public void put(WebURL url) throws DatabaseException {
/*
* The key that is used for storing URLs determines the order
* they are crawled. Lower key values results in earlier crawling.
* Here our keys are 6 bytes. The first byte comes from the URL priority.
* The second byte comes from depth of crawl at which this URL is first found.
* The rest of the 4 bytes come from the docid of the URL. As a result,
* URLs with lower priority numbers will be crawled earlier. If priority
* numbers are the same, those found at lower depths will be crawled earlier.
* If depth is also equal, those found earlier (therefore, smaller docid) will
* be crawled earlier.
*/
byte[] keyData = new byte[6];
keyData[0] = url.getPriority();
keyData[1] = (url.getDepth() > Byte.MAX_VALUE ? Byte.MAX_VALUE : (byte) url.getDepth());
Util.putIntInByteArray(url.getDocid(), keyData, 2);
DatabaseEntry value = new DatabaseEntry();
webURLBinding.objectToEntry(url, value);
Transaction txn;
if (resumable) {
txn = env.beginTransaction(null, null);
} else {
txn = null;
}
urlsDB.put(txn, new DatabaseEntry(keyData), value);
if (resumable) {
if (txn != null) {
txn.commit();
}
}
}
public List<WebURL> get(int max) throws DatabaseException {
synchronized (mutex) {
int matches = 0;
List<WebURL> results = new ArrayList<WebURL>(max);
Cursor cursor = null;
OperationStatus result;
DatabaseEntry key = new DatabaseEntry();
DatabaseEntry value = new DatabaseEntry();
Transaction txn;
if (resumable) {
txn = env.beginTransaction(null, null);
} else {
txn = null;
}
try {
cursor = urlsDB.openCursor(txn, null);
result = cursor.getFirst(key, value, null);
while (matches < max && result == OperationStatus.SUCCESS) {
if (value.getData().length > 0) {
results.add(webURLBinding.entryToObject(value));
matches++;
}
result = cursor.getNext(key, value, null);
}
} catch (DatabaseException e) {
if (txn != null) {
txn.abort();
txn = null;
}
throw e;
} finally {
if (cursor != null) {
cursor.close();
}
if (txn != null) {
txn.commit();
}
}
return results;
}
}
