#define FTS5_POS2COLUMN(iPos) (int)(iPos >> 32)
#define FTS5_POS2OFFSET(iPos) (int)(iPos & 0xFFFFFFFF)

typedef struct Fts5PoslistReader Fts5PoslistReader;
struct Fts5PoslistReader {
  /* Variables used only by sqlite3Fts5PoslistIterXXX() functions. */
  int iCol;                       /* If (iCol>=0), this column only */
  const u8 *a;                    /* Position list to iterate through */
  int n;                          /* Size of buffer at a[] in bytes */
  int i;                          /* Current offset in a[] */

  u8 bFlag;                       /* For client use (any custom purpose) */

  /* Output variables */
  u8 bEof;                        /* Set to true at EOF */
  i64 iPos;                       /* (iCol<<32) + iPos */
};
int sqlite3Fts5PoslistReaderInit(
  int iCol,                       /* If (iCol>=0), this column only */
  const u8 *a, int n,             /* Poslist buffer to iterate through */
  Fts5PoslistReader *pIter        /* Iterator object to initialize */
);
int sqlite3Fts5PoslistReaderNext(Fts5PoslistReader*);

typedef struct Fts5PoslistWriter Fts5PoslistWriter;
struct Fts5PoslistWriter {
................................................................................
** The various operations on open token or token prefix iterators opened
** using sqlite3Fts5IndexQuery().
*/
int sqlite3Fts5IterEof(Fts5IndexIter*);
int sqlite3Fts5IterNext(Fts5IndexIter*);
int sqlite3Fts5IterNextFrom(Fts5IndexIter*, i64 iMatch);
i64 sqlite3Fts5IterRowid(Fts5IndexIter*);
int sqlite3Fts5IterPoslist(Fts5IndexIter*, const u8 **pp, int *pn, i64 *pi);
int sqlite3Fts5IterPoslistBuffer(Fts5IndexIter *pIter, Fts5Buffer *pBuf);

/*
** Close an iterator opened by sqlite3Fts5IndexQuery().
*/
void sqlite3Fts5IterClose(Fts5IndexIter*);

#define FTS5_POS2COLUMN(iPos) (int)(iPos >> 32)
#define FTS5_POS2OFFSET(iPos) (int)(iPos & 0xFFFFFFFF)

typedef struct Fts5PoslistReader Fts5PoslistReader;
struct Fts5PoslistReader {
  /* Variables used only by sqlite3Fts5PoslistIterXXX() functions. */

  const u8 *a;                    /* Position list to iterate through */
  int n;                          /* Size of buffer at a[] in bytes */
  int i;                          /* Current offset in a[] */

  u8 bFlag;                       /* For client use (any custom purpose) */

  /* Output variables */
  u8 bEof;                        /* Set to true at EOF */
  i64 iPos;                       /* (iCol<<32) + iPos */
};
int sqlite3Fts5PoslistReaderInit(

  const u8 *a, int n,             /* Poslist buffer to iterate through */
  Fts5PoslistReader *pIter        /* Iterator object to initialize */
);
int sqlite3Fts5PoslistReaderNext(Fts5PoslistReader*);

typedef struct Fts5PoslistWriter Fts5PoslistWriter;
struct Fts5PoslistWriter {
................................................................................
** The various operations on open token or token prefix iterators opened
** using sqlite3Fts5IndexQuery().
*/
int sqlite3Fts5IterEof(Fts5IndexIter*);
int sqlite3Fts5IterNext(Fts5IndexIter*);
int sqlite3Fts5IterNextFrom(Fts5IndexIter*, i64 iMatch);
i64 sqlite3Fts5IterRowid(Fts5IndexIter*);
int sqlite3Fts5IterPoslist(Fts5IndexIter*,Fts5Colset*, const u8**, int*, i64*);
int sqlite3Fts5IterPoslistBuffer(Fts5IndexIter *pIter, Fts5Buffer *pBuf);

/*
** Close an iterator opened by sqlite3Fts5IndexQuery().
*/
void sqlite3Fts5IterClose(Fts5IndexIter*);

/*
** Advance the iterator object passed as the only argument. Return true
** if the iterator reaches EOF, or false otherwise.
*/
int sqlite3Fts5PoslistReaderNext(Fts5PoslistReader *pIter){
  if( sqlite3Fts5PoslistNext64(pIter->a, pIter->n, &pIter->i, &pIter->iPos) 
   || (pIter->iCol>=0 && (pIter->iPos >> 32) > pIter->iCol)
  ){
    pIter->bEof = 1;
  }
  return pIter->bEof;
}

int sqlite3Fts5PoslistReaderInit(
  int iCol,                       /* If (iCol>=0), this column only */
  const u8 *a, int n,             /* Poslist buffer to iterate through */
  Fts5PoslistReader *pIter        /* Iterator object to initialize */
){
  memset(pIter, 0, sizeof(*pIter));
  pIter->a = a;
  pIter->n = n;
  pIter->iCol = iCol;
  do {
    sqlite3Fts5PoslistReaderNext(pIter);
  }while( pIter->bEof==0 && (pIter->iPos >> 32)<iCol );
  return pIter->bEof;
}

int sqlite3Fts5PoslistWriterAppend(
  Fts5Buffer *pBuf, 
  Fts5PoslistWriter *pWriter,
  i64 iPos

/*
** Advance the iterator object passed as the only argument. Return true
** if the iterator reaches EOF, or false otherwise.
*/
int sqlite3Fts5PoslistReaderNext(Fts5PoslistReader *pIter){
  if( sqlite3Fts5PoslistNext64(pIter->a, pIter->n, &pIter->i, &pIter->iPos) ){


    pIter->bEof = 1;
  }
  return pIter->bEof;
}

int sqlite3Fts5PoslistReaderInit(

  const u8 *a, int n,             /* Poslist buffer to iterate through */
  Fts5PoslistReader *pIter        /* Iterator object to initialize */
){
  memset(pIter, 0, sizeof(*pIter));
  pIter->a = a;
  pIter->n = n;


  sqlite3Fts5PoslistReaderNext(pIter);

  return pIter->bEof;
}

int sqlite3Fts5PoslistWriterAppend(
  Fts5Buffer *pBuf, 
  Fts5PoslistWriter *pWriter,
  i64 iPos

