPos);
    i += nPos / 2;
    i += fts5GetPoslistSize(&a[i], &nPos, &bDummy);
    i += nPos;
    if( i>=n ) break;
    i += getVarint(&a[i], (u64*)&iDelta);
    if( iDelta==0 ) break;
    pIter->iRowid += iDelta;

    if( iRowidOffset>=pIter->nRowidOffset ){
      int nNew = pIter->nRowidOffset + 8;
      int *aNew = (int*)sqlite3_realloc(pIter->aRowidOffset, nNew*sizeof(int));
      if( aNew==0 ){
        p->rc = SQLITE_NOMEM;
        break;
      }
      pIter->aRowidOffset = aNew;
      pIter->nRowidOffset = nNew;
    }

    pIter->aRowidOffset[iRowidOffset++] = pIter->iLeafOffset;
    pIter->iLeafOffset = i;
  }
  pIter->iRowidOffset = iRowidOffset;
  fts5SegIterLoadNPos(p, pIter);
}

/*
**
*/
static void fts5SegIterReverseNewPage(Fts5Index *p, Fts5SegIter *pIter){
  assert( pIter->flags & FTS5_SEGITER_REVERSE );

static int fts5SegIterIsDelete(
  Fts5Index *p,                   /* FTS5 backend object */
  Fts5SegIter *pIter              /* Iterator to advance */
){
  int bRet = 0;
  Fts5Data *pLeaf = pIter->pLeaf;
  if( p->rc==SQLITE_OK && pLeaf ){
    bRet = pIter->nPos==0;
    /* bRet = pIter->bDel; */
#if 0
    if( pIter->iLeafOffset<pLeaf->n ){
      bRet = (pLeaf->p[pIter->iLeafOffset]==0x00);
      bRet = ((pLeaf->p[pIter->iLeafOffset] & 0xFE)==0x00);
    }else{
      Fts5Data *pNew = fts5DataRead(p, FTS5_SEGMENT_ROWID(
            pIter->iIdx, pIter->pSeg->iSegid, 0, pIter->iLeafPgno+1
      ));
      if( pNew ){
        bRet = (pNew->p[4]==0x00);
        bRet = ((pNew->p[4] & 0xFE)==0x00);
        fts5DataRelease(pNew);
      }
    }
#endif
  }
  return bRet;
}

/*
** Advance iterator pIter to the next entry. 
**
** If an error occurs, Fts5Index.rc is set to an appropriate error code. It 
** is not considered an error if the iterator reaches EOF. If an error has 
** already occurred when this function is called, it is a no-op.
*/
static void fts5SegIterNext(
  Fts5Index *p,                   /* FTS5 backend object */
  Fts5SegIter *pIter,             /* Iterator to advance */
  int *pbNewTerm                  /* OUT: Set for new term */
){
  assert( pbNewTerm==0 || *pbNewTerm==0 );
  if( p->rc==SQLITE_OK ){
    if( pIter->flags & FTS5_SEGITER_REVERSE ){

      if( pIter->iRowidOffset>0 ){
        u8 *a = pIter->pLeaf->p;
        int iOff;
        int nPos;
        int bDummy;
        i64 iDelta;
        pIter->iRowidOffset--;

        if( p->rc==SQLITE_OK ){
          pIter->iRowidOffset--;
        pIter->iLeafOffset = iOff = pIter->aRowidOffset[pIter->iRowidOffset];
          pIter->iLeafOffset = iOff = pIter->aRowidOffset[pIter->iRowidOffset];
        /* READPOSLISTSIZE */
        iOff += fts5GetVarint32(&a[iOff], nPos);
        iOff += (nPos / 2);
        getVarint(&a[iOff], (u64*)&iDelta);
        pIter->iRowid -= iDelta;
          iOff += fts5GetPoslistSize(&a[iOff], &nPos, &bDummy);
          iOff += nPos;
          getVarint(&a[iOff], (u64*)&iDelta);
          pIter->iRowid -= iDelta;
          fts5SegIterLoadNPos(p, pIter);
        }
      }else{
        fts5SegIterReverseNewPage(p, pIter);
      }
    }else{
      Fts5Data *pLeaf = pIter->pLeaf;
      int iOff;
      int bNewTerm = 0;
      int nKeep = 0;

