SQLite

  *pVal += iVal;
}

/*
** When this function is called, *pp points to the first byte following a
** varint that is part of a doclist (or position-list, or any other list
** of varints). This function moves *pp to point to the start of that varint,
** and decrements the value stored in *pVal by the varint value.
** and sets *pVal by the varint value.
**
** Argument pStart points to the first byte of the doclist that the
** varint is part of.
*/
static void fts3GetReverseDeltaVarint(
static void fts3GetReverseVarint(
  char **pp, 
  char *pStart, 
  sqlite3_int64 *pVal
){
  sqlite3_int64 iVal;
  char *p = *pp;

  /* Pointer p now points at the first byte past the varint we are 
  ** interested in. So, unless the doclist is corrupt, the 0x80 bit is
  ** clear on character p[-1]. */
  for(p = (*pp)-2; p>=pStart && *p&0x80; p--);
  p++;
  *pp = p;

  sqlite3Fts3GetVarint(p, &iVal);
  *pVal -= iVal;
  *pVal = iVal;
}

/*
** As long as *pp has not reached its end (pEnd), then do the same
** as fts3GetDeltaVarint(): read a single varint and add it to *pVal.
** But if we have reached the end of the varint, just set *pp=0 and
** leave *pVal unchanged.

  int iCol;                       /* Column index */
  int nString = 0;                /* Bytes required to hold all column names */
  int nCol = 0;                   /* Number of columns in the FTS table */
  char *zCsr;                     /* Space for holding column names */
  int nDb;                        /* Bytes required to hold database name */
  int nName;                      /* Bytes required to hold table name */
  int isFts4 = (argv[0][3]=='4'); /* True for FTS4, false for FTS3 */
  int bNoDocsize = 0;             /* True to omit %_docsize table */
  const char **aCol;              /* Array of column names */
  sqlite3_tokenizer *pTokenizer = 0;        /* Tokenizer for this table */

  char *zPrefix = 0;              /* Prefix parameter value (or NULL) */
  int nIndex;                     /* Size of aIndex[] array */
  struct Fts3Index *aIndex;       /* Array of indexes for this table */
  struct Fts3Index *aFree = 0;    /* Free this before returning */

  int bNoDocsize = 0;             /* True to omit %_docsize table */
  int bDescIdx = 0;               /* True to store descending indexes */

  char *zMatchinfo = 0;           /* Prefix parameter value (or NULL) */
  char *zPrefix = 0;              /* Prefix parameter value (or NULL) */
  char *zCompress = 0;
  char *zUncompress = 0;
  char *zCompress = 0;            /* compress=? parameter (or NULL) */
  char *zUncompress = 0;          /* uncompress=? parameter (or NULL) */
  char *zOrder = 0;               /* order=? parameter (or NULL) */
  struct Fts4Option {
    const char *zOpt;
    int nOpt;
    char **pzVar;
  } aFts4Opt[] = {
    { "matchinfo",   9, 0 },
    { "prefix",      6, 0 },
    { "compress",    8, 0 },
    { "uncompress", 10, 0 },
    { "order",       5, 0 }
  };
  aFts4Opt[0].pzVar = &zMatchinfo;
  aFts4Opt[1].pzVar = &zPrefix;
  aFts4Opt[2].pzVar = &zCompress;
  aFts4Opt[3].pzVar = &zUncompress;
  aFts4Opt[4].pzVar = &zOrder;

  assert( strlen(argv[0])==4 );
  assert( (sqlite3_strnicmp(argv[0], "fts4", 4)==0 && isFts4)
       || (sqlite3_strnicmp(argv[0], "fts3", 4)==0 && !isFts4)
  );

  nDb = (int)strlen(argv[1]) + 1;

     && 0==sqlite3Fts3IsIdChar(z[8])
    ){
      rc = sqlite3Fts3InitTokenizer(pHash, &z[9], &pTokenizer, pzErr);
    }

    /* Check if it is an FTS4 special argument. */
    else if( isFts4 && fts3IsSpecialColumn(z, &nKey, &zVal) ){
      int iOpt;
      if( !zVal ){
        rc = SQLITE_NOMEM;
        goto fts3_init_out;
      }
      if( nKey==9 && 0==sqlite3_strnicmp(z, "matchinfo", 9) ){
        if( strlen(zVal)==4 && 0==sqlite3_strnicmp(zVal, "fts3", 4) ){
          bNoDocsize = 1;
        }else{
      }else{
          *pzErr = sqlite3_mprintf("unrecognized matchinfo: %s", zVal);
          rc = SQLITE_ERROR;
        }
      }else if( nKey==8 && 0==sqlite3_strnicmp(z, "compress", 8) ){
        for(iOpt=0; iOpt<SizeofArray(aFts4Opt); iOpt++){
          if( nKey==aFts4Opt[iOpt].nOpt 
        zCompress = zVal;
        zVal = 0;
      }else if( nKey==10 && 0==sqlite3_strnicmp(z, "uncompress", 10) ){
           && !sqlite3_strnicmp(z, aFts4Opt[iOpt].zOpt, aFts4Opt[iOpt].nOpt) 
        zUncompress = zVal;
        zVal = 0;
          ){
            char **pzVar = aFts4Opt[iOpt].pzVar;
      }else if( nKey==6 && 0==sqlite3_strnicmp(z, "prefix", 6) ){
        sqlite3_free(zPrefix);
        zPrefix = zVal;
        zVal = 0;
      }else{
        *pzErr = sqlite3_mprintf("unrecognized parameter: %s", z);
        rc = SQLITE_ERROR;
            sqlite3_free(*pzVar);
            *pzVar = zVal;
            zVal = 0;
            break;
          }
        }
        if( zVal ){
          *pzErr = sqlite3_mprintf("unrecognized parameter: %s", z);
          rc = SQLITE_ERROR;
      }
      sqlite3_free(zVal);
          sqlite3_free(zVal);
        }
      }
    }

    /* Otherwise, the argument is a column name. */
    else {
      nString += (int)(strlen(z) + 1);
      aCol[nCol++] = z;
    }
  }
  if( rc!=SQLITE_OK ) goto fts3_init_out;

  if( nCol==0 ){
    assert( nString==0 );
    aCol[0] = "content";
    nString = 8;
    nCol = 1;
  }

  if( zMatchinfo ){
    if( strlen(zMatchinfo)!=4 || sqlite3_strnicmp(zMatchinfo, "fts3", 4) ){
      *pzErr = sqlite3_mprintf("unrecognized matchinfo: %s", zMatchinfo);
      rc = SQLITE_ERROR;
      goto fts3_init_out;
    }
    bNoDocsize = 1;
  }

  if( zOrder ){
    if( (strlen(zOrder)!=3 || sqlite3_strnicmp(zOrder, "asc", 3)) 
     && (strlen(zOrder)!=4 || sqlite3_strnicmp(zOrder, "desc", 3)) 
    ){
      *pzErr = sqlite3_mprintf("unrecognized order: %s", zOrder);
      rc = SQLITE_ERROR;
      goto fts3_init_out;
    }
    bDescIdx = (zOrder[0]=='d' || zOrder[0]=='D');
  }

  if( pTokenizer==0 ){
    rc = sqlite3Fts3InitTokenizer(pHash, "simple", &pTokenizer, pzErr);
    if( rc!=SQLITE_OK ) goto fts3_init_out;
  }
  assert( pTokenizer );

  p->nPendingData = 0;
  p->azColumn = (char **)&p[1];
  p->pTokenizer = pTokenizer;
  p->nNodeSize = 1000;
  p->nMaxPendingData = FTS3_MAX_PENDING_DATA;
  p->bHasDocsize = (isFts4 && bNoDocsize==0);
  p->bHasStat = isFts4;
  p->bDescIdx = bDescIdx;
  TESTONLY( p->inTransaction = -1 );
  TESTONLY( p->mxSavepoint = -1 );

  p->aIndex = (struct Fts3Index *)&p->azColumn[nCol];
  memcpy(p->aIndex, aIndex, sizeof(struct Fts3Index) * nIndex);
  p->nIndex = nIndex;
  for(i=0; i<nIndex; i++){

  fts3DeclareVtab(&rc, p);

fts3_init_out:
  sqlite3_free(zPrefix);
  sqlite3_free(aFree);
  sqlite3_free(zCompress);
  sqlite3_free(zUncompress);
  sqlite3_free(zOrder);
  sqlite3_free(zMatchinfo);
  sqlite3_free((void *)aCol);
  if( rc!=SQLITE_OK ){
    if( p ){
      fts3DisconnectMethod((sqlite3_vtab *)p);
    }else if( pTokenizer ){
      pTokenizer->pModule->xDestroy(pTokenizer);
    }