}

/*
** Argument pTerm must be a synonym iterator.
*/
static int fts5ExprSynonymPoslist(
  Fts5ExprTerm *pTerm, 

  i64 iRowid,
  int *pbDel,                     /* OUT: Caller should sqlite3_free(*pa) */
  u8 **pa, int *pn
){
  Fts5PoslistReader aStatic[4];
  Fts5PoslistReader *aIter = aStatic;
  int nIter = 0;
................................................................................
  assert( pTerm->pSynonym );
  for(p=pTerm; p; p=p->pSynonym){
    Fts5IndexIter *pIter = p->pIter;
    if( sqlite3Fts5IterEof(pIter)==0 && sqlite3Fts5IterRowid(pIter)==iRowid ){
      const u8 *a;
      int n;
      i64 dummy;
      rc = sqlite3Fts5IterPoslist(pIter, &a, &n, &dummy);
      if( rc!=SQLITE_OK ) goto synonym_poslist_out;
      if( nIter==nAlloc ){
        int nByte = sizeof(Fts5PoslistReader) * nAlloc * 2;
        Fts5PoslistReader *aNew = (Fts5PoslistReader*)sqlite3_malloc(nByte);
        if( aNew==0 ){
          rc = SQLITE_NOMEM;
          goto synonym_poslist_out;
        }
        memcpy(aNew, aIter, sizeof(Fts5PoslistReader) * nIter);
        nAlloc = nAlloc*2;
        if( aIter!=aStatic ) sqlite3_free(aIter);
        aIter = aNew;
      }
      sqlite3Fts5PoslistReaderInit(-1, a, n, &aIter[nIter]);
      assert( aIter[nIter].bEof==0 );
      nIter++;
    }
  }

  assert( *pbDel==0 );
  if( nIter==1 ){
................................................................................
  int *pbMatch                    /* OUT: Set to true if really a match */
){
  Fts5PoslistWriter writer = {0};
  Fts5PoslistReader aStatic[4];
  Fts5PoslistReader *aIter = aStatic;
  int i;
  int rc = SQLITE_OK;
  int iCol = -1;
  
  if( pColset && pColset->nCol==1 ){
    iCol = pColset->aiCol[0];
    pColset = 0;
  }

  fts5BufferZero(&pPhrase->poslist);

  /* If the aStatic[] array is not large enough, allocate a large array
  ** using sqlite3_malloc(). This approach could be improved upon. */
  if( pPhrase->nTerm>(sizeof(aStatic) / sizeof(aStatic[0])) ){
    int nByte = sizeof(Fts5PoslistReader) * pPhrase->nTerm;
    aIter = (Fts5PoslistReader*)sqlite3_malloc(nByte);
................................................................................
  for(i=0; i<pPhrase->nTerm; i++){
    Fts5ExprTerm *pTerm = &pPhrase->aTerm[i];
    i64 dummy;
    int n = 0;
    int bFlag = 0;
    const u8 *a = 0;
    if( pTerm->pSynonym ){
      rc = fts5ExprSynonymPoslist(pTerm, pNode->iRowid, &bFlag, (u8**)&a, &n);


    }else{
      rc = sqlite3Fts5IterPoslist(pTerm->pIter, &a, &n, &dummy);
    }
    if( rc!=SQLITE_OK ) goto ismatch_out;
    sqlite3Fts5PoslistReaderInit(iCol, a, n, &aIter[i]);
    aIter[i].bFlag = bFlag;
    if( aIter[i].bEof ) goto ismatch_out;
  }

  while( 1 ){
    int bMatch;
    i64 iPos = aIter[0].iPos;
................................................................................
            if( sqlite3Fts5PoslistReaderNext(pPos) ) goto ismatch_out;
          }
          if( pPos->iPos>iAdj ) iPos = pPos->iPos-i;
        }
      }
    }while( bMatch==0 );

    if( pColset==0 || fts5ExprColsetTest(pColset, FTS5_POS2COLUMN(iPos)) ){
      /* Append position iPos to the output */
      rc = sqlite3Fts5PoslistWriterAppend(&pPhrase->poslist, &writer, iPos);
      if( rc!=SQLITE_OK ) goto ismatch_out;
    }

    for(i=0; i<pPhrase->nTerm; i++){
      if( sqlite3Fts5PoslistReaderNext(&aIter[i]) ) goto ismatch_out;
    }
  }

 ismatch_out:
................................................................................
    bEof = 1;
  }else{
    *piLast = fts5ExprSynonymRowid(pTerm, bDesc, &bEof);
  }
  return bEof;
}

/*
** IN/OUT parameter (*pa) points to a position list n bytes in size. If
** the position list contains entries for column iCol, then (*pa) is set
** to point to the sub-position-list for that column and the number of
** bytes in it returned. Or, if the argument position list does not
** contain any entries for column iCol, return 0.
*/
static int fts5ExprExtractCol(
  const u8 **pa,                  /* IN/OUT: Pointer to poslist */
  int n,                          /* IN: Size of poslist in bytes */
  int iCol                        /* Column to extract from poslist */
){
  int iCurrent = 0;
  const u8 *p = *pa;
  const u8 *pEnd = &p[n];         /* One byte past end of position list */
  u8 prev = 0;

  while( iCol!=iCurrent ){
    /* Advance pointer p until it points to pEnd or an 0x01 byte that is
    ** not part of a varint */
    while( (prev & 0x80) || *p!=0x01 ){
      prev = *p++;
      if( p==pEnd ) return 0;
    }
    *pa = p++;
    p += fts5GetVarint32(p, iCurrent);
  }

