int offset = 0;
for(int i=0; i<_bat_blocks.size(); i++) {
int numSectors = bigBlockSize.getBATEntriesPerBlock();
// Check this one
BATBlock bat = _bat_blocks.get(i);
if(bat.hasFreeSectors()) {
// Claim one of them and return it
for(int j=0; j<numSectors; j++) {
int batValue = bat.getValueAt(j);
if(batValue == POIFSConstants.UNUSED_BLOCK) {
// Bingo
return offset + j;
}
}
}
// Move onto the next BAT
offset += numSectors;
}
// If we get here, then there aren't any free sectors
// in any of the BATs, so we need another BAT
BATBlock bat = createBAT(offset, true);
bat.setValueAt(0, POIFSConstants.FAT_SECTOR_BLOCK);
_bat_blocks.add(bat);
// Now store a reference to the BAT in the required place
if(_header.getBATCount() >= 109) {
// Needs to come from an XBAT
BATBlock xbat = null;
for(BATBlock x : _xbat_blocks) {
if(x.hasFreeSectors()) {
xbat = x;
break;
}
}
if(xbat == null) {
// Oh joy, we need a new XBAT too...
xbat = createBAT(offset+1, false);
xbat.setValueAt(0, offset);
bat.setValueAt(1, POIFSConstants.DIFAT_SECTOR_BLOCK);
// Will go one place higher as XBAT added in
offset++;
// Chain it
if(_xbat_blocks.size() == 0) {
_header.setXBATStart(offset);
} else {
_xbat_blocks.get(_xbat_blocks.size()-1).setValueAt(
bigBlockSize.getXBATEntriesPerBlock(), offset
);
}
_xbat_blocks.add(xbat);
_header.setXBATCount(_xbat_blocks.size());
}
// Allocate us in the XBAT
for(int i=0; i<bigBlockSize.getXBATEntriesPerBlock(); i++) {
if(xbat.getValueAt(i) == POIFSConstants.UNUSED_BLOCK) {
xbat.setValueAt(i, offset);
}
}
} else {
// Store us in the header
int[] newBATs = new int[_header.getBATCount()+1];