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/*************************************************************************************************
* The Java API of cursor functions of Villa
* Copyright (C) 2000-2006 Mikio Hirabayashi
* This file is part of QDBM, Quick Database Manager.
* QDBM is free software; you can redistribute it and/or modify it under the terms of the GNU
* Lesser General Public License as published by the Free Software Foundation; either version
* 2.1 of the License or any later version. QDBM is distributed in the hope that it will be
* useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
* details.
* You should have received a copy of the GNU Lesser General Public License along with QDBM; if
* not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
* 02111-1307 USA.
*************************************************************************************************/
package qdbm;
/**
* The Java API of cursor functions of Villa
* This class depends on the native library `jqdbm'.
*/
public class VillaCursor {
//----------------------------------------------------------------
// instance fields
//----------------------------------------------------------------
/** pointer to the native object */
private long coreptr;
/** database handle */
private Villa villa;
//----------------------------------------------------------------
// constructors and finalizers
//----------------------------------------------------------------
/**
* Get a multiple cursor handle.
* @param villa a database handle connected as a reader.
* @throws VillaException if an error occurs.
*/
VillaCursor(Villa villa) throws VillaException {
this.villa = villa;
synchronized(ADBM.class){
int index = villa.getindex();
if(index < 0) throw new VillaException();
if(vlmulcurnew(index) == 0) throw new VillaException(vlmulcurecode());
}
}
/**
* Release resources.
*/
protected void finalize(){
vlmulcurdelete();
}
//----------------------------------------------------------------
// public or protected methods
//----------------------------------------------------------------
/**
* Move the multiple cursor to the first record.
* @return always true. However, if the silent flag is true and no record corresponds, false
* is returned instead of exception.
* @throws VillaException if an error occurs or there is no record in the database.
*/
public boolean first() throws VillaException {
synchronized(ADBM.class){
int index = villa.getindex();
if(index < 0) throw new VillaException();
if(vlmulcurfirst(index) == 0){
if(villa.silent && vlmulcurecode() == Villa.ENOITEM) return false;
throw new VillaException(vlmulcurecode());
}
return true;
}
}
/**
* Move the multiple cursor to the last record.
* @return always true. However, if the silent flag is true and no record corresponds, false
* is returned instead of exception.
* @throws VillaException if an error occurs or there is no record in the database.
*/
public boolean last() throws VillaException {
synchronized(ADBM.class){
int index = villa.getindex();
if(index < 0) throw new VillaException();
if(vlmulcurlast(index) == 0){
if(villa.silent && vlmulcurecode() == Villa.ENOITEM) return false;
throw new VillaException(vlmulcurecode());
}
return true;
}
}
/**
* Move the multiple cursor to the next record.
* @return always true. However, if the silent flag is true and no record corresponds, false
* is returned instead of exception.
* @throws VillaException if an error occurs or there is no previous record.
*/
public boolean prev() throws VillaException {
synchronized(ADBM.class){
int index = villa.getindex();
if(index < 0) throw new VillaException();
if(vlmulcurprev(index) == 0){
if(villa.silent && vlmulcurecode() == Villa.ENOITEM) return false;
throw new VillaException(vlmulcurecode());
}
return true;
}
}
/**
* Move the multiple cursor to the next record.
* @return always true. However, if the silent flag is true and no record corresponds, false
* is returned instead of exception.
* @throws VillaException if an error occurs or there is no next record.
*/
public boolean next() throws VillaException {
synchronized(ADBM.class){
int index = villa.getindex();
if(index < 0) throw new VillaException();
if(vlmulcurnext(index) == 0){
if(villa.silent && vlmulcurecode() == Villa.ENOITEM) return false;
throw new VillaException(vlmulcurecode());
}
return true;
}
}
/**
* Move the multiple cursor to a position around a record.
* @param key a byte array of a key.
* @param jmode detail adjustment: `Villa.JFORWARD', which means that the cursor is set to
* the first record of the same key and that the cursor is set to the next substitute if
* completely matching record does not exist, `Villa.JBACKWARD', which means that the cursor
* is set to the last record of the same key and that the cursor is set to the previous
* substitute if completely matching record does not exist.