  /* Advance pointer p until it points to pEnd or an 0x01 byte that is
  ** not part of a varint */
  assert( (prev & 0x80)==0 );
  while( p<pEnd && ((prev & 0x80) || *p!=0x01) ){
    prev = *p++;
  }
  return p - (*pa);
}

static int fts5ExprExtractColset (
  Fts5Colset *pColset,            /* Colset to filter on */
  const u8 *pPos, int nPos,       /* Position list */
  Fts5Buffer *pBuf                /* Output buffer */
){
  int rc = SQLITE_OK;
  int i;

  fts5BufferZero(pBuf);
  for(i=0; i<pColset->nCol; i++){
    const u8 *pSub = pPos;
    int nSub = fts5ExprExtractCol(&pSub, nPos, pColset->aiCol[i]);
    if( nSub ){
      fts5BufferAppendBlob(&rc, pBuf, nSub, pSub);
    }
  }
  return rc;
}

static int fts5ExprNearTest(
  int *pRc,
  Fts5Expr *pExpr,                /* Expression that pNear is a part of */
  Fts5ExprNode *pNode             /* The "NEAR" node (FTS5_STRING) */
){
  Fts5ExprNearset *pNear = pNode->pNear;
................................................................................
  ** fts5_index.c iterator object. This is much faster than synthesizing 
  ** a new poslist the way we have to for more complicated phrase or NEAR
  ** expressions.  */
  Fts5ExprNearset *pNear = pNode->pNear;
  Fts5ExprPhrase *pPhrase = pNear->apPhrase[0];
  Fts5IndexIter *pIter = pPhrase->aTerm[0].pIter;
  Fts5Colset *pColset = pNear->pColset;
  const u8 *pPos;
  int nPos;
  int rc;

  assert( pNode->eType==FTS5_TERM );
  assert( pNear->nPhrase==1 && pPhrase->nTerm==1 );
  assert( pPhrase->aTerm[0].pSynonym==0 );

  rc = sqlite3Fts5IterPoslist(pIter, &pPos, &nPos, &pNode->iRowid);

  /* If the term may match any column, then this must be a match. 
  ** Return immediately in this case. Otherwise, try to find the
  ** part of the poslist that corresponds to the required column.
  ** If it can be found, return. If it cannot, the next iteration
  ** of the loop will test the next rowid in the database for this
  ** term.  */
  if( pColset==0 ){
    assert( pPhrase->poslist.nSpace==0 );
    pPhrase->poslist.p = (u8*)pPos;
    pPhrase->poslist.n = nPos;
  }else if( pColset->nCol==1 ){
    assert( pPhrase->poslist.nSpace==0 );
    pPhrase->poslist.n = fts5ExprExtractCol(&pPos, nPos, pColset->aiCol[0]);
    pPhrase->poslist.p = (u8*)pPos;
  }else if( rc==SQLITE_OK ){
    rc = fts5ExprExtractColset(pColset, pPos, nPos, &pPhrase->poslist);
  }


  pNode->bNomatch = (pPhrase->poslist.n==0);
  return rc;
}

/*
** All individual term iterators in pNear are guaranteed to be valid when
** this function is called. This function checks if all term iterators

}

/*
** Argument pTerm must be a synonym iterator.
*/
static int fts5ExprSynonymPoslist(
  Fts5ExprTerm *pTerm, 
  Fts5Colset *pColset,
  i64 iRowid,
  int *pbDel,                     /* OUT: Caller should sqlite3_free(*pa) */
  u8 **pa, int *pn
){
  Fts5PoslistReader aStatic[4];
  Fts5PoslistReader *aIter = aStatic;
  int nIter = 0;
................................................................................
  assert( pTerm->pSynonym );
  for(p=pTerm; p; p=p->pSynonym){
    Fts5IndexIter *pIter = p->pIter;
    if( sqlite3Fts5IterEof(pIter)==0 && sqlite3Fts5IterRowid(pIter)==iRowid ){
      const u8 *a;
      int n;
      i64 dummy;
      rc = sqlite3Fts5IterPoslist(pIter, pColset, &a, &n, &dummy);
      if( rc!=SQLITE_OK ) goto synonym_poslist_out;
      if( nIter==nAlloc ){
        int nByte = sizeof(Fts5PoslistReader) * nAlloc * 2;
        Fts5PoslistReader *aNew = (Fts5PoslistReader*)sqlite3_malloc(nByte);
        if( aNew==0 ){
          rc = SQLITE_NOMEM;
          goto synonym_poslist_out;
        }
        memcpy(aNew, aIter, sizeof(Fts5PoslistReader) * nIter);
        nAlloc = nAlloc*2;
        if( aIter!=aStatic ) sqlite3_free(aIter);
        aIter = aNew;
      }
      sqlite3Fts5PoslistReaderInit(a, n, &aIter[nIter]);
      assert( aIter[nIter].bEof==0 );
      nIter++;
    }
  }

  assert( *pbDel==0 );
  if( nIter==1 ){
................................................................................
  int *pbMatch                    /* OUT: Set to true if really a match */
){
  Fts5PoslistWriter writer = {0};
  Fts5PoslistReader aStatic[4];
  Fts5PoslistReader *aIter = aStatic;
  int i;
  int rc = SQLITE_OK;

  





  fts5BufferZero(&pPhrase->poslist);

  /* If the aStatic[] array is not large enough, allocate a large array
  ** using sqlite3_malloc(). This approach could be improved upon. */
  if( pPhrase->nTerm>(sizeof(aStatic) / sizeof(aStatic[0])) ){
    int nByte = sizeof(Fts5PoslistReader) * pPhrase->nTerm;
    aIter = (Fts5PoslistReader*)sqlite3_malloc(nByte);
................................................................................
  for(i=0; i<pPhrase->nTerm; i++){
    Fts5ExprTerm *pTerm = &pPhrase->aTerm[i];
    i64 dummy;
    int n = 0;
    int bFlag = 0;
    const u8 *a = 0;
    if( pTerm->pSynonym ){
      rc = fts5ExprSynonymPoslist(
          pTerm, pColset, pNode->iRowid, &bFlag, (u8**)&a, &n
      );
    }else{
      rc = sqlite3Fts5IterPoslist(pTerm->pIter, pColset, &a, &n, &dummy);
    }
    if( rc!=SQLITE_OK ) goto ismatch_out;
    sqlite3Fts5PoslistReaderInit(a, n, &aIter[i]);
    aIter[i].bFlag = bFlag;
    if( aIter[i].bEof ) goto ismatch_out;
  }

  while( 1 ){
    int bMatch;
    i64 iPos = aIter[0].iPos;
................................................................................
            if( sqlite3Fts5PoslistReaderNext(pPos) ) goto ismatch_out;
          }
          if( pPos->iPos>iAdj ) iPos = pPos->iPos-i;
        }
      }
    }while( bMatch==0 );


