/**
* Try to set or remove the value. When updating only unchanged entries, then the value is only
* changed if it was not changed after opening the map.
*
* @param key the key
* @param value the new value (null to remove the value)
* @param onlyIfUnchanged only set the value if it was not changed (by this or another
* transaction) since the map was opened
* @return true if the value was set
*/
public boolean trySet(K key, V value, boolean onlyIfUnchanged) {
Object[] current = map.get(key);
if (onlyIfUnchanged) {
Object[] old = getArray(key, readLogId);
if (!map.areValuesEqual(old, current)) {
long tx = (Long) current[0];
if (tx == transaction.transactionId) {
if (value == null) {
// ignore removing an entry
// if it was added or changed
// in the same statement
return true;
} else if (current[2] == null) {
// add an entry that was removed
// in the same statement
} else {
return false;
}
} else {
return false;
}
}
}
int opType;
if (current == null || current[2] == null) {
if (value == null) {
// remove a removed value
opType = Transaction.OP_SET;
} else {
opType = Transaction.OP_ADD;
}
} else {
if (value == null) {
opType = Transaction.OP_REMOVE;
} else {
opType = Transaction.OP_SET;
}
}
Object[] newValue = {transaction.transactionId, transaction.logId, value};
if (current == null) {
// a new value
Object[] old = map.putIfAbsent(key, newValue);
if (old == null) {
transaction.log(opType, mapId, key, current);
return true;
}
return false;
}
long tx = (Long) current[0];
if (tx == transaction.transactionId) {
// added or updated by this transaction
if (map.replace(key, current, newValue)) {
transaction.log(opType, mapId, key, current);
return true;
}
// strange, somebody overwrite the value
// even thought the change was not committed
return false;
}
// added or updated by another transaction
boolean open = transaction.store.openTransactions.containsKey(tx);
if (!open) {
// the transaction is committed:
// overwrite the value
if (map.replace(key, current, newValue)) {
transaction.log(opType, mapId, key, current);
return true;
}
// somebody else was faster
return false;
}
// the transaction is not yet committed
return false;
}
