SQLite

  sqlite3_int64 *piFirst,         /* OUT: Selected child node */
  sqlite3_int64 *piLast           /* OUT: Selected child node */
){
  int rc = SQLITE_OK;             /* Return code */
  const char *zCsr = zNode;       /* Cursor to iterate through node */
  const char *zEnd = &zCsr[nNode];/* End of interior node buffer */
  char *zBuffer = 0;              /* Buffer to load terms into */
  i64 nAlloc = 0;                 /* Size of allocated buffer */
  int isFirstTerm = 1;            /* True when processing first term on page */
  sqlite3_int64 iChild;           /* Block id of child node to descend to */

  /* Skip over the 'height' varint that occurs at the start of every 
  ** interior node. Then load the blockid of the left-child of the b-tree
  ** node into variable iChild.  
  **

    if( !isFirstTerm ){
      zCsr += fts3GetVarint32(zCsr, &nPrefix);
    }
    isFirstTerm = 0;
    zCsr += fts3GetVarint32(zCsr, &nSuffix);
    
    assert( nPrefix>=0 && nSuffix>=0 );
    if( nPrefix>zCsr-zNode || nSuffix>zEnd-zCsr ){
      rc = FTS_CORRUPT_VTAB;
      goto finish_scan;
    }
    if( (i64)nPrefix+nSuffix>nAlloc ){
      char *zNew;
      nAlloc = ((i64)nPrefix+nSuffix) * 2;
      zNew = (char *)sqlite3_realloc64(zBuffer, nAlloc);
      if( !zNew ){
        rc = SQLITE_NOMEM;
        goto finish_scan;
      }
      zBuffer = zNew;
    }
    assert( zBuffer );

  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. */
  pNext += fts3GetVarint32(pNext, &nPrefix);
  pNext += fts3GetVarint32(pNext, &nSuffix);
  if( nSuffix<=0 
   || (&pReader->aNode[pReader->nNode] - pNext)<nSuffix
   || nPrefix>pReader->nTermAlloc
  ){
    return FTS_CORRUPT_VTAB;
  }

  /* Both nPrefix and nSuffix were read by fts3GetVarint32() and so are
  ** between 0 and 0x7FFFFFFF. But the sum of the two may cause integer
  ** overflow - hence the (i64) casts.  */
  if( (i64)nPrefix+nSuffix>(i64)pReader->nTermAlloc ){
    i64 nNew = ((i64)nPrefix+nSuffix)*2;
    char *zNew = sqlite3_realloc64(pReader->zTerm, nNew);
    if( !zNew ){
      return SQLITE_NOMEM;
    }
    pReader->zTerm = zNew;
    pReader->nTermAlloc = nNew;
  }

  pReader->aDoclist = pNext;
  pReader->pOffsetList = 0;

  /* Check that the doclist does not appear to extend past the end of the
  ** b-tree node. And that the final byte of the doclist is 0x00. If either 
  ** of these statements is untrue, then the data structure is corrupt.
  */
  if( (&pReader->aNode[pReader->nNode] - pReader->aDoclist)<pReader->nDoclist
   || (pReader->nPopulate==0 && pReader->aDoclist[pReader->nDoclist-1])
  ){
    return FTS_CORRUPT_VTAB;
  }
  return SQLITE_OK;
}

    p->aNode = 0;
  }else{
    if( bFirst==0 ){
      p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &nPrefix);
    }
    p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &nSuffix);

    if( nPrefix>p->iOff || nSuffix>p->nNode-p->iOff ){
      return SQLITE_CORRUPT_VTAB;
    }
    blobGrowBuffer(&p->term, nPrefix+nSuffix, &rc);
    if( rc==SQLITE_OK ){
      memcpy(&p->term.a[nPrefix], &p->aNode[p->iOff], nSuffix);
      p->term.n = nPrefix+nSuffix;
      p->iOff += nSuffix;
      if( p->iChild==0 ){
        p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &p->nDoclist);
        if( (p->nNode-p->iOff)<p->nDoclist ){
          return SQLITE_CORRUPT_VTAB;
        }
        p->aDoclist = &p->aNode[p->iOff];
        p->iOff += p->nDoclist;
      }
    }
  }

  assert( p->iOff<=p->nNode );

  return rc;
}

/*
** Release all dynamic resources held by node-reader object *p.
*/
static void nodeReaderRelease(NodeReader *p){

# 2006 September 9
#
# 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.
#
#*************************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is testing the FTS3 module.
#
# $Id: fts3aa.test,v 1.1 2007/08/20 17:38:42 shess Exp $
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix fts3corrupt4