    /* Append position iPos to the output */
    rc = sqlite3Fts5PoslistWriterAppend(&pPhrase->poslist, &writer, iPos);
    if( rc!=SQLITE_OK ) goto ismatch_out;


    for(i=0; i<pPhrase->nTerm; i++){
      if( sqlite3Fts5PoslistReaderNext(&aIter[i]) ) goto ismatch_out;
    }
  }

 ismatch_out:
................................................................................
    bEof = 1;
  }else{
    *piLast = fts5ExprSynonymRowid(pTerm, bDesc, &bEof);
  }
  return bEof;
}

























































static int fts5ExprNearTest(
  int *pRc,
  Fts5Expr *pExpr,                /* Expression that pNear is a part of */
  Fts5ExprNode *pNode             /* The "NEAR" node (FTS5_STRING) */
){
  Fts5ExprNearset *pNear = pNode->pNear;
................................................................................
  ** fts5_index.c iterator object. This is much faster than synthesizing 
  ** a new poslist the way we have to for more complicated phrase or NEAR
  ** expressions.  */
  Fts5ExprNearset *pNear = pNode->pNear;
  Fts5ExprPhrase *pPhrase = pNear->apPhrase[0];
  Fts5IndexIter *pIter = pPhrase->aTerm[0].pIter;
  Fts5Colset *pColset = pNear->pColset;


  int rc;

  assert( pNode->eType==FTS5_TERM );
  assert( pNear->nPhrase==1 && pPhrase->nTerm==1 );
  assert( pPhrase->aTerm[0].pSynonym==0 );

  rc = sqlite3Fts5IterPoslist(pIter, pColset, 









      (const u8**)&pPhrase->poslist.p, &pPhrase->poslist.n, &pNode->iRowid









  );
  pNode->bNomatch = (pPhrase->poslist.n==0);
  return rc;
}

/*
** All individual term iterators in pNear are guaranteed to be valid when
** this function is called. This function checks if all term iterators

struct Fts5IndexIter {
  Fts5Index *pIndex;              /* Index that owns this iterator */
  Fts5Structure *pStruct;         /* Database structure for this iterator */
  Fts5Buffer poslist;             /* Buffer containing current poslist */

  int nSeg;                       /* Size of aSeg[] array */
  int bRev;                       /* True to iterate in reverse order */
  int bSkipEmpty;                 /* True to skip deleted entries */
  int bEof;                       /* True at EOF */


  i64 iSwitchRowid;               /* Firstest rowid of other than aFirst[1] */
  Fts5CResult *aFirst;            /* Current merge state (see above) */
  Fts5SegIter aSeg[1];            /* Array of segment iterators */
};


................................................................................
** 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);
  assert_nc( nSz>=0 );
  *pnSz = nSz/2;
  *pbDel = nSz & 0x0001;
  return n;
}

/*
................................................................................
**
** 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 */

    ASSERT_SZLEAF_OK(pIter->pLeaf);
    if( iOff>=pIter->pLeaf->szLeaf ){
      p->rc = FTS5_CORRUPT;
    }else{
      const u8 *a = &pIter->pLeaf->p[iOff];
      pIter->iLeafOffset += fts5GetPoslistSize(a, &pIter->nPos, &pIter->bDel);
    }
  }
}

static void fts5SegIterLoadRowid(Fts5Index *p, Fts5SegIter *pIter){
  u8 *a = pIter->pLeaf->p;        /* Buffer to read data from */
  int iOff = pIter->iLeafOffset;

................................................................................
  Fts5IndexIter **ppOut           /* New object */
){
  Fts5IndexIter *pNew;
  pNew = fts5MultiIterAlloc(p, 2);
  if( pNew ){
    Fts5SegIter *pIter = &pNew->aSeg[1];


    pIter->flags = FTS5_SEGITER_ONETERM;
    if( pData->szLeaf>0 ){
      pIter->pLeaf = pData;
      pIter->iLeafOffset = fts5GetVarint(pData->p, (u64*)&pIter->iRowid);
      pIter->iEndofDoclist = pData->nn;
      pNew->aFirst[1].iFirst = 1;
      if( bDesc ){
................................................................................
static void fts5PoslistCallback(
  Fts5Index *p, 
  void *pContext, 
  const u8 *pChunk, int nChunk
){
  assert_nc( nChunk>=0 );
  if( nChunk>0 ){
    fts5BufferAppendBlob(&p->rc, (Fts5Buffer*)pContext, nChunk, pChunk);
  }
}

typedef struct PoslistCallbackCtx PoslistCallbackCtx;
struct PoslistCallbackCtx {
  Fts5Buffer *pBuf;               /* Append to this buffer */
  Fts5Colset *pColset;            /* Restrict matches to this column */
................................................................................
    int iStart = 0;

    if( pCtx->eState==2 ){
      int iCol;
      fts5FastGetVarint32(pChunk, i, iCol);
      if( fts5IndexColsetTest(pCtx->pColset, iCol) ){
        pCtx->eState = 1;
        fts5BufferAppendVarint(&p->rc, pCtx->pBuf, 1);
      }else{
        pCtx->eState = 0;
      }
    }

