SQLite

  sqlite3_value **apVal           /* Array of arguments */
){
  Fts3Cursor *pCsr;               /* Cursor handle passed through apVal[0] */
  const char *zStart = "<b>";
  const char *zEnd = "</b>";
  const char *zEllipsis = "<b>...</b>";
  int iCol = -1;
  int nToken = 15;                /* Default number of tokens in snippet */

  /* There must be at least one argument passed to this function (otherwise
  ** the non-overloaded version would have been called instead of this one).
  */
  assert( nVal>=1 );

  if( nVal>6 ){

static int fts3ExprIterate(
  Fts3Expr *pExpr,                /* Expression to iterate phrases of */
  int (*x)(Fts3Expr *, void *),   /* Callback function to invoke for phrases */
  void *pCtx                      /* Second argument to pass to callback */
){
  int rc;
  int eType = pExpr->eType;


  if( eType!=FTSQUERY_PHRASE ){
    assert( pExpr->pLeft && pExpr->pRight );
    rc = fts3ExprIterate(pExpr->pLeft, x, pCtx);
    if( rc==SQLITE_OK && eType!=FTSQUERY_NOT ){
      rc = fts3ExprIterate(pExpr->pRight, x, pCtx);
    }
  }else{
    rc = x(pExpr, pCtx);
  }
  return rc;
}

  p->nPhrase++;
  p->nToken += pExpr->pPhrase->nToken;

  if( pExpr->isLoaded==0 ){
    rc = sqlite3Fts3ExprLoadDoclist(p->pTab, pExpr);
    pExpr->isLoaded = 1;
    if( rc==SQLITE_OK ){
      rc = fts3ExprNearTrim(pExpr);
    }
  }

  return rc;
}

static int fts3ExprLoadDoclistsCb2(Fts3Expr *pExpr, void *ctx){

      }
      pC->pTokenizer = pTab->pTokenizer;
      while( rc==SQLITE_OK && iCurrent<(nSnippet+nDesired) ){
        const char *ZDUMMY; int DUMMY1, DUMMY2, DUMMY3;
        rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &DUMMY2, &DUMMY3, &iCurrent);
      }
      pMod->xClose(pC);
      if( rc!=SQLITE_OK && rc!=SQLITE_DONE ){ return rc; }


      nShift = (rc==SQLITE_DONE)+iCurrent-nSnippet;
      assert( nShift<=nDesired );
      if( nShift>0 ){
        *piPos += nShift;
        *pHlmask = hlmask >> nShift;
      }
    }
  }
  return SQLITE_OK;
}

static int fts3SnippetText(
  Fts3Cursor *pCsr,               /* FTS3 Cursor */
  SnippetFragment *pFragment,     /* Snippet to extract */
  int iFragment,                  /* Fragment number */
  int isLast,                     /* True for final fragment in snippet */
  int nSnippet,                   /* Number of tokens in extracted snippet */
  const char *zOpen,              /* String inserted before highlighted term */
  const char *zClose,             /* String inserted after highlighted term */
  const char *zEllipsis,
  StrBuffer *pOut
){
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
  int rc;                         /* Return code */
  const char *zDoc;               /* Document text to extract snippet from */
  int nDoc;                       /* Size of zDoc in bytes */
  int iCurrent = 0;               /* Current token number of document */

  int iEnd = 0;                   /* Byte offset of end of current token */
  int isShiftDone = 0;
  int iPos = pFragment->iPos;
  u64 hlmask = pFragment->hlmask;

  sqlite3_tokenizer_module *pMod; /* Tokenizer module methods object */
  sqlite3_tokenizer_cursor *pC;   /* Tokenizer cursor open on zDoc/nDoc */
  const char *ZDUMMY;             /* Dummy arguments used with tokenizer */
  int DUMMY1;                     /* Dummy arguments used with tokenizer */
  
  zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, pFragment->iCol+1);
  if( zDoc==0 ){
    if( sqlite3_column_type(pCsr->pStmt, pFragment->iCol+1)!=SQLITE_NULL ){
      return SQLITE_NOMEM;
    }
    return SQLITE_OK;
  }
  nDoc = sqlite3_column_bytes(pCsr->pStmt, pFragment->iCol+1);

  /* Open a token cursor on the document. */



  pMod = (sqlite3_tokenizer_module *)pTab->pTokenizer->pModule;
  rc = pMod->xOpen(pTab->pTokenizer, zDoc, nDoc, &pC);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  pC->pTokenizer = pTab->pTokenizer;

  while( rc==SQLITE_OK ){
    int iBegin;                   /* Offset in zDoc of start of token */
    int iFin;                     /* Offset in zDoc of end of token */
    int isHighlight;

    rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &iBegin, &iFin, &iCurrent);
    if( rc!=SQLITE_OK ){
      if( rc==SQLITE_DONE ){

        /* Special case - the last token of the snippet is also the last token

        ** of the column. Append any punctuation that occurred between the end
        ** of the previous token and the end of the document to the output. 
        ** Then break out of the loop. */
        rc = fts3StringAppend(pOut, &zDoc[iEnd], -1);

