/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.waveprotocol.wave.concurrencycontrol.client;
import org.waveprotocol.wave.concurrencycontrol.server.DeltaHistory;
import org.waveprotocol.wave.model.operation.wave.TransformedWaveletDelta;
import org.waveprotocol.wave.model.util.CollectionUtils;
import org.waveprotocol.wave.model.util.Preconditions;
import org.waveprotocol.wave.model.version.HashedVersion;
import java.util.HashMap;
/**
* Simple dumb implementation of delta history using hashtables.
*
* @author zdwang@google.com (David Wang)
*/
public class SimpleDeltaHistory implements DeltaHistory {
private HashedVersion currentSignature;
/**
* maps version -> delta
*/
private final HashMap<Long, TransformedWaveletDelta> history = CollectionUtils.newHashMap();
/**
* All the signatures we have. Knowing a signature does not mean we have a
* delta at that signature.
*
* e.g. we don't have a delta for the most recent signature
*/
private final HashMap<Long, HashedVersion> signatures =
new HashMap<Long, HashedVersion>();
/**
* We always start at version 0
*/
public SimpleDeltaHistory(HashedVersion v0) {
Preconditions.checkArgument(v0.getVersion() == 0, "Delta history must start at zero");
currentSignature = v0;
// We always have a signature at version 0, but we have no operation for it.
signatures.put(0L, currentSignature);
}
@Override
public TransformedWaveletDelta getDeltaStartingAt(long version) {
return history.get(version);
}
@Override
public boolean hasSignature(HashedVersion signatureInformation) {
HashedVersion found = signatures.get(signatureInformation.getVersion());
if (found == null) {
return false;
}
return found.equals(signatureInformation);
}
/**
* @return last known signature.
*/
public HashedVersion getCurrentSignature() {
return currentSignature;
}
@Override
public long getCurrentVersion() {
return currentSignature.getVersion();
}
/**
* Make the current signature the given one
* @param currentSignature
*/
public void setCurrentSignature(HashedVersion currentSignature) {
assert currentSignature == signatures.get(currentSignature.getVersion());
this.currentSignature = currentSignature;
}
/**
* Add a delta to the hash tables.
*/
public void addDelta(TransformedWaveletDelta delta) {
history.put(delta.getAppliedAtVersion(), delta);
signatures.put(delta.getResultingVersion().getVersion(), delta.getResultingVersion());
}
/**
* Removes a delta from the hash tables.
*/
public void removeDelta(TransformedWaveletDelta delta) {
history.remove(delta.getAppliedAtVersion());
signatures.remove(delta.getResultingVersion().getVersion());
}
/**
* Gets the signature at the given version.
*/
public HashedVersion getSignatureAt(long version) {
return signatures.get(version);
}
/**
* Truncate to the given version.
*/
public void truncateAt(long version) {
HashedVersion signature = getSignatureAt(version);
setCurrentSignature(signature);
TransformedWaveletDelta currentDelta = getDeltaStartingAt(version);
while(currentDelta != null) {
removeDelta(currentDelta);
currentDelta = getDeltaStartingAt(currentDelta.getResultingVersion().getVersion());
}
}
}