/*
** Values that may be used as the first parameter to fts3DoclistMerge().
*/
#define MERGE_NOT        2        /* D + D -> D */
#define MERGE_AND        3        /* D + D -> D */
#define MERGE_OR         4        /* D + D -> D */
#define MERGE_POS_OR     5        /* P + P -> P */
#define MERGE_PHRASE     6        /* P + P -> D */
#define MERGE_POS_PHRASE 7        /* P + P -> P */
#define MERGE_NEAR       8        /* P + P -> D */

#define MERGE_POS_OR     5        /* P + P -> P */
#define MERGE_POS_PHRASE 7        /* P + P -> P */
#define MERGE_POS_NEAR   9        /* P + P -> P */

/*
** Merge the two doclists passed in buffer a1 (size n1 bytes) and a2
** (size n2 bytes). The output is written to pre-allocated buffer aBuffer,
** which is guaranteed to be large enough to hold the results. The number
** of bytes written to aBuffer is stored in *pnBuffer before returning.

  int nDoc = 0;

  assert( mergetype==MERGE_OR     || mergetype==MERGE_POS_OR 
       || mergetype==MERGE_AND    || mergetype==MERGE_NOT
       || mergetype==MERGE_PHRASE || mergetype==MERGE_POS_PHRASE
       || mergetype==MERGE_NEAR   || mergetype==MERGE_POS_NEAR
  );
  assert( mergetype==MERGE_POS_PHRASE || mergetype==MERGE_POS_NEAR );

  if( !aBuffer ){
    *pnBuffer = 0;
    return SQLITE_NOMEM;
  }

  /* Read the first docid from each doclist */

*/
typedef struct TermSelect TermSelect;
struct TermSelect {
  int isReqPos;
  char *aaOutput[16];             /* Malloc'd output buffer */
  int anOutput[16];               /* Size of output in bytes */
};


static void fts3GetDeltaVarint3(
  char **pp, 
  char *pEnd, 
  int bDescIdx,
  sqlite3_int64 *pVal
){
  if( *pp>=pEnd ){
    *pp = 0;
  }else{
    sqlite3_int64 iVal;
    *pp += sqlite3Fts3GetVarint(*pp, &iVal);
    if( bDescIdx ){
      *pVal -= iVal;
    }else{
      *pVal += iVal;
    }
  }
}

static void fts3PutDeltaVarint3(
  char **pp,                      /* IN/OUT: Output pointer */
  int bDescIdx,                   /* True for descending docids */
  sqlite3_int64 *piPrev,          /* IN/OUT: Previous value written to list */
  int *pbFirst,                   /* IN/OUT: True after first int written */
  sqlite3_int64 iVal              /* Write this value to the list */
){
  sqlite3_int64 iWrite;
  if( bDescIdx==0 || *pbFirst==0 ){
    iWrite = iVal - *piPrev;
  }else{
    iWrite = *piPrev - iVal;
  }
  assert( *pbFirst || *piPrev==0 );
  assert( *pbFirst==0 || iWrite>0 );
  *pp += sqlite3Fts3PutVarint(*pp, iWrite);
  *piPrev = iVal;
  *pbFirst = 1;
}

#define COMPARE_DOCID(i1, i2) ((bDescIdx?-1:1) * (i1-i2))

static int fts3DoclistOrMerge(
  int bDescIdx,                   /* True if arguments are desc */
  u8 *a1, int n1,                 /* First doclist */
  u8 *a2, int n2,                 /* Second doclist */
  u8 **paOut, int *pnOut          /* OUT: Malloc'd doclist */
){
  sqlite3_int64 i1 = 0;
  sqlite3_int64 i2 = 0;
  sqlite3_int64 iPrev = 0;
  char *pEnd1 = &a1[n1];
  char *pEnd2 = &a2[n2];
  char *p1 = a1;
  char *p2 = a2;
  char *p;
  int nOut;
  char *aOut;
  int bFirstOut = 0;

  *paOut = 0;
  *pnOut = 0;
  aOut = sqlite3_malloc(n1+n2);
  if( !aOut ) return SQLITE_NOMEM;

  p = aOut;
  fts3GetDeltaVarint3(&p1, pEnd1, 0, &i1);
  fts3GetDeltaVarint3(&p2, pEnd2, 0, &i2);
  while( p1 || p2 ){
    sqlite3_int64 iDiff = COMPARE_DOCID(i1, i2);

    if( p2 && p1 && iDiff==0 ){
      fts3PutDeltaVarint3(&p, bDescIdx, &iPrev, &bFirstOut, i1);
      fts3PoslistMerge(&p, &p1, &p2);
      fts3GetDeltaVarint3(&p1, pEnd1, bDescIdx, &i1);
      fts3GetDeltaVarint3(&p2, pEnd2, bDescIdx, &i2);
    }else if( !p2 || (p1 && iDiff<0) ){
      fts3PutDeltaVarint3(&p, bDescIdx, &iPrev, &bFirstOut, i1);
      fts3PoslistCopy(&p, &p1);
      fts3GetDeltaVarint3(&p1, pEnd1, bDescIdx, &i1);
    }else{
      fts3PutDeltaVarint3(&p, bDescIdx, &iPrev, &bFirstOut, i2);
      fts3PoslistCopy(&p, &p2);
      fts3GetDeltaVarint3(&p2, pEnd2, bDescIdx, &i2);
    }
  }

  *paOut = aOut;
  *pnOut = (p-aOut);
  return SQLITE_OK;
}

static void fts3DoclistPhraseMerge(
  int bDescIdx,                   /* True if arguments are desc */
  int nDist,                      /* Distance from left to right (1=adjacent) */
  u8 *aLeft, int nLeft,           /* Left doclist */
  u8 *aRight, int *pnRight        /* IN/OUT: Right/output doclist */
){
  sqlite3_int64 i1 = 0;
  sqlite3_int64 i2 = 0;
  sqlite3_int64 iPrev = 0;
  char *pEnd1 = &aLeft[nLeft];
  char *pEnd2 = &aRight[*pnRight];
  char *p1 = aLeft;
  char *p2 = aRight;
  char *p;
  int bFirstOut = 0;
  char *aOut = aRight;

  assert( nDist>0 );

  p = aOut;
  fts3GetDeltaVarint3(&p1, pEnd1, 0, &i1);
  fts3GetDeltaVarint3(&p2, pEnd2, 0, &i2);

  while( p1 && p2 ){
    sqlite3_int64 iDiff = COMPARE_DOCID(i1, i2);
    if( iDiff==0 ){
      char *pSave = p;
      sqlite3_int64 iPrevSave = iPrev;
      int bFirstOutSave = bFirstOut;

      fts3PutDeltaVarint3(&p, bDescIdx, &iPrev, &bFirstOut, i1);
      if( 0==fts3PoslistPhraseMerge(&p, nDist, 0, 1, &p1, &p2) ){
        p = pSave;
        iPrev = iPrevSave;
        bFirstOut = bFirstOutSave;
      }
      fts3GetDeltaVarint3(&p1, pEnd1, bDescIdx, &i1);
      fts3GetDeltaVarint3(&p2, pEnd2, bDescIdx, &i2);
    }else if( iDiff<0 ){
      fts3PoslistCopy(0, &p1);
      fts3GetDeltaVarint3(&p1, pEnd1, bDescIdx, &i1);
    }else{
      fts3PoslistCopy(0, &p2);
      fts3GetDeltaVarint3(&p2, pEnd2, bDescIdx, &i2);
    }
  }

  *pnRight = p - aOut;
}

/*
** This function merges two doclists according to the requirements of a
** NEAR operator.
*/
static int fts3DoclistNearMerge(
  int bDescIdx,
  int mergetype,                  /* MERGE_POS_NEAR or MERGE_NEAR */
  int nNear,                      /* Parameter to NEAR operator */
  int nTokenLeft,                 /* Number of tokens in LHS phrase arg */
  char *aLeft,                    /* Doclist for LHS (incl. positions) */
  int nLeft,                      /* Size of LHS doclist in bytes */
  int nTokenRight,                /* As nTokenLeft */
  char *aRight,                   /* As aLeft */
  int nRight,                     /* As nRight */
  char **paOut,                   /* OUT: Results of merge (malloced) */
  int *pnOut                      /* OUT: Sized of output buffer */
){
  char *aOut;                     /* Buffer to write output doclist to */
  char *aTmp;                     /* Temp buffer used by PoslistNearMerge() */

  sqlite3_int64 i1 = 0;
  sqlite3_int64 i2 = 0;
  sqlite3_int64 iPrev = 0;
  int bFirstOut = 0;

  char *pEnd1 = &aLeft[nLeft];
  char *pEnd2 = &aRight[nRight];
  char *p1 = aLeft;
  char *p2 = aRight;
  char *p;

  int nParam1 = nNear+nTokenRight;
  int nParam2 = nNear+nTokenLeft;

  p = aOut = sqlite3_malloc(nLeft+nRight+1);
  aTmp = sqlite3_malloc(2*(nLeft+nRight+1));
  if( !aOut || !aTmp ){
    sqlite3_free(aOut);
    sqlite3_free(aTmp);
    *paOut = 0;
    *pnOut = 0;
    return SQLITE_NOMEM;
  }