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

do_execsql_test 1.0 {
  BEGIN;
    CREATE VIRTUAL TABLE ft USING fts3;
    INSERT INTO ft VALUES('aback');
    INSERT INTO ft VALUES('abaft');
    INSERT INTO ft VALUES('abandon');
  COMMIT;
}

proc blob {a} { binary decode hex $a }
db func blob blob

do_execsql_test 1.1 {
  SELECT quote(root) FROM ft_segdir;
} {X'0005616261636B03010200030266740302020003046E646F6E03030200'}

do_execsql_test 1.2 {
  UPDATE ft_segdir SET root = blob(
    '0005616261636B03010200 FFFFFFFF0702 66740302020003046E646F6E03030200'
  );
}

do_catchsql_test 1.3 {
  SELECT * FROM ft WHERE ft MATCH 'abandon';
} {1 {database disk image is malformed}}

#-------------------------------------------------------------------------
reset_db
do_execsql_test 2.0.0 {
  CREATE VIRTUAL TABLE ft USING fts3;
  INSERT INTO ft(ft) VALUES('nodesize=32');
}
do_test 2.0.1 {
  for {set i 0} {$i < 12} {incr i} {
    execsql {
      BEGIN;
        INSERT INTO ft VALUES('abc' || $i);
        INSERT INTO ft VALUES('abc' || $i || 'x' );
        INSERT INTO ft VALUES('abc' || $i || 'xx' );
      COMMIT
    }
  }
  execsql {
    SELECT count(*) FROM ft_segdir;
    SELECT count(*) FROM ft_segments;
  }
} {12 0}

do_execsql_test 2.1 {
  INSERT INTO ft(ft) VALUES('merge=1,4');
  SELECT count(*) FROM ft_segdir;
  SELECT count(*) FROM ft_segments;
} {12 3}

do_execsql_test 2.2 {
  SELECT quote(block) FROM ft_segments WHERE blockid=2
} {X'00056162633130031F0200'}

db func blob blob
do_execsql_test 2.3.1 {
  UPDATE ft_segments SET block = 
    blob('00056162633130031F0200 FFFFFFFF07FF55 66740302020003046E646F6E03030200')
    WHERE blockid=2;
} {}
do_catchsql_test 2.3.2 {
  INSERT INTO ft(ft) VALUES('merge=1,4');
} {1 {database disk image is malformed}}

do_execsql_test 2.4.1 {
  UPDATE ft_segments SET block = 
    blob('00056162633130031F0200 02FFFFFFFF07 66740302020003046E646F6E03030200')
    WHERE blockid=2;
} {}
do_catchsql_test 2.4.2 {
  INSERT INTO ft(ft) VALUES('merge=1,4');
} {1 {database disk image is malformed}}

do_execsql_test 2.5.1 {
  UPDATE ft_segments SET block = 
    blob('00056162633130031F0200 0202 6674 FFFFFF070302020003046E646F6E030200')
    WHERE blockid=2;
} {}
do_catchsql_test 2.5.2 {
  INSERT INTO ft(ft) VALUES('merge=1,4');
} {1 {database disk image is malformed}}

#-------------------------------------------------------------------------
reset_db
do_execsql_test 3.0.0 {
  CREATE VIRTUAL TABLE ft USING fts3;
  INSERT INTO ft(ft) VALUES('nodesize=32');
}
do_test 3.0.1 {
  execsql BEGIN
  for {set i 0} {$i < 20} {incr i} {
    execsql { INSERT INTO ft VALUES('abc' || $i) }
  }
  execsql {
    COMMIT;
    SELECT count(*) FROM ft_segdir;
    SELECT count(*) FROM ft_segments;
  }
} {1 5}

do_execsql_test 3.1 {
  SELECT quote(root) FROM ft_segdir
} {X'0101056162633132040136030132030136'}

db func blob blob
do_execsql_test 3.2 {
  UPDATE ft_segdir 
  SET root = blob('0101056162633132FFFFFFFF070236030132030136');
}

do_catchsql_test 3.1 {
  SELECT * FROM ft WHERE ft MATCH 'abc20'
} {1 {database disk image is malformed}}

finish_test

} -files {
  fts3aa.test fts3ab.test fts3ac.test fts3ad.test
  fts3ae.test fts3af.test fts3ag.test fts3ah.test
  fts3ai.test fts3aj.test fts3ak.test fts3al.test
  fts3am.test fts3an.test fts3ao.test fts3atoken.test
  fts3auto.test fts3aux1.test fts3aux2.test fts3b.test
  fts3comp1.test fts3conf.test fts3corrupt2.test fts3corrupt.test
  fts3corrupt4.test
  fts3cov.test fts3c.test fts3defer2.test fts3defer3.test
  fts3defer.test fts3drop.test fts3d.test fts3e.test
  fts3expr2.test fts3expr3.test fts3expr4.test fts3expr5.test
  fts3expr.test fts3fault2.test fts3fault.test fts3first.test
  fts3join.test fts3malloc.test fts3matchinfo.test fts3near.test
  fts3offsets.test fts3prefix2.test fts3prefix.test fts3query.test
  fts3shared.test fts3snippet.test fts3sort.test fts3tok1.test