private RecordHeader readRecordHeaderFromMappedBuffer(int pos) {
RecordHeader header = new RecordHeader();
mappedDataBuffer.position(pos);
header.setPosition(pos);
header.setDataSize(mappedDataBuffer.getInt());
header.setFragmented(mappedDataBuffer.get());
if (header.isFragmented()) {
header.setNextPos(mappedDataBuffer.getInt());
}
return header;
}
private RecordHeader readRecordHeaderFromChannel(int pos) throws IOException {
RecordHeader header = new RecordHeader();
header.setPosition(pos);
ByteBuffer buffer = ByteBuffer.allocate(RecordHeader.HEADER_BYTES);
dataChannel.position(pos);
dataChannel.read(buffer);
buffer.flip();
header.setDataSize(buffer.getInt());
header.setFragmented(buffer.get());
if (header.isFragmented()) {
header.setNextPos(buffer.getInt());
}
return header;
}
/* (non-Javadoc)
* @see com.ongraphdb.store.DiskSore1#updateData(int, byte[], int)
*/
public void updateData(int pos, byte[] data, int blockSize) throws IOException {
RecordHeader oldHeader = readRecordHeader(pos);
RecordHeader newHeader =
new RecordHeader().setPosition(pos).setDataSize(data.length).setFragmented(false);
int oldRecordSize = getRecordSize(blockSize, oldHeader);
int newRecordSize = getRecordSize(blockSize, newHeader);
if (oldRecordSize >= newRecordSize) {
if (oldHeader.isFragmented() || (oldRecordSize - newRecordSize > blockSize)) {
// write tail to hole
// write rest blocks to hole
}
writeRecordHeader(newHeader);
writeRecordData(newHeader, data);
} else {
newHeader.setFragmented(true);
newHeader.setDataSize(oldRecordSize - newHeader.getSize());
byte[] headData = new byte[newHeader.getDataSize()];
byte[] tailData = new byte[data.length - newHeader.getDataSize()];
System.arraycopy(data, 0, headData, 0, newHeader.getDataSize());
System.arraycopy(data, headData.length, tailData, 0, tailData.length);
RecordHeader newTailHeader =
new RecordHeader().setDataSize(tailData.length).setFragmented(false);
int newRecordTailSize = getRecordSize(blockSize, newTailHeader);
if (oldHeader.isFragmented()) {
RecordHeader oldHeaderTail = readRecordHeader(oldHeader.getNextPos());
int oldRecordTailSize = getRecordSize(blockSize, oldHeaderTail);
if (oldRecordTailSize >= newRecordSize) {
newTailHeader.setPosition(oldHeaderTail.getPosition());
// write rest blocks to hole
} else {
// write tail to hole
newTailHeader.setPosition(getNextPosition(newRecordTailSize));
}
} else {
newTailHeader.setPosition(getNextPosition(newRecordTailSize));
}
newHeader.setNextPos(newTailHeader.getPosition());
writeRecordHeader(newHeader);
writeRecordData(newHeader, headData);
writeRecordHeader(newTailHeader);
writeRecordData(newTailHeader, tailData);
}
}