  fts3GetDeltaVarint3(&p1, pEnd1, 0, &i1);
  fts3GetDeltaVarint3(&p2, pEnd2, 0, &i2);

  while( p1 && p2 ){
    sqlite3_int64 iDiff = COMPARE_DOCID(i1, i2);
    if( iDiff==0 ){
      char *pSave = p;
      sqlite3_int64 iPrevSave = iPrev;
      int bFirstOutSave = bFirstOut;
      fts3PutDeltaVarint3(&p, bDescIdx, &iPrev, &bFirstOut, i1);
      if( !fts3PoslistNearMerge(&p, aTmp, nParam1, nParam2, &p1, &p2) ){
        p = pSave;
        iPrev = iPrevSave;
        bFirstOut = bFirstOutSave;
      }

      fts3GetDeltaVarint3(&p1, pEnd1, bDescIdx, &i1);
      fts3GetDeltaVarint3(&p2, pEnd2, bDescIdx, &i2);
    }else if( iDiff<0 ){
      fts3PoslistCopy(0, &p1);
      fts3GetDeltaVarint3(&p1, pEnd1, bDescIdx, &i1);
    }else{
      fts3PoslistCopy(0, &p2);
      fts3GetDeltaVarint3(&p2, pEnd2, bDescIdx, &i2);
    }
  }

  sqlite3_free(aTmp);
  *paOut = aOut;
  *pnOut = p - aOut;
  return SQLITE_OK;
}



/*
** Merge all doclists in the TermSelect.aaOutput[] array into a single
** doclist stored in TermSelect.aaOutput[0]. If successful, delete all
** other doclists (except the aaOutput[0] one) and return SQLITE_OK.
**
** If an OOM error occurs, return SQLITE_NOMEM. In this case it is
** the responsibility of the caller to free any doclists left in the
** TermSelect.aaOutput[] array.
*/
static int fts3TermSelectMerge(TermSelect *pTS){
static int fts3TermSelectMerge(Fts3Table *p, TermSelect *pTS){
  int mergetype = (pTS->isReqPos ? MERGE_POS_OR : MERGE_OR);
  char *aOut = 0;
  int nOut = 0;
  int i;

  /* Loop through the doclists in the aaOutput[] array. Merge them all
  ** into a single doclist.
  */
  for(i=0; i<SizeofArray(pTS->aaOutput); i++){
    if( pTS->aaOutput[i] ){
      if( !aOut ){
        aOut = pTS->aaOutput[i];
        nOut = pTS->anOutput[i];
        pTS->aaOutput[i] = 0;
      }else{
        int nNew = nOut + pTS->anOutput[i];
        char *aNew = sqlite3_malloc(nNew);
        if( !aNew ){
        int nNew;
        u8 *aNew;

        int rc = fts3DoclistOrMerge(p->bDescIdx, 
            pTS->aaOutput[i], pTS->anOutput[i], aOut, nOut, &aNew, &nNew
        );
        if( rc!=SQLITE_OK ){
          sqlite3_free(aOut);
          return SQLITE_NOMEM;
          return rc;
        }
        fts3DoclistMerge(mergetype, 0, 0,

            aNew, &nNew, pTS->aaOutput[i], pTS->anOutput[i], aOut, nOut, 0
        );
        sqlite3_free(pTS->aaOutput[i]);
        sqlite3_free(aOut);
        pTS->aaOutput[i] = 0;
        aOut = aNew;
        nOut = nNew;
      }
    }

  UNUSED_PARAMETER(p);
  UNUSED_PARAMETER(zTerm);
  UNUSED_PARAMETER(nTerm);

  if( pTS->aaOutput[0]==0 ){
    /* If this is the first term selected, copy the doclist to the output
    ** buffer using memcpy(). TODO: Add a way to transfer control of the
    ** buffer using memcpy(). */
    ** aDoclist buffer from the caller so as to avoid the memcpy().
    */
    pTS->aaOutput[0] = sqlite3_malloc(nDoclist);
    pTS->anOutput[0] = nDoclist;
    if( pTS->aaOutput[0] ){
      memcpy(pTS->aaOutput[0], aDoclist, nDoclist);
    }else{
      return SQLITE_NOMEM;
    }
  }else{
    int mergetype = (pTS->isReqPos ? MERGE_POS_OR : MERGE_OR);
    char *aMerge = aDoclist;
    int nMerge = nDoclist;
    int iOut;

    for(iOut=0; iOut<SizeofArray(pTS->aaOutput); iOut++){
      char *aNew;
      int nNew;
      if( pTS->aaOutput[iOut]==0 ){
        assert( iOut>0 );
        pTS->aaOutput[iOut] = aMerge;
        pTS->anOutput[iOut] = nMerge;
        break;
      }
      }else{
        u8 *aNew;
        int nNew;

        int rc = fts3DoclistOrMerge(p->bDescIdx, aMerge, nMerge, 
      nNew = nMerge + pTS->anOutput[iOut];
      aNew = sqlite3_malloc(nNew);
      if( !aNew ){
        if( aMerge!=aDoclist ){
            pTS->aaOutput[iOut], pTS->anOutput[iOut], &aNew, &nNew
        );
        if( rc!=SQLITE_OK ){
          if( aMerge!=aDoclist ) sqlite3_free(aMerge);
          sqlite3_free(aMerge);
        }
        return SQLITE_NOMEM;
      }
          return rc;
        }
      fts3DoclistMerge(mergetype, 0, 0, aNew, &nNew, 
          pTS->aaOutput[iOut], pTS->anOutput[iOut], aMerge, nMerge, 0
      );

      if( iOut>0 ) sqlite3_free(aMerge);
      sqlite3_free(pTS->aaOutput[iOut]);
      pTS->aaOutput[iOut] = 0;

      aMerge = aNew;
      nMerge = nNew;
      if( (iOut+1)==SizeofArray(pTS->aaOutput) ){
        pTS->aaOutput[iOut] = aMerge;
        pTS->anOutput[iOut] = nMerge;
        if( aMerge!=aDoclist ) sqlite3_free(aMerge);
        sqlite3_free(pTS->aaOutput[iOut]);
        pTS->aaOutput[iOut] = 0;
  
        aMerge = aNew;
        nMerge = nNew;
        if( (iOut+1)==SizeofArray(pTS->aaOutput) ){
          pTS->aaOutput[iOut] = aMerge;
          pTS->anOutput[iOut] = nMerge;
        }
      }
    }
  }
  return SQLITE_OK;
}

/*

  ){
    rc = fts3TermSelectCb(p, (void *)&tsc, 
        pSegcsr->zTerm, pSegcsr->nTerm, pSegcsr->aDoclist, pSegcsr->nDoclist
    );
  }

  if( rc==SQLITE_OK ){
    rc = fts3TermSelectMerge(&tsc);
    rc = fts3TermSelectMerge(p, &tsc);
  }
  if( rc==SQLITE_OK ){
    *ppOut = tsc.aaOutput[0];
    *pnOut = tsc.anOutput[0];
  }else{
    int i;
    for(i=0; i<SizeofArray(tsc.aaOutput); i++){

      }
    }
  }

  return nDoc;
}

/*
** This function merges two doclists according to the requirements of a
** NEAR operator.
**
** Both input doclists must include position information. The output doclist 
** includes position information if the first argument to this function
** is MERGE_POS_NEAR, or does not if it is MERGE_NEAR.
*/
static int fts3NearMerge(
  int mergetype,                  /* MERGE_POS_NEAR or MERGE_NEAR */
  int nNear,                      /* Parameter to NEAR operator */
  int nTokenLeft,                 /* Number of tokens in LHS phrase arg */
  char *aLeft,                    /* Doclist for LHS (incl. positions) */
  int nLeft,                      /* Size of LHS doclist in bytes */
  int nTokenRight,                /* As nTokenLeft */
  char *aRight,                   /* As aLeft */
  int nRight,                     /* As nRight */
  char **paOut,                   /* OUT: Results of merge (malloced) */
  int *pnOut                      /* OUT: Sized of output buffer */
){
  char *aOut;                     /* Buffer to write output doclist to */
  int rc;                         /* Return code */

  assert( mergetype==MERGE_POS_NEAR || MERGE_NEAR );

  aOut = sqlite3_malloc(nLeft+nRight+1);
  if( aOut==0 ){
    rc = SQLITE_NOMEM;
  }else{
    rc = fts3DoclistMerge(mergetype, nNear+nTokenRight, nNear+nTokenLeft, 
      aOut, pnOut, aLeft, nLeft, aRight, nRight, 0
    );
    if( rc!=SQLITE_OK ){
      sqlite3_free(aOut);
      aOut = 0;
    }
  }

  *paOut = aOut;
  return rc;
}

/*
** Advance the cursor to the next row in the %_content table that
** matches the search criteria.  For a MATCH search, this will be
** the next row that matches. For a full-table scan, this will be
** simply the next row in the %_content table.  For a docid lookup,
** this routine simply sets the EOF flag.
**