      /* Search for the end of the position list within the current page. */
      u8 *a = pLeaf->p;
      int n = pLeaf->n;

      iOff = pIter->iLeafOffset;
      iOff = pIter->iLeafOffset + pIter->nPos;
      if( iOff<n ){
        int nPoslist;
        /* READPOSLISTSIZE */
        iOff += fts5GetVarint32(&a[iOff], nPoslist);
        iOff += nPoslist / 2;
      }

      if( iOff<n ){
        /* The next entry is on the current page */
        u64 iDelta;
        iOff += sqlite3GetVarint(&a[iOff], &iDelta);
        pIter->iLeafOffset = iOff;
        if( iDelta==0 ){

          fts5DataRelease(pIter->pLeaf);
          pIter->pLeaf = 0;
        }else{
          pIter->pLeaf->p = (u8*)pList;
          pIter->pLeaf->n = nList;
          sqlite3Fts5BufferSet(&p->rc, &pIter->term, strlen(zTerm), (u8*)zTerm);
          pIter->iLeafOffset = getVarint(pList, (u64*)&pIter->iRowid);
          if( pIter->flags & FTS5_SEGITER_REVERSE ){
            assert( 0 );
            fts5SegIterReverseInitPage(p, pIter);
          }
        }
      }else{
        iOff = 0;
        /* Next entry is not on the current page */
        while( iOff==0 ){
          fts5SegIterNextPage(p, pIter);
          pLeaf = pIter->pLeaf;
          if( pLeaf==0 ) break;
          if( (iOff = fts5GetU16(&pLeaf->p[0])) ){
            iOff += sqlite3GetVarint(&pLeaf->p[iOff], (u64*)&pIter->iRowid);
            pIter->iLeafOffset = iOff;
          }
          else if( (iOff = fts5GetU16(&pLeaf->p[2])) ){
            pIter->iLeafOffset = iOff;
            bNewTerm = 1;
          }
        }
      }

      /* Check if the iterator is now at EOF. If so, return early. */
      if( pIter->pLeaf && bNewTerm ){
        if( pIter->flags & FTS5_SEGITER_ONETERM ){
          fts5DataRelease(pIter->pLeaf);
          pIter->pLeaf = 0;
        }else{
          fts5SegIterLoadTerm(p, pIter, nKeep);
          if( pbNewTerm ) *pbNewTerm = 1;
      if( pIter->pLeaf ){
        if( bNewTerm ){
          if( pIter->flags & FTS5_SEGITER_ONETERM ){
            fts5DataRelease(pIter->pLeaf);
            pIter->pLeaf = 0;
          }else{
            fts5SegIterLoadTerm(p, pIter, nKeep);
            fts5SegIterLoadNPos(p, pIter);
            if( pbNewTerm ) *pbNewTerm = 1;
          }
        }else{
          fts5SegIterLoadNPos(p, pIter);
        }
      }
    }
  }
}

#define SWAPVAL(T, a, b) { T tmp; tmp=a; a=b; b=tmp; }

/*
** Iterator pIter currently points to the first rowid in a doclist. This
** function sets the iterator up so that iterates in reverse order through
** the doclist.
*/
static void fts5SegIterReverse(Fts5Index *p, int iIdx, Fts5SegIter *pIter){
  Fts5Data *pLeaf;                /* Current leaf data */
  int iOff = pIter->iLeafOffset;  /* Byte offset within current leaf */
  Fts5Data *pLast = 0;
  int pgnoLast = 0;

  /* Move to the page that contains the last rowid in this doclist. */
  pLeaf = pIter->pLeaf;

  if( pIter->pDlidx ){
    int iSegid = pIter->pSeg->iSegid;
    pgnoLast = pIter->pDlidx->iLeafPgno;
    pLast = fts5DataRead(p, FTS5_SEGMENT_ROWID(iIdx, iSegid, 0, pgnoLast));
  }else{
    int iOff;                               /* Byte offset within pLeaf */
    Fts5Data *pLeaf = pIter->pLeaf;         /* Current leaf data */

