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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.hosted.provision.provisioning;
import java.util.List;
import static java.util.Comparator.naturalOrder;
/**
* Tracks indices of a node cluster, and proposes the index of the next allocation.
*
* @author jonmv
*/
class NodeIndices {
private final List<Integer> used;
private int last;
private int probe;
/** Pass the list of current indices in the cluster. */
NodeIndices(List<Integer> used) {
this.used = List.copyOf(used);
this.last = -1;
this.probe = last;
}
/** Returns the next available index and commits to using it. Throws if a probe is ongoing. */
int next() {
if (probe != last)
throw new IllegalStateException("Must commit ongoing probe before calling 'next'");
probeNext();
commitProbe();
return last;
}
/** Returns the next available index, without committing to using it. Yields increasing indices when called multiple times. */
int probeNext() {
while (used.contains(++probe));
return probe;
}
/** Commits to using all indices returned by an ongoing probe. */
void commitProbe() {
last = probe;
}
/** Resets any probed state to what's currently committed. */
void resetProbe() {
probe = last;
}
}
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