  /* In case the cursor has been used before, clear it now. */
  sqlite3_finalize(pCsr->pStmt);
  sqlite3_free(pCsr->aDoclist);
  sqlite3Fts3ExprFree(pCsr->pExpr);
  memset(&pCursor[1], 0, sizeof(Fts3Cursor)-sizeof(sqlite3_vtab_cursor));

  if( idxStr ){
  pCsr->bDesc = (idxStr && idxStr[0]=='D');
    pCsr->bDesc = (idxStr[0]=='D');
  }else{
    pCsr->bDesc = p->bDescIdx;
  }
  pCsr->eSearch = (i16)idxNum;

  if( idxNum!=FTS3_DOCID_SEARCH && idxNum!=FTS3_FULLSCAN_SEARCH ){
    int iCol = idxNum-FTS3_FULLTEXT_SEARCH;
    const char *zQuery = (const char *)sqlite3_value_text(apVal[0]);

    if( zQuery==0 && sqlite3_value_type(apVal[0])!=SQLITE_NULL ){

  /* Compile a SELECT statement for this cursor. For a full-table-scan, the
  ** statement loops through all rows of the %_content table. For a
  ** full-text query or docid lookup, the statement retrieves a single
  ** row by docid.
  */
  if( idxNum==FTS3_FULLSCAN_SEARCH ){
    const char *zSort = (idxStr ? idxStr : "ASC");
    const char *zSort = (pCsr->bDesc ? "DESC" : "ASC");
    const char *zTmpl = "SELECT %s FROM %Q.'%q_content' AS x ORDER BY docid %s";
    zSql = sqlite3_mprintf(zTmpl, p->zReadExprlist, p->zDb, p->zName, zSort);
  }else{
    const char *zTmpl = "SELECT %s FROM %Q.'%q_content' AS x WHERE docid = ?";
    zSql = sqlite3_mprintf(zTmpl, p->zReadExprlist, p->zDb, p->zName);
  }
  if( !zSql ) return SQLITE_NOMEM;

          nDoclist = 0;
          break;
        }else if( aDoclist==0 ){
          aDoclist = pThis;
          nDoclist = nThis;
        }else{
          assert( iPrev>=0 );
          fts3DoclistMerge(MERGE_POS_PHRASE, iToken-iPrev, 
              0, pThis, &nThis, aDoclist, nDoclist, pThis, nThis, 0
          fts3DoclistPhraseMerge(pTab->bDescIdx,
              iToken-iPrev, aDoclist, nDoclist, pThis, &nThis
          );
          sqlite3_free(aDoclist);
          aDoclist = pThis;
          nDoclist = nThis;
        }
        iPrev = iToken;
      }

** function has been called successfully on an Fts3Phrase, it may be
** used with fts3EvalPhraseNext() to iterate through the matching docids.
*/
static int fts3EvalPhraseStart(Fts3Cursor *pCsr, int bOptOk, Fts3Phrase *p){
  int rc;
  Fts3Doclist *pList = &p->doclist;
  Fts3PhraseToken *pFirst = &p->aToken[0];
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;

  assert( pList->aAll==0 );

  if( pCsr->bDesc==0 && bOptOk==1 && p->nToken==1 
  if( pCsr->bDesc==pTab->bDescIdx && bOptOk==1 && p->nToken==1 
   && pFirst->pSegcsr && pFirst->pSegcsr->bLookup 
  ){
    /* Use the incremental approach. */
    Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
    int iCol = (p->iColumn >= pTab->nColumn ? -1 : p->iColumn);
    rc = sqlite3Fts3MsrIncrStart(
        pTab, pFirst->pSegcsr, iCol, pFirst->z, pFirst->n);
    p->bIncr = 1;

  }else{
    /* Load the full doclist for the phrase into memory. */
    rc = fts3EvalPhraseLoad(pCsr, p);
    p->bIncr = 0;
  }

  assert( rc!=SQLITE_OK || p->nToken<1 || p->aToken[0].pSegcsr==0 || p->bIncr );
  return rc;
}

void sqlite3Fts3DoclistPrev(
  int bDescIdx,                   /* True if the doclist is desc */
  char *aDoclist,                 /* Pointer to entire doclist */
  int nDoclist,                   /* Length of aDoclist in bytes */
  char **ppIter,                  /* IN/OUT: Iterator pointer */
  sqlite3_int64 *piDocid,         /* IN/OUT: Docid pointer */
  int *pnList,                    /* IN/OUT: List length pointer */
  u8 *pbEof                       /* OUT: End-of-file flag */
){
  char *p = *ppIter;
  int iMul = (bDescIdx ? -1 : 1);

  assert( *pbEof==0 );
  assert( p || *piDocid==0 );
  assert( !p || (p>aDoclist && p<&aDoclist[nDoclist]) );

  if( p==0 ){
    sqlite3_int64 iDocid = 0;
    char *pNext = 0;
    char *pDocid = aDoclist;
    char *pEnd = &aDoclist[nDoclist];

    pDocid += sqlite3Fts3GetVarint(pDocid, &iDocid);
    pNext = pDocid;
    fts3PoslistCopy(0, &pDocid);
    while( pDocid<pEnd ){
      sqlite3_int64 iDelta;
      pDocid += sqlite3Fts3GetVarint(pDocid, &iDelta);
      iDocid += (iMul * iDelta);
      pNext = pDocid;
      fts3PoslistCopy(0, &pDocid);
    }

    *pnList = pEnd - pNext;
    *ppIter = pNext;
    *piDocid = iDocid;
  }else{
    sqlite3_int64 iDelta;
    fts3GetReverseVarint(&p, aDoclist, &iDelta);
    *piDocid -= (iMul * iDelta);

    if( p==aDoclist ){
      *pbEof = 1;
    }else{
      char *pSave = p;
      fts3ReversePoslist(aDoclist, &p);
      *pnList = (pSave - p);
    }
    *ppIter = p;
  }
}

/*
** Attempt to move the phrase iterator to point to the next matching docid. 
** If an error occurs, return an SQLite error code. Otherwise, return 
** SQLITE_OK.
**
** If there is no "next" entry and no error occurs, then *pbEof is set to
** 1 before returning. Otherwise, if no error occurs and the iterator is
** successfully advanced, *pbEof is set to 0.
*/
static int fts3EvalPhraseNext(
  Fts3Cursor *pCsr, 
  Fts3Phrase *p, 
  u8 *pbEof
){
  int rc = SQLITE_OK;
  Fts3Doclist *pDL = &p->doclist;
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;

  if( p->bIncr ){
    Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
    assert( p->nToken==1 );
    rc = sqlite3Fts3MsrIncrNext(pTab, p->aToken[0].pSegcsr, 
        &pDL->iDocid, &pDL->pList, &pDL->nList
    );
    if( rc==SQLITE_OK && !pDL->pList ){
      *pbEof = 1;
    }
  }else if( pCsr->bDesc && pDL->aAll ){

    if( pDL->pNextDocid==0 ){
  }else if( pCsr->bDesc!=pTab->bDescIdx && pDL->aAll ){
    sqlite3Fts3DoclistPrev(pTab->bDescIdx, pDL->aAll, pDL->nAll, 
        &pDL->pNextDocid, &pDL->iDocid, &pDL->nList, pbEof
      sqlite3_int64 iDocid = 0;
      char *pNext;
      char *pDocid = pDL->aAll;
      char *pEnd = &pDocid[pDL->nAll];

      while( pDocid<pEnd ){
        fts3GetDeltaVarint(&pDocid, &iDocid);
        pDL->pNextDocid = pDocid;
        pDL->pList = pDocid;
        fts3PoslistCopy(0, &pDocid);
      }
      pDL->nList = (pEnd - pDL->pList);
      pDL->iDocid = iDocid;
    }else{

      assert( *pbEof==0 );
      assert( pDL->pNextDocid>pDL->aAll );

      fts3GetReverseDeltaVarint(
          &pDL->pNextDocid, pDL->aAll, &pDL->iDocid
      );
    );
      if( pDL->pNextDocid==pDL->aAll ){
        *pbEof = 1;
      }else{
        char *pSave = pDL->pNextDocid;
        fts3ReversePoslist(pDL->aAll, &pDL->pNextDocid);
        pDL->pList = pDL->pNextDocid;
    pDL->pList = pDL->pNextDocid;
        pDL->nList = pSave - pDL->pNextDocid;
      }
    }

