How to use jdbm.recman

/**
 * Allocate a new rowid with the indicated size.
 */
private long alloc(int size) throws IOException {
  size = RecordHeader.roundAvailableSize(size);
  long retval = freeman.get(size);
  if (retval == 0) {
    retval = allocNew(size, pageman.getLast(Magic.USED_PAGE));
  }
  return retval;
}

public synchronized void rollback()
  throws IOException
{
  checkIfClosed();
  _physMgr.commit();
  _logicMgr.commit();
  _physPageman.rollback();
  _physPagemanFree.rollback();
  _logicPageman.rollback();
  _logicPagemanFree.rollback();
}

private void free( Location id ) throws IOException
{
  // get the rowid, and write a zero current size into it.
  BlockIo curBlock = file.get( id.getBlock() );
  RecordHeader hdr = new RecordHeader( curBlock, id.getOffset() );
  hdr.setCurrentSize( 0 );
  file.release( id.getBlock(), true );
  // write the rowid to the free list
  freePageManager.put( id, hdr.getAvailableSize() );
}
 

private void free(long id) throws IOException {
  // get the rowid, and write a zero current size into it.
  BlockIo curBlock = file.get(Location.getBlock(id));
  DataPage curPage = DataPage.getDataPageView(curBlock,BLOCK_SIZE);
  RecordHeader.setCurrentSize(curBlock, Location.getOffset(id), 0);
  file.release(Location.getBlock(id), true);
  // write the rowid to the free list
  freeman.put(id, RecordHeader.getAvailableSize(curBlock, Location.getOffset(id)));	
}

/**
 * Releases the indicated logical rowid.
 */
void delete(long rowid) throws IOException {
  //zero out old location, is needed for defragmentation
  TranslationPage xlatPage = TranslationPage.getTranslationPageView(file.get(Location.getBlock(rowid)),blockSize);
  xlatPage.setLocationBlock(Location.getOffset(rowid), 0);
  xlatPage.setLocationOffset(Location.getOffset(rowid), (short)0);
  file.release(Location.getBlock(rowid), true);
  freeman.put(rowid);
}

/** Allocates a slot */
PhysicalRowId alloc(int slot) {
  setCount((short) (getCount() + 1));
  get(slot).setBlock(-1);
  return get(slot);
}

/** Frees a slot */
void free( int slot ) 
{
  get( slot ).setSize( 0 );
  setCount( ( short ) ( getCount() - 1 ) );
}

/**
 *  Returns the indicated root rowid.
 *
 *  @see #getRootCount
 */
public synchronized long getRoot( int id ) throws IOException
{
  checkIfClosed();
  return pageMgr.getFileHeader().getRoot( id );
}

public synchronized void setRoot( int id, long rowid )
  throws IOException
{
  checkIfClosed();
  _physPageman.getFileHeader().setRoot( id, rowid );
}

/**
 * Constructs a new PageHeader of the indicated type. Used for newly
 * created pages.
 */
PageHeader( BlockIo block, short type )
{
  this.block = block;
  block.setView( this );
  setType( type );
}

/**
 * Returns the first block of the indicated list
 */
long getFirstOf( int list ) 
{
  return block.readLong( offsetOfFirst( list ) );
}

/** Returns the next block. */
long getNext() 
{
  paranoiaMagicOk();
  return block.readLong( O_NEXT );
}

/**
 *  Returns the last block of the indicated list
 */
long getLastOf(int list) {
  return block.readLong(offsetOfLast(list));
}

/**
 * Factory method to create or return a data page for the indicated block.
 */
static FreePhysicalRowIdPage getFreePhysicalRowIdPageView(BlockIo block,int pageSize) {
  BlockView view = block.getView();
  if (view != null && view instanceof FreePhysicalRowIdPage)
    return (FreePhysicalRowIdPage) view;
  else
    return new FreePhysicalRowIdPage(block, pageSize);
}

/**
 *  Factory method to create or return a page header for the
 *  indicated block.
 */
static PageHeader getView(BlockIo block) {
  BlockView view = block.getView();
  if (view != null && view instanceof PageHeader)
    return (PageHeader) view;
  else
    return new PageHeader(block);
}

/** Sets the next block. */
void setNext(long next) {
  paranoiaMagicOk();
  block.writeLong(O_NEXT, next);
}

/** Returns the value of the indicated slot */
FreePhysicalRowId get( int slot ) 
{
  if ( slots[slot] == null )
  {
    slots[slot] = new FreePhysicalRowId( block, slotToOffset( slot ) ) ;
  }
  return slots[slot];
}

/** Returns the size */
int FreePhysicalRowId_getSize(short pos) {
  int slot = offsetToSlot(pos);
  if(sizeCache[slot] == -1)
    sizeCache[slot] =  block.readInt(pos + FreePhysicalRowId_O_SIZE);
  return sizeCache[slot];
}

private void free( Location id )
  throws IOException
{
  // get the rowid, and write a zero current size into it.
  BlockIo curBlock = file.get( id.getBlock() );
  RecordHeader hdr = new RecordHeader( curBlock, id.getOffset() );
  hdr.setCurrentSize( 0 );
  file.release( id.getBlock(), true );
  // write the rowid to the free list
  freeman.put( id, hdr.getAvailableSize() );
}

private void free( Location id )
  throws IOException
{
  // get the rowid, and write a zero current size into it.
  BlockIo curBlock = file.get( id.getBlock() );
  RecordHeader hdr = new RecordHeader( curBlock, id.getOffset() );
  hdr.setCurrentSize( 0 );
  file.release( id.getBlock(), true );
  // write the rowid to the free list
  freeman.put( id, hdr.getAvailableSize() );
}