    /* Currently, Fts5SegIter.iLeafOffset (and iOff) points to the first 
    ** byte of position-list content for the current rowid. Back it up
    ** so that it points to the start of the position-list size field. */
    pIter->iLeafOffset -= sqlite3Fts5GetVarintLen(pIter->nPos*2 + pIter->bDel);
    iOff = pIter->iLeafOffset;
    assert( iOff>=4 );

    /* Search for a new term within the current leaf. If one can be found,
    ** then this page contains the largest rowid for the current term. */
    while( iOff<pLeaf->n ){
      int nPos;
      i64 iDelta;
      int bDummy;

      /* Position list size in bytes */
      /* Read the position-list size field */
      /* READPOSLISTSIZE */
      iOff += fts5GetVarint32(&pLeaf->p[iOff], nPos);
      iOff += (nPos / 2);
      iOff += fts5GetPoslistSize(&pLeaf->p[iOff], &nPos, &bDummy);
      iOff += nPos;
      if( iOff>=pLeaf->n ) break;

      /* Rowid delta. Or, if 0x00, the end of doclist marker. */
      nPos = getVarint(&pLeaf->p[iOff], (u64*)&iDelta);
      if( iDelta==0 ) break;
      iOff += nPos;
    }

    /* If this condition is true then the largest rowid for the current
    ** term may not be stored on the current page. So search forward to
    ** see where said rowid really is.  */
    if( iOff>=pLeaf->n ){
      int pgno;
      Fts5StructureSegment *pSeg = pIter->pSeg;
      i64 iAbs = FTS5_SEGMENT_ROWID(iIdx, pSeg->iSegid, 0, pIter->iLeafPgno);
      i64 iLast = FTS5_SEGMENT_ROWID(iIdx, pSeg->iSegid, 0, pSeg->pgnoLast);

      /* The last rowid in the doclist may not be on the current page. Search
       ** forward to find the page containing the last rowid.  */
      ** forward to find the page containing the last rowid.  */
      for(iAbs++; p->rc==SQLITE_OK && iAbs<=iLast; iAbs++){
      for(pgno=pIter->iLeafPgno+1; !p->rc && pgno<=pSeg->pgnoLast; pgno++){
        i64 iAbs = FTS5_SEGMENT_ROWID(iIdx, pSeg->iSegid, 0, pgno);
        Fts5Data *pNew = fts5DataRead(p, iAbs);
        if( pNew ){
          int iRowid, iTerm;
          fts5LeafHeader(pNew, &iRowid, &iTerm);
          if( iRowid ){
            Fts5Data *pTmp = pLast;
            pLast = pNew;
            SWAPVAL(Fts5Data*, pNew, pLast);
            pgnoLast = pgno;
            pNew = pTmp;
            pgnoLast = iAbs & (((i64)1 << FTS5_DATA_PAGE_B) - 1);
          }
          if( iTerm ){
            iAbs = iLast;
          }
          fts5DataRelease(pNew);
          if( iTerm ) break;
        }
      }
    }
  }

  /* If pLast is NULL at this point, then the last rowid for this doclist
  ** lies on the page currently indicated by the iterator. In this case 
  ** iLastOff is set to the value that pIter->iLeafOffset will take when
  ** the iterator points to that rowid.
  ** pIter->iLeafOffset is already set to point to the position-list size
  ** field associated with the first relevant rowid on the page.
  **
  ** Or, if pLast is non-NULL, then it is the page that contains the last
  ** rowid.
  ** rowid. In this case configure the iterator so that it points to the
  ** first rowid on this page.
  */
  if( pLast ){
    int dummy;
    int iOff;
    fts5DataRelease(pIter->pLeaf);
    pIter->pLeaf = pLast;
    pIter->iLeafPgno = pgnoLast;
    fts5LeafHeader(pLast, &iOff, &dummy);
    iOff += getVarint(&pLast->p[iOff], (u64*)&pIter->iRowid);
    pIter->iLeafOffset = iOff;
  }

  assert( pIter->flags & FTS5_SEGITER_ONETERM );
  assert( pIter->pDlidx==0 );