* @return always true. However, if the silent flag is true and no record corresponds, false
* is returned instead of exception.
* @throws VillaException if an error occurs or there is no record corresponding the condition.
*/
public boolean jump(byte[] key, int jmode) throws VillaException {
synchronized(ADBM.class){
int index = villa.getindex();
if(index < 0) throw new VillaException();
if(vlmulcurjump(index, key, key.length, jmode) == 0){
if(villa.silent && vlmulcurecode() == Villa.ENOITEM) return false;
throw new VillaException(vlmulcurecode());
}
return true;
}
}
/**
* Move the multiple cursor to a position around a record for stepping forward.
* The same as `jump(key, Villa.JFORFARD)'.
* @see #jump(byte[], int)
*/
public boolean jump(byte[] key) throws VillaException {
return jump(key, Villa.JFORWARD);
}
/**
* Move the multiple cursor to a position around a record composed of serializable objects.
* The same as `jump(qdbm.Util.serialize(key), jmode)'.
* @see #jump(byte[], int)
* @note If serialization is failed, an instance of `VillaException' is thrown.
*/
public boolean jumpobj(Object key, int jmode) throws VillaException {
byte[] kbuf = Util.serialize(key);
if(kbuf == null) throw new VillaException();
return jump(kbuf, jmode);
}
/**
* Get the key of the record where the multiple cursor is.
* @return a byte array of the key of the corresponding record. If the silent flag is true and
* no record corresponds, `null' is returned instead of exception.
* @throws VillaException if an error occurs or no record corresponds to the cursor.
*/
public byte[] key() throws VillaException {
synchronized(ADBM.class){
int index = villa.getindex();
if(index < 0) throw new VillaException();
byte[] val = vlmulcurkey(index);
if(val == null){
if(villa.silent && vlmulcurecode() == Villa.ENOITEM) return null;
throw new VillaException(vlmulcurecode());
}
return val;
}
}
/**
* Get the key of the record composed of serializable objects, where the multiple cursor is.
* The same as `qdbm.Util.deserialize(key())'.
* @see #key()
* @note If serialization is failed, an instance of `VillaException' is thrown.
*/
public Object keyobj() throws VillaException {
byte[] kbuf = key();
if(kbuf == null) return null;
Object key = Util.deserialize(kbuf);
if(key == null) throw new VillaException();
return key;
}
/**
* Get the value of the record where the multiple cursor is.
* @return a byte array of the value of the corresponding record. If the silent flag is true
* and no record corresponds, `null' is returned instead of exception.
* @throws VillaException if an error occurs or no record corresponds to the cursor.
*/
public byte[] val() throws VillaException {
synchronized(ADBM.class){
int index = villa.getindex();
if(index < 0) throw new VillaException();
byte[] val = vlmulcurval(index);
if(val == null){
if(villa.silent && vlmulcurecode() == Villa.ENOITEM) return null;
throw new VillaException(vlmulcurecode());
}
return val;
}
}
/**
* Get the value of the record where the multiple cursor is.
* The same as `qdbm.Util.deserialize(val())'.
* @see #val()
* @note If serialization is failed, an instance of `VillaException' is thrown.
*/
public Object valobj() throws VillaException {
byte[] vbuf = val();
if(vbuf == null) return vbuf;
Object val = Util.deserialize(vbuf);
if(val == null) throw new VillaException();
return val;
}
//----------------------------------------------------------------
// native methods
//----------------------------------------------------------------
private static synchronized final native int vlmulcurecode();
private synchronized final native int vlmulcurnew(int index);
private synchronized final native void vlmulcurdelete();
private synchronized final native int vlmulcurfirst(int index);
private synchronized final native int vlmulcurlast(int index);
private synchronized final native int vlmulcurprev(int index);
private synchronized final native int vlmulcurnext(int index);
private synchronized final native int vlmulcurjump(int index, byte[] key, int ksiz, int jmode);
private synchronized final native byte[] vlmulcurkey(int index);
private synchronized final native byte[] vlmulcurval(int index);
}
/* END OF FILE */
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