  }else{

    char *pIter;
    if( pDL->pNextDocid ){
      pIter = pDL->pNextDocid;
    }else{
      pIter = pDL->aAll;
    }

    if( pIter>=&pDL->aAll[pDL->nAll] ){
      /* We have already reached the end of this doclist. EOF. */
      *pbEof = 1;
    }else{
      sqlite3_int64 iDelta;
      pIter += sqlite3Fts3GetVarint(pIter, &iDelta);
      if( pTab->bDescIdx==0 || pDL->pNextDocid==0 ){
      fts3GetDeltaVarint(&pIter, &pDL->iDocid);
        pDL->iDocid += iDelta;
      }else{
        pDL->iDocid -= iDelta;
      }
      pDL->pList = pIter;
      fts3PoslistCopy(0, &pIter);
      pDL->nList = (pIter - pDL->pList);
      pDL->pNextDocid = pIter;
      *pbEof = 0;
    }
  }

      fts3EvalStartReaders(pCsr, pExpr->pRight, bOptOk, pRc);
      pExpr->bDeferred = (pExpr->pLeft->bDeferred && pExpr->pRight->bDeferred);
    }
  }
}

static void fts3EvalNearMerge(
  int bDescIdx,
  Fts3Expr *p1,
  Fts3Expr *p2,
  int nNear,
  int *pRc
){
  if( *pRc==SQLITE_OK ){
    int rc;                         /* Return code */

      sqlite3_free(pRight->doclist.aAll);
      pRight->doclist.aAll = 0;
      pRight->doclist.nAll = 0;
    }else if( pRight->doclist.aAll ){
      char *aOut;                 /* Buffer in which to assemble new doclist */
      int nOut;                   /* Size of buffer aOut in bytes */
  
      *pRc = fts3NearMerge(MERGE_POS_NEAR, nNear, 
      *pRc = fts3DoclistNearMerge(bDescIdx, MERGE_POS_NEAR, nNear, 
          pLeft->nToken, pLeft->doclist.aAll, pLeft->doclist.nAll,
          pRight->nToken, pRight->doclist.aAll, pRight->doclist.nAll,
          &aOut, &nOut
      );
      sqlite3_free(pRight->doclist.aAll);
      pRight->doclist.aAll = aOut;
      pRight->doclist.nAll = nOut;

        nPhrase++;
      }

      aPhrase = (Fts3Expr **)sqlite3_malloc(sizeof(Fts3Expr *) * nPhrase);
      if( !aPhrase ){
        *pRc = SQLITE_NOMEM;
      }else{
        Fts3Table *p = (Fts3Table *)pCsr->base.pVtab;
        int i = 1;
        aPhrase[0] = pLeft;
        do {
          pLeft = pLeft->pParent;
          aPhrase[i++] = pLeft->pRight;
        }while( pLeft!=pExpr );

        for(i=0; i<(nPhrase-1); i++){
          int nNear = aPhrase[i+1]->pParent->nNear;
          fts3EvalNearMerge(aPhrase[i], aPhrase[i+1], nNear, pRc);
          fts3EvalNearMerge(p->bDescIdx, aPhrase[i], aPhrase[i+1], nNear, pRc);
        }
        for(i=nPhrase-2; i>=0; i--){
          int nNear = aPhrase[i+1]->pParent->nNear;
          fts3EvalNearMerge(aPhrase[i+1], aPhrase[i], nNear, pRc);
          fts3EvalNearMerge(p->bDescIdx, aPhrase[i+1], aPhrase[i], nNear, pRc);
        }

        sqlite3_free(aPhrase);
      }

    }else{
      fts3EvalNearTrim(pCsr, pExpr->pLeft, pRc);

  char *zReadExprlist;
  char *zWriteExprlist;

  int nNodeSize;                  /* Soft limit for node size */
  u8 bHasStat;                    /* True if %_stat table exists */
  u8 bHasDocsize;                 /* True if %_docsize table exists */
  u8 bDescIdx;                    /* True if doclists are in reverse order */
  int nPgsz;                      /* Page size for host database */
  char *zSegmentsTbl;             /* Name of %_segments table */
  sqlite3_blob *pSegments;        /* Blob handle open on %_segments table */

  /* TODO: Fix the first paragraph of this comment.
  **
  ** The following hash table is used to buffer pending index updates during

  Fts3Expr *pExpr;                /* Parsed MATCH query string */
  int nPhrase;                    /* Number of matchable phrases in query */
  Fts3DeferredToken *pDeferred;   /* Deferred search tokens, if any */
  sqlite3_int64 iPrevId;          /* Previous id read from aDoclist */
  char *pNextId;                  /* Pointer into the body of aDoclist */
  char *aDoclist;                 /* List of docids for full-text queries */
  int nDoclist;                   /* Size of buffer at aDoclist */
  int bDesc;                      /* True to sort in descending order */
  u8 bDesc;                       /* True to sort in descending order */
  int eEvalmode;                  /* An FTS3_EVAL_XX constant */
  int nRowAvg;                    /* Average size of database rows, in pages */

  int isMatchinfoNeeded;          /* True when aMatchinfo[] needs filling in */
  u32 *aMatchinfo;                /* Information about most recent match */
  int nMatchinfo;                 /* Number of elements in aMatchinfo[] */
  char *zMatchinfo;               /* Matchinfo specification */

/* fts3.c */
int sqlite3Fts3PutVarint(char *, sqlite3_int64);
int sqlite3Fts3GetVarint(const char *, sqlite_int64 *);
int sqlite3Fts3GetVarint32(const char *, int *);
int sqlite3Fts3VarintLen(sqlite3_uint64);
void sqlite3Fts3Dequote(char *);
void sqlite3Fts3DoclistPrev(int,char*,int,char**,sqlite3_int64*,int*,u8*);

int sqlite3Fts3ExprLoadDoclist(Fts3Cursor *, Fts3Expr *);
int sqlite3Fts3ExprNearTrim(Fts3Expr *, Fts3Expr *, int);

/* fts3_tokenizer.c */
const char *sqlite3Fts3NextToken(const char *, int *);
int sqlite3Fts3InitHashTable(sqlite3 *, Fts3Hash *, const char *);

    Fts3Table*, Fts3MultiSegReader*, int, const char*, int);
int sqlite3Fts3MsrIncrNext(
    Fts3Table *, Fts3MultiSegReader *, sqlite3_int64 *, char **, int *);
char *sqlite3Fts3EvalPhrasePoslist(Fts3Cursor *, Fts3Expr *, int iCol); 
int sqlite3Fts3MsrOvfl(Fts3Cursor *, Fts3MultiSegReader *, int *);

int sqlite3Fts3DeferredTokenList(Fts3DeferredToken *, char **, int *);


#endif /* _FTSINT_H */

/* #define FTS3_NODE_CHUNK_THRESHOLD 1 */

typedef struct PendingList PendingList;
typedef struct SegmentNode SegmentNode;
typedef struct SegmentWriter SegmentWriter;

/*
** Data structure used while accumulating terms in the pending-terms hash
** table. The hash table entry maps from term (a string) to a malloc'd
** instance of this structure.
** An instance of the following data structure is used to build doclists
** incrementally. See function fts3PendingListAppend() for details.
*/
struct PendingList {
  int nData;
  char *aData;
  int nSpace;
  sqlite3_int64 iLastDocid;
  sqlite3_int64 iLastCol;

  */
  int nTerm;                      /* Number of bytes in current term */
  char *zTerm;                    /* Pointer to current term */
  int nTermAlloc;                 /* Allocated size of zTerm buffer */
  char *aDoclist;                 /* Pointer to doclist of current entry */
  int nDoclist;                   /* Size of doclist in current entry */

  /* The following variables are used to iterate through the current doclist */
  /* The following variables are used by fts3SegReaderNextDocid() to iterate 
  ** through the current doclist (aDoclist/nDoclist).
  */
  char *pOffsetList;
  int nOffsetList;                /* For descending pending seg-readers only */
  sqlite3_int64 iDocid;
};

#define fts3SegReaderIsPending(p) ((p)->ppNextElem!=0)
#define fts3SegReaderIsRootOnly(p) ((p)->aNode==(char *)&(p)[1])

/*

  if( p!=*pp ){
    *pp = p;
    return 1;
  }
  return 0;
}

/*
** Free a PendingList object allocated by fts3PendingListAppend().
*/
static void fts3PendingListDelete(PendingList *pList){
  sqlite3_free(pList);
}

/*
** Add an entry to one of the pending-terms hash tables.
*/
static int fts3PendingTermsAddOne(
  Fts3Table *p,
  int iCol,
  int iPos,
  Fts3Hash *pHash,
  Fts3Hash *pHash,                /* Pending terms hash table to add entry to */
  const char *zToken,
  int nToken
){
  PendingList *pList;
  int rc = SQLITE_OK;

  pList = (PendingList *)fts3HashFind(pHash, zToken, nToken);

*/
void sqlite3Fts3PendingTermsClear(Fts3Table *p){
  int i;
  for(i=0; i<p->nIndex; i++){
    Fts3HashElem *pElem;
    Fts3Hash *pHash = &p->aIndex[i].hPending;
    for(pElem=fts3HashFirst(pHash); pElem; pElem=fts3HashNext(pElem)){
      sqlite3_free(fts3HashData(pElem));
      PendingList *pList = (PendingList *)fts3HashData(pElem);
      fts3PendingListDelete(pList);
    }
    fts3HashClear(pHash);
  }
  p->nPendingData = 0;
}

