/**
* Pre-generate enough keys to reach the lookahead size, but only if there are more than the
* lookaheadThreshold to be generated, so that the Bloom filter does not have to be regenerated
* that often.
*
* <p>The returned mutable list of keys must be inserted into the basic key chain.
*/
private List<DeterministicKey> maybeLookAhead(
DeterministicKey parent, int issued, int lookaheadSize, int lookaheadThreshold) {
checkState(lock.isHeldByCurrentThread());
final int numChildren = hierarchy.getNumChildren(parent.getPath());
final int needed = issued + lookaheadSize + lookaheadThreshold - numChildren;
if (needed <= lookaheadThreshold) return new ArrayList<DeterministicKey>();
log.info(
"{} keys needed for {} = {} issued + {} lookahead size + {} lookahead threshold - {} num children",
needed,
parent.getPathAsString(),
issued,
lookaheadSize,
lookaheadThreshold,
numChildren);
List<DeterministicKey> result = new ArrayList<DeterministicKey>(needed);
long now = System.currentTimeMillis();
int nextChild = numChildren;
for (int i = 0; i < needed; i++) {
DeterministicKey key = HDKeyDerivation.deriveThisOrNextChildKey(parent, nextChild);
key = key.getPubOnly();
hierarchy.putKey(key);
result.add(key);
nextChild = key.getChildNumber().num() + 1;
}
log.info("Took {} msec", System.currentTimeMillis() - now);
return result;
}
