SQLite

** The application must eventually free every [sqlite3_snapshot] object
** using this routine to avoid a memory leak.
**
** The [sqlite3_snapshot_free()] interface is only available when the
** SQLITE_ENABLE_SNAPSHOT compile-time option is used.
*/
SQLITE_EXPERIMENTAL void sqlite3_snapshot_free(sqlite3_snapshot*);

/*
** CAPI3REF: Compare the ages of two snapshot handles.
** EXPERIMENTAL
**
** The sqlite3_snapshot_cmp(P1, P2) interface is used to compare the ages
** of two valid snapshot handles. 
**
** If the two snapshot handles are not associated with the same database 
** file, the results are undefined. If either of the snapshot handles
** is no longer valid because the database snapshot they refer to has been
** destroyed by a checkpoint, the results are undefined. 
**
** Otherwise, this API returns a negative value if P1 refers to an older
** snapshot than P2, zero if the two handles refer to the same database
** snapshot, and a positive value if P1 is a newer snapshot than P2.
*/
SQLITE_EXPERIMENTAL int sqlite3_snapshot_cmp(
  sqlite3_snapshot *p1,
  sqlite3_snapshot *p2
);

/*
** Undo the hack that converts floating point types to integer for
** builds on processors without floating point support.
*/
#ifdef SQLITE_OMIT_FLOATING_POINT
# undef double

  }
  pSnapshot = (sqlite3_snapshot*)sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
  sqlite3_snapshot_free(pSnapshot);
  return TCL_OK;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */

#ifdef SQLITE_ENABLE_SNAPSHOT
/*
** Usage: sqlite3_snapshot_cmp SNAPSHOT1 SNAPSHOT2
*/
static int test_snapshot_cmp(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  int res;
  sqlite3_snapshot *p1;
  sqlite3_snapshot *p2;
  if( objc!=3 ){
    Tcl_WrongNumArgs(interp, 1, objv, "SNAPSHOT1 SNAPSHOT2");
    return TCL_ERROR;
  }
  p1 = (sqlite3_snapshot*)sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
  p2 = (sqlite3_snapshot*)sqlite3TestTextToPtr(Tcl_GetString(objv[2]));
  res = sqlite3_snapshot_cmp(p1, p2);
  Tcl_SetObjResult(interp, Tcl_NewIntObj(res));
  return TCL_OK;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */

/*
** Usage:  sqlite3_next_stmt  DB  STMT
**
** Return the next statment in sequence after STMT.
*/
static int test_next_stmt(
  void * clientData,

     { "sqlite3_config_sqllog",         test_config_sqllog,   0 },
#endif
     { "vfs_current_time_int64",           vfsCurrentTimeInt64,   0 },
#ifdef SQLITE_ENABLE_SNAPSHOT
     { "sqlite3_snapshot_get", test_snapshot_get, 0 },
     { "sqlite3_snapshot_open", test_snapshot_open, 0 },
     { "sqlite3_snapshot_free", test_snapshot_free, 0 },
     { "sqlite3_snapshot_cmp", test_snapshot_cmp, 0 },
#endif
  };
  static int bitmask_size = sizeof(Bitmask)*8;
  static int longdouble_size = sizeof(LONGDOUBLE_TYPE);
  int i;
  extern int sqlite3_sync_count, sqlite3_fullsync_count;
  extern int sqlite3_opentemp_count;

}

/* Try to open on pSnapshot when the next read-transaction starts
*/
void sqlite3WalSnapshotOpen(Wal *pWal, sqlite3_snapshot *pSnapshot){
  pWal->pSnapshot = (WalIndexHdr*)pSnapshot;
}

/* 
** Return a +ve value if snapshot p1 is newer than p2. A -ve value if
** p1 is older than p2 and zero if p1 and p2 are the same snapshot.
*/
int sqlite3_snapshot_cmp(sqlite3_snapshot *p1, sqlite3_snapshot *p2){
  WalIndexHdr *pHdr1 = (WalIndexHdr*)p1;
  WalIndexHdr *pHdr2 = (WalIndexHdr*)p2;

  /* aSalt[0] is a copy of the value stored in the wal file header. It
  ** is incremented each time the wal file is restarted.  */
  if( pHdr1->aSalt[0]<pHdr2->aSalt[0] ) return -1;
  if( pHdr1->aSalt[0]>pHdr2->aSalt[0] ) return +1;
  if( pHdr1->mxFrame<pHdr2->mxFrame ) return -1;
  if( pHdr1->mxFrame>pHdr2->mxFrame ) return +1;
  return 0;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */

#ifdef SQLITE_ENABLE_ZIPVFS
/*
** If the argument is not NULL, it points to a Wal object that holds a
** read-lock. This function returns the database page-size if it is known,
** or zero if it is not (or if pWal is NULL).

  db2 close
  sqlite3 db2 test.db 
  db2 eval "BEGIN"
  list [catch {sqlite3_snapshot_open db2 main $::snapshot} msg] $msg
} {1 SQLITE_ERROR}

sqlite3_snapshot_free $snapshot

#-------------------------------------------------------------------------
# The following tests investigate the sqlite3_snapshot_cmp() API.
#
catch { db2 close }
reset_db
do_execsql_test 7.1 {
  PRAGMA journal_mode = wal;
  CREATE TABLE t1(x);
} wal

do_test 7.1.2 {
  execsql { BEGIN ; PRAGMA application_id }
  set p1 [sqlite3_snapshot_get db main]
  execsql {
    INSERT INTO t1 VALUES(10);
    COMMIT;
  }
  execsql { BEGIN ; PRAGMA application_id }
  set p2 [sqlite3_snapshot_get db main]
  execsql COMMIT

  sqlite3_snapshot_cmp $p1 $p2
} {-1}

do_test 7.1.3 {
  sqlite3_snapshot_cmp $p2 $p1
} {1}

do_test 7.1.4 {
  list [sqlite3_snapshot_cmp $p1 $p1] [sqlite3_snapshot_cmp $p2 $p2]
} {0 0}
sqlite3_snapshot_free $p1
sqlite3_snapshot_free $p2

finish_test