  /* Check if the current doclist ends on this page. If it does, return
  ** early without loading the doclist-index (as it belongs to a different
  ** term. */
  if( pIter->iTermLeafPgno==pIter->iLeafPgno ){
    int nPos = pIter->nPos;
    while( iOff<pLeaf->n ){
      i64 iDelta;
      int nPoslist;

      /* iOff is currently the offset of the size field of a position list. */
      /* iOff is currently the offset of the start of position list data */
      /* READPOSLISTSIZE */
      iOff += fts5GetVarint32(&pLeaf->p[iOff], nPoslist);
      iOff += nPoslist / 2;
      iOff += nPos;
      iOff += getVarint(&pLeaf->p[iOff], (u64*)&iDelta);
      if( iDelta==0 ) return;

      if( iOff<pLeaf->n ){
        int bDummy;
        iOff += getVarint(&pLeaf->p[iOff], (u64*)&iDelta);
        iOff += fts5GetPoslistSize(&pLeaf->p[iOff], &nPos, &bDummy);
        if( iDelta==0 ) return;
      }
    }
  }

  fts5DlidxIterInit(p, bRev, iIdx, iSeg, pIter->iTermLeafPgno, &pIter->pDlidx);
}

  pIter->iLeafPgno = iPg - 1;
  fts5SegIterNextPage(p, pIter);

  if( pIter->pLeaf ){
    int res;
    pIter->iLeafOffset = fts5GetU16(&pIter->pLeaf->p[2]);
    fts5SegIterLoadTerm(p, pIter, 0);
    fts5SegIterLoadNPos(p, pIter);
    do {
      res = fts5BufferCompareBlob(&pIter->term, pTerm, nTerm);
      if( res>=0 ) break;
      fts5SegIterNext(p, pIter, 0);
    }while( pIter->pLeaf && p->rc==SQLITE_OK );

    if( bGe==0 && res ){

    pLeaf->n = nList;
    pIter->pLeaf = pLeaf;
    pIter->iLeafOffset = getVarint(pLeaf->p, (u64*)&pIter->iRowid);

    if( flags & FTS5INDEX_QUERY_DESC ){
      pIter->flags |= FTS5_SEGITER_REVERSE;
      fts5SegIterReverseInitPage(p, pIter);
    }else{
      fts5SegIterLoadNPos(p, pIter);
    }
  }
}

/*
** Zero the iterator passed as the only argument.
*/

    iOff = fts5GetU16(&a[0]);
    if( iOff<4 || iOff>=n ){
      p->rc = FTS5_CORRUPT;
    }else{
      iOff += getVarint(&a[iOff], (u64*)&pIter->iRowid);
      pIter->iLeafOffset = iOff;
      fts5SegIterLoadNPos(p, pIter);
    }
  }
}

/*
** Advance the iterator passed as the second argument until it is at or 
** past rowid iFrom. Regardless of the value of iFrom, the iterator is

** iterated data.
*/
static void fts5MultiIterNew(
  Fts5Index *p,                   /* FTS5 backend to iterate within */
  Fts5Structure *pStruct,         /* Structure of specific index */
  int iIdx,                       /* Config.aHash[] index of FTS index */
  int bSkipEmpty,                 /* True to ignore delete-keys */
  int flags,                      /* True for >= */
  int flags,                      /* FTS5INDEX_QUERY_XXX flags */
  const u8 *pTerm, int nTerm,     /* Term to seek to (or NULL/0) */
  int iLevel,                     /* Level to iterate (-1 for all) */
  int nSegment,                   /* Number of segments to merge (iLevel>=0) */
  Fts5MultiSegIter **ppOut        /* New object */
){
  int nSeg;                       /* Number of segments merged */
  int nSlot;                      /* Power of two >= nSeg */

