/**
* Reader factory method. Build a Node object (of the right type) by reading a block in the file.
*
* @param config Configuration of the History Tree
* @param fc FileChannel to the history file, ALREADY SEEKED at the start of the node.
* @return The node object
* @throws IOException If there was an error reading from the file channel
*/
public static final HTNode readNode(HTConfig config, FileChannel fc) throws IOException {
HTNode newNode = null;
int res, i;
ByteBuffer buffer = ByteBuffer.allocate(config.getBlockSize());
buffer.order(ByteOrder.LITTLE_ENDIAN);
buffer.clear();
res = fc.read(buffer);
assert (res == config.getBlockSize());
buffer.flip();
/* Read the common header part */
byte typeByte = buffer.get();
NodeType type = NodeType.fromByte(typeByte);
long start = buffer.getLong();
long end = buffer.getLong();
int seqNb = buffer.getInt();
int parentSeqNb = buffer.getInt();
int intervalCount = buffer.getInt();
int stringSectionOffset = buffer.getInt();
buffer.get(); // TODO Used to be "isDone", to be removed from the header
/* Now the rest of the header depends on the node type */
switch (type) {
case CORE:
/* Core nodes */
newNode = new CoreNode(config, seqNb, parentSeqNb, start);
newNode.readSpecificHeader(buffer);
break;
case LEAF:
/* Leaf nodes */
newNode = new LeafNode(config, seqNb, parentSeqNb, start);
newNode.readSpecificHeader(buffer);
break;
default:
/* Unrecognized node type */
throw new IOException();
}
/*
* At this point, we should be done reading the header and 'buffer'
* should only have the intervals left
*/
for (i = 0; i < intervalCount; i++) {
HTInterval interval = HTInterval.readFrom(buffer);
newNode.fIntervals.add(interval);
newNode.fSizeOfIntervalSection += interval.getIntervalSize();
}
/* Assign the node's other information we have read previously */
newNode.fNodeEnd = end;
newNode.fStringSectionOffset = stringSectionOffset;
newNode.fIsOnDisk = true;
return newNode;
}
/**
* Add an interval to this node
*
* @param newInterval Interval to add to this node
*/
public void addInterval(HTInterval newInterval) {
fRwl.writeLock().lock();
try {
/* Just in case, should be checked before even calling this function */
assert (newInterval.getIntervalSize() <= getNodeFreeSpace());
/* Find the insert position to keep the list sorted */
int index = fIntervals.size();
while (index > 0 && newInterval.compareTo(fIntervals.get(index - 1)) < 0) {
index--;
}
fIntervals.add(index, newInterval);
fSizeOfIntervalSection += newInterval.getIntervalSize();
/* Update the in-node offset "pointer" */
fStringSectionOffset -= (newInterval.getStringsEntrySize());
} finally {
fRwl.writeLock().unlock();
}
}