    do {
      while( i<nChunk && pChunk[i]!=0x01 ){
        while( pChunk[i] & 0x80 ) i++;
        i++;
      }
      if( pCtx->eState ){
        fts5BufferAppendBlob(&p->rc, pCtx->pBuf, i-iStart, &pChunk[iStart]);
      }
      if( i<nChunk ){
        int iCol;
        iStart = i;
        i++;
        if( i>=nChunk ){
          pCtx->eState = 2;
        }else{
          fts5FastGetVarint32(pChunk, i, iCol);
          pCtx->eState = fts5IndexColsetTest(pCtx->pColset, iCol);
          if( pCtx->eState ){
            fts5BufferAppendBlob(&p->rc, pCtx->pBuf, i-iStart, &pChunk[iStart]);
            iStart = i;
          }
        }
      }
    }while( i<nChunk );
  }
}
................................................................................
*/
static void fts5SegiterPoslist(
  Fts5Index *p,
  Fts5SegIter *pSeg,
  Fts5Colset *pColset,
  Fts5Buffer *pBuf
){

  if( pColset==0 ){
    fts5ChunkIterate(p, pSeg, (void*)pBuf, fts5PoslistCallback);
  }else{
    PoslistCallbackCtx sCtx;
    sCtx.pBuf = pBuf;
    sCtx.pColset = pColset;
    sCtx.eState = pColset ? fts5IndexColsetTest(pColset, 0) : 1;
    assert( sCtx.eState==0 || sCtx.eState==1 );
    fts5ChunkIterate(p, pSeg, (void*)&sCtx, fts5PoslistFilterCallback);
  }
}


/*






































** Iterator pMulti currently points to a valid entry (not EOF). This
** function appends a copy of the position-list of the entry pMulti 
** currently points to to buffer pBuf.

**








** If an error occurs, an error code is left in p->rc. It is assumed
** no error has already occurred when this function is called.
*/
static int fts5MultiIterPoslist(
  Fts5Index *p,

  Fts5IndexIter *pMulti,
  Fts5Colset *pColset,
  Fts5Buffer *pBuf
){
  if( p->rc==SQLITE_OK ){




    int iSz;

    int iData;

    Fts5SegIter *pSeg = &pMulti->aSeg[ pMulti->aFirst[1].iFirst ];
    assert( fts5MultiIterEof(p, pMulti)==0 );




    /* WRITEPOSLISTSIZE */
    iSz = pBuf->n;
    fts5BufferSafeAppendVarint(pBuf, pSeg->nPos*2);
    iData = pBuf->n;













    fts5SegiterPoslist(p, pSeg, pColset, pBuf);


    if( pColset ){
      int nActual = pBuf->n - iData;
      if( nActual!=pSeg->nPos ){
        /* WRITEPOSLISTSIZE */
        if( nActual==0 ){

          return 1;
        }else{
          int nReq = sqlite3Fts5GetVarintLen((u32)(nActual*2));
          while( iSz<(iData-nReq) ){ pBuf->p[iSz++] = 0x80; }
          sqlite3Fts5PutVarint(&pBuf->p[iSz], nActual*2);

        }
      }
    }
  }

  return 0;
}
................................................................................
            fts5MergePrefixLists(p, &doclist, &aBuf[i]);
            fts5BufferZero(&aBuf[i]);
          }
        }
        iLastRowid = 0;
      }

      if( 0==sqlite3Fts5BufferGrow(&p->rc, &doclist, 9) ){
        int iSave = doclist.n;
        assert( doclist.n!=0 || iLastRowid==0 );
        fts5BufferSafeAppendVarint(&doclist, iRowid - iLastRowid);
        if( fts5MultiIterPoslist(p, p1, pColset, &doclist) ){
          doclist.n = iSave;
        }else{
          iLastRowid = iRowid;
        }
      }
    }

    for(i=0; i<nBuf; i++){
      if( p->rc==SQLITE_OK ){
        fts5MergePrefixLists(p, &doclist, &aBuf[i]);
      }
................................................................................
const char *sqlite3Fts5IterTerm(Fts5IndexIter *pIter, int *pn){
  int n;
  const char *z = (const char*)fts5MultiIterTerm(pIter, &n);
  *pn = n-1;
  return &z[1];
}






















/*
** Return a pointer to a buffer containing a copy of the position list for
** the current entry. Output variable *pn is set to the size of the buffer 
** in bytes before returning.
**
** The returned position list does not include the "number of bytes" varint
** field that starts the position list on disk.
*/
int sqlite3Fts5IterPoslist(
  Fts5IndexIter *pIter, 

  const u8 **pp,                  /* OUT: Pointer to position-list data */
  int *pn,                        /* OUT: Size of position-list in bytes */
  i64 *piRowid                    /* OUT: Current rowid */
){
  Fts5SegIter *pSeg = &pIter->aSeg[ pIter->aFirst[1].iFirst ];
  assert( pIter->pIndex->rc==SQLITE_OK );
  *piRowid = pSeg->iRowid;
  *pn = pSeg->nPos;
  if( pSeg->iLeafOffset+pSeg->nPos <= pSeg->pLeaf->szLeaf ){
    *pp = &pSeg->pLeaf->p[pSeg->iLeafOffset];






  }else{
    fts5BufferZero(&pIter->poslist);






    fts5SegiterPoslist(pIter->pIndex, pSeg, 0, &pIter->poslist);
    *pp = pIter->poslist.p;

  }
  return fts5IndexReturn(pIter->pIndex);
}

/*
** This function is similar to sqlite3Fts5IterPoslist(), except that it
** copies the position list into the buffer supplied as the second 
................................................................................
  int rc = sqlite3Fts5IndexQuery(p, z, n, flags, 0, &pIdxIter);

  while( rc==SQLITE_OK && 0==sqlite3Fts5IterEof(pIdxIter) ){
    i64 dummy;
    const u8 *pPos;
    int nPos;
    i64 rowid = sqlite3Fts5IterRowid(pIdxIter);
    rc = sqlite3Fts5IterPoslist(pIdxIter, &pPos, &nPos, &dummy);
    if( rc==SQLITE_OK ){
      Fts5PoslistReader sReader;
      for(sqlite3Fts5PoslistReaderInit(-1, pPos, nPos, &sReader);
          sReader.bEof==0;
          sqlite3Fts5PoslistReaderNext(&sReader)
      ){
        int iCol = FTS5_POS2COLUMN(sReader.iPos);
        int iOff = FTS5_POS2OFFSET(sReader.iPos);
        cksum ^= fts5IndexEntryCksum(rowid, iCol, iOff, iIdx, z, n);
      }

struct Fts5IndexIter {
  Fts5Index *pIndex;              /* Index that owns this iterator */
  Fts5Structure *pStruct;         /* Database structure for this iterator */
  Fts5Buffer poslist;             /* Buffer containing current poslist */

  int nSeg;                       /* Size of aSeg[] array */
  int bRev;                       /* True to iterate in reverse order */
  u8 bSkipEmpty;                  /* True to skip deleted entries */
  u8 bEof;                        /* True at EOF */
  u8 bFiltered;                   /* True if column-filter already applied */

  i64 iSwitchRowid;               /* Firstest rowid of other than aFirst[1] */
  Fts5CResult *aFirst;            /* Current merge state (see above) */
  Fts5SegIter aSeg[1];            /* Array of segment iterators */
};