      }
      break;

    }

    if( iCurrent<iPos ){ continue; }











    if( !isShiftDone ){
      int n = nDoc - iBegin;
      rc = fts3SnippetShift(pTab, nSnippet, &zDoc[iBegin], n, &iPos, &hlmask);
      isShiftDone = 1;

      /* Now that the shift has been done, check if the initial "..." are
      ** required. They are required if (a) this is not the first fragment,
      ** or (b) this fragment does not begin at position 0 of its column. 
      */
      if( rc==SQLITE_OK && (iPos>0 || iFragment>0) ){
        rc = fts3StringAppend(pOut, zEllipsis, -1);
      }
      if( rc!=SQLITE_OK || iCurrent<iPos ) continue;
    }


    if( iCurrent>=(iPos+nSnippet) ){

      if( isLast ){




        rc = fts3StringAppend(pOut, zEllipsis, -1);
      }
      break;
    }

    /* Set isHighlight to true if this term should be highlighted. */
    isHighlight = (hlmask & ((u64)1 << (iCurrent-iPos)))!=0;

    if( iCurrent>iPos ) rc = fts3StringAppend(pOut, &zDoc[iEnd], iBegin-iEnd);
    if( rc==SQLITE_OK && isHighlight ) rc = fts3StringAppend(pOut, zOpen, -1);
    if( rc==SQLITE_OK ) rc = fts3StringAppend(pOut, &zDoc[iBegin], iFin-iBegin);
    if( rc==SQLITE_OK && isHighlight ) rc = fts3StringAppend(pOut, zClose, -1);

    iEnd = iFin;
  }

  pMod->xClose(pC);
  return rc;
}

    assert( (mCovered&mSeen)==mCovered );
    if( mSeen==mCovered ) break;
  }while( nSnippet<SizeofArray(aSnippet) );

  assert( nFToken>0 );

  for(i=0; i<nSnippet && rc==SQLITE_OK; i++){
    rc = fts3SnippetText(pCsr, &aSnippet[i], 
        i, (i==nSnippet-1), nFToken, zStart, zEnd, zEllipsis, &res
    );




  }

 snippet_out:
  if( rc!=SQLITE_OK ){
    sqlite3_result_error_code(pCtx, rc);
    sqlite3_free(res.z);
  }else{

          rc = pMod->xNext(pC, &ZDUMMY, &NDUMMY, &iStart, &iEnd, &iCurrent);
        }
        if( rc==SQLITE_OK ){
          char aBuffer[64];
          sqlite3_snprintf(sizeof(aBuffer), aBuffer, 
              "%d %d %d %d ", iCol, pTerm-sCtx.aTerm, iStart, iEnd-iStart
          );
          rc = fts3StringAppend(&res, aBuffer, -1);
        }
      }
    }
    if( rc==SQLITE_DONE ){
      rc = SQLITE_ERROR;
    }

# 2010 January 07
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#*************************************************************************
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# If SQLITE_ENABLE_FTS3 is not defined, omit this file.
ifcapable !fts3 { finish_test ; return }

# Transform the list $L to its "normal" form. So that it can be compared to
# another list with the same set of elements using [string compare].
#
proc normalize {L} {
  set ret [list]
  foreach l $L {lappend ret $l}
  return $ret
}

do_test fts3snippet-1.1 {
  execsql {
    CREATE VIRTUAL TABLE ft USING fts3;
    INSERT INTO ft VALUES('xxx xxx xxx xxx');
  }
} {}







do_test fts3snippet-1.2 {
  execsql { SELECT offsets(ft) FROM ft WHERE ft MATCH 'xxx' }
} {{0 0 0 3 0 0 4 3 0 0 8 3 0 0 12 3}}

do_test fts3snippet-1.3 {
  execsql { SELECT offsets(ft) FROM ft WHERE ft MATCH '"xxx xxx"' }
} [list [normalize {

    0 2  4 3 
    0 0  8 3 
    0 1  8 3 
    0 2  8 3 
    0 0 12 3
    0 2 12 3
}]]

do_test fts3snippet-2.1 {
  execsql {
    DROP TABLE IF EXISTS ft;
    CREATE VIRTUAL TABLE ft USING fts3;
    INSERT INTO ft VALUES('one two three four five six seven eight nine ten');
  }
} {}
foreach {tn expr res} {
   1 one       "[one] two three four five..."
   2 two       "one [two] three four five..."
   3 three     "one two [three] four five..."
   4 four      "...two three [four] five six..."
   5 five      "...three four [five] six seven..."
   6 six       "...four five [six] seven eight..."
   7 seven     "...five six [seven] eight nine..."
   8 eight     "...six seven [eight] nine ten"
   9 nine      "...six seven eight [nine] ten"
  10 ten       "...six seven eight nine [ten]"
} {
  do_test fts3snippet-2.2.$tn {
    execsql {
      SELECT snippet(ft, '[', ']', '...', 0, 5) FROM ft WHERE ft MATCH $expr
    }
  } [list $res]
}

finish_test