/*

    assert( pReader->pBlob==0 );
    if( bIncr && pReader->nPopulate<pReader->nNode ){
      pReader->pBlob = p->pSegments;
      p->pSegments = 0;
    }
    pNext = pReader->aNode;
  }

  assert( !fts3SegReaderIsPending(pReader) );

  rc = fts3SegReaderRequire(pReader, pNext, FTS3_VARINT_MAX*2);
  if( rc!=SQLITE_OK ) return rc;
  
  /* Because of the FTS3_NODE_PADDING bytes of padding, the following is 
  ** safe (no risk of overread) even if the node data is corrupted.  
  ** safe (no risk of overread) even if the node data is corrupted. */
  */
  pNext += sqlite3Fts3GetVarint32(pNext, &nPrefix);
  pNext += sqlite3Fts3GetVarint32(pNext, &nSuffix);
  if( nPrefix<0 || nSuffix<=0 
   || &pNext[nSuffix]>&pReader->aNode[pReader->nNode] 
  ){
    return SQLITE_CORRUPT_VTAB;
  }

  return SQLITE_OK;
}

/*
** Set the SegReader to point to the first docid in the doclist associated
** with the current term.
*/
static int fts3SegReaderFirstDocid(Fts3SegReader *pReader){
  int rc;
static int fts3SegReaderFirstDocid(Fts3Table *pTab, Fts3SegReader *pReader){
  int rc = SQLITE_OK;
  assert( pReader->aDoclist );
  assert( !pReader->pOffsetList );
  if( pTab->bDescIdx && fts3SegReaderIsPending(pReader) ){
    u8 bEof = 0;
    pReader->iDocid = 0;
    pReader->nOffsetList = 0;
    sqlite3Fts3DoclistPrev(0,
        pReader->aDoclist, pReader->nDoclist, &pReader->pOffsetList, 
        &pReader->iDocid, &pReader->nOffsetList, &bEof
    );
  }else{
  rc = fts3SegReaderRequire(pReader, pReader->aDoclist, FTS3_VARINT_MAX);
  if( rc==SQLITE_OK ){
    int n = sqlite3Fts3GetVarint(pReader->aDoclist, &pReader->iDocid);
    pReader->pOffsetList = &pReader->aDoclist[n];
    rc = fts3SegReaderRequire(pReader, pReader->aDoclist, FTS3_VARINT_MAX);
    if( rc==SQLITE_OK ){
      int n = sqlite3Fts3GetVarint(pReader->aDoclist, &pReader->iDocid);
      pReader->pOffsetList = &pReader->aDoclist[n];
    }
  }
  return rc;
}

/*
** Advance the SegReader to point to the next docid in the doclist
** associated with the current term.
** 
** If arguments ppOffsetList and pnOffsetList are not NULL, then 
** *ppOffsetList is set to point to the first column-offset list
** in the doclist entry (i.e. immediately past the docid varint).
** *pnOffsetList is set to the length of the set of column-offset
** lists, not including the nul-terminator byte. For example:
*/
static int fts3SegReaderNextDocid(
  Fts3Table *pTab,
  Fts3SegReader *pReader,
  char **ppOffsetList,
  int *pnOffsetList
  Fts3SegReader *pReader,         /* Reader to advance to next docid */
  char **ppOffsetList,            /* OUT: Pointer to current position-list */
  int *pnOffsetList               /* OUT: Length of *ppOffsetList in bytes */
){
  int rc = SQLITE_OK;
  char *p = pReader->pOffsetList;
  char c = 0;

  /* Pointer p currently points at the first byte of an offset list. The
  ** following two lines advance it to point one byte past the end of
  ** the same offset list.
  */
  while( 1 ){
    int nRead;
    int rc;

    while( *p | c ) c = *p++ & 0x80;
    assert( *p==0 );
  assert( p );
    if( pReader->pBlob==0 || (p - pReader->aNode)!=pReader->nPopulate ) break;
    rc = fts3SegReaderIncrRead(pReader);
    if( rc!=SQLITE_OK ) return rc;
  }

  p++;

  if( pTab->bDescIdx && fts3SegReaderIsPending(pReader) ){
  /* If required, populate the output variables with a pointer to and the
  ** size of the previous offset-list.
    /* A pending-terms seg-reader for an FTS4 table that uses order=desc.
    ** Pending-terms doclists are always built up in ascending order, so
    ** we have to iterate through them backwards here. */
    u8 bEof = 0;
  */
  if( ppOffsetList ){
    *ppOffsetList = pReader->pOffsetList;
    *pnOffsetList = (int)(p - pReader->pOffsetList - 1);
  }

  /* If there are no more entries in the doclist, set pOffsetList to
  ** NULL. Otherwise, set Fts3SegReader.iDocid to the next docid and
  ** Fts3SegReader.pOffsetList to point to the next offset list before
  ** returning.
    if( ppOffsetList ){
      *ppOffsetList = pReader->pOffsetList;
      *pnOffsetList = pReader->nOffsetList - 1;
    }
    sqlite3Fts3DoclistPrev(0,
        pReader->aDoclist, pReader->nDoclist, &p, &pReader->iDocid,
        &pReader->nOffsetList, &bEof
    );
    if( bEof ){
      pReader->pOffsetList = 0;
    }else{
  */
  if( p>=&pReader->aDoclist[pReader->nDoclist] ){
    pReader->pOffsetList = 0;
      pReader->pOffsetList = p;
    }
  }else{

    /* Pointer p currently points at the first byte of an offset list. The
    ** following block advances it to point one byte past the end of
    ** the same offset list. */
    while( 1 ){
  
      /* The following line of code (and the "p++" below the while() loop) is
      ** normally all that is required to move pointer p to the desired 
      ** position. The exception is if this node is being loaded from disk
      ** incrementally and pointer "p" now points to the first byte passed
      ** the populated part of pReader->aNode[].
      */
      while( *p | c ) c = *p++ & 0x80;
      assert( *p==0 );
  
      if( pReader->pBlob==0 || p<&pReader->aNode[pReader->nPopulate] ) break;
      rc = fts3SegReaderIncrRead(pReader);
      if( rc!=SQLITE_OK ) return rc;
    }
    p++;
  
    /* If required, populate the output variables with a pointer to and the
    ** size of the previous offset-list.
    */
    if( ppOffsetList ){
      *ppOffsetList = pReader->pOffsetList;
      *pnOffsetList = (int)(p - pReader->pOffsetList - 1);
    }
  
    /* If there are no more entries in the doclist, set pOffsetList to
    ** NULL. Otherwise, set Fts3SegReader.iDocid to the next docid and
    ** Fts3SegReader.pOffsetList to point to the next offset list before
    ** returning.
    */
    if( p>=&pReader->aDoclist[pReader->nDoclist] ){
      pReader->pOffsetList = 0;
    }else{
    rc = fts3SegReaderRequire(pReader, p, FTS3_VARINT_MAX);
    if( rc==SQLITE_OK ){
      sqlite3_int64 iDelta;
      pReader->pOffsetList = p + sqlite3Fts3GetVarint(p, &iDelta);
      pReader->iDocid += iDelta;
      rc = fts3SegReaderRequire(pReader, p, FTS3_VARINT_MAX);
      if( rc==SQLITE_OK ){
        sqlite3_int64 iDelta;
        pReader->pOffsetList = p + sqlite3Fts3GetVarint(p, &iDelta);
        if( pTab->bDescIdx ){
          pReader->iDocid -= iDelta;
        }else{
          pReader->iDocid += iDelta;
        }
      }
    }
  }

  return SQLITE_OK;
}

/*

  int rc = (pLhs->pOffsetList==0)-(pRhs->pOffsetList==0);
  if( rc==0 ){
    if( pLhs->iDocid==pRhs->iDocid ){
      rc = pRhs->iIdx - pLhs->iIdx;
    }else{
      rc = (pLhs->iDocid > pRhs->iDocid) ? 1 : -1;
    }
  }
  assert( pLhs->aNode && pRhs->aNode );
  return rc;
}
static int fts3SegReaderDoclistCmpRev(Fts3SegReader *pLhs, Fts3SegReader *pRhs){
  int rc = (pLhs->pOffsetList==0)-(pRhs->pOffsetList==0);
  if( rc==0 ){
    if( pLhs->iDocid==pRhs->iDocid ){
      rc = pRhs->iIdx - pLhs->iIdx;
    }else{
      rc = (pLhs->iDocid < pRhs->iDocid) ? 1 : -1;
    }
  }
  assert( pLhs->aNode && pRhs->aNode );
  return rc;
}

/*
** Compare the term that the Fts3SegReader object passed as the first argument