  ** to calculate.  */
  if( pSeg->pSeg ){
    int iId = pSeg->pSeg->iSegid;
    i64 rowid = FTS5_SEGMENT_ROWID(pSeg->iIdx, iId, 0, pSeg->iLeafPgno);
    pIter->iLeafRowid = rowid;
  }

  if( iOff<pLeaf->n ){
    fts5DataReference(pLeaf);
    pIter->pLeaf = pLeaf;
  fts5DataReference(pLeaf);
  pIter->pLeaf = pLeaf;
  }else{
    pIter->nRem = 1;
  pIter->nRem = pSeg->nPos;
    fts5ChunkIterNext(p, pIter);
    if( p->rc ) return;
    iOff = 4;
    pLeaf = pIter->pLeaf;
  }

  /* READPOSLISTSIZE */
  iOff += fts5GetVarint32(&pLeaf->p[iOff], pIter->nRem);
  pIter->nRem = pIter->nRem / 2;
  pIter->n = MIN(pLeaf->n - iOff, pIter->nRem);
  pIter->p = pLeaf->p + iOff;

  if( pIter->n==0 ){
    fts5ChunkIterNext(p, pIter);
  }
}

static void fts5ChunkIterRelease(Fts5ChunkIter *pIter){
  fts5DataRelease(pIter->pLeaf);

  if( pPage->buf.n>=p->pConfig->pgsz ){
    fts5WriteFlushLeaf(p, pWriter);
    pWriter->bFirstRowidInPage = 1;
  }
}

/*
** Append a docid to the writers output. 
** Append a docid and position-list size field to the writers output. 
*/
static void fts5WriteAppendRowid(
  Fts5Index *p, 
  Fts5SegWriter *pWriter,
  i64 iRowid
  i64 iRowid,
  int nPos
){
  if( p->rc==SQLITE_OK ){
    Fts5PageWriter *pPage = &pWriter->aWriter[0];

    /* If this is to be the first docid written to the page, set the 
    ** docid-pointer in the page-header. Also append a value to the dlidx
    ** buffer, in case a doclist-index is required.  */

    }else{
      assert( p->rc || iRowid>pWriter->iPrevRowid );
      fts5BufferAppendVarint(&p->rc, &pPage->buf, iRowid - pWriter->iPrevRowid);
    }
    pWriter->iPrevRowid = iRowid;
    pWriter->bFirstRowidInDoclist = 0;
    pWriter->bFirstRowidInPage = 0;

    fts5BufferAppendVarint(&p->rc, &pPage->buf, nPos);

    if( pPage->buf.n>=p->pConfig->pgsz ){
      fts5WriteFlushLeaf(p, pWriter);
      pWriter->bFirstRowidInPage = 1;
    }
  }
}

        }
        fts5WriteAppendTerm(p, &writer, nTerm, pTerm);
        fts5BufferSet(&p->rc, &term, nTerm, pTerm);
        bRequireDoclistTerm = 1;
      }

      /* Append the rowid to the output */
      /* WRITEPOSLISTSIZE */
      fts5WriteAppendRowid(p, &writer, fts5MultiIterRowid(pIter));
      fts5WriteAppendRowid(p, &writer, fts5MultiIterRowid(pIter), sPos.nRem*2);

      /* Copy the position list from input to output */
      /* WRITEPOSLISTSIZE */
      fts5WriteAppendPoslistInt(p, &writer, sPos.nRem * 2);
      for(/* noop */; !fts5ChunkIterEof(p, &sPos); fts5ChunkIterNext(p, &sPos)){
        fts5WriteAppendPoslistData(p, &writer, sPos.p, sPos.n);
      }
    }

    fts5ChunkIterRelease(&sPos);
  }

/*
** Buffer aBuf[] contains a list of varints, all small enough to fit
** in a 32-bit integer. Return the size of the largest prefix of this 
** list nMax bytes or less in size.
*/
static int fts5PoslistPrefix(const u8 *aBuf, int nMax){
  int ret = 0;
  int ret;
  while( 1 ){
    u32 dummy;
  u32 dummy;
  ret = fts5GetVarint32(aBuf, dummy);
  while( 1 ){
    int i = fts5GetVarint32(&aBuf[ret], dummy);
    if( (ret + i) > nMax ) break;
    ret += i;
  }
  return ret;
}

        int iOff = 0;
        int bFirstDocid = 0;