................................................................................
** 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 = 0;
  fts5FastGetVarint32(p, n, nSz);
  assert_nc( nSz>=0 );
  *pnSz = nSz/2;
  *pbDel = nSz & 0x0001;
  return n;
}

/*
................................................................................
**
** 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 */
    int nSz;
    ASSERT_SZLEAF_OK(pIter->pLeaf);

    fts5FastGetVarint32(pIter->pLeaf->p, iOff, nSz);
    pIter->bDel = (nSz & 0x0001);
    pIter->nPos = nSz>>1;
    pIter->iLeafOffset = iOff;

  }
}

static void fts5SegIterLoadRowid(Fts5Index *p, Fts5SegIter *pIter){
  u8 *a = pIter->pLeaf->p;        /* Buffer to read data from */
  int iOff = pIter->iLeafOffset;

................................................................................
  Fts5IndexIter **ppOut           /* New object */
){
  Fts5IndexIter *pNew;
  pNew = fts5MultiIterAlloc(p, 2);
  if( pNew ){
    Fts5SegIter *pIter = &pNew->aSeg[1];

    pNew->bFiltered = 1;
    pIter->flags = FTS5_SEGITER_ONETERM;
    if( pData->szLeaf>0 ){
      pIter->pLeaf = pData;
      pIter->iLeafOffset = fts5GetVarint(pData->p, (u64*)&pIter->iRowid);
      pIter->iEndofDoclist = pData->nn;
      pNew->aFirst[1].iFirst = 1;
      if( bDesc ){
................................................................................
static void fts5PoslistCallback(
  Fts5Index *p, 
  void *pContext, 
  const u8 *pChunk, int nChunk
){
  assert_nc( nChunk>=0 );
  if( nChunk>0 ){
    fts5BufferSafeAppendBlob((Fts5Buffer*)pContext, pChunk, nChunk);
  }
}

typedef struct PoslistCallbackCtx PoslistCallbackCtx;
struct PoslistCallbackCtx {
  Fts5Buffer *pBuf;               /* Append to this buffer */
  Fts5Colset *pColset;            /* Restrict matches to this column */
................................................................................
    int iStart = 0;

    if( pCtx->eState==2 ){
      int iCol;
      fts5FastGetVarint32(pChunk, i, iCol);
      if( fts5IndexColsetTest(pCtx->pColset, iCol) ){
        pCtx->eState = 1;
        fts5BufferSafeAppendVarint(pCtx->pBuf, 1);
      }else{
        pCtx->eState = 0;
      }
    }

    do {
      while( i<nChunk && pChunk[i]!=0x01 ){
        while( pChunk[i] & 0x80 ) i++;
        i++;
      }
      if( pCtx->eState ){
        fts5BufferSafeAppendBlob(pCtx->pBuf, &pChunk[iStart], i-iStart);
      }
      if( i<nChunk ){
        int iCol;
        iStart = i;
        i++;
        if( i>=nChunk ){
          pCtx->eState = 2;
        }else{
          fts5FastGetVarint32(pChunk, i, iCol);
          pCtx->eState = fts5IndexColsetTest(pCtx->pColset, iCol);
          if( pCtx->eState ){
            fts5BufferSafeAppendBlob(pCtx->pBuf, &pChunk[iStart], i-iStart);
            iStart = i;
          }
        }
      }
    }while( i<nChunk );
  }
}
................................................................................
*/
static void fts5SegiterPoslist(
  Fts5Index *p,
  Fts5SegIter *pSeg,
  Fts5Colset *pColset,
  Fts5Buffer *pBuf
){
  if( 0==fts5BufferGrow(&p->rc, pBuf, pSeg->nPos) ){
    if( pColset==0 ){
      fts5ChunkIterate(p, pSeg, (void*)pBuf, fts5PoslistCallback);
    }else{
      PoslistCallbackCtx sCtx;
      sCtx.pBuf = pBuf;
      sCtx.pColset = pColset;
      sCtx.eState = pColset ? fts5IndexColsetTest(pColset, 0) : 1;
      assert( sCtx.eState==0 || sCtx.eState==1 );
      fts5ChunkIterate(p, pSeg, (void*)&sCtx, fts5PoslistFilterCallback);
    }
  }
}

/*
** IN/OUT parameter (*pa) points to a position list n bytes in size. If
** the position list contains entries for column iCol, then (*pa) is set
** to point to the sub-position-list for that column and the number of
** bytes in it returned. Or, if the argument position list does not
** contain any entries for column iCol, return 0.
*/
static int fts5IndexExtractCol(
  const u8 **pa,                  /* IN/OUT: Pointer to poslist */
  int n,                          /* IN: Size of poslist in bytes */
  int iCol                        /* Column to extract from poslist */
){
  int iCurrent = 0;               /* Anything before the first 0x01 is col 0 */
  const u8 *p = *pa;
  const u8 *pEnd = &p[n];         /* One byte past end of position list */
  u8 prev = 0;

  while( iCol!=iCurrent ){
    /* Advance pointer p until it points to pEnd or an 0x01 byte that is
    ** not part of a varint */
    while( (prev & 0x80) || *p!=0x01 ){
      prev = *p++;
      if( p==pEnd ) return 0;
    }
    *pa = p++;
    p += fts5GetVarint32(p, iCurrent);
  }

  /* Advance pointer p until it points to pEnd or an 0x01 byte that is
  ** not part of a varint */
  assert( (prev & 0x80)==0 );
  while( p<pEnd && ((prev & 0x80) || *p!=0x01) ){
    prev = *p++;
  }
  return p - (*pa);
}


/*
** Iterator pMulti currently points to a valid entry (not EOF). This


** function appends the following to buffer pBuf:
**
**   * The varint iDelta, and
**   * the position list that currently points to, including the size field.
**
** If argument pColset is NULL, then the position list is filtered according
** to pColset before being appended to the buffer. If this means there are
** no entries in the position list, nothing is appended to the buffer (not
** even iDelta).
**
** If an error occurs, an error code is left in p->rc. 