  Fts3MultiSegReader *pCsr,       /* Cursor object */
  int iCol,                       /* Column to match on. */
  const char *zTerm,              /* Term to iterate through a doclist for */
  int nTerm                       /* Number of bytes in zTerm */
){
  int i;
  int nSegment = pCsr->nSegment;
  int (*xCmp)(Fts3SegReader *, Fts3SegReader *) = (
    p->bDescIdx ? fts3SegReaderDoclistCmpRev : fts3SegReaderDoclistCmp
  );

  assert( pCsr->pFilter==0 );
  assert( zTerm && nTerm>0 );

  /* Advance each segment iterator until it points to the term zTerm/nTerm. */
  for(i=0; i<nSegment; i++){
    Fts3SegReader *pSeg = pCsr->apSegment[i];

      break;
    }
  }
  pCsr->nAdvance = i;

  /* Advance each of the segments to point to the first docid. */
  for(i=0; i<pCsr->nAdvance; i++){
    int rc = fts3SegReaderFirstDocid(pCsr->apSegment[i]);
    int rc = fts3SegReaderFirstDocid(p, pCsr->apSegment[i]);
    if( rc!=SQLITE_OK ) return rc;
  }
  fts3SegReaderSort(pCsr->apSegment, i, i, fts3SegReaderDoclistCmp);
  fts3SegReaderSort(pCsr->apSegment, i, i, xCmp);

  assert( iCol<0 || iCol<p->nColumn );
  pCsr->iColFilter = iCol;

  return SQLITE_OK;
}

int sqlite3Fts3MsrIncrNext(
  Fts3Table *p,                   /* Virtual table handle */
  Fts3MultiSegReader *pMsr,       /* Multi-segment-reader handle */
  sqlite3_int64 *piDocid,         /* OUT: Docid value */
  char **paPoslist,               /* OUT: Pointer to position list */
  int *pnPoslist                  /* OUT: Size of position list in bytes */
){
  int nMerge = pMsr->nAdvance;
  Fts3SegReader **apSegment = pMsr->apSegment;
  int (*xCmp)(Fts3SegReader *, Fts3SegReader *) = (
    p->bDescIdx ? fts3SegReaderDoclistCmpRev : fts3SegReaderDoclistCmp
  );

  if( nMerge==0 ){
    *paPoslist = 0;
    return SQLITE_OK;
  }

  while( 1 ){

    }else{
      int rc;
      char *pList;
      int nList;
      int j;
      sqlite3_int64 iDocid = apSegment[0]->iDocid;

      rc = fts3SegReaderNextDocid(apSegment[0], &pList, &nList);
      rc = fts3SegReaderNextDocid(p, apSegment[0], &pList, &nList);
      j = 1;
      while( rc==SQLITE_OK 
        && j<nMerge
        && apSegment[j]->pOffsetList
        && apSegment[j]->iDocid==iDocid
      ){
        fts3SegReaderNextDocid(apSegment[j], 0, 0);
        rc = fts3SegReaderNextDocid(p, apSegment[j], 0, 0);
        j++;
      }
      if( rc!=SQLITE_OK ) return rc;

      fts3SegReaderSort(pMsr->apSegment, nMerge, j, fts3SegReaderDoclistCmp);
      fts3SegReaderSort(pMsr->apSegment, nMerge, j, xCmp);

      if( pMsr->iColFilter>=0 ){
        fts3ColumnFilter(pMsr->iColFilter, &pList, &nList);
      }

      if( nList>0 ){
        *piDocid = iDocid;

  int isColFilter =    (pCsr->pFilter->flags & FTS3_SEGMENT_COLUMN_FILTER);
  int isPrefix =       (pCsr->pFilter->flags & FTS3_SEGMENT_PREFIX);
  int isScan =         (pCsr->pFilter->flags & FTS3_SEGMENT_SCAN);

  Fts3SegReader **apSegment = pCsr->apSegment;
  int nSegment = pCsr->nSegment;
  Fts3SegFilter *pFilter = pCsr->pFilter;
  int (*xCmp)(Fts3SegReader *, Fts3SegReader *) = (
    p->bDescIdx ? fts3SegReaderDoclistCmpRev : fts3SegReaderDoclistCmp
  );

  if( pCsr->nSegment==0 ) return SQLITE_OK;

  do {
    int nMerge;
    int i;
  

        && apSegment[nMerge]->nTerm==pCsr->nTerm 
        && 0==memcmp(pCsr->zTerm, apSegment[nMerge]->zTerm, pCsr->nTerm)
    ){
      nMerge++;
    }

    assert( isIgnoreEmpty || (isRequirePos && !isColFilter) );
    if( nMerge==1 && !isIgnoreEmpty ){
    if( nMerge==1 
     && !isIgnoreEmpty 
     && (p->bDescIdx==0 || fts3SegReaderIsPending(apSegment[0])==0)
    ){
      pCsr->aDoclist = apSegment[0]->aDoclist;
      pCsr->nDoclist = apSegment[0]->nDoclist;
      rc = SQLITE_ROW;
    }else{
      int nDoclist = 0;           /* Size of doclist */
      sqlite3_int64 iPrev = 0;    /* Previous docid stored in doclist */

      /* The current term of the first nMerge entries in the array
      ** of Fts3SegReader objects is the same. The doclists must be merged
      ** and a single term returned with the merged doclist.
      */
      for(i=0; i<nMerge; i++){
        fts3SegReaderFirstDocid(apSegment[i]);
        fts3SegReaderFirstDocid(p, apSegment[i]);
      }
      fts3SegReaderSort(apSegment, nMerge, nMerge, fts3SegReaderDoclistCmp);
      fts3SegReaderSort(apSegment, nMerge, nMerge, xCmp);
      while( apSegment[0]->pOffsetList ){
        int j;                    /* Number of segments that share a docid */
        char *pList;
        int nList;
        int nByte;
        sqlite3_int64 iDocid = apSegment[0]->iDocid;
        fts3SegReaderNextDocid(apSegment[0], &pList, &nList);
        fts3SegReaderNextDocid(p, apSegment[0], &pList, &nList);
        j = 1;
        while( j<nMerge
            && apSegment[j]->pOffsetList
            && apSegment[j]->iDocid==iDocid
        ){
          fts3SegReaderNextDocid(apSegment[j], 0, 0);
          fts3SegReaderNextDocid(p, apSegment[j], 0, 0);
          j++;
        }

        if( isColFilter ){
          fts3ColumnFilter(pFilter->iCol, &pList, &nList);
        }

        if( !isIgnoreEmpty || nList>0 ){

          /* Calculate the 'docid' delta value to write into the merged 
          ** doclist. */
          sqlite3_int64 iDelta;
          if( p->bDescIdx && nDoclist>0 ){
            iDelta = iPrev - iDocid;
          }else{
            iDelta = iDocid - iPrev;
          }
          assert( iDelta>0 || (nDoclist==0 && iDelta==iDocid) );
          assert( nDoclist>0 || iDelta==iDocid );

          nByte = sqlite3Fts3VarintLen(iDocid-iPrev) + (isRequirePos?nList+1:0);
          nByte = sqlite3Fts3VarintLen(iDelta) + (isRequirePos?nList+1:0);
          if( nDoclist+nByte>pCsr->nBuffer ){
            char *aNew;
            pCsr->nBuffer = (nDoclist+nByte)*2;
            aNew = sqlite3_realloc(pCsr->aBuffer, pCsr->nBuffer);
            if( !aNew ){
              return SQLITE_NOMEM;
            }
            pCsr->aBuffer = aNew;
          }
          nDoclist += sqlite3Fts3PutVarint(
          nDoclist += sqlite3Fts3PutVarint(&pCsr->aBuffer[nDoclist], iDelta);
              &pCsr->aBuffer[nDoclist], iDocid-iPrev
          );
          iPrev = iDocid;
          if( isRequirePos ){
            memcpy(&pCsr->aBuffer[nDoclist], pList, nList);
            nDoclist += nList;
            pCsr->aBuffer[nDoclist++] = '\0';
          }
        }

        fts3SegReaderSort(apSegment, nMerge, j, fts3SegReaderDoclistCmp);
        fts3SegReaderSort(apSegment, nMerge, j, xCmp);
      }
      if( nDoclist>0 ){
        pCsr->aDoclist = pCsr->aBuffer;
        pCsr->nDoclist = nDoclist;
        rc = SQLITE_ROW;
      }
    }

    *pnByte = pDeferred->pList->nData;
    return pDeferred->pList->aData;
  }
  *pnByte = 0;
  return 0;
}

/*
** Helper fucntion for FreeDeferredDoclists(). This function removes all
** references to deferred doclists from within the tree of Fts3Expr 
** structures headed by 
*/
static void fts3DeferredDoclistClear(Fts3Expr *pExpr){
  if( pExpr ){
    Fts3Phrase *pPhrase = pExpr->pPhrase;
    fts3DeferredDoclistClear(pExpr->pLeft);
    fts3DeferredDoclistClear(pExpr->pRight);
  }
}