        /* The entire doclist will not fit on this leaf. The following 
        ** loop iterates through the poslists that make up the current 
        ** doclist.  */
        while( iOff<nDoclist ){
          u32 nPos;
          int nPos;
          int nCopy;
          int bDummy;
          iOff += getVarint(&pDoclist[iOff], (u64*)&iDelta);
          /* READPOSLISTSIZE */
          nCopy = fts5GetVarint32(&pDoclist[iOff], nPos);
          nCopy += (nPos / 2);
          nCopy = fts5GetPoslistSize(&pDoclist[iOff], &nPos, &bDummy);
          nCopy += nPos;
          iRowid += iDelta;
          
          if( bFirstDocid ){
            fts5PutU16(&pBuf->p[0], pBuf->n);   /* first docid on page */
            pBuf->n += sqlite3PutVarint(&pBuf->p[pBuf->n], iRowid);
            bFirstDocid = 0;
          }else{

            /* The entire poslist will not fit on this leaf. So it needs
            ** to be broken into sections. The only qualification being
            ** that each varint must be stored contiguously.  */
            const u8 *pPoslist = &pDoclist[iOff];
            int iPos = 0;
            while( 1 ){
              int nSpace = pgsz - pBuf->n;
              int n;
              int n = 0;
              if( (nCopy - iPos)<=nSpace ){
                n = nCopy - iPos;
              }else{
                n = fts5PoslistPrefix(&pPoslist[iPos], nSpace);
              }
              assert( n>0 );
              fts5BufferSafeAppendBlob(pBuf, &pPoslist[iPos], n);
              iPos += n;
              if( iPos>=nCopy ) break;
              fts5WriteFlushLeaf(p, &writer);
              pBuf = &writer.aWriter[0].buf;
            }
            bFirstDocid = 1;
          }
          assert( pBuf->n<=pgsz );
          iOff += nCopy;
        }
      }

      pBuf->p[pBuf->n++] = '\0';
      assert( pBuf->n<=pBuf->nSpace );
      zPrev = (const u8*)zTerm;

    }
    fts5ChunkIterRelease(&iter);
  }
}

static void fts5DoclistIterNext(Fts5DoclistIter *pIter){
  if( pIter->i<pIter->n ){
    int bDummy;
    if( pIter->i ){
      i64 iDelta;
      pIter->i += getVarint(&pIter->a[pIter->i], (u64*)&iDelta);
      if( pIter->bDesc ){
        pIter->iRowid -= iDelta;
      }else{
        pIter->iRowid += iDelta;
      }
    }else{
      pIter->i += getVarint(&pIter->a[pIter->i], (u64*)&pIter->iRowid);
    }
    /* READPOSLISTSIZE */
    pIter->i += fts5GetVarint32(&pIter->a[pIter->i], pIter->nPoslist);
    pIter->nPoslist = pIter->nPoslist / 2;
    pIter->i += fts5GetPoslistSize(
        &pIter->a[pIter->i], &pIter->nPoslist, &bDummy
    );
    pIter->aPoslist = &pIter->a[pIter->i];
    pIter->i += pIter->nPoslist;
  }else{
    pIter->aPoslist = 0;
  }
}