*/
static int fts5AppendPoslist(
  Fts5Index *p,
  i64 iDelta,
  Fts5IndexIter *pMulti,
  Fts5Colset *pColset,
  Fts5Buffer *pBuf
){
  if( p->rc==SQLITE_OK ){
    Fts5SegIter *pSeg = &pMulti->aSeg[ pMulti->aFirst[1].iFirst ];
    assert( fts5MultiIterEof(p, pMulti)==0 );
    assert( pSeg->nPos>0 );
    if( 0==fts5BufferGrow(&p->rc, pBuf, pSeg->nPos+9+9) ){
      int iSv1;
      int iSv2;
      int iData;



      /* Append iDelta */
      iSv1 = pBuf->n;
      fts5BufferSafeAppendVarint(pBuf, iDelta);

      /* WRITEPOSLISTSIZE */
      iSv2 = pBuf->n;
      fts5BufferSafeAppendVarint(pBuf, pSeg->nPos*2);
      iData = pBuf->n;

      if( pSeg->iLeafOffset+pSeg->nPos<=pSeg->pLeaf->szLeaf 
       && (pColset==0 || pColset->nCol==1)
      ){
        const u8 *pPos = &pSeg->pLeaf->p[pSeg->iLeafOffset];
        int nPos;
        if( pColset ){
          nPos = fts5IndexExtractCol(&pPos, pSeg->nPos, pColset->aiCol[0]);
        }else{
          nPos = pSeg->nPos;
        }
        fts5BufferSafeAppendBlob(pBuf, pPos, nPos);
      }else{
        fts5SegiterPoslist(p, pSeg, pColset, pBuf);
      }

      if( pColset ){
        int nActual = pBuf->n - iData;
        if( nActual!=pSeg->nPos ){

          if( nActual==0 ){
            pBuf->n = iSv1;
            return 1;
          }else{
            int nReq = sqlite3Fts5GetVarintLen((u32)(nActual*2));
            while( iSv2<(iData-nReq) ){ pBuf->p[iSv2++] = 0x80; }
            sqlite3Fts5PutVarint(&pBuf->p[iSv2], nActual*2);
          }
        }
      }
    }
  }

  return 0;
}
................................................................................
            fts5MergePrefixLists(p, &doclist, &aBuf[i]);
            fts5BufferZero(&aBuf[i]);
          }
        }
        iLastRowid = 0;
      }





      if( !fts5AppendPoslist(p, iRowid-iLastRowid, p1, pColset, &doclist) ){


        iLastRowid = iRowid;

      }
    }

    for(i=0; i<nBuf; i++){
      if( p->rc==SQLITE_OK ){
        fts5MergePrefixLists(p, &doclist, &aBuf[i]);
      }
................................................................................
const char *sqlite3Fts5IterTerm(Fts5IndexIter *pIter, int *pn){
  int n;
  const char *z = (const char*)fts5MultiIterTerm(pIter, &n);
  *pn = n-1;
  return &z[1];
}


static int fts5IndexExtractColset (
  Fts5Colset *pColset,            /* Colset to filter on */
  const u8 *pPos, int nPos,       /* Position list */
  Fts5Buffer *pBuf                /* Output buffer */
){
  int rc = SQLITE_OK;
  int i;

  fts5BufferZero(pBuf);
  for(i=0; i<pColset->nCol; i++){
    const u8 *pSub = pPos;
    int nSub = fts5IndexExtractCol(&pSub, nPos, pColset->aiCol[i]);
    if( nSub ){
      fts5BufferAppendBlob(&rc, pBuf, nSub, pSub);
    }
  }
  return rc;
}


/*
** Return a pointer to a buffer containing a copy of the position list for
** the current entry. Output variable *pn is set to the size of the buffer 
** in bytes before returning.
**
** The returned position list does not include the "number of bytes" varint
** field that starts the position list on disk.
*/
int sqlite3Fts5IterPoslist(
  Fts5IndexIter *pIter, 
  Fts5Colset *pColset,            /* Column filter (or NULL) */
  const u8 **pp,                  /* OUT: Pointer to position-list data */
  int *pn,                        /* OUT: Size of position-list in bytes */
  i64 *piRowid                    /* OUT: Current rowid */
){
  Fts5SegIter *pSeg = &pIter->aSeg[ pIter->aFirst[1].iFirst ];
  assert( pIter->pIndex->rc==SQLITE_OK );
  *piRowid = pSeg->iRowid;

  if( pSeg->iLeafOffset+pSeg->nPos<=pSeg->pLeaf->szLeaf ){
    u8 *pPos = &pSeg->pLeaf->p[pSeg->iLeafOffset];
    if( pColset==0 || pIter->bFiltered ){
      *pn = pSeg->nPos;
      *pp = pPos;
    }else if( pColset->nCol==1 ){
      *pp = pPos;
      *pn = fts5IndexExtractCol(pp, pSeg->nPos, pColset->aiCol[0]);
    }else{
      fts5BufferZero(&pIter->poslist);
      fts5IndexExtractColset(pColset, pPos, pSeg->nPos, &pIter->poslist);
      *pp = pIter->poslist.p;
      *pn = pIter->poslist.n;
    }
  }else{
    fts5BufferZero(&pIter->poslist);
    fts5SegiterPoslist(pIter->pIndex, pSeg, pColset, &pIter->poslist);
    *pp = pIter->poslist.p;
    *pn = pIter->poslist.n;
  }
  return fts5IndexReturn(pIter->pIndex);
}