/*
** Delete all cached deferred doclists. Deferred doclists are cached
** (allocated) by the sqlite3Fts3CacheDeferredDoclists() function.
*/
void sqlite3Fts3FreeDeferredDoclists(Fts3Cursor *pCsr){
  Fts3DeferredToken *pDef;
  for(pDef=pCsr->pDeferred; pDef; pDef=pDef->pNext){
    sqlite3_free(pDef->pList);
    fts3PendingListDelete(pDef->pList);
    pDef->pList = 0;
  }
  if( pCsr->pDeferred ){
    fts3DeferredDoclistClear(pCsr->pExpr);
  }
}

/*
** Free all entries in the pCsr->pDeffered list. Entries are added to 
** this list using sqlite3Fts3DeferToken().
*/
void sqlite3Fts3FreeDeferredTokens(Fts3Cursor *pCsr){
  Fts3DeferredToken *pDef;
  Fts3DeferredToken *pNext;
  for(pDef=pCsr->pDeferred; pDef; pDef=pNext){
    pNext = pDef->pNext;
    sqlite3_free(pDef->pList);
    fts3PendingListDelete(pDef->pList);
    sqlite3_free(pDef);
  }
  pCsr->pDeferred = 0;
}

/*
** Generate deferred-doclists for all tokens in the pCsr->pDeferred list

# If SQLITE_ENABLE_FTS3 is defined, omit this file.
ifcapable !fts3 {
  finish_test
  return
}

set testprefix fts3sort

proc build_database {nRow} {
proc build_database {nRow param} {
  db close
  forcedelete test.db
  sqlite3 db test.db

  set vocab [list    aa ab ac   ba bb bc    ca cb cc   da]
  expr srand(0)

  execsql { CREATE VIRTUAL TABLE t1 USING fts4 }
  execsql "CREATE VIRTUAL TABLE t1 USING fts4($param)"
  for {set i 0} {$i < $nRow} {incr i} {
    set v [expr int(rand()*1000000)]
    set doc [list]
    for {set div 1} {$div < 1000000} {set div [expr $div*10]} {
      lappend doc [lindex $vocab [expr ($v/$div) % 10]]
    }
    execsql { INSERT INTO t1 VALUES($doc) }
  }
}

set testprefix fts3sort

unset -nocomplain CONTROL
foreach {t param} {
  1     ""
  2     "order=asc"
  3     "order=desc"
} {

  set testprefix fts3sort-1.$t

set nRow 1000
do_test 1.0 {
  build_database $nRow
  execsql { SELECT count(*) FROM t1 }
} $nRow

foreach {tn query} {
  set nRow 1000
  do_test 1.0 {
    build_database $nRow $param
    execsql { SELECT count(*) FROM t1 }
  } $nRow
  
  foreach {tn query} {
  1   "SELECT docid, * FROM t1"
  2   "SELECT docid, * FROM t1 WHERE t1 MATCH 'aa'"
  3   "SELECT docid, * FROM t1 WHERE t1 MATCH 'a*'"
  4   "SELECT docid, quote(matchinfo(t1)) FROM t1 WHERE t1 MATCH 'a*'"
  5   "SELECT docid, quote(matchinfo(t1,'pcnxals')) FROM t1 WHERE t1 MATCH 'b*'"
  6   "SELECT docid, * FROM t1 WHERE t1 MATCH 'a* b* c*'"
  7   "SELECT docid, * FROM t1 WHERE t1 MATCH 'aa OR da'"
  8   "SELECT docid, * FROM t1 WHERE t1 MATCH 'nosuchtoken'"
  9   "SELECT docid, snippet(t1) FROM t1 WHERE t1 MATCH 'aa OR da'"
  10  "SELECT docid, snippet(t1) FROM t1 WHERE t1 MATCH 'aa OR nosuchtoken'"
  11  "SELECT docid, snippet(t1) FROM t1 WHERE t1 MATCH 'aa NEAR bb'"
  12  "SELECT docid, snippet(t1) FROM t1 WHERE t1 MATCH '\"aa bb\"'"
  13  "SELECT docid, content FROM t1 WHERE t1 MATCH 'aa NEAR/2 bb NEAR/3 cc'"
  14  "SELECT docid, content FROM t1 WHERE t1 MATCH '\"aa bb cc\"'"
} {

  unset -nocomplain A B C D
  set A_list [list]
  set B_list [list]
  set C_list [list]
  set D_list [list]

  unset -nocomplain X
  db eval "$query ORDER BY rowid ASC"  X  { 
    set A($X(docid)) [array get X] 
    lappend A_list $X(docid)
  }
  unset -nocomplain X
  db eval "$query ORDER BY rowid DESC" X  { 
    set B($X(docid)) [array get X] 
    lappend B_list $X(docid)
  }
  unset -nocomplain X
  db eval "$query ORDER BY docid ASC"  X  { 
    set C($X(docid)) [array get X] 
    lappend C_list $X(docid)
  }
  unset -nocomplain X
  db eval "$query ORDER BY docid DESC" X  { 
    set D($X(docid)) [array get X] 
    lappend D_list $X(docid)
  }

  do_test 1.$tn.1 { set A_list } [lsort -integer -increasing $A_list]
  do_test 1.$tn.2 { set B_list } [lsort -integer -decreasing $B_list]
  do_test 1.$tn.3 { set C_list } [lsort -integer -increasing $C_list]
  do_test 1.$tn.4 { set D_list } [lsort -integer -decreasing $D_list]

  unset -nocomplain DATA
  unset -nocomplain X
  db eval "$query" X  { 
    set DATA($X(docid)) [array get X] 
  }

  do_test 1.$tn.5 { lsort [array get A] } [lsort [array get DATA]]
  do_test 1.$tn.6 { lsort [array get B] } [lsort [array get DATA]]
  do_test 1.$tn.7 { lsort [array get C] } [lsort [array get DATA]]
  do_test 1.$tn.8 { lsort [array get D] } [lsort [array get DATA]]
}

  } {
  
    unset -nocomplain A B C D
    set A_list [list]
    set B_list [list]
    set C_list [list]
    set D_list [list]
  
    unset -nocomplain X
    db eval "$query ORDER BY rowid ASC"  X  { 
      set A($X(docid)) [array get X] 
      lappend A_list $X(docid)
    }
    unset -nocomplain X
    db eval "$query ORDER BY rowid DESC" X  { 
      set B($X(docid)) [array get X] 
      lappend B_list $X(docid)
    }
    unset -nocomplain X
    db eval "$query ORDER BY docid ASC"  X  { 
      set C($X(docid)) [array get X] 
      lappend C_list $X(docid)
    }
    unset -nocomplain X
    db eval "$query ORDER BY docid DESC" X  { 
      set D($X(docid)) [array get X] 
      lappend D_list $X(docid)
    }
  
    do_test $tn.1 { set A_list } [lsort -integer -increasing $A_list]
    do_test $tn.2 { set B_list } [lsort -integer -decreasing $B_list]
    do_test $tn.3 { set C_list } [lsort -integer -increasing $C_list]
    do_test $tn.4 { set D_list } [lsort -integer -decreasing $D_list]
  
    unset -nocomplain DATA
    unset -nocomplain X
    db eval "$query" X  { 
      set DATA($X(docid)) [array get X] 
    }
  
    do_test $tn.5 { lsort [array get A] } [lsort [array get DATA]]
    do_test $tn.6 { lsort [array get B] } [lsort [array get DATA]]
    do_test $tn.7 { lsort [array get C] } [lsort [array get DATA]]
    do_test $tn.8 { lsort [array get D] } [lsort [array get DATA]]

    if {[info exists CONTROL($tn)]} {
      do_test $tn.9 { set CONTROL($tn) } [lsort [array get DATA]]
    } else {
      set CONTROL($tn) [lsort [array get DATA]]
    }
  }
}
unset -nocomplain CONTROL

set testprefix fts3sort

#-------------------------------------------------------------------------
# Tests for parsing the "order=asc" and "order=desc" directives.
#
foreach {tn param res} {
  1 "order=asc"             {0 {}}
  2 "order=desc"            {0 {}}
  3 "order=dec"             {1 {unrecognized order: dec}}
  4 "order=xxx, order=asc"  {0 {}}
} {
  execsql { DROP TABLE IF EXISTS t1 }
  do_catchsql_test 2.1.$tn "
    CREATE VIRTUAL TABLE t1 USING fts4(a, b, $param)
  " $res
}

do_execsql_test 2.2 {
  BEGIN;
    CREATE VIRTUAL TABLE t2 USING fts4(order=desc);
    INSERT INTO t2 VALUES('aa bb');
    INSERT INTO t2 VALUES('bb cc');
    INSERT INTO t2 VALUES('cc aa');
    SELECT docid FROM t2 WHERE t2 MATCH 'aa';
  END;
} {3 1}
do_execsql_test 2.3 {
  SELECT docid FROM t2 WHERE t2 MATCH 'aa';
} {3 1}

finish_test