    Fts5Buffer out;
    Fts5Buffer tmp;
    memset(&out, 0, sizeof(out));
    memset(&tmp, 0, sizeof(tmp));

    fts5DoclistIterInit(p1, bDesc, &i1);
    fts5DoclistIterInit(p2, bDesc, &i2);
    while( i1.aPoslist!=0 || i2.aPoslist!=0 ){
    while( p->rc==SQLITE_OK && (i1.aPoslist!=0 || i2.aPoslist!=0) ){
      if( i2.aPoslist==0 || (i1.aPoslist && 
           ( (bDesc && i1.iRowid>i2.iRowid) || (!bDesc && i1.iRowid<i2.iRowid) )
      )){
        /* Copy entry from i1 */
        fts5MergeAppendDocid(&p->rc, bDesc, &out, &iLastRowid, i1.iRowid);
        /* WRITEPOSLISTSIZE */
        fts5BufferAppendVarint(&p->rc, &out, i1.nPoslist * 2);

        }
        if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;

        /* If this is a prefix query, check that the results returned if the
        ** the index is disabled are the same. In both ASC and DESC order. */
        if( iIdx>0 && rc==SQLITE_OK ){
          int f = flags|FTS5INDEX_QUERY_TEST_NOIDX;
static int nCall = 0;
nCall++;
          ck2 = 0;
          rc = fts5QueryCksum(p, z, n, f, &ck2);
          if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;
        }
        if( iIdx>0 && rc==SQLITE_OK ){
          int f = flags|FTS5INDEX_QUERY_TEST_NOIDX|FTS5INDEX_QUERY_DESC;
          ck2 = 0;

  if( iOff<n ){
    iOff += sqlite3GetVarint(&a[iOff], (u64*)&iDocid);
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, " rowid=%lld", iDocid);
  }
  while( iOff<n ){
    int nPos;
    /* READPOSLISTSIZE */
    iOff += fts5GetVarint32(&a[iOff], nPos);
    iOff += fts5DecodePoslist(pRc, pBuf, &a[iOff], MIN(n-iOff, nPos / 2));
    int bDummy;
    iOff += fts5GetPoslistSize(&a[iOff], &nPos, &bDummy);
    iOff += fts5DecodePoslist(pRc, pBuf, &a[iOff], MIN(n-iOff, nPos));
    if( iOff<n ){
      i64 iDelta;
      iOff += sqlite3GetVarint(&a[iOff], (u64*)&iDelta);
      if( iDelta==0 ) return iOff;
      iDocid += iDelta;
      sqlite3Fts5BufferAppendPrintf(pRc, pBuf, " rowid=%lld", iDocid);
    }

# If SQLITE_ENABLE_FTS3 is defined, omit this file.
ifcapable !fts5 {
  finish_test
  return
}

if 1 {

do_execsql_test 1.0 {
  CREATE VIRTUAL TABLE t1 USING fts5(a, b, c);
  SELECT name, sql FROM sqlite_master;
} {
  t1 {CREATE VIRTUAL TABLE t1 USING fts5(a, b, c)}
  t1_data {CREATE TABLE 't1_data'(id INTEGER PRIMARY KEY, block BLOB)}
  t1_content {CREATE TABLE 't1_content'(id INTEGER PRIMARY KEY, c0, c1, c2)}

  SELECT rowid FROM t1 WHERE t1 MATCH 'o';
} {1}

do_execsql_test 13.6 {
  SELECT rowid FROM t1 WHERE t1 MATCH '.';
} {}

}
#-------------------------------------------------------------------------
#
reset_db
do_execsql_test 14.1 {
  CREATE VIRTUAL TABLE t1 USING fts5(x, y);
  INSERT INTO t1(t1, rank) VALUES('pgsz', 32);
  WITH d(x,y) AS (

  do_test 1.6.$tn.1 {
    set n [execsql_reads $q]
    expr {$n < ($nReadX / 10)}
  } {1}

  do_test 1.6.$tn.2 {
    set n [execsql_reads "$q ORDER BY rowid ASC"]
    set n [execsql_reads "$q ORDER BY rowid DESC"]
    expr {$n < ($nReadX / 10)}
  } {1}

  do_execsql_test 1.6.$tn.3 $q [lsort -int -incr $res]
  do_execsql_test 1.6.$tn.4 "$q ORDER BY rowid DESC" [lsort -int -decr $res]
}