/*
** This function is similar to sqlite3Fts5IterPoslist(), except that it
** copies the position list into the buffer supplied as the second 
................................................................................
  int rc = sqlite3Fts5IndexQuery(p, z, n, flags, 0, &pIdxIter);

  while( rc==SQLITE_OK && 0==sqlite3Fts5IterEof(pIdxIter) ){
    i64 dummy;
    const u8 *pPos;
    int nPos;
    i64 rowid = sqlite3Fts5IterRowid(pIdxIter);
    rc = sqlite3Fts5IterPoslist(pIdxIter, 0, &pPos, &nPos, &dummy);
    if( rc==SQLITE_OK ){
      Fts5PoslistReader sReader;
      for(sqlite3Fts5PoslistReaderInit(pPos, nPos, &sReader);
          sReader.bEof==0;
          sqlite3Fts5PoslistReaderNext(&sReader)
      ){
        int iCol = FTS5_POS2COLUMN(sReader.iPos);
        int iOff = FTS5_POS2OFFSET(sReader.iPos);
        cksum ^= fts5IndexEntryCksum(rowid, iCol, iOff, iIdx, z, n);
      }

    int nInst = 0;                /* Number instances seen so far */
    int i;

    /* Initialize all iterators */
    for(i=0; i<nIter; i++){
      const u8 *a;
      int n = fts5CsrPoslist(pCsr, i, &a);
      sqlite3Fts5PoslistReaderInit(-1, a, n, &aIter[i]);
    }

    while( 1 ){
      int *aInst;
      int iBest = -1;
      for(i=0; i<nIter; i++){
        if( (aIter[i].bEof==0) 

    int nInst = 0;                /* Number instances seen so far */
    int i;

    /* Initialize all iterators */
    for(i=0; i<nIter; i++){
      const u8 *a;
      int n = fts5CsrPoslist(pCsr, i, &a);
      sqlite3Fts5PoslistReaderInit(a, n, &aIter[i]);
    }

    while( 1 ){
      int *aInst;
      int iBest = -1;
      for(i=0; i<nIter; i++){
        if( (aIter[i].bEof==0) 

      assert( pTab->eType==FTS5_VOCAB_COL || pTab->eType==FTS5_VOCAB_ROW );
      while( rc==SQLITE_OK ){
        i64 dummy;
        const u8 *pPos; int nPos;   /* Position list */
        i64 iPos = 0;               /* 64-bit position read from poslist */
        int iOff = 0;               /* Current offset within position list */

        rc = sqlite3Fts5IterPoslist(pCsr->pIter, &pPos, &nPos, &dummy);
        if( rc==SQLITE_OK ){
          if( pTab->eType==FTS5_VOCAB_ROW ){
            while( 0==sqlite3Fts5PoslistNext64(pPos, nPos, &iOff, &iPos) ){
              pCsr->aVal[1]++;
            }
            pCsr->aVal[0]++;
          }else{

      assert( pTab->eType==FTS5_VOCAB_COL || pTab->eType==FTS5_VOCAB_ROW );
      while( rc==SQLITE_OK ){
        i64 dummy;
        const u8 *pPos; int nPos;   /* Position list */
        i64 iPos = 0;               /* 64-bit position read from poslist */
        int iOff = 0;               /* Current offset within position list */

        rc = sqlite3Fts5IterPoslist(pCsr->pIter, 0, &pPos, &nPos, &dummy);
        if( rc==SQLITE_OK ){
          if( pTab->eType==FTS5_VOCAB_ROW ){
            while( 0==sqlite3Fts5PoslistNext64(pPos, nPos, &iOff, &iPos) ){
              pCsr->aVal[1]++;
            }
            pCsr->aVal[0]++;
          }else{

  INSERT INTO t3 VALUES('bac aab bab', 'c bac c', 'acb aba abb'); -- 1
  INSERT INTO t3 VALUES('bab abc c', 'acb c abb', 'c aaa c');     -- 2
}

do_execsql_test 10.1 {
  SELECT rowid FROM t3('c: c*');
} {2}





#-------------------------------------------------------------------------
# Test that character 0x1A is allowed in fts5 barewords.
#
do_test 11.0 {
  execsql "CREATE VIRTUAL TABLE t4 USING fts5(x, tokenize=\"ascii tokenchars '\x1A'\")"
  execsql "
................................................................................
do_test 11.4 {
  catchsql "SELECT rowid FROM t4('d\x1B')"
} {/fts5: syntax error/}
do_test 11.5 {
  catchsql "SELECT rowid FROM t4('d\x19')"
} {/fts5: syntax error/}
















finish_test

  INSERT INTO t3 VALUES('bac aab bab', 'c bac c', 'acb aba abb'); -- 1
  INSERT INTO t3 VALUES('bab abc c', 'acb c abb', 'c aaa c');     -- 2
}

do_execsql_test 10.1 {
  SELECT rowid FROM t3('c: c*');
} {2}

do_execsql_test 10.2 {
  SELECT rowid FROM t3('b: acb');
} {2}

#-------------------------------------------------------------------------
# Test that character 0x1A is allowed in fts5 barewords.
#
do_test 11.0 {
  execsql "CREATE VIRTUAL TABLE t4 USING fts5(x, tokenize=\"ascii tokenchars '\x1A'\")"
  execsql "
................................................................................
do_test 11.4 {
  catchsql "SELECT rowid FROM t4('d\x1B')"
} {/fts5: syntax error/}
do_test 11.5 {
  catchsql "SELECT rowid FROM t4('d\x19')"
} {/fts5: syntax error/}

#-------------------------------------------------------------------------
#
do_test 12.1 {
  execsql {
    CREATE VIRTUAL TABLE xx USING fts5(x,y);
    BEGIN;
      INSERT INTO xx VALUES('1 2 3', 'a b c');
  }
} {}

do_execsql_test 12.2 {
  SELECT rowid FROM xx('x:a');
  COMMIT;
